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Article

Assessing Seed Vigor for Direct-Seeded Rice: A Novel High-Temperature Germination Protocol for Late-Season Cropping

by
Yang Wang
1,2,†,
Jie Zhou
1,†,
Xiaoyang Chen
3,
Yixin Cheng
1,
Xiaohang Jiang
1,
Ruo Qi
1,
Liangquan Jia
4,* and
Guangwu Zhao
1,2,*
1
College of Advanced Agricultural Science, Zhejiang A&F University, Hangzhou 311300, China
2
Southern Zhejiang Key Laboratory of Crop Breeding, Wenzhou Vocational College of Science and Technology, Wenzhou 325006, China
3
Zhejiang Provincial Seed Management Station, Hangzhou 310020, China
4
School of Information Engineering, Huzhou University, Huzhou 313000, China
*
Authors to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Agriculture 2026, 16(5), 512; https://doi.org/10.3390/agriculture16050512
Submission received: 27 January 2026 / Revised: 18 February 2026 / Accepted: 24 February 2026 / Published: 26 February 2026
(This article belongs to the Section Seed Science and Technology)
Versions Notes

Abstract

Rapid and uniform seedling establishment is critical for the productivity of direct-seeded rice, particularly in late-season cropping systems where sowing frequently coincides with high-temperature stress. Current seed quality assessment relies predominantly on the Standard Germination Test (SGT); however, this method, conducted under optimal conditions, often fails to predict field performance in thermally stressful environments. To resolve this discrepancy, this study established a High-Temperature Germination (HTG) protocol optimized specifically for late-season rice. Twenty-three diverse rice genotypes—comprising conventional japonica, indica-japonica hybrids, and indica hybrids—were evaluated using SGT and HTG assays at 35 °C, 38 °C, and 41 °C, incorporating a pre-treatment with trichloroisocyanuric acid (TCCA) to standardize initial seed conditions. Validation was conducted through field trials at two distinct locations in Zhejiang, China. The results demonstrated that while SGT indicated high viability (>85%) for most varieties, it exhibited a poor correlation with field emergence (r < 0.31). In contrast, HTG tests conducted at 38 °C and 41 °C showed reliable predictive validity, yielding highly significant correlations with field establishment (r > 0.70, p < 0.001). Significant genotypic variation was observed: hybrid varieties displayed superior thermotolerance and stable germination even at 41 °C, whereas conventional japonica varieties exhibited marked sensitivity to temperatures exceeding 35 °C. These findings highlight the potential of the HTG assay (specifically at 38 °C or 41 °C) as an effective, cost-efficient, and rapid screening tool. By accurately simulating the acute thermal stress of the sowing-to-emergence window, this method facilitates the identification of climate-resilient germplasm and supports reliable stand establishment in direct-seeded rice production.

1. Introduction

Rice (Oryza sativa L.) serves as a staple food for approximately half of the global population, playing a critical role in ensuring global food security [1]. In modern agriculture, particularly with the widespread adoption of direct seeding and mechanized planting, the demand for high-quality seeds has intensified. Central to seed quality is the concept of seed vigor, which encompasses the sum of those properties that determine the activity and performance of seed lots of acceptable germination in a wide range of environments [2]. High-vigor seeds are a prerequisite for rapid, uniform emergence and robust seedling establishment, which ultimately dictates crop yield and production efficiency [3]. Conversely, low-vigor seeds are susceptible to biotic and abiotic stresses, often leading to poor stand establishment and significant economic losses.
Traditionally, seed quality has been assessed using the Standard Germination Test (SGT). However, SGT is conducted under optimal conditions and frequently fails to predict field emergence accurately, particularly under stressful environments [4]. While the Accelerated Aging (AA) test is widely used to predict storability and field emergence [5,6], it simulates cumulative physiological aging rather than the acute heat stress experienced during germination in the field. Similarly, cold tests are established for early-season planting [7] but are irrelevant for late-season cropping systems.
In recent years, advancements in non-destructive phenotyping and omics have expanded the toolkit for vigor assessment. Techniques such as computer vision and image processing—exemplified by the Vigor-S system [8] and SVRice [9]—allow for the precise measurement of radicle emergence and seedling geometry. Advanced spectroscopic methods, including terahertz spectroscopy [10] and metabolomic analyses identifying biomarkers like galactose and gluconic acid [11], offer rapid and highly sensitive evaluations. Despite these advancements, significant limitations persist in their practical application. High-throughput phenotyping and molecular approaches often require expensive instrumentation, complex data analysis pipelines, and specialized technical expertise [12], rendering them less accessible for routine, low-cost testing in breeding programs or seed stations.
A critical gap remains in the standardization of vigor tests for late-season rice. In double-cropping systems, late-season rice is sown during mid-summer, when seedling establishment frequently coincides with high ambient temperatures, often exceeding 35 °C. Currently, there is a conspicuous lack of standardized protocols that specifically simulate these high-temperature germination conditions. Germination under supra-optimal temperatures involves distinct physiological challenges, such as the inhibition of α-amylase activity and oxidative damage [13,14], which are not adequately mimicked by standard aging tests. Furthermore, freshly harvested seeds often exhibit dormancy or carry surface pathogens, which can confound vigor assessments.
To address these challenges, this study establishes a novel, stress-specific High-Temperature Germination (HTG) protocol. The novelty of this approach lies in the systematic integration of acute thermal stress (38/41 °C) during the germination window with a trichloroisocyanuric acid (TCCA) pre-treatment to standardize initial seed conditions (sterilization and dormancy breaking). Unlike previous studies that focus separately on heat stress or dormancy, this protocol combines these elements to isolate physiological thermal tolerance. We validated this method using a diverse set of 23 rice genotypes through field trials at two distinct locations, providing a robust tool for predicting stand establishment in direct-seeded, late-season rice.

2. Materials and Methods

2.1. Plant Materials

In this study, 23 late-season rice (Oryza sativa L.) varieties were selected (obtained from Zhejiang Provincial Seed Management Station, Hangzhou, China), comprising three distinct types: eight conventional japonica varieties (‘Jia 58’, ‘Xiushui 134’, ‘Xiushui 121’, ‘Zhehujing 25’, ‘Xiushui 519’, ‘Zhejing 100’, ‘Ning 88’, and ‘Ning 84’), eight indica-japonica hybrids (‘Chunyou 927’, ‘Chunyou 84’, ‘Zheyou 18’, ‘Zheyou 12’, ‘Yongyou 1540’, ‘Yongyou 15’, ‘Yongyou 538’, and ‘Yongyou 2640’), and seven indica hybrids (‘Zheliangyou 274’, ‘II You 7954’, ‘Qianyou 0508’, ‘Y Liangyou 689’, ‘Shenyou 26’, ‘Zhongzheyou 8’, and ‘Huazheyou 1’). After harvest, all seed samples were naturally dried to a moisture content of approximately 13% and stored in a cold room at 4 °C to maintain their initial physiological state.

2.2. Seed Pre-Treatment and Standard Germination Test

To standardize the initial condition of the seeds, a chemical pre-treatment was applied to sterilize the seed surface and break dormancy. Clean seeds from each variety were soaked in a 1% (w/v) trichloroisocyanuric acid (TCCA, Aladdin Biochemical Technology Co., Ltd., Shanghai, China) aqueous solution for 24 h at room temperature in unsealed containers. Following the treatment, seeds were rinsed three times with tap water and immediately subjected to germination assays.
The Standard Germination Test (SGT) was conducted in accordance with standard protocols. Seeds were placed in germination boxes (12 cm × 12 cm × 6 cm) lined with three layers of moistened filter paper. The boxes were incubated in a growth chamber (Ningbo Jiangnan Instrument Factory, Ningbo, China) under an alternating cycle of 30 °C for 8 h (light intensity: 750–1250 lux) and 20 °C for 16 h (dark). The experiment followed a completely randomized design with three replicates of 100 seeds per variety. The germination percentage was recorded on the 14th day. A seed was classified as germinated when the radicle length equaled the seed length and the shoot length reached half the seed length.

2.3. Laboratory High-Temperature Germination Test

To simulate the thermal stress frequently encountered during the sowing-to-emergence window of late-season rice, a High-Temperature Germination (HTG) test was established. The temperature thresholds were selected based on agro-climatic rationale: 35 °C represents typical high ambient air temperatures during the sowing season in the Yangtze River Valley; 38 °C approximates the elevated soil surface temperatures often experienced by direct-seeded rice under high solar radiation; and 41 °C was selected as an extreme screening pressure to effectively differentiate the thermotolerance limits of diverse genotypes, similar to stress-testing principles used in other vigor assays.
Seeds underwent the same TCCA pre-treatment described in Section 2.2. Subsequently, seeds were incubated under the same photoperiod (8 h light/16 h dark) and moisture conditions as the SGT. However, the temperature was maintained constantly at the respective stress levels (35 °C, 38 °C, or 41 °C) throughout the incubation period. To ensure consistent moisture during high-temperature exposure, germination boxes were initially supplied with water until the filter paper was fully saturated (approx. 15 mL). Moisture levels were monitored daily, and sterile distilled water (pre-warmed to the incubation temperature) was added as necessary to maintain saturation without creating waterlogging. Three replicates of 100 seeds were tested for each variety at each temperature gradient. Germination percentage was calculated on the 14th day using the same morphological criteria as the SGT.

2.4. Field Emergence Test

Field validation trials were conducted from 18 August to 31 August 2020, at two distinct locations in Zhejiang Province, China: the Pingshan Experimental Base of Zhejiang A&F University in Lin’an (Hangzhou) and the Rice Breeding Base of Ke’ao Seed Industry Co., Ltd. in Huzhou. During the experimental period, the daily mean air temperatures ranged from 24.7 °C to 34.7 °C in Lin’an and from 26.0 °C to 34.2 °C in Huzhou (Figure S1). The two experimental sites presented distinct edaphic conditions: the Lin’an site is characterized by sandy loam soil, which generally drains well but warms rapidly, whereas the Huzhou site features clay loam soil, typically exhibiting higher water retention capacity. Despite these differences, field management practices (sowing depth, irrigation) were standardized across both locations.
A randomized block design was employed with four replicates of 100 seeds per variety at each site. Seeds were sown directly into the paddy soil. Field emergence was evaluated on the 14th day after sowing; a seedling was considered established when the shoot extended ≥ 1 cm above the soil surface.

2.5. Statistical Analysis

Data were analyzed using SAS software version 8.1 (SAS Institute, Cary, NC, USA). Prior to statistical analysis, percentage data were transformed using the arcsine square root function (y = arcsin[sqrt(×/100)]) to ensure normality. Analysis of Variance (ANOVA) was performed to detect significant differences among treatments and genotypes. Means were separated using the Least Significant Difference (LSD) test at a significance level of α = 0.05. Pearson’s correlation analysis was conducted to evaluate the relationships between laboratory germination metrics and field emergence rates.

3. Results

3.1. Germination Performance Under Standard Conditions

The results of the Standard Germination Test (SGT) indicated variations in seed viability among the tested varieties (Table 1). Among the conventional japonica varieties, ‘Xiushui 519’, ‘Zhejing 100’, and ‘Ning 84’ recorded germination rates below the 85% minimum threshold mandated for conventional seeds by the National Crop Seed Quality Standard (GB 4404.1-2024) [15]. The remaining conventional varieties exceeded this standard, with ‘Xiushui 134’ displaying the highest germination rate of 93%. Regarding the hybrid rice varieties (indica-japonica and indica hybrids), with the exception of ‘II You 7954’, all varieties met or exceeded the minimum requirement of 82% stipulated by GB 4404.1-2024 for hybrid seeds. Notably, ‘Zheyou 12’ achieved the highest germination rate at 98%. Collectively, these findings suggest that under optimal laboratory conditions, the majority of the selected late-season rice varieties demonstrated adequate germination capacity.

3.2. Germination Characteristics Under High-Temperature Stress

The HTG tests revealed a significant inverse relationship between temperature and germination percentage across all genotypes (Table 2). Generally, germination rates followed the trend: 35 °C > 38 °C > 41 °C.
At the initial stress level of 35 °C, germination rates remained relatively high for most hybrid varieties but began to decline in conventional japonica varieties compared to SGT. As the temperature was elevated to 38 °C, significant genotypic differences emerged. Conventional japonica varieties (except ‘Xiushui 134’) showed significantly lower germination compared to the 35 °C treatment (p < 0.05). In contrast, most hybrid varieties maintained stable germination rates comparable to those at 35 °C, indicating superior thermotolerance. Under the most extreme stress condition of 41 °C, a sharp decline in germination was observed for all genotypes. Conventional japonica varieties were severely inhibited. However, specific hybrid varieties, such as ‘Chunyou 927’, ‘Yongyou 1540’, and ‘Qianyou 0508’, showed no significant difference between the 35 °C and 41 °C treatments, suggesting exceptional heat stability. Notably, ‘Yongyou 1540’ exhibited a slightly higher germination rate at 41 °C compared to 38 °C.
Overall, conventional japonica varieties displayed marked sensitivity to high-temperature stress, whereas hybrid varieties—particularly indica-japonica crosses—exhibited robust tolerance.

3.3. Field Emergence Performance

Field emergence rates were influenced by both location and genotype (Table 3). Emergence rates for conventional japonica rice were notably low, ranging from 2.0 to 16.3% in Lin’an and 4.5 to 16.0% in Huzhou. Hybrid varieties demonstrated significantly superior stand establishment, with rates ranging from 17.0 to 61.0% (Lin’an) and 13.5 to 56.5% (Huzhou). Despite the environmental differences between the two sites, a highly significant positive correlation (r = 0.777, p < 0.001) was observed between the emergence rates in Lin’an and Huzhou (Table 4). These results confirm that hybrid rice varieties established significantly better than conventional japonica varieties under the high-temperature conditions typical of the late-season sowing window.

3.4. Correlation Between Laboratory Tests and Field Emergence

Correlation analysis revealed that the Standard Germination Test (SGT) was a poor predictor of field performance (Table 4). The correlation coefficients between SGT results and field emergence in Lin’an (r = 0.301) and Huzhou (r = 0.246) were not statistically significant.
In contrast, the HTG tests demonstrated significant predictive power. Germination rates at 35 °C showed moderate positive correlations with field emergence (r = 0.544 and 0.551, p < 0.01). However, the predictive accuracy improved substantially at higher stress levels. The 38 °C HTG test yielded highly significant correlations with field emergence in Lin’an (r = 0.651, p < 0.001) and Huzhou (r = 0.709, p < 0.001). Similarly, the 41 °C HTG test exhibited strong correlations (r = 0.710 and 0.757, p < 0.001). Linear regression analysis further confirmed the predictive power of the HTG test. Laboratory germination at 41 °C explained a significant proportion of the variance in field emergence (R2 = 0.50 for Lin’an; R2 = 0.57 for Huzhou, p < 0.001), establishing a quantitative link between the lab assay and field performance. These findings suggest that laboratory germination tests conducted at 38 °C or 41 °C are far superior to the standard method for predicting the field establishment potential of late-season rice seeds.

4. Discussion

4.1. The Limitation of Standard Germination in Predicting Field Emergence

The primary challenge in seed quality assurance is the frequent discordance between laboratory germination results and actual field performance. In this study, while the Standard Germination Test (SGT) indicated high viability (>85%) for the majority of late-season rice varieties, it showed a negligible correlation with actual field emergence (r < 0.31). This result reinforces the widely accepted consensus in seed science that SGT, conducted under optimal conditions, significantly overestimates the establishment potential of seeds in suboptimal field environments [16,17].
For late-season rice, the field environment is characterized by high-temperature stress rather than the ideal 25–30 °C used in SGT. Our data confirm that standard tests often mask latent physiological weaknesses that manifest only under stress—a limitation particularly evident in the conventional japonica varieties evaluated in this study. This failure of SGT to detect cryptic physiological deterioration aligns with broader findings in maize [18], wheat [19], and other crops [20,21]. Such discrepancies underscore the urgent need for vigor assessments that mimic specific agro-ecological constraints, reinforcing the concept that ‘vigor’ is not an absolute trait but a dynamic interaction between the seed’s physiological status and the specific environmental window of sowing [2].

4.2. Efficacy and Physiological Basis of the HTG Test

The High-Temperature Germination (HTG) test developed in this study, particularly at 38 °C and 41 °C, demonstrated a robust capability to predict field emergence (r > 0.70), identifying acute thermal tolerance as the primary limiting factor for late-season rice establishment. Physiologically, germination at supra-optimal temperatures imposes severe metabolic constraints. Previous studies indicate that it induces oxidative stress and inhibits the biosynthesis of gibberellins and α-amylase, thereby impairing the mobilization of starch reserves essential for embryo growth [13,14]. Consequently, the high vigor observed in certain genotypes likely reflects a superior metabolic plasticity—potentially mediated through antioxidant defense systems and heat shock protein (HSP) expression—allowing them to sustain radicle protrusion under such conditions [22].
Crucially, the incorporation of TCCA pre-treatment serves as a methodological standardization step. Freshly harvested rice seeds often harbor surface pathogens or exhibit varying degrees of dormancy. By using TCCA to sterilize the surface and break shallow dormancy [23], our protocol ensures that the observed germination differences are primarily attributable to the embryo’s physiological tolerance to heat stress, rather than being confounded by external biotic factors or dormancy blocks.

4.3. Comparison with Existing Vigor Assessment Methods

The assessment of seed vigor relies on a diverse toolkit of established methodologies; however, aligning these tests with the specific agro-ecological constraints of late-season rice remains a critical objective. The Accelerated Aging (AA) test, for instance, serves as the industry standard for predicting storage potential [24] and has been successfully applied to crops such as soybean [5] and rice [4,6]. Nevertheless, AA protocols typically expose seeds to heat and humidity prior to germination under optimal conditions. While this effectively simulates cumulative physiological deterioration (aging), it may not fully capture the acute heat shock response required for establishment in hot soils. In contrast, the HTG method imposes thermal stress concurrent with germination, providing a more ecologically relevant assessment of the “sowing-to-emergence” capability under the specific high-temperature regimes of late-season cultivation. Similarly, other standardized tests may not be directly transferable to this context: the Cold Test is invaluable for early-season rice but contrasts with the thermal dynamics of late-season cropping [7]; the Electrical Conductivity (EC) test, though rapid, is often confounded in rice by the semi-permeable husk [25,26]; and the Radicle Emergence (RE) test, while efficient [27], may not fully reflect the long-term morphological impact of sustained environmental stress [28].
In parallel, recent technological advancements—such as computer vision systems [8,9], terahertz spectroscopy [10], and metabolomic profiling [11]—have introduced unprecedented resolution and mechanistic insights to vigor analysis. Despite their precision, the practical implementation of these high-throughput approaches is often constrained by substantial equipment costs, complex data processing requirements, and the need for specialized technical expertise [3,12]. The HTG method proposed here effectively bridges the gap between physiological accuracy and operational accessibility. While indices such as root/shoot length or metabolomic profiles provide finer resolution, the germination percentage under stress serves as a robust, binary indicator of establishment potential. By requiring only standard germination chambers and basic reagents, it offers a cost-effective and robust solution for routine quality control in seed stations and breeding programs, particularly in regions where advanced phenotyping platforms may not yet be widely available.

4.4. Genotypic Divergence: Indica vs. Japonica and Heterosis

A distinct feature of our results was the pronounced divergence in thermal tolerance between hybrid varieties (predominantly indica or indica-japonica crosses) and conventional japonica cultivars. While germination in japonica varieties was severely inhibited at 41 °C, hybrid varieties consistently maintained high viability. This disparity aligns with the evolutionary trajectory of the subspecies: indica rice, having evolved in tropical lowlands, typically harbors alleles conferring superior heat tolerance, whereas japonica originated in temperate zones and lacks the adaptive plasticity required for extreme thermal regimes [29,30].
Beyond subspecific divergence, the robust performance of these hybrids is consistent with the phenomenon of heterosis. Hybrid progeny frequently exhibit enhanced stress tolerance, a trait suggested to be linked to the upregulation of stress-responsive genes and more efficient mitochondrial energy metabolism [31,32]. While not directly measured in this study, these mechanisms are consistent with broader physiological studies, such as those by Ramya et al. (2024) [33], which suggest that superior antioxidant modulation is a key driver of vigor and longevity under stress.
The pronounced susceptibility of conventional japonica varieties to temperatures exceeding 35 °C indicates a significant agronomic risk for expanding cultivation into warmer regions or delaying sowing dates. As global climate variability intensifies, ensuring stand establishment becomes increasingly challenging. In this context, the HTG test serves as a vital screening tool to identify thermosensitive genotypes prior to commercial deployment, thereby facilitating proactive risk management in late-season rice production.

4.5. Limitations and Future Perspectives

Several limitations of this study should be acknowledged. First, the field validation was conducted over a single growing season at two locations within Zhejiang Province. Given that seed vigor and emergence are strongly influenced by annual climatic variability and soil types, multi-year and multi-environment trials are necessary to further confirm the universal applicability of the HTG protocol across different ecological zones. Second, this study focused on the final germination percentage. Future research should incorporate germination dynamics (speed) and seedling morphometrics (root and shoot length) to provide a more granular assessment of vigor among the heat-tolerant genotypes.
Although the HTG protocol effectively predicts seedling establishment under high-temperature conditions, it isolates thermal stress as the sole variable. In actual field scenarios, particularly for direct-seeded rice, seedling emergence is often governed by a complex matrix of abiotic factors, including soil moisture deficits, hypoxia, and mechanical impedance [34]. Consequently, future research should aim to develop multi-dimensional stress models, such as coupling high-temperature regimes with osmotic stress (e.g., polyethylene glycol) or anaerobic conditions, to better mimic the specific microclimates of rainfed or submerged paddy systems.
Furthermore, while this study characterized the phenotypic divergence between japonica and hybrid varieties, the underlying molecular mechanisms driving this heterosis-dependent thermotolerance remain to be fully elucidated. Integrating physiological assays with omics-based approaches—specifically transcriptomics to target heat shock protein families [21] or metabolomics to track biomarkers like galactose [11]—would provide deeper insights into the metabolic plasticity that defines high-vigor seeds. Finally, to enhance the throughput of the proposed method for large-scale breeding programs, future iterations could incorporate low-cost computer vision technologies [3] to automate germination scoring, thereby reducing labor intensity and combining physiological precision with phenotypic efficiency.

5. Conclusions

This study demonstrates that standard germination tests often fail to accurately predict the field emergence of late-season rice, primarily due to their inability to capture the acute physiological responses required for establishment under high-temperature conditions. To address this methodological gap, the High-Temperature Germination (HTG) protocol—specifically utilizing 38 °C or 41 °C coupled with TCCA pre-treatment—provides a robust, ecologically relevant, and reproducible measure of seed vigor. Our results further highlight a significant genotypic divergence, where hybrid varieties exhibit superior thermotolerance compared to conventional japonica cultivars, underscoring the potential of heterosis in conferring resilience to thermal stress during the heterotrophic phase of germination.
The widespread adoption of direct seeding systems imposes stricter requirements on seed vigor, particularly as seedling establishment is increasingly exposed to thermal stress [35]. Consequently, the HTG assay offers a vital strategy for both germplasm enhancement and commercial quality assurance. By effectively differentiating heat-resilient genotypes from sensitive ones, this method facilitates the development of climate-smart rice varieties and mitigates the agronomic risks associated with late-season planting. Ultimately, aligning vigor assessment with the specific environmental constraints of the sowing window is essential for improving the stability of sustainable crop production in a warming climate [36].

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/agriculture16050512/s1, Figure S1: Daily maximum and minimum air temperatures recorded during the field experiment period (18 August to 31 August 2020). (a) Lin’an experimental site (Pingshan Base); (b) Huzhou experimental site (Wuxing District).

Author Contributions

Conceptualization, Y.W., X.C. and L.J.; methodology, X.C.; validation, J.Z., X.J. and R.Q.; formal analysis, Y.W. and Y.C.; investigation, J.Z., Y.C., X.J. and R.Q.; data curation, Y.W. and J.Z.; writing—original draft preparation, Y.W. and J.Z.; writing—review and editing, Y.W., L.J. and G.Z.; supervision, Y.W. and G.Z.; project administration, Y.W.; funding acquisition, Y.W. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Zhejiang Province “Three Rural Areas and Nine Parties” Science and Technology Cooperation Project (2024SNJF007), China; the Fundamental Research Funds for the Provincial Universities of Zhejiang (2025TD002), China; Zhejiang A&F University Scientific Research Development Fund Project (2023LFR034), China.

Institutional Review Board Statement

Not applicable.

Data Availability Statement

The data presented in this study can be requested from the first author for further use (Y.W.).

Conflicts of Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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Table 1. Standard germination test results for different late-season rice varieties.
Table 1. Standard germination test results for different late-season rice varieties.
TypeVarietyStandard Germination (%)
Conventional JaponicaJia 5887 ± 1.1
Xiushui 13493 ± 3.1
Xiushui 12192 ± 2.0
Zhehujing 2587 ± 0.8
Xiushui 51980 ± 1.2
Zhejing 10079 ± 0.6
Ning 8887 ± 2.5
Ning 8481 ± 1.6
Indica-Japonica HybridChunyou 92796 ± 1.5
Chunyou 8485 ± 1.3
Zheyou 1895 ± 2.1
Zheyou 1298 ± 2.2
Yongyou 154093 ± 0.9
Yongyou 1590 ± 0.7
Yongyou 53889 ± 1.4
Yongyou 264086 ± 0.6
Indica HybridZheliangyou 27493 ± 1.5
II You 795481 ± 0.5
Qianyou 050885 ± 1.9
Y Liangyou 68987 ± 0.4
Shenyou 2696 ± 0.3
Zhongzheyou 888 ± 1.3
Huazheyou 192 ± 2.5
Table 2. Germination percentages of different late-season rice varieties under laboratory high-temperature stress conditions.
Table 2. Germination percentages of different late-season rice varieties under laboratory high-temperature stress conditions.
TypeVarietyGermination at 35 °C (%)Germination at 38 °C (%)Germination at 41 °C (%)
Conventional JaponicaJia 5884.3 ± 1.20 a76.0 ± 2.52 b45.3 ± 2.19 c
Xiushui 13489.0 ± 0.58 a86.3 ± 3.76 a54.3 ± 1.86 b
Xiushui 12184.3 ± 2.19 a48.7 ± 3.18 b17.3 ± 0.88 c
Zhehujing 2577.7 ± 3.18 a53.0 ± 4.04 b29.3 ± 0.33 c
Xiushui 51979.3 ± 3.84 a45.3 ± 1.45 b31.3 ± 1.67 c
Zhejing 10075.7 ± 3.38 a39.0 ± 3.51 b19.0 ± 0.58 c
Ning 8887.3 ± 1.45 a34.0 ± 1.00 b25.0 ± 1.15 c
Ning 8485.7 ± 1.67 a50.0 ± 3.46 b37.3 ± 2.60 c
Indica-Japonica HybridChunyou 92798.3 ± 0.33 a95.7 ± 1.76 a95.3 ± 1.45 a
Chunyou 8485.7 ± 0.33 a85.0 ± 3.61 a66.3 ± 2.60 b
Zheyou 1893.0 ± 1.15 a88.7 ± 2.40 ab84.0 ± 2.31 b
Zheyou 1297.3 ± 0.33 a86.7 ± 5.84 ab76.0 ± 3.51 b
Yongyou 154092.0 ± 1.15 a88.0 ± 2.65 a88.7 ± 3.38 a
Yongyou 1593.3 ± 0.88 a92.3 ± 0.88 a86.7 ± 0.67 b
Yongyou 53888.7 ± 0.67 a88.0 ± 1.73 a78.7 ± 1.45 b
Yongyou 264086.3 ± 1.86 a82.0 ± 2.65 a73.0 ± 1.53 b
Indica HybridZheliangyou 27495.3 ± 0.88 a84.7 ± 5.24 ab74.7 ± 1.45 b
II You 795485.0 ± 2.31 a84.3 ± 2.03 a73.0 ± 3.06 b
Qianyou 050888.0 ± 3.51 a78.7 ± 4.98 a77.3 ± 2.60 a
Y Liangyou 68993.7 ± 2.40 a84.7 ± 3.53 a73.0 ± 3.79 b
Shenyou 2698.0 ± 1.00 a91.0 ± 2.08 b89.7 ± 2.03 b
Zhongzheyou 889.3 ± 1.76 a87.3 ± 1.45 a66.3 ± 1.86 b
Huazheyou 191.7 ± 1.67 a90.3 ± 1.45 a73.0 ± 5.51 b
Note: Data are presented as mean ± SD (n = 3). Different lowercase letters within the same row indicate significant differences between temperature treatments according to the LSD test (p < 0.05).
Table 3. Field emergence rates of different late-season rice varieties at two experimental sites.
Table 3. Field emergence rates of different late-season rice varieties at two experimental sites.
TypeVarietyField Emergence Rate (%)
Lin’anHuzhou
Conventional JaponicaJia 5815.0 ± 1.2013.0 ± 1.06
Xiushui 1345.7 ± 0.5112.5 ± 1.08
Xiushui 1212.0 ± 0.187.5 ± 0.65
Zhehujing 2512.0 ± 1.016.5 ± 0.49
Xiushui 5197.0 ± 0.6115.5 ± 1.23
Zhejing 1009.3 ± 0.7016.0 ± 1.31
Ning 888.0 ± 0.6612.5 ± 0.99
Ning 8416.3 ± 1.284.5 ± 0.35
Indica-Japonica HybridChunyou 92731.7 ± 2.4350.5 ± 3.85
Chunyou 8417.0 ± 1.4235.5 ± 2.95
Zheyou 1819.3 ± 1.5820.5 ± 1.68
Zheyou 1217.3 ± 1.4132.5 ± 2.72
Yongyou 154041.7 ± 3.1247.0 ± 3.79
Yongyou 1561.0 ± 4.5950.5 ± 4.12
Yongyou 53829.0 ± 2.1648.5 ± 3.56
Yongyou 264020.7 ± 1.5513.5 ± 0.73
Indica HybridZheliangyou 27424.7 ± 1.8735.0 ± 2.83
II You 795422.3 ± 1.6349.0 ± 3.84
Qianyou 050821.3 ± 1.7551.5 ± 4.22
Y Liangyou 68926.7 ± 2.2243.5 ± 3.56
Shenyou 2627.7 ± 2.1036.0 ± 2.95
Zhongzheyou 833.0 ± 2.6456.5 ± 4.56
Huazheyou 150.0 ± 3.4556.0 ± 3.51
Table 4. Correlation analysis between laboratory germination tests and field emergence.
Table 4. Correlation analysis between laboratory germination tests and field emergence.
VariableField Emergence (Lin’an)Field Emergence (Huzhou)Standard Germination (SGT)High-Temp Germination (35 °C)High-Temp Germination (38 °C)
Field Emergence (Huzhou)0.777 ***————
Standard Germination0.3010.246———
High-Temp Germination (35 °C)0.544 **0.551 **0.801 ***——
High-Temp Germination (38 °C)0.651 ***0.709 ***0.580 **0.741 ***—
High-Temp Germination (41 °C)0.710 ***0.757 ***0.543 **0.804 ***0.928 ***
Note: “**” Indicates significant correlation at the 0.01 probability level; “***” indicates significant correlation at the 0.001 probability level.
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MDPI and ACS Style

Wang, Y.; Zhou, J.; Chen, X.; Cheng, Y.; Jiang, X.; Qi, R.; Jia, L.; Zhao, G. Assessing Seed Vigor for Direct-Seeded Rice: A Novel High-Temperature Germination Protocol for Late-Season Cropping. Agriculture 2026, 16, 512. https://doi.org/10.3390/agriculture16050512

AMA Style

Wang Y, Zhou J, Chen X, Cheng Y, Jiang X, Qi R, Jia L, Zhao G. Assessing Seed Vigor for Direct-Seeded Rice: A Novel High-Temperature Germination Protocol for Late-Season Cropping. Agriculture. 2026; 16(5):512. https://doi.org/10.3390/agriculture16050512

Chicago/Turabian Style

Wang, Yang, Jie Zhou, Xiaoyang Chen, Yixin Cheng, Xiaohang Jiang, Ruo Qi, Liangquan Jia, and Guangwu Zhao. 2026. "Assessing Seed Vigor for Direct-Seeded Rice: A Novel High-Temperature Germination Protocol for Late-Season Cropping" Agriculture 16, no. 5: 512. https://doi.org/10.3390/agriculture16050512

APA Style

Wang, Y., Zhou, J., Chen, X., Cheng, Y., Jiang, X., Qi, R., Jia, L., & Zhao, G. (2026). Assessing Seed Vigor for Direct-Seeded Rice: A Novel High-Temperature Germination Protocol for Late-Season Cropping. Agriculture, 16(5), 512. https://doi.org/10.3390/agriculture16050512

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