Evaluation of Commercial Tomato Hybrids for Climate Resilience and Low-Input Farming: Yield and Nutritional Assessment Across Cultivation Systems

Abstract

Commercial tomato hybrids exhibit robust performance in modern high-input agricultural systems. However, their suitability for low-input farming remains uncertain. With the goal that by 2030, 25% of European agricultural production must be organic as part of the European Green Deal, this study aims to assess whether existing commercial tomato hybrids can offer a viable solution for low-input farming. Additionally, the impact of beneficial microorganisms such as plant growth-promoting rhizobacteria (PGPR), in relation to the growth and productivity of tomato hybrids under low-input cultivation is assessed. For this purpose, a well-defined microbial consortium, including Azotobacter chroococcum, Clostridium pasteurianum, Lactobacillus plantarum, Bacillus subtilis, and Acetobacter diazotrophicus, was applied as a liquid suspension to enhance root colonization and promote plant growth. Seven commercial tomatoes (Solanum lycopersicum L.) hybrids—the most popular in the Greek market—were evaluated for their performance under high-input (hydroponic) and low-input cultivation systems (with and without the use of PGPR). Several parameters related to yield, fruit quality, nutritional value, descriptive traits, and leaf elemental concentration were evaluated. In addition, a techno-economic analysis was conducted to assess whether hybrids developed under high-input conditions and intended for such cultivation environments suit low-input farming systems. The results indicated that such hybrids are not a viable, efficient, or profitable strategy for low-input cultivation. These findings underscore the importance of breeding tomato varieties, specifically adapted to low-input farming, highlighting the need for targeted breeding strategies to enhance sustainability and resilience in future agricultural systems. Notably, this study is among the first to comprehensively assess the response of commercial tomato hybrids under low-input conditions, addressing a critical gap in the current literature.

1. Introduction

Climate change intensifies global food insecurity by directly impacting crop production and indirectly straining essential resources. This puts immense pressure on the global food system to produce more food with less, all while minimizing its environmental impact. The European Green Deal provides a crucial framework for building a more sustainable and robust agricultural sector to combat this challenge [1]. Achieving this requires a radical shift in farming practices and a critical evaluation of crop suitability for low-input systems. Especially for the Mediterranean region, new data indicate that heat stress and drought will appear more quickly and aggressively than in any other area worldwide [2,3]. Within this context, selecting appropriate cultivation systems becomes crucial for sustaining agricultural productivity. Therefore, given the rising threat posed by climate change, adaptability strategies represent a challenging approach for Mediterranean farming communities, aiming to maintain low-input cultivation methods and yields [4]. As a result, researchers emphasize the importance of comparing hydroponics and conventional agriculture to address the increasing global food demand, scarcity of natural resources, limited arable land, and recent energy consumption restrictions. By evaluating aspects such as environmental impact, water and energy consumption, and land use, they aim to identify sustainable agricultural practices that can meet these challenges [5].

The cultivated tomato (Solanum lycopersicum L.) represents a vegetable of considerable global significance, as evidenced by its extensive production and consumption [6] and the fact that there are over 4000 registered varieties in Europe [7]. It is a nutritionally rich crop, grown in both open fields and greenhouses, and a particularly vital dietary component in the Mediterranean region [8], and a particularly vital dietary component in the Mediterranean region [9,10]. Tomatoes offer a diverse array of nutrients, including carbohydrates, proteins, lipids, vitamins (A, C, thiamine, riboflavin, and B vitamins), minerals (Ca, Mg, P, K, Mn, Na, and Zn), fiber, essential amino acids, monounsaturated fatty acids, carotenoids, and phytosterols [9,10]. Tomato hybrids address high yields and strong processing attributes to be accepted by farmers, stakeholders, and markets [11]. Most tomato hybrids perform better under current high-input cultivation systems, exhibiting excellent quality traits and high yield. However, they require significant financial investment, including the use of pesticides, irrigation, and fertilizers. Consequently, these hybrids often struggle in low-input systems due to their inefficient resource utilization [10,11,12]. A key question remains unanswered: can existing commercial tomato hybrids adapt successfully to low-input cultivation, or is the development of specialized varieties necessary to ensure sustainable tomato production in resource-limited agricultural systems?

A review study by Pomoni et al. [5] compared the environmental, water, and energy impacts of conventional and hydroponic tomato cultivation, highlighting the advantages and drawbacks of each method. While hydroponics outperformed conventional agriculture in plant density, water efficiency, and yield, it had significantly higher investment costs, required more technical expertise, and consumed more energy per kilogram of harvested tomatoes, making conventional agriculture a more sustainable option in terms of energy consumption [5,13]. The requirements of new cultivation systems, considering climate change, and the legislation of various countries, which aim to adapt to these new requirements, highlight the need for cultivation systems with minimal input and reduced consumption of natural resources. While existing research often focuses on heirloom varieties or specific breeding lines in low-input systems [14,15], modern commercial tomato hybrids are typically bred for high-input environments [16]. Exploring the potential of these widely used hybrids in low-input systems, and leveraging their heterosis, could be an effective way to reduce inputs [17]. At present, the available data regarding the performance of commercial tomato hybrids within low-input cultivation systems are still limited [18].

Low-input agriculture emphasizes resource efficiency and environmental sustainability, often by leveraging natural processes like soil fertility management and biological pest control [19]. This approach aligns with the principles of sustainable agriculture, driving increased scientific interest in soil microbes. The plant rhizosphere harbors a diverse community of microorganisms, with beneficial bacteria and fungi being the most abundant [20]. Numerous research studies reveal that their interaction with plant species impacts key plant physiological processes [21,22]. Soil microbiomes’ beneficial impact on abiotic stress factors has extensively been reported and introduces a new eco-friendly approach to sustainable agriculture [23]. Zhang et al., in 2021 refers that the use of Bacillus species increased the antioxidant defense mechanisms of Glycyrrhiza uralensis under salt stress [24].

Plant growth-promoting rhizobacteria (PGPR) represent a particularly promising strategy for improving crop performance in low-input systems. PGPR enhance plant growth through mechanisms such as nitrogen fixation, phosphate solubilization, siderophore production, and plant hormone synthesis [25]. They have also been shown to increase root development under conditions of water deficiency [26,27]. Regarding tomato crops, the use of PGPR has been reported in several research studies. Andryei et al. in their study demonstrate that the use of PGPR products can increase some important nutritional value traits in berry tomato fruits, like total soluble solids (TSS) and vitamin C [28]. Furthermore, in their review of research work, Singh et al. discuss how microbiological interventions can enhance tomato crop production in a sustainable and eco-friendly manner, highlighting the need for research and development of commercially viable microbial formulations [29]. However, the existing literature raises the fact that there is still a gap between the potential of PGPR and its effective implementation as a sustainable biofertilizer in agriculture [30]. Significant knowledge gaps remain regarding the specific physiological effects of PGPR formulations suitable for tomato production, optimal bacterial strain combinations, and ideal application timing relative to fruit ripening [20]. Therefore, despite the recognized benefits of PGPR and the increasing demand for low-input agricultural practices, a comprehensive evaluation of existing commercial tomato hybrids under such conditions is currently lacking.

This study evaluates the most widely cultivated commercial tomato hybrids in Greece under low- and high-input cultivation systems, focusing on physiological characteristics, yield, and fruit nutritional value. Additionally, the impact of rhizobacterial strains on commercial hybrids is assessed under low-input conditions. Given the high production costs and potential yield limitations that challenge tomato cultivation in Greece, identifying suitable hybrids and microbial tools for low-input systems is crucial. To support sustainable agriculture and enhance economic feasibility, this study also includes a techno-economic analysis and an assessment of the gross margin under different cultivation systems.

2. Materials and Methods

2.1. Plant Material and Methodology

In this research study, seven commercial tomato (S. lycopersicum) hybrids, some of the most frequent tomato-cultivated hybrids in the Greek market, were examined regarding their performance under high-input and low-input cultivation systems. The hybrid seeds used in this study were provided by major Greek seed production companies. Tomato genotypes were Belladona F1 (Hazera Seeds Company), Bellfort F1 (Spirou Seeds company), Ekstasis F1 (Nirit Seeds Ltd.), Formula F1 (Spirou Seeds S.A.), Elpida F1 (Spirou Seeds S.A.), Finalist F1 (Nirit Seeds Ltd.) and Nissos F1 (Hazera Seeds) (Figure 1). The experiments were conducted at the farm located on the Alexandria Campus of International Hellenic University in Sindos-Thessaloniki (40°40′ N latitude, 22°47′ E longitude, 4 m elevation).

The experiment of the high-input cultivation was performed in a plastic greenhouse with controlled conditions in a hydroponic system, during the spring–summer of 2024. Tomato seeds were sown in rockwool cubes and kept at 25 °C for 5 days to germinate. After 20 days, the seedlings were transplanted into larger rockwool cubes and provided with a nutrient solution for another 20 days. Tomato seedlings were put in lines (50 cm between plants) and substrate rockwool was used. Four water irrigations were performed per day (from 8:00 p.m. to 2:00 a.m.) during the whole cultivation period with a gradual increase in the amount of water. Fertilizer was added to the irrigation water while pesticides were applied to roots through irrigation water and by spraying on the leaves. For the preparation of the nutrient solution, three 1000 L tanks were employed. Tank A was charged with 60 kg calcium nitrate, 19 kg potassium nitrate, 2 kg ammonium nitrate, and 2 kg iron. Tank B received 29 kg potassium sulfate, 19 kg magnesium sulfate, and 21 kg monopotassium phosphate, along with trace elements (20 g copper, 150 g boron, 15 g sodium molybdate, 150 g manganese, and 150 g zinc). Tank C contained 27.4 kg of nitric acid. The nutrient tanks were automatically agitated every hour, with continuous mixing during irrigation, to ensure the homogeneity of the solution.

The low-input experiment was conducted at the farm of the Alexandria Campus, under organic farming conditions, in a non-heated greenhouse, during the spring–summer of 2024. Two different treatments were applied to the low-input cultivation system. The experimental plant material was prepared conventionally for the first treatment. For the second treatment, a mixture of plant-growth-promoting rhizobacteria (PGPR) (Azotobacter chroococcum, Clostridium pasteurianum, Lactobacillus plantarum, Bacillus subtilis, and Acetobacter diazotrophicus) was added to the greenhouse soil right before transplantation. The PGPR were applied at a concentration of 5 mL per liter of water, with a precise bacterial concentration of 10¹⁰ CFU/mL, and root drenching was performed using 50 mL of the solution per plant. For both treatments, tomato seeds were sown in a peat-based substrate and kept at 25 °C for 5 days to germinate. Twenty days later, the seedlings were transplanted into individual seedling trays filled with peat substrate and grown for an additional 20 days without any fertilizer application. Irrigation was carried out every two days. Subsequently, the seedlings were transplanted into the field with a planting distance of 50 cm between plants within rows and 1 m between rows. Drip irrigation was applied every two days to maintain the appropriate water supply. A randomized complete block design (RCBD) was applied, with three replicates. Each experimental unit consists of ten plants, in a single steam cultivation system. The cropping practices applied were identical to organic farming principles (field rotation with legumes, added manure, and no chemical or agrochemical applications). Composted poultry manure was applied at 3 tons/ha (dry weight). Regarding weed management, black plastic mulch was employed in the low-input experiments (both with and without PGPRs). This approach was chosen to effectively suppress weed growth, minimize competition for resources, and maintain the integrity of experimental treatments. The use of black plastic mulch is a common practice in low-input agricultural systems, as it reduces the need for chemical herbicides and contributes to sustainable crop management. All observations were taken on an individual plant basis, and for each genotype, while yield, descriptive, and qualitative characteristics were determined (Figure 2).

2.2. Traits Evaluated

2.2.1. Descriptive Characteristics

Descriptive characteristics were determined according to the UPOV system concerning plants, leaves, flowers, and fruits of all the seven genotypes studied (https://www.upov.int/test_guidelines/en/list.jsp, code 044, accessed on 10 July 2024). In addition to UPOV descriptors, other important agronomic and commercial traits were also assessed (

Table 1. List of evaluated traits in tomato genotypes, including UPOV descriptors with their corresponding scoring systems and units of measurement. Traits not explicitly included in UPOV guidelines are also presented for a comprehensive assessment of agronomic and commercial characteristics.

Trait	Scoring System
Plant growth type	1: Determinate → 2: Indeterminate
Number of inflorescences on the main stem	Count
Plant height	cm
Height of the 4th inflorescence	cm
Length of internodes	cm
Anthocyanin coloration of the stem	1: Absent → 5: Very strong
Leaf attitude	1: Erect → 3: Horizontal → 5: Drooping
Leaf length	cm
Leaf width	cm
Leaf’s intensity of green color	1: Very light → 9: Very dark
Attitude of the petiolule of leaflets in relation to the petiole	1: Erect → 2: Horizontal → 3: Drooping
Type of leaf	1: Pinnate → 2: Bipinnate
Type of inflorescence	1: Mainly uniparous → 2: Equally uniparous and multiparous → 3: Mainly multiparous
Flower color	1: Yellow → 2: Orange
Pedicel abscission layer	1: Absent → 9: Present
Pubescence of pedicel	1: Absent → 9: Very strong
Presence of green shoulder in fruits	1: Absent → 9: Present
Extent of green shoulder	1: Very small → 9: Very large
Intensity of green color of shoulder	1: Very light → 9: Very dark
Intensity of green color excluding the shoulder	1: Very light → 9: Very dark
Root weight	g

). More specifically twenty-one characteristics were estimated: plant growth type, number of inflorescences on the main stem, plant height, height of the 4th inflorescence, length of internodes, anthocyanin coloration of the stem, leaf attitude, leaf length, leaf width, leaf’s intensity of green color, attitude of the petiole of leaflets in relation to the petiole, type of leaf, type of inflorescence, flower color, pedicel abscission layer, pubescence of pedicle, presence of green shoulder in fruits, extent of green shoulder, intensity of green color of shoulder, intensity of green color excluding the shoulder and root weight. Four out of the twenty-one evaluated characteristics are presented in the manuscript based on their importance and performance under the three cultivation systems.

2.2.2. Yield Characteristics

Table-ripe fruit yield was estimated for each plant individually over six harvests in all cultivation systems. Earliness was determined 65 days after transplantation (D.A.T.), based on the quantity of fruit harvested during the first three harvests. After harvest, table-ripe fruits were counted, weighted, and graded into different classes according to fruit weight (fruit up to 100 g was classified as commercial and under 100 g to no commercial yield).

2.2.3. Leaf Nutrient Diagnostics

Fully developed tomato leaves were collected from the upper third of each plant to measure the nutrient content. The leaf samples were washed with tap and distilled water, dried at 72 °C until constant weight, and ground to a fine powder. Afterwards, 1.0 g subsamples ached at 500 °C for four hours [31]. The ash was dissolved in 6 N hydrochloric acid (HCl), filtered, and evaluated for macronutrients (phosphorus, potassium, calcium, magnesium) and micronutrients (iron, manganese, copper, and zinc) in PerkinElmer Optima 8300 ICP-OES Spectrometer. The concentrations of macronutrients were expressed as a percentage (%), and the concentrations of micronutrients were expressed in ppm.

2.2.4. Fruit Quality and Nutritional Value Characteristics

To estimate the fruit’s quality and nutritional value, two red ripe-stage tomato fruits were harvested (the first and second fruit of the second cluster of each plant) for the seven genotypes from the three cultivation systems.

Flavonoid content of the peel was measured using a colorimetric assay [32], while total phenolics content was estimated using the Folin-Ciocalteu colorimetric method, as explained by Scalbert et al. [33], with several modifications. The ferric-reducing antioxidant power (FRAP) assay was used to assess the total antioxidant capacity of the peel.

Regarding the nutritional traits of the flesh, total phenolic content was measured using the Folin-Ciocalteu colorimetric method, while the content of lycopene was measured spectrophotometrically as described by Fish et al. [34]. Antioxidant capacity was determined using the Trolox equivalent antioxidant capacity (TEAC) assay and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, as described by Su et al. [35]. Carotenoid content was determined following the method of Lichtenthaler [36]. Ascorbic acid content was quantified using the 2,6-dichlorophenolindophenol (DIP) titration method, as described by Deepa et al. [37], with slight modifications.

Extraction was performed according to Fish et al. [34] after small modifications [38]. Samples were first chopped and homogenized in a laboratory homogenizer. Approximately 0.3–0.6 g samples were weighed and 5 mL of 0.05% (w/v) BHT in acetone, 5 mL of ethanol, and 10 mL of hexane were added. Spectrophotometry at 503 nm was used to measure the absorbance of the hexane layer (upper layer), employing the re-determined extinction coefficients from Fish et al. [34].

2.3. Statistical Analysis Techno-Economic Analysis and Visualizations

The results of this study were statistically analyzed by applying Multifactor ANOVA (p value < 0.05). The statistical package SPSS (Version 18.0) was used, and the Duncan test was performed for the homogenous subsets (SSPS 2009). Visualizations and cross-validation of the SPSS results were generated using R packages [39]. ANOVA results were further analyzed using Duncan’s test, which was conducted with the agricolae package in R [40]. Line graphs with error bars and heatmaps were generated for each task using the ggplot2 [41] (version 4.3.3) and heatmap (version 1.0.12) [42] packages in R. Hierarchical Cluster Analysis (HCA) was also applied to identify relationships and groupings among the seven varieties based on the thirty-three traits. Clustering was performed using Ward’s method and the Euclidean distance metric. The resulting dendrogram provided a visual representation of the similarity and dissimilarity between varieties. Principal Component Analysis (PCA) was employed to reduce the dimensionality of the dataset and to identify patterns of variation among the varieties. PCA was conducted on the normalized dataset using SPSS (Version 18.0), extracting components with eigenvalues greater than 1. The first three principal components, explaining 70% of the total variance, were retained for further interpretation. Furthermore, the technical and economic analysis was conducted based on the methodology developed for farm production economics. The data were collected by interviews and on-site visits.

3. Results

3.1. Descriptive Characteristics

Regarding plant height and the height of the 4th inflorescence in 65 days after transplanting (65 DAT), commercial tomato hybrids exhibited statistically lower values under the high-input system (hydroponics) compared to the other two cultivation systems (Table 1), which is a desirable result. Overall, the best performance (lower values) was observed in the hybrids Formula, Ekstasis, and Belladona.

The high-input system positively affected the leaf size, with the highest average leaf size recorded at 44.10 cm. The low-input system with the added beneficial PGPR ranked second with an average leaf size of 38.86 cm, followed by the low-input system with statistically significant differences (

Table 2. Descriptive characteristics regarding plants’ height (cm) (65 D.A.T.), the 4th inflorescence’s height, leaