Sesame Production Under Water-Limited Environments: Integrating Physiology, Agronomy, Breeding and Climate Adaption Perspectives for Sustainable Systems

Abstract

Sesame (Sesamum indicum L.) is increasingly recognised as a drought-tolerant oilseed crop, particularly important for water-limited agriculture. However, evidence supporting its drought resilience is scattered across various studies in physiology, agronomy, genetics, and environmental science. This review aims to synthesise current understanding of sesame’s water use, responses to drought, irrigation management, water-use efficiency, interactions with nutrients, disease dynamics, breeding strategies, and adaptation to climate change. Sesame has several mechanisms to adapt to water deficits, such as deep rooting, stomatal regulation, osmotic adjustment, efficient carbon allocation, and the ability to recover after rewatering. However, these traits offer only partial protection against drought. Research shows that flowering and early capsule development are particularly sensitive to drought, with water shortages during these stages leading to significant yield losses. Strategic application of moderate deficit or supplemental irrigation can enhance water productivity, although the effectiveness varies among different genotypes and environmental conditions. The review points out major knowledge gaps, including inconsistent metrics for water-use efficiency, a lack of studies examining genotype x irrigation interactions, limited understanding of drought–disease relationships, and an over-reliance on pot experiments and short-term studies. Evidence from field-scale research, especially in emerging production regions like Australia, is still lacking. In summary, sesame should be viewed as drought-resilient rather than drought-proof. Future advancements will rely on integrating drought-resilient breeding, precision irrigation, root phenotyping, remote sensing, crop modelling, and improved management of water and nutrients within a genotype x environment x management framework, thereby strengthening the role of sesame in climate-resilient and sustainable farming systems under increasing water scarcity.

1. Introduction

Sesame (Sesamum indicum L., 2n = 2x = 26) is one of the world’s oldest oilseed crops and is cultivated widely across tropical and subtropical regions [1,2]. Its seeds contain 40–60% oil and are valued for their nutritional quality, industrial applications, and contribution to rural livelihoods in many sesame-producing countries [3,4]. Although traditionally grown in Asia and Africa, sesame production is expanding into new regions where water scarcity and climate variability are increasing pressure on existing farming systems [5,6,7,8].

Sesame is often regarded as a drought-tolerant crop because it can survive periods of limited soil moisture and produce acceptable yields under rainfed conditions [5,6]. This reputation is largely attributed to a range of adaptive traits, including deep rooting, stomatal regulation, osmotic adjustment, and the ability to recover following moderate drought stress [5,9,10,11]. However, survival under drought does not necessarily translate into stable productivity. Numerous studies have shown that seed yield can decline substantially when moisture deficits occur during flowering, capsule development, or seed filling [11,12]. This suggests that the drought resilience of sesame is more nuanced than commonly assumed.

The response of sesame to water limitation is influenced by several interacting factors. Drought intensity, stress duration, growth stage, genotype, soil conditions, and agronomic management all contribute to final crop performance [5,6,9]. In many production regions, water deficits are also accompanied by other constraints such as heat stress, nutrient limitations, disease pressure, salinity, or waterlogging, creating complex environmental conditions that are rarely captured in controlled experiments [13,14,15,16]. As a result, findings from individual studies are often difficult to compare or apply broadly across production environments.

Research on sesame and drought has increased considerably over the past decade, with advances in plant physiology, irrigation management, breeding, genomics, and climate adaptation studies [17,18]. However, much of this work has been conducted within disciplinary boundaries. Physiological studies frequently focus on stress-response mechanisms and agronomic studies emphasise irrigation and management, while breeding programs concentrate on cultivar improvement. In particular, the relationships among physiological drought responses, actual crop water use, evapotranspiration, water-use efficiency, critical growth-stage sensitivity, nutrient and disease interactions, and genetic improvement have not been comprehensively synthesized across contrasting production environments. Moreover, differences between rainfed and irrigated systems and the roles of genotype, environment, and management in determining drought resilience remain insufficiently connected [15,16,18]. Relatively few studies have attempted to integrate these perspectives to explain why some production systems maintain yield under water-limited conditions while others do not.

This review brings together evidence from physiology, agronomy, irrigation, nutrient management, disease ecology, breeding, and climate adaptation to provide a more integrated understanding of sesame performance under water-limited environments. Attention is given to areas where current evidence is inconsistent, incomplete, or poorly connected across disciplines. The review also identifies research priorities needed to support the development of productive and climate-resilient sesame production systems.

A recurring theme throughout this review is that sesame performance under drought cannot be explained by any single trait or management practice. Rather, crop responses emerge from interactions among genotype, environment, and management factors. Understanding these interactions will be essential for improving water productivity, maintaining yield stability, and strengthening the role of sesame in future climate-resilient farming systems.

2. Review Methodology

This study was conducted as a narrative literature review, with the literature search strategy and selection criteria summarized in Table 1. In addition, “EdrawMax AI (version 16.0.0) was used solely to generate the conceptual schematic shown in Table 1. The authors reviewed, edited, and verified all content before publication.

Table 1. Summary of literature search and selection parameters used in the narrative review.

Search Parameter	Description
Review type	Narrative literature review
Databases	Scopus, Web of Science, and Google Scholar
Publication period	1986–2026
Main search terms	Sesame; drought; water stress; water limitation; irrigation; evapotranspiration; water-use efficiency; physiology; nutrient management; disease; breeding; genetics; genomics; climate resilience
Inclusion criteria	Peer-reviewed studies relevant to sesame production, water limitation, crop management, physiology, irrigation, disease, genetic improvement, or climate resilience
Exclusion criteria	Duplicate records, studies with limited relevance to sesame or the review objectives, and non-substantive publications
Additional literature identification	Backward citation searching of key publications
Synthesis approach	Thematic/narrative synthesis across physiology, agronomy, irrigation and water relations, nutrient management, disease, breeding/genomics, and climate adaptation
Systematic-review protocol	Not applied; the review was designed as a narrative synthesis

3. Global Production Environments and Water-Limitation Context

3.1. Global Production Trends

Sesame is grown throughout the tropics and subtropics and remains one of the most widely cultivated oilseed crops in Africa and Asia [19] (Table 2). According to FAOSTAT, global production reached approximately 6.68 Mt in 2024, increasing from about 4.5 Mt in 2010. This increase was accompanied by expansion of the harvested area, which increased from approximately 8.30 to 11.72 million ha globally [20]. Africa now accounts for more than half of global production alongside an increase in harvested area from 3.43 to 6.49 million ha, while Asia remains the second-largest producing region [20,21].

Table 2. Global and regional trends in sesame production and harvested area from 2010 to 2024.

Year	World Production (Million Tonnes)	World Harvested Area (Million ha)	Africa Production (Million Tonnes)	Africa Harvested Area (Million ha)	Asia Production (Million Tonnes)	Asia Harvested Area (Million ha)
2010	4.53	8.3	1.74	3.43	2.62	4.57
2011	5.12	8.77	2.3	4.09	2.63	4.36
2012	5.73	8.8	3.09	4.44	2.46	4.09
2013	5.51	10.1	2.83	5.82	2.51	4.05
2014	6.17	11.19	3.36	6.82	2.57	4.05
2015	5.85	10.32	3.16	5.67	2.45	4.3
2016	6.06	10.99	3.63	6.86	2.23	3.82
2017	6.2	11.24	3.81	7.25	2.19	3.68
2018	6.35	11.99	4.02	8.15	2.13	3.56
2019	7.02	13.61	4.57	9.29	2.19	3.89
2020	6.57	13.71	4.03	9.3	2.31	3.99
2021	6.23	12.51	3.62	8.13	2.36	3.97
2022	5.5	10.61	3.18	6.56	1.98	3.42
2023	6.36	11.3	3.33	6.43	2.5	3.96
2024	6.68	11.72	3.48	6.49	2.64	4.37

Source: [20] FAOSTAT, 2024.

The world’s major producers include India, Sudan, Nigeria, Ethiopia, China, Myanmar, Pakistan, and Tanzania [20]. Production systems vary widely among these countries. In many African regions, sesame is grown as a low-input rainfed crop by smallholder farmers, whereas Asian production systems often make greater use of improved cultivars, irrigation, and other agronomic inputs [22,23,24,25,26]. Differences in management practices, access to technology, and environmental conditions contribute substantially to variation in productivity among regions [19,27].

Expansion of sesame cultivation into dry environments is often cited as evidence of drought tolerance. However, increases in production have largely resulted from expansion of cultivated area rather than major gains in yield. As a result, production statistics alone provide limited insight into crop performance under water-limited conditions. Yield stability, rather than total production, is a more meaningful indicator when evaluating drought resilience.

3.2. Emerging Production Regions

Although sesame has traditionally been concentrated in Asia and Africa, interest in the crop is increasing in several emerging production regions [26,28,29,30,31,32]. In Australia, sesame is being evaluated as a potential summer broadacre crop for northern production systems, where its modest water requirement and adaptability may support diversification under increasing climate variability [28,29]. Commercial production has also expanded in the southern United States following the development of non-shattering cultivars and improved harvesting technologies [30,31]. The growing interest in sesame reflects broader efforts to identify crops capable of maintaining productivity under increasing pressure on water resources [33,34,35]. Traits such as deep rooting, moderate drought adaptation, and the ability to produce economically useful yields under rainfed conditions have contributed to the perception of sesame as a climate-smart crop [36,37]. However, its performance remains strongly dependent on genotype, environmental conditions, and management practices.

Consequently, sesame should not be regarded as inherently drought-proof or universally climate resilient. Yield reductions remain common when water deficits occur during flowering and capsule development, and successful production depends on the integration of suitable cultivars, irrigation practices, nutrient management, and disease management within specific production environments [9,38,39,40].

3.3. Sesame as a Climate-Smart Crop

Sesame is frequently described as a drought-tolerant or climate-smart crop because it can be grown successfully under low water inputs compared with many conventional summer crops [37,38]. Traits such as deep rooting, moderate water-use efficiency, and the ability to recover following periods of moisture stress contribute to this reputation [5,9,38]. At the same time, the available evidence shows that sesame performance remains highly dependent on when and how drought occurs. Yield reductions are commonly reported when water deficits coincide with flowering or capsule development [9,11,40]. For this reason, drought tolerance should not be viewed as an inherent guarantee of stable productivity. The growing interest in sesame reflects a broader search for crops that can remain profitable under increasing pressure on water resources. Whether sesame fulfils this role will depend not only on its physiological characteristics but also on cultivar selection, irrigation management, disease management, and adaptation to local production environments [9,36].

3.4. Environmental and Water-Limitation Context of Sesame Production

Sesame is mainly cultivated in warm tropical and subtropical environments, with substantial variation in rainfall, temperature, soil-water availability, and irrigation. African production is largely rainfed, whereas several Asian systems have greater access to irrigation and improved management [7,9,21]. Rainfall timing and distribution are important because dry periods can deplete soil moisture, while high temperature and evaporative demand can intensify water stress [13,16].

Seasonal sesame water requirements are generally about 350–650 mm but vary with climate, soil, genotype, crop duration, and irrigation method [41,42]. Water demand increases with canopy development and is mainly important during flowering and capsule development, making reproductive-stage deficits especially damaging to yield [37,42,43]. Irrigation studies from Ethiopia, India, Turkey, and other semi-arid environments show that supplemental or deficit irrigation can improve performance, although responses vary with genotype, soil, climate, and irrigation timing [7,9,42,44].

Thus, sesame productivity and drought resilience reflect genotype × environment × management (G × E × M) interactions rather than water availability alone. These environmental differences provide an important basis for understanding sesame physiology, irrigation, evapotranspiration, water-use efficiency, nutrient management, disease interactions, and genetic improvement for climate resilience.

4. Water Requirements of Sesame

4.1. Crop Water Use of Sesame

Sesame is widely regarded as a relatively low-input crop but reported water requirements vary among environments. Seasonal crop water use ranges from 350 to 650 mm, although lower and higher values have been reported depending on climate, soil type, genotype, crop duration, and irrigation method [41,43,45]. Water demand is low during establishment and early vegetative growth, increases during canopy expansion, and reaches its maximum during flowering and capsule development before declining towards maturity [45,46]. The reproductive phase is consistently identified as the period most sensitive to water deficit. Water shortage during flowering, capsule development, or seed filling reduces photosynthesis, assimilate supply, and reproductive success, resulting in lower capsule numbers, fewer seeds per capsule, and reduced seed weight [9,47,48,49]. By contrast, mild water stress during vegetative growth is often less damaging because plants can partially compensate if favourable moisture conditions return before flowering [5,9]. Moderate water demand alone should not be interpreted as evidence of drought tolerance. A crop may require little water yet still suffer substantial yield losses when water deficits occur during critical growth stages. This distinction is especially relevant for sesame, where survival under drought is often much less affected than seed production.

4.2. Water Productivity of Sesame

Water productivity in sesame varies widely among environments and management systems. Published values are influenced by irrigation regime, climate, soil conditions, genotype, and the method used to estimate crop water use [7,42,44,45]. Moderate deficit irrigation frequently improves water productivity because reductions in water use are proportionally greater than reductions in yield [7,42]. However, these benefits decline when water deficits become severe, particularly during reproductive development. Reported differences in water productivity should be interpreted cautiously. Studies use different measures of water use, including evapotranspiration, irrigation water applied, soil-water balance, and effective rainfall, making direct comparisons difficult [50,51]. Consequently, differences among studies often reflect methodology as much as biological variation.

Despite these limitations, the available evidence indicates that sesame can produce acceptable yields with lower water inputs than many conventional summer crops. Whether this advantage translates into greater profitability depends on local conditions, yield potential, and the value of water within the production system.

4.3. Comparison with Major Summer Crops

Compared with major summer crops, sesame requires less water than cotton, maize, and soybeans and has water requirements broadly like sorghum and sunflower Table 3 [52,53,54,55,56,57,58]. However, comparisons based solely on seasonal water use can be misleading because drought adaptation arises from different biological mechanisms. Sorghum, for example, maintains productivity through exceptional physiological tolerance and efficient water use under stress Table 3 [56,59,60]. Sesame often survives comparable drought conditions but may experience larger reductions in reproductive output when moisture deficits coincide with flowering or capsule development [9,42]. Cotton and soybeans typically require more water but achieve higher potential yields under favourable conditions Table 3 [53,55]. These comparisons suggest that the value of sesame lies less in absolute drought tolerance and more in its ability to produce economically useful yields under moderate water limitation. For this reason, sesame is best viewed as a drought-resilient crop rather than an inherently water-efficient crop.

Table 3. Comparative seasonal water requirements of major summer crops.

Crop	Seasonal Water Requirement (mm)	Growing Environment	Season/Growth Period	Drought Tolerance	Critical Water-Sensitive Stage	References
Sesame (Sesamum indicum)	350–650	Tropical and subtropical	summer/monsoon	Moderate	Flowering, capsule development, seed filling	[52]
Cotton (Gossypium hirsutum)	600–900	Tropical and subtropical	Long-season warm-season	Moderate-High	Flowering and boll development	[53]
Maize (Zea mays)	500–800	Tropical to temperate	Warm-season crop; varies with production region	Moderate	Tasselling and grain filling	[54]
Sorghum (Sorghum bicolor)	350–650	Semi-arid to subhumid	Warm-season crop	High	Flowering	[56]
Soybean (Glycine max)	450–700	Tropical, subtropical, and temperate	Warm-season crop	Moderate	Flowering and pod filling	[55]
Mung bean (Vigna radiata)	250–450	Tropical and subtropical	Short-duration warm-season crop	Moderate	Flowering and pod development	[61]
Sunflower (Helianthus annuus)	500–1000	Temperate, subtropical, and semi-arid	Warm-season crop; season varies with latitude	Moderate	Flowering and seed filling	[57]
Groundnut (Arachis hypogaea)	500–700	Tropical and subtropical	Warm-season crop	Moderate	Flowering, pegging and pod development	[58]

Source: Adapted from FAO crop water requirement information and published literature on crop-specific water use and drought responses. Note: Drought-tolerance classifications are generalised from published literature and should not be interpreted as fixed species-level rankings. Drought tolerance varies considerably among cultivars/genotypes and is strongly influenced by environmental conditions, soil characteristics, drought severity and duration, crop developmental stage, and management practices. Seasonal water requirements likewise vary according to climate, soil, crop duration, cultivar, planting date, and irrigation regime. Therefore, the values presented should be regarded as approximate comparative ranges rather than universal crop-specific requirements.

5. Physiological Responses to Water Deficit

5.1. Root System Architecture

Root traits are widely regarded as an important component of drought adaptation because they influence the plant’s ability to access water from deeper soil layers as surface soil dries [62]. Sesame generally responds to declining soil moisture by increasing root growth relative to shoot growth, thereby improving water acquisition under drought conditions [63,64,65]. Substantial variation has been reported among genotypes for root length, root biomass, root volume, and root length density, suggesting that root architecture may contribute to differences in drought performance [63,64].

Interest in root traits has increased because they offer a potential target for breeding programs. However, much of the available evidence comes from pot, rhizobox, or controlled-environment studies where root development is physically constrained [63,64]. Whether these measurements accurately predict field performance remains uncertain. Deep rooting is often assumed to improve drought tolerance, but relatively few studies have demonstrated a direct relationship between root traits and yield stability under field drought conditions.

At the molecular level, several drought-responsive genes have been associated with root development and water acquisition, including SiMYB75 and other regulators linked to abscisic acid signalling pathways [65]. While these findings improve understanding of drought responses, their practical value for cultivar development remains largely untested.

5.2. Stomatal Regulation

Stomatal regulation plays a vital role in drought adaptation because it determines the balance between carbon gain and water loss [66,67]. As soil moisture declines, sesame reduces stomatal conductance, limiting transpiration and helping maintain leaf water status [68,69]. This response improves survival under water stress but also restricts carbon assimilation and growth. Differences among genotypes suggest that drought adaptation is associated not simply with stomatal closure but with the ability to maintain photosynthesis while limiting excessive water loss [65,68]. Several transcription factors involved in ABA-mediated signalling have been linked to these responses, including members of the MYB, NAC, WRKY, and DREB gene families [65,70].

Despite considerable interest in stomatal behaviour, its value as a breeding target remains uncertain. Most studies have been conducted under controlled conditions, and little evidence links stomatal traits directly with yield performance across diverse field environments. As a result, improved physiological understanding has not yet translated into routine selection criteria for drought tolerance.

5.3. Photosynthesis and Transpiration

Reduced photosynthesis is one of the most consistently reported effects of drought in sesame [17,71,72]. During mild stress, declines in photosynthetic activity are largely associated with stomatal closure and reduced carbon dioxide uptake. Under more severe water deficits, additional limitations arise from chlorophyll degradation, disruption of electron transport, reduced enzyme activity, and oxidative damage to the photosynthetic apparatus [72,73]. Several studies have reported declines in photosynthetic rate, stomatal conductance, transpiration, and leaf water status under drought stress, particularly during flowering and capsule development [17,49,74]. These responses are frequently accompanied by reductions in reproductive growth and yield.

Transpiration presents a similar trade-off. Reduced water loss conserves soil moisture, yet excessive suppression of transpiration may restrict canopy cooling and increase susceptibility to heat stress [75]. Evidence from field studies suggests that maintaining a balance between water conservation and continued carbon assimilation is more important than minimizing water use alone [9]. This balance may partly explain why some genotypes achieve greater productivity under drought despite comparable reductions in soil moisture.

5.4. Osmotic Adjustment

Osmotic adjustment helps maintain cell hydration and physiological activity when soil water availability declines [76]. In sesame, drought stress stimulates the accumulation of compatible solutes such as proline, soluble sugars, proteins, and potassium ions, allowing cells to retain water and continue metabolic processes under stress [5,40,69]. Among these compounds, proline has received the greatest attention because of its role in osmotic regulation, membrane stabilisation, and protection against oxidative damage [77]. Increased accumulation of proline and soluble sugars has been reported consistently in drought-stressed plants and is often used as an indicator of stress tolerance [5,69].

Nevertheless, the significance of osmotic adjustment remains debated. Many studies demonstrate improved physiological performance under stress but do not establish whether greater osmolyte accumulation results in higher seed yield under field conditions. Consequently, osmotic adjustment may contribute to stress survival without necessarily improving economic productivity.

5.5. Carbon Partitioning

Drought affects not only carbon assimilation but also the way assimilates are distributed within the plant [78,79]. Under favourable conditions, photosynthates are allocated to vegetative and reproductive organs in proportions that support growth and seed development. Water limitation disrupts this balance by reducing carbon supply and altering sink demand. One of the earliest responses to drought is a shift in carbon allocation towards root growth, increasing the root-to-shoot ratio and improving access to soil moisture [62]. While this response may enhance survival, prolonged drought often reduces assimilate allocation to flowers, capsules, and developing seeds [12,80,81]. The result is lower capsule production, reduced seed filling, and diminished harvest index. A recurring finding across drought studies is that genotypes capable of maintaining carbon allocation to reproductive structures tend to show greater yield stability under stress [9,12]. However, direct studies of carbon transport and source–sink dynamics in sesame remain relatively limited, and many conclusions are inferred from biomass measurements rather than direct physiological evidence.

5.6. Recovery After Drought

Recovery after drought is particularly important in rainfed environments where dry periods are often followed by rainfall events [82,83]. Rewatering restores plant water status, promotes stomatal reopening, and allows photosynthesis to resume. However, the extent of recovery varies according to genotype and the timing and severity of the preceding drought [5]. Studies have shown that some sesame genotypes recover rapidly following rewatering, whereas others exhibit sustained physiological impairment [5,84]. Recovery tends to be more successful when drought occurs during vegetative growth than when stress affects flowering or capsule development, stages at which damage is often irreversible.

Despite its importance, recovery physiology remains poorly understood. Most studies have been conducted using single drought–rewatering cycles under controlled conditions, which do not reflect the repeated stress events commonly experienced in production environments. Consequently, whether rapid physiological recovery translates into improved yield under field conditions remains unresolved.

5.7. Critical Synthesis

Despite major advances in understanding drought responses in sesame, much of the available evidence is derived from controlled-environment experiments conducted on seedlings or young plants. Root architecture, stomatal regulation, osmotic adjustment, and recovery responses have frequently been assessed in pots, rhizoboxes, or growth chambers where soil volume, water availability, and environmental conditions differ substantially from field environments [5,63,64,69,85]. As a result, the extent to which these traits predict performance under commercial production conditions remains uncertain.

This limitation is particularly evident for root traits. Deep rooting and increased root length density are commonly proposed as indicators of drought tolerance, yet relatively few studies have confirmed their relationship with yield stability under field drought [63,64,86]. Similar concerns apply to stomatal regulation and photosynthetic responses, which are generally measured under controlled conditions and rarely validated across multiple environments or growing seasons [9,17,74]. Accumulation of proline, soluble sugars, and other osmolytes is widely interpreted as evidence of stress tolerance, but most studies focus on physiological responses rather than yield outcomes [5,69,87]. Likewise, carbon partitioning and post-drought recovery are increasingly recognised as important determinants of productivity, yet direct evidence relating these processes to yield maintenance remains limited [5,84,88].

A recurring assumption in the literature is that improved stress survival equates to improved productivity. However, traits that enable plants to remain alive during drought do not necessarily maintain seed yield. This distinction is particularly relevant in sesame, where plants often survive prolonged water deficits but experience substantial reductions in capsule production and seed yield [9,12].

6. Growth Stage Sensitivity to Water Stress

The impact of drought on sesame depends not only on stress severity but also on the timing of its occurrence. Although sesame is widely regarded as drought-tolerant, susceptibility varies markedly throughout the crop cycle. Water deficits during reproductive development generally cause greater and often irreversible yield losses than stress occurring during vegetative growth because reproductive processes depend on a continuous supply of water, assimilates, and nutrients [5,9,10].

6.1. Vegetative Stage

During early growth, water stress reduces plant height, leaf area development, branching, and biomass accumulation [9,11]. However, sesame often shows a degree of plasticity during this stage. Mild to moderate drought may promote greater root development relative to shoot growth, improving access to deeper soil moisture and partially compensating for reduced aboveground growth [12,89]. If favourable moisture conditions return before flowering, plants can recover a substantial proportion of their yield potential [9].

6.2. Flowering and Capsule Initiation

Most studies identify flowering as the most drought-sensitive stage of sesame development [9,74,90]. Water deficit during this period reduces pollen viability, flower retention, capsule formation, and seed set, often resulting in irreversible yield losses. Capsule number is consistently reported as the yield component most affected by drought, reflecting the strong dependence of reproductive development on adequate water supply [9,12].

Early capsule development is similarly vulnerable. Drought during capsule initiation restricts photosynthesis and assimilate transport, leading to capsule abortion and fewer seeds per capsule [5,91]. Because sesame produces capsules sequentially, stress during early reproductive development can also affect the formation of later capsules, amplifying yield losses.

6.3. Seed Filling and Maturity

Water deficit during seed filling reduces the duration and rate of seed growth, resulting in smaller seeds and lower yield [92]. In general, however, seed filling appears less sensitive than flowering and capsule initiation because developing seeds can draw upon stored assimilates accumulated earlier in the season [12,92].

As plants approach physiological maturity, water demand declines rapidly and mild moisture stress has relatively negligible effect on yield [93]. Nevertheless, severe late-season drought combined with high temperatures may accelerate senescence and reduce seed quality, particularly if physiological maturity has not been reached [10,94].

6.4. Critical Synthesis

Across diverse environments and experimental approaches, a consistent pattern emerges: flowering and early capsule development represent the periods of greatest vulnerability to drought, whereas vegetative growth and late maturity are comparatively less sensitive [9,74,90] (Figure 1). The practical implication is that maintaining adequate moisture during reproductive development is likely to provide a greater return than attempting to maximise water availability throughout the entire season.

Figure 1. Relative drought sensitivity of major sesame growth stages and associated physiological responses. Flowering and early capsule development are consistently identified as the most drought-sensitive periods across published studies. Source: Generated using EdrawMax AI and edited by the authors based on the synthesis of published literature; no figure or graphical element was reproduced from any single source [9,12,62,74,90,91,93,94].

A limitation of the current literature is that growth-stage sensitivity is often evaluated using a small number of genotypes under controlled or single-location conditions. Consequently, the extent to which these responses vary among cultivars and production environments remains incompletely understood.

7. Yield Responses to Deficit Irrigation

7.1. Full Irrigation Versus Deficit Irrigation

Irrigation management in sesame involves balancing seed yield against water use. Full irrigation maximises crop growth and yield by minimising water limitations throughout the growing season [42,95]. However, in many water-limited regions, applying sufficient water to meet full crop demand is neither practical nor economically desirable.

Deficit irrigation has therefore received considerable attention as a strategy for improving water productivity. Under moderate water deficits, sesame is often able to maintain a considerable proportion of its yield while using less water [7,42,44]. Studies from Ethiopia, Egypt, Turkey, and other semi-arid environments consistently show that applying 70–80% of crop water requirements frequently achieves near-maximum yields while improving water productivity [7,42,45,96] (Table 4). For example, Mekonnen and Sintayehu [7] reported higher crop water productivity under a 75% water-application treatment than under optimal irrigation, whereas the 50% treatment resulted in substantially lower productivity. Yield losses become much more pronounced when water deficits coincide with flowering or capsule development, highlighting the importance of irrigation timing rather than total water application alone [42,47].

Table 4. Water-use efficiency and crop water productivity of sesame under different irrigation regimes. 

Location	Irrigation Method	Water Regime	Estimation Method	Growth Stage/Kc	Relative Yield (%)	WUE (kg m−3)	Metric/Denominator	Reference
Ethiopia	Drip	50%	Lysimeter	Early; Kc = 0.60	80	0.233	CWP; Y/ET	[7]
Ethiopia	Drip	75%	Lysimeter	Vegetative; Kc = 0.80	94	0.428	CWP; Y/ET	[7]
Ethiopia	Drip	120%	Lysimeter	Flowering; Kc = 1.10	96	0.236	CWP; Y/ET	[7]
Turkey	Furrow	100%	Lysimeter	7 days	97	0.421	ET-based WUE; Y/ET	[46]
Turkey	Furrow	75%	Lysimeter	14 days	96	0.436	ET-based WUE; Y/ET	[46]
Turkey	Furrow	50%	Lysimeter	21 days	96	0.390	ET-based WUE; Y/ET	[46]
Turkey	Furrow	25%	Lysimeter	28 days	89	0.362	ET-based WUE; Y/ET	[46]
Turkey	Furrow	0%	Lysimeter	35 days	85	0.311	ET-based WUE; Y/ET	[46]
India	Furrow	100%	Lysimeter	Vegetative;	80	0.333	CWP; Y/ET	[47]
India	Furrow	100%	Lysimeter	Flowering;	92	0.32	CWP; Y/ET	[47]
India	Furrow	100%	Lysimeter	Capsule initiation;	96	0.37	CWP; Y/ET	[47]
India	Furrow	100%	Lysimeter	Capsule filling; Kc	100	0.375	CWP; Y/ET	[47]
Egypt	Drip	100%	Lysimeter	Initial; Kc = 0.31	88	0.285	ET-based WUE; Y/ET	[96]
Egypt	Drip	100%	Lysimeter	Development; Kc = 0.75	100	0.486	ET-based WUE; Y/ET	[96]
Egypt	Drip	100%	Lysimeter	Mid-season; Kc = 0.98	100	0.567	ET-based WUE; Y/ET	[96]
Egypt	Drip	100%	Lysimeter	Late-season; Kc = 0.50	88	0.322	ET-based WUE; Y/ET	[96]
Ethiopia	Sprinkler	100%	Lysimeter	Initial; Kc = 0.23	86	0.296	ET-based WUE; Y/ET	[97]
Ethiopia	Sprinkler	80%	Lysimeter	Development; Kc = 0.66	100	0.273	ET-based WUE; Y/ET	[97]
Ethiopia	Sprinkler	60%	Lysimeter	Mid-season; Kc = 0.87	94	0.243	ET-based WUE; Y/ET	[97]
Ethiopia	Sprinkler	50%	Lysimeter	Late-season; Kc = 0.43	90	0.206	ET-based WUE; Y/ET	[97]

Notes: Irrigation treatments, irrigation intervals, growth stages, and crop coefficient (K_c) values are presented as reported in the original studies. These parameters reflect different experimental conditions and are therefore not directly comparable across experiments. Differences in irrigation scheduling, water regimes, growth stages, and evapotranspiration estimation methods should be considered when interpreting the reported WUE values. WUE/CWP values are expressed in kg m⁻³. The table retains the metric terminology used or supported by the respective studies. Y = seed yield; ET = evapotranspiration; ETc = crop evapotranspiration. Values reported in kg ha⁻¹ mm⁻¹ were converted to kg m⁻³ using 1 kg ha⁻¹ mm⁻¹ = 0.1 kg m⁻³. WUE/CWP values should not be interpreted as stage-specific unless the original study explicitly calculated them for the corresponding growth stage.

These findings suggest that sesame possesses a degree of flexibility in water use. Nevertheless, responses differ among environments, irrigation systems, and cultivars, making it difficult to identify a universally optimal irrigation strategy.

7.2. Regulated Deficit Irrigation (RDI)

Regulated deficit irrigation (RDI) attempts to exploit differences in drought sensitivity across growth stages by reducing irrigation during less sensitive periods while maintaining adequate moisture during reproductive development [98]. The approach recognises that the crop does not require the same level of water throughout the season. Results from several studies indicate that water savings can be achieved with relatively small yield penalties when deficits are imposed during vegetative growth and irrigation is maintained through flowering and early capsule development [42,98,99]. In contrast, water restrictions during reproductive stages rarely provide comparable benefits because yield reductions generally outweigh any gains in water productivity [9,47].

Although RDI is often promoted as an efficient irrigation strategy, most supporting evidence comes from short-term experiments conducted in specific environments. More information is needed on its performance across different climates, soil types, and production systems before broad recommendations can be made.

7.3. Productivity, Water Savings and Economic Considerations

The value of an irrigation strategy cannot be assessed on yield alone. In many production regions, water availability, pumping costs, infrastructure requirements, and seasonal market conditions influence profitability as much as biological performance [100,101]. Moderate deficit irrigation often improves water productivity because relatively small yield reductions are accompanied by larger reductions in water use [9,42]. However, improvements in water productivity do not automatically translate into greater profitability. Economic outcomes depend on factors such as water pricing, irrigation costs, seed value, and production risk [100,101]. A notable limitation of the current literature is that many irrigation studies focus primarily on yield and water-use metrics while giving little attention to profitability, disease risk, nutrient dynamics, or long-term sustainability. As a result, irrigation recommendations are often based on biological performance alone. Future research would benefit from a broader systems perspective that evaluates irrigation management within the context of productivity, profitability, and resilience.

7.4. Critical Synthesis

Across most environments, full irrigation maximises yield, whereas moderate water deficits often maximise water productivity. The challenge is identifying where the balance between these two objectives lies. A consistent finding across the literature is that water applied during flowering and early capsule development has the greatest influence on yield, whereas some reduction in irrigation during vegetative growth can often be tolerated with limited consequences [9,42,47].

Despite the large number of irrigation studies available, relatively few have examined genotype × irrigation interactions, long-term economic performance, or responses under the highly variable conditions typically encountered by commercial growers. The main unresolved issue is how irrigation strategies perform across genotypes, environments, and production systems when economic outcomes are considered alongside yield and water use.

8. Water Use Efficiency of Sesame

8.1. Defining Water Use Efficiency

Water-use efficiency (WUE) is frequently used to evaluate crop performance under water-limited conditions, yet the term is often applied inconsistently [102,103]. In sesame research, WUE may refer to seed yield per unit evapotranspiration, irrigation water applied, total water use, or physiological measures based on carbon assimilation and transpiration. Because these metrics describe different processes, direct comparisons among studies are often problematic [51,104]. Standardized reporting of water-productivity denominators is therefore important for meaningful comparison across environments and management systems [103].

More importantly, WUE should not be regarded as a fixed property of sesame, but as an outcome emerging from interactions among genotype, environment, and management (G × E × M). Genotypic differences in rooting depth, phenology, canopy development, stomatal regulation, and reproductive sensitivity to water stress can influence water uptake and yield, while environmental conditions and management practices determine the amount and timing of water available to the crop. Thus, reported WUE values should be interpreted within their specific genotype, climatic, soil, and irrigation context rather than as universal cultivar or crop characteristics [102,103].

Evapotranspiration-based WUE is expressed as:

WUE = Y/ET

(1)

where Y is seed yield and ET is evapotranspiration as defined in the individual study [45,51].

For water productivity based on actual crop evapotranspiration:

CWP = Y/Eta

(2)

where ETa is actual crop evapotranspiration. ETa represents the actual water consumed by the crop under field conditions [103,104].

Estimated crop evapotranspiration-based WUE is expressed as:

WUE = Y/ETc

(3)

where Y is seed yield and ETc is crop evapotranspiration [45,103], calculated as:

ETc = Kc × ET₀

(4)

with Kc representing the crop coefficient and ET₀ the reference evapotranspiration [45,103].

Other studies use irrigation water-use efficiency (IWUE),

IWUE = Y/I

(5)

where I is the amount of irrigation water applied, which relates yield to irrigation water supplied rather than total crop water use [50,104]. Although both metrics are useful, they should not be considered interchangeable.

For this reason, reported WUE values should be interpreted within the context of how water use was measured and the conditions under which the study was conducted.

8.2. Variability in WUE Across Environments

Published WUE values for sesame vary widely across environments [41,44,45,105]. Differences in rainfall, evaporative demand, soil properties, irrigation management, cultivar, and growing season all influence the relationship between yield and water use [106,107,108]. Consequently, WUE should be regarded as an environmentally responsive trait rather than a fixed crop characteristic. Moderate water deficits often improve WUE because reductions in water use exceed reductions in yield [41,105]. However, this relationship is not indefinite. As water stress becomes more severe, both yield and WUE decline, particularly when drought occurs during flowering and capsule development [9,42].

Genotypic variation in WUE has also been reported, although environmental and management effects typically account for a large proportion of the variation observed among studies [9,108,109]. This suggests that improvements in water productivity are likely to come from a combination of cultivar selection and improved management rather than genetic improvement alone.

8.3. How Does Sesame Compare with Other Crops?

Sesame is often promoted as a water-efficient crop, but the available evidence provides a more nuanced picture. Comparisons among crops are complicated by differences in climate, management practices, and the way WUE is calculated [51,103]. When evaluated using comparable measures, sesame achieves WUE values similar to several other broadacre crops grown under water-limited conditions [103,110,111] (Table 5). Crops such as sorghum, maize, soybean, and sunflower frequently achieve comparable or higher water productivity depending on environment and management [103,110,111,112]. This suggests that sesame cannot be considered uniquely efficient in terms of water use alone. Its advantage lies elsewhere. Sesame combines moderate water requirements with the ability to produce acceptable yields in environments where irrigation is limited or rainfall is unreliable [41,42,52]. This characteristic may be more important than absolute WUE when assessing suitability for dryland and supplemental irrigation systems.

Table 5. Comparative agronomic water use efficiency (WUE) of sesame and other broadacre crops under irrigated conditions in comparable environments.

Crop	WUE Range (kg ha−1 m−3)	Water-Use Metric/Denominator	Key References
Sesame (Sesamum indicum)	0.25–0.65	(ET)-based crop WUE	[113,114,115]
Groundnut (Arachis hypogaea)	0.3–0.7	ET/crop water use	[116,117]
Soybean (Glycine max)	0.4–0.8	ET/crop water use	[55]
Sunflower (Helianthus annuus)	0.5–0.9	ET/crop water use	[57]
Maize (Zea mays)	0.8–1.8	ET-based	[103,112]
Sorghum (Sorghum bicolor)	0.6–1.5	ET/crop water use	[56]
Cotton (Gossypium hirsutum)	0.2–0.5	ET/crop water use	[103,118]
Mung bean (Vigna radiata)	0.3–1.0	ET/crop water use	[119,120]

Note: WUE values are expressed as harvested yield per unit water use (kg ha⁻¹ mm⁻¹). The denominator was not defined uniformly across all cited studies and may represent evapotranspiration (ET) or another measure of crop water use. Therefore, the reported ranges are presented as study-specific literature ranges rather than standardized cross-crop estimates or rankings. Differences among studies may reflect genotype, environment, soil conditions, crop duration, irrigation regime, and the method used to quantify water use. ET-based WUE and irrigation water-use efficiency (IWUE; yield per unit irrigation water applied) are distinct metrics and should not be directly compared.

8.4. Challenges in Measuring and Comparing WUE

One of the recurring problems in the sesame literature is inconsistent reporting of water-use metrics [51,121]. Water use may be based on evapotranspiration, irrigation applied, rainfall received, soil-water depletion, or combinations of these variables. Studies also express WUE using different units, making comparisons difficult and sometimes misleading [51,104]. As a result, apparent differences among cultivars or irrigation treatments may reflect methodology as much as biological performance. This issue becomes particularly important when attempting to compare findings across regions or synthesise results from multiple studies.

Future research would benefit from more consistent reporting of water balance components, including evapotranspiration, irrigation applied, effective rainfall, soil-water storage, and the equations used to calculate WUE [51,121]. Greater standardisation would improve the comparability of studies and strengthen evidence-based recommendations.

8.5. Critical Synthesis

Much of the literature treats WUE as a direct indicator of drought tolerance. However, high WUE does not necessarily imply high productivity, and crops with lower WUE may still provide superior economic returns under certain conditions [50,103]. The most water-efficient treatment is therefore not always the most profitable or agronomically desirable option. Future research should place less emphasis on maximising WUE alone and more emphasis on understanding how water productivity contributes to yield stability, profitability, and resilience within commercial production systems.

9. Interaction Between Water Stress and Nutrient Management

Water and nutrient availability are closely linked in crop production. Drought reduces nutrient acquisition by restricting root growth, mass flow, diffusion, and transpiration, while nutrient deficiencies can limit many of the physiological processes required for drought adaptation, including photosynthesis, osmotic regulation, and reproductive development [10,69,121,122]. As a result, crop performance under water-limited conditions often reflects the combined effects of water and nutrient availability rather than either factor alone.

Although nutrient management is frequently discussed as a tool for improving drought resilience, the available evidence is uneven. Most studies have focused on individual nutrients under specific environmental conditions, making it difficult to separate true drought adaptation from the correction of underlying nutrient limitations.

9.1. Nitrogen (N)

Nitrogen plays a fundamental role in canopy development, photosynthesis, and biomass production. Adequate nitrogen supply generally improves crop growth and yield, but its benefits become less predictable under drought conditions [122,123]. Excessive nitrogen can stimulate vegetative growth and increase crop water demand, potentially intensifying moisture stress during reproductive development. Several studies have reported positive interactions between nitrogen fertilisation and water availability, although responses vary considerably among environments and irrigation regimes [106,123,124]. This variability suggests that fixed nitrogen recommendations may be poorly suited to water-limited systems. Matching nitrogen supply to expected moisture availability is likely to be more effective than maximising fertiliser inputs [125].

9.2. Phosphorus (P)

Phosphorus is often associated with drought adaptation because of its role in root development, energy transfer, and reproductive growth [126,127]. Improved phosphorus nutrition can promote root exploration and potentially increase access to soil moisture, particularly in nutrient-deficient soils. However, surprisingly little research has directly examined phosphorus × drought interactions in sesame. Most studies report yield responses to phosphorus fertilisation under either irrigated or rainfed conditions without investigating the physiological basis for these responses [128,129]. Consequently, the contribution of phosphorus to drought resilience remains less clearly defined than for some other nutrients.

9.3. Potassium (K)

Among the major nutrients, potassium has the strongest and most consistent association with drought adaptation [40,124]. Its functions in stomatal regulation, osmotic adjustment, enzyme activation, and maintenance of cellular water balance provide several mechanisms through which it may help plants cope with water deficits. Experimental studies have shown that improved potassium nutrition can reduce oxidative damage, maintain chlorophyll content, and improve plant water status under drought conditions [40,69,130]. Compared with nitrogen and phosphorus, the physiological role of potassium under moisture stress is better established, although most evidence still originates from relatively short-term experiments. Current evidence suggests that potassium management may offer one of the more reliable opportunities to improve sesame performance under water-limited conditions, particularly where soil potassium availability is low.

9.4. Micronutrients

Several micronutrients, including zinc, boron, iron, and manganese, have been linked to drought responses through their roles in photosynthesis, enzyme activity, antioxidant defence, and reproductive development [131,132,133,134,135,136,137]. Zinc has received the most attention in sesame, with foliar applications often improving physiological performance and yield under water stress [133].

Despite these findings, the evidence base remains relatively limited. Most studies examine individual micronutrients in isolation and frequently involve a small number of environments or growing seasons [131,134,135,136]. The importance of micronutrient management therefore remains less certain than that of macronutrient nutrition.

9.5. Biological Interactions: AMF and PGPR

Biological approaches such as arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR) have attracted increasing interest as tools for improving nutrient acquisition and drought adaptation simultaneously [137,138,139,140]. By altering root–soil interactions, these organisms may improve access to nutrients and water while enhancing physiological responses to stress. Field studies have shown that AMF inoculation can improve nutrient uptake, water productivity, and yield under drought conditions [82,139]. However, responses are not always consistent. Benefits depend on environmental conditions, soil fertility, native microbial communities, and the compatibility of plant and microbial partners [138,140]. Similar variability has been reported for PGPR-based approaches. These findings indicate that biological solutions have potential, but they remain less predictable than conventional fertiliser management.

9.6. Critical Synthesis

The literature clearly demonstrates that water and nutrient management cannot be considered independently in sesame production systems. Nutrient availability influences many of the physiological mechanisms commonly associated with drought adaptation, while drought simultaneously affects nutrient uptake and utilisation [69,122,123]. A notable weakness in the current evidence base is that irrigation, fertilisation, and biological amendments are usually studied in isolation. As a result, it remains difficult to determine whether observed improvements in drought performance reflect genuine increases in drought tolerance or simply improved crop nutrition. The resulting evidence gap is the limited understanding of how combined water and nutrient management affects crop performance across soil fertility conditions and production environments.

10. Water Stress and Sesame Diseases

Water availability is a critical determinant of disease expression in sesame because drought influences host physiology, pathogen activity, soil microbial communities, and plant defence responses simultaneously [141,142,143]. While drought is commonly examined as an abiotic stress and disease as a biotic stress, these factors frequently occur together under field conditions. Consequently, disease development should be viewed as the outcome of interacting host, pathogen, and environmental processes rather than as an isolated biological phenomenon [143]. Distinguishing drought-induced stress symptoms from pathogen-induced disease is particularly challenging because wilting, chlorosis, and reduced growth may result from either factor or their interaction [5,143].

10.1. Soilborne Diseases in Sesame Under Water Stress

Water availability strongly influences disease development in sesame because it affects the host, pathogen, and soil environment simultaneously [141,142,143]. In practice, drought and disease rarely occur as separate stresses. Water limitation can alter plant defence responses, root growth, nutrient uptake, and microbial activity, while disease can further restrict water acquisition and plant function [5,143]. Despite these interactions, drought and disease are still commonly studied in isolation.

10.1.1. Charcoal Rot/Dry Root Rot

Charcoal rot, caused by Macrophomina phaseolina, is one of the diseases most closely associated with drought conditions in sesame [142,144]. The pathogen is favoured by high temperatures and low soil moisture, and disease severity frequently increases when plants are exposed to prolonged water stress [142,144,145]. Symptoms such as wilting, premature senescence, and reduced yield often resemble drought stress itself, making diagnosis difficult under field conditions.

Research has shown substantial variation in host resistance and pathogen aggressiveness, suggesting that disease outcomes are influenced by both host and pathogen genetics [146,147,148]. However, relatively little is known about how drought intensity alters these interactions under commercial production conditions.

10.1.2. Fusarium Wilt

Fusarium oxysporum f. sp. sesami causes vascular wilt by disrupting water movement within the plant [149,150,151]. Although the pathogen is not as strongly associated with drought as M. phaseolina, water stress may intensify disease impacts by reducing plant vigour and limiting recovery following infection [5,150]. Considerable variation in disease severity has been reported among sesame genotypes and pathogen populations [151,152]. This suggests that host resistance remains an important management option, particularly where water stress and disease occur simultaneously.

10.1.3. Rhizoctonia and Pythium

The relationship between water stress and other soil-borne pathogens is less straightforward. Rhizoctonia solani may become more damaging when drought reduces seedling vigour and delays establishment [153,154,155,156]. In contrast, Pythium species are typically favoured by wet soils, waterlogging, and poor drainage rather than drought [157,158]. These contrasting responses highlight an important point: disease risk cannot be predicted from drought intensity alone. Different pathogens respond very differently to changes in soil moisture [155].

10.2. Foliar Diseases

Foliar diseases such as Alternaria leaf blight, Cercospora leaf spot, and powdery mildew reduce photosynthetically active leaf area and can limit crop productivity during reproductive development [159,160,161,162,163,164]. Unlike charcoal rot, these diseases are generally favoured by humid conditions, extended leaf wetness, or dense crop canopies [160,161,162,163,164,165]. The interaction between drought and foliar diseases is therefore more complex than for soil-borne pathogens. Dry conditions may suppress disease development by reducing canopy humidity, yet drought-stressed plants often have a reduced capacity to compensate for disease-related losses in photosynthetic area [5,159]. As a result, the combined effects of drought and foliar disease may sometimes exceed the impact of either stress acting alone. Most disease-management studies have evaluated pathogens under relatively favourable moisture conditions [162,166]. Far less attention has been given to understanding how drought alters disease development, crop physiology, and yield loss relationships.

10.3. Critical Synthesis

The relationship between drought and disease remains one of the least understood aspects of sesame production. Most studies continue to examine abiotic and biotic stresses independently despite the likelihood that crops experience both simultaneously under field conditions [5,142,143]. A major limitation of the current literature is the absence of factorial studies combining water stress and pathogen pressure. Consequently, it is often unclear whether observed yield losses result primarily from drought, disease, or their interaction. This uncertainty is particularly important for soil-borne pathogens such as M. phaseolina and F. oxysporum, where both stresses may affect the same physiological processes associated with water uptake and transport [142,150].

Climate variability can shift sesame disease dynamics by favoring pathogens under different environmental conditions. Drought and high soil temperatures may promote Macrophomina phaseolina infection, whereas excessive soil moisture favors Pythium spp. and other damping-off pathogens [142,157]. The development of Fusarium, Rhizoctonia, and foliar diseases also depends on temperature, moisture, and host susceptibility [149,156]. Thus, climate variability may alter pathogen communities and disease prevalence rather than uniformly increase disease pressure, highlighting the importance of integrated disease management and climate-resilient cultivars.

Future research should move beyond single-stress experiments and evaluate drought × pathogen interactions under realistic field conditions. Such studies would improve understanding of disease risk under climate variability and support the development of integrated management strategies that address water limitation and disease simultaneously.

11. Breeding and Genetic Improvement for Drought Tolerance

11.1. Conventional and Trait-Based Breeding

Breeding for drought adaptation in sesame has traditionally relied on selection under rainfed environments and the use of landraces originating from drought-prone regions [167,168,169]. Several physiological characteristics have been proposed as useful selection criteria, including root system architecture, maintenance of relative water content, canopy temperature, harvest index, and reproductive stability under stress [9,68,170,171,172]. Among these, traits associated with the maintenance of capsule production and seed set appear to have the strongest relationship with yield under drought [9,12]. Factorial field studies combining water-deficit treatments with pathogen pressure are needed to distinguish individual and interactive effects on disease severity and seed yield.

11.2. Molecular Breeding Genomic Approaches

Advances in genomics have improved understanding of the genetic basis of drought responses in sesame. Genome-wide association studies, quantitative trait locus (QTL) mapping, transcriptomics, and candidate-gene analyses have identified numerous loci associated with drought-related traits [65,173,174,175,176,177]. One of the most influential studies evaluated a diverse panel of sesame accessions and identified multiple genomic regions associated with drought adaptation, together with candidate genes involved in hormone signalling, osmotic adjustment, and oxidative stress responses [65]. These findings confirmed that substantial genetic variation for drought adaptation exists within the crop.

QTL and GWAS approaches have expanded the list of candidate genes and drought-associated genomic regions [173,176,177]. Nevertheless, most discoveries remain at the validation stage. Few markers have been incorporated into applied breeding programs, and even fewer have contributed directly to cultivar release. A recurring challenge is that many reported marker–trait associations are derived from specific environments or experimental conditions and may not remain stable across diverse production systems [65,176,177]. Given the strong influence of genotype × environment interactions on drought responses, validation across multiple environments remains essential before markers can be used confidently for selection.

11.3. Phenomics, High-Throughput Phenotyping and Artificial Intelligence

Recent advances in phenomics provide new opportunities to accelerate breeding for drought adaptation. Remote sensing, UAV platforms, multispectral imaging, thermal sensors, and machine-learning approaches allow large breeding populations to be assessed more rapidly and consistently than conventional field phenotyping [178,179,180]. Traits such as canopy temperature, vegetation indices, canopy architecture, biomass accumulation, and chlorophyll dynamics can now be monitored throughout the growing season using non-destructive methods [178,179]. These technologies may help bridge the gap between physiological research and practical breeding by enabling large-scale evaluation of drought responses under field conditions. Machine-learning approaches have also shown potential for improving yield prediction and genotype selection by integrating genomic, phenotypic, and environmental data [180,181]. However, most applications remain at the research stage, and the practical benefits for commercial sesame breeding have yet to be fully demonstrated.

11.4. Critical Synthesis

Considerable progress has been made in identifying physiological traits, genomic regions, and candidate genes associated with drought adaptation in sesame [65,173,174,175,176,177]. A central challenge is that drought tolerance is not a single trait. Crop performance under water limitation reflects interactions among water acquisition, water use, reproductive resilience, and environmental adaptation [9,65]. Consequently, traits that improve plant survival do not necessarily improve yield, while traits associated with high productivity under moderate stress may provide little advantage under severe drought. A key priority is validating useful markers and phenotypic traits across environments and linking them to stable seed yield under water limitation.

12. Sesame Under Climate Change

Climate change is expected to alter many of the environmental conditions under which sesame is grown, including temperature, rainfall patterns, drought frequency, and the occurrence of extreme weather events [22,182]. The effects of these changes are unlikely to be driven by drought alone. Instead, crop performance will depend on how sesame responds to combinations of water stress, heat, disease pressure, and management interventions operating simultaneously. Table 6 summarises the principal responses and current strength of evidence for major climate-related stresses affecting sesame.

Table 6. Major Climate-Related Stresses and Their Effects on Sesame. 

Climate Factor	Response in Sesame	Evidence Level
Heat	Negative	Strong
Drought	Moderate–negative	Strong
Elevated CO2	Positive but uncertain	Moderate
Waterlogging	Negative	Moderate

Note: Responses may vary with cultivar/genotype, stress intensity and duration, developmental stage, soil type, atmospheric demand, and management conditions. “Strong” indicates relatively consistent evidence across multiple studies, whereas “moderate” indicates greater uncertainty or fewer field-scale studies.

12.1. Heat Stress

Sesame is considered more heat-tolerant than many temperate crops because it evolved under warm growing conditions [182,183]. However, tolerance to warm environments should not be confused with tolerance to extreme heat. High temperatures during flowering and seed development can shorten crop duration, reduce pollen viability, impair seed set, and reduce yield [182,183,184]. The effects of heat stress are often amplified when high temperatures coincide with limited water availability. In these situations, reduced transpiration limits canopy cooling and increase the risk of reproductive failure [81,185,186]. As a result, future breeding efforts will likely need to address combined heat and drought stress rather than either factor individually.

12.2. Elevated Carbon Dioxide

As a C₃ species, sesame may benefit from increasing atmospheric carbon dioxide concentrations through improved photosynthetic efficiency and reduced stomatal conductance [187,188,189,190]. Experimental and modelling studies suggest that elevated CO₂ could increase biomass production and improve intrinsic water-use efficiency under some conditions [187,188,189].

However, potential benefits should be interpreted cautiously. Positive responses to elevated CO₂ may be limited by nutrient availability, heat stress, disease pressure, and severe water deficits [189,190]. Moreover, little empirical evidence is available for sesame compared with major crops such as wheat, maize, and soybean. The extent to which elevated CO₂ will offset future climatic constraints therefore remains uncertain.

12.3. Increasing Climate Variability

Changes in rainfall patterns may be as important as changes in average rainfall amounts [191,192]. Many sesame-growing regions already experience irregular rainfall, and future climates are expected to increase the frequency of prolonged dry periods, intense rainfall events, and rapid shifts between wet and dry conditions [22,191,192]. Such variability creates several challenges. Dry periods can increase the likelihood of drought-associated diseases and reproductive failure, whereas intense rainfall events may promote waterlogging, foliar diseases, and harvesting difficulties [13,142,157]. Consequently, climate resilience depends not only on tolerance to individual stresses but also on the ability to withstand fluctuating environmental conditions throughout the season.

12.4. Critical Synthesis

Sesame is frequently described as a climate-resilient crop because of its ability to produce under low water inputs. While there is some justification for this view, the available evidence suggests that resilience is conditional rather than intrinsic. Water deficits during flowering and capsule development remain major constraints, and crop performance is strongly influenced by environment, genotype, and management [9,81,186]. A notable limitation of current research is that most studies continue to examine single stress factors in isolation. Drought, heat, elevated CO₂, disease pressure, and nutrient limitations are commonly investigated independently, despite the likelihood that future production systems will experience several of these stresses simultaneously [183,185,190]. As a result, current understanding may underestimate the complexity of crop responses under commercial conditions. The principal uncertainty is how these interacting climatic factors influence reproductive development and yield under realistic production conditions.

13. Lessons from Major Sesame-Producing Regions

The agronomic challenges facing sesame producers vary considerably among regions. Differences in climate, production systems, access to irrigation, market structure, mechanisation, and technology adoption all influence how the crop is managed and the traits that determine success. As a result, lessons from one region are not always directly transferable to another. Nevertheless, experiences from major production regions provide useful insights into the opportunities and limitations of sesame under water-limited conditions.

13.1. Africa: Production Under Rainfall Uncertainty

Much of Africa’s sesame production occurs in low-input, rainfed systems where seasonal rainfall remains the dominant factor influencing yield [21,193,194]. Countries such as Sudan, Ethiopia, and Tanzania have expanded sesame production substantially over recent decades, largely because the crop can generate income under conditions where more water-demanding crops are difficult to grow [21,195,196].

A common lesson emerging from these regions is that drought tolerance alone is insufficient to ensure productivity. Yield is often constrained by poor soil fertility, limited access to improved cultivars, inadequate pest and disease management, and restricted access to mechanisation and markets [197,198,199]. In many areas, productivity remains low despite the widespread cultivation of sesame.

The African experience highlights an important point often overlooked in drought studies: adaptation is not solely a physiological issue. Crop performance depends as much on farm resources, management practices, and access to technology as it does on genetic tolerance to water stress.

13.2. Asia: Intensification and Genetic Improvement

Asia remains the historical centre of sesame production and breeding, with countries such as India, China, Myanmar, and Vietnam contributing substantially to both production and research [22,23,200,201]. Compared with many African systems, production is generally more intensive and benefits from greater investment in cultivar development, irrigation, mechanisation, and agronomic research [16,23].

Much of the progress in understanding drought responses, irrigation management, breeding, genomics, and disease resistance has originated from Asian research programs [9,65,173,174,175,176,177]. These efforts have contributed to the development of improved cultivars and management practices capable of increasing productivity under variable environmental conditions.

At the same time, challenges remain. Yield gaps continue to exist across production regions, and increasing climate variability is creating new pressures on water resources and production stability [30,202]. The Asian experience demonstrates that improved genetics can contribute significantly to productivity, but genetic improvement alone rarely overcomes environmental and management limitations.

13.3. Australia: Building a New Industry

Australia represents a different stage of development. Rather than improving an established sesame industry, current efforts are focused on determining whether sesame can become a profitable component of modern broadacre farming systems [28,203,204].

Research has concentrated on questions that differ somewhat from those addressed in traditional production regions. Issues such as mechanisation, rotational fit, disease management, irrigation efficiency, and adaptation to northern Australian environments are central to industry development [28,29,203]. In this context, drought resilience is important, but it is only one part of a broader system that must also be economically viable and compatible with existing farming practices. The Australian experience illustrates how the role of sesame is evolving. Rather than being viewed simply as a drought-tolerant crop, sesame is increasingly being evaluated as a component of climate-adaptive farming systems designed to diversify production and reduce exposure to water-related risk.

13.4. Comparative Synthesis

The experiences of major sesame-producing regions suggest that there is no single pathway to successful production. In Africa, productivity is strongly influenced by rainfall variability and access to agricultural inputs. In Asia, investment in breeding, irrigation, and production intensification has played a greater role in improving performance. Australia presents a third model, where the focus is on integrating sesame into mechanised broadacre systems under increasing climate uncertainty [28,198,203,204].

These differences highlight the limitations of searching for a universal drought-resilient sesame ideotype. Traits that improve performance in one environment may provide little advantage elsewhere because production objectives and constraints differ among regions [9,170]. The future of sesame production is therefore likely to depend on local adaptation rather than universal solutions. Across all regions, one lesson emerges consistently: the resilience of sesame is determined not by drought tolerance alone but by interactions among genetics, management, environment, and socio-economic factors. Understanding these interactions remains one of the key challenges for future research and industry development.

14. Knowledge Gaps and Research Priorities

Despite substantial progress in understanding drought responses in sesame, important gaps remain. Much of the current knowledge has been generated through studies focused on individual traits, management practices, or stress factors. As a result, our understanding of how these components interact under commercial production conditions remains limited.

14.1. Limited Field Validation

A large proportion of sesame drought research has been conducted in controlled environments, short-duration field trials, or individual locations [5,29,63,69]. These studies have improved understanding of physiological responses, but they provide only limited insight into crop performance under the highly variable conditions experienced by growers.

Traits such as root architecture, osmotic adjustment, canopy temperature, and physiological recovery are frequently proposed as indicators of drought adaptation. However, relatively few studies have evaluated whether these traits consistently improve yield stability across seasons, environments, and production systems [9,63,85]. Greater emphasis on long-term and multi-environment field experiments is needed to determine which traits have practical value for crop improvement and management.

14.2. Genotype × Environment × Management Interactions

Many studies continue to evaluate cultivars, irrigation treatments, nutrient management, or breeding traits independently. Yet crop performance under drought is rarely determined by any single factor [9,65,205]. The same genotype may respond differently under contrasting irrigation regimes, soil conditions, or climatic environments, while management practices that improve productivity in one location may have little benefit elsewhere. Understanding these interactions remains one of the major challenges for sesame research. Future studies should move beyond single-factor experiments and evaluate crop responses within integrated genotype × environment × management frameworks that more closely reflect commercial production systems [65,205,206].

14.3. Compound Stress Environments

Drought rarely occurs in isolation. Heat stress, nutrient limitations, disease pressure, salinity, and waterlogging frequently occur alongside water deficits, particularly under increasingly variable climatic conditions [5,142,183]. However, most studies continue to investigate these stresses separately.

One notable example is the lack of information on drought × disease interactions. Although both stresses affect water relations, plant health, and yield, surprisingly few studies have quantified their combined impact in sesame [5,142,143]. Similar gaps exist for drought × heat and drought × nutrient interactions. Improved understanding of compound stresses is likely to become increasingly important as climate variability intensifies.

14.4. Emerging Production Regions and Systems-Level Research

Much of the existing knowledge on sesame has been generated in traditional production regions such as India, China, Sudan, and Ethiopia [28,29]. Far less information is available for emerging industries, including Australia, where environmental conditions, farming systems, and production objectives differ considerably from those of established growing regions [28,203,207]. At the same time, relatively few studies have adopted a systems perspective that integrates productivity, water use, disease management, profitability, and climate resilience within the same framework [205,206]. Consequently, important trade-offs among these factors remain poorly understood.

Future research should place greater emphasis on integrated field-based studies that evaluate both biological and economic outcomes. Such approaches are likely to provide more useful information for growers than studies focused on individual traits or management practices alone.

14.5. Research Priority

Future sesame research should also evaluate the combined effects of water availability, heat, disease, nutrition, and irrigation rather than examining these factors independently. Integrating these components with modern phenotyping and breeding approaches can help identify genotypes and management practices that perform consistently across contrasting environments [36,65,143,206]. Linking these responses with yield, water productivity, and economic performance will further support practical and climate-resilient sesame production systems.

15. Future Directions

Future progress in sesame production will depend less on identifying additional drought-response mechanisms and more on translating existing knowledge into practical management and breeding outcomes. Considerable advances have been made in physiology, irrigation management, genetics, and climate adaptation research, yet relatively few of these advances have been integrated into commercial production systems [65,173,174,175,176,177,178,179,180,181,205]. Bridging this gap remains one of the major challenges for both researchers and industry.

Improving crop performance under water-limited conditions will require a stronger focus on yield stability rather than drought survival alone. From a production perspective, the ability to maintain reproductive development and economic returns under variable water availability is likely to be more important than the expression of individual drought-response traits [9,12,81]. Future breeding programs should therefore prioritise traits linked to stable yield performance across diverse environments, including root system architecture, reproductive resilience, and recovery following intermittent drought [62,108,172,208].

Advances in digital agriculture also offer new opportunities for sesame research and crop management. Remote sensing unmanned aerial vehicles (UAVs), crop simulation models, machine learning, and decision-support tools have the potential to improve drought monitoring, irrigation scheduling, and field-based phenotyping [178,179,180,181,209,210]. However, the value of these technologies will ultimately depend on their ability to improve productivity and profitability under commercial farming conditions rather than simply increasing data collection capacity.

A further priority is the transition towards more integrated research frameworks. Future production systems are likely to be shaped by multiple interacting stresses, including drought, heat, disease pressure, and nutrient limitations [9,142,183]. Understanding how these factors influence one another will be more informative than studying individual stresses separately. Integrated genotype × environment × management approaches are therefore likely to provide a more realistic basis for future crop improvement and management recommendations [65,205,206].

Australia–Vietnam Collaborative Opportunities

Australia and Vietnam provide an opportunity to evaluate sesame across contrasting production environments. Australia brings expertise in broadacre farming, mechanisation, crop modelling, and water management, while Vietnam offers experience in sesame production under tropical conditions [204,211]. Multi-environment trials and collaborative research programs could improve understanding of genotype adaptation, irrigation responses, disease risks, and management strategies across a broader range of production systems.

Ultimately, the future role of sesame will depend on more than drought tolerance alone. Its long-term value is likely to come from its contribution to diversified, resource-efficient, and climate-resilient farming systems. Achieving this goal will require closer integration of breeding, agronomy, water management, disease management, and climate adaptation research than has occurred in the past [36,205,206].

16. Conclusions

Sesame possesses several characteristics that favour production in water-limited environments, including moderate water requirements, deep rooting ability, physiological plasticity, and the capacity to recover from periods of drought stress [5,40,62]. These traits have contributed to its expansion in many dryland production regions and have strengthened interest in the crop as agriculture adapts to increasing climate variability [7,8,28].

At the same time, the evidence reviewed here shows that sesame is not drought-proof. Crop performance remains highly dependent on the timing, severity, and duration of water deficits, with flowering and early capsule development consistently emerging as the most vulnerable stages [9,74,90]. Yield responses are also strongly influenced by genotype, soil conditions, irrigation management, nutrition, disease pressure, and climatic environment [42,143,205].

A recurring finding across the literature is that drought adaptation cannot be explained by any single trait or technology. Progress has been made in understanding physiological responses, improving irrigation strategies, identifying drought-associated genes, and developing modern breeding tools [65,173,174,175,176,177,178,179,180,181]. However, relatively few of these advances have been translated into consistent gains under commercial production conditions. Much of the current evidence remains fragmented across disciplines, making it difficult to understand how individual components contribute to productivity in the field [9,205,206].

Future progress will depend on greater integration of physiology, agronomy, breeding, pathology, and climate adaptation research. In particular, more attention should be given to understanding how genotype, environment, and management interact to influence yield stability under variable conditions [65,205,206]. Approaches that combine field validation, modern phenotyping, improved water management, and resilient cultivars are likely to provide greater benefits than reliance on any single drought-adaptation strategy.

Ultimately, the value of sesame lies not in exceptional drought tolerance alone, but in its potential to contribute to diversified and resilient farming systems where water availability is increasingly uncertain. Its future role will depend on how effectively existing knowledge is translated into practical production systems capable of maintaining productivity under changing environmental conditions.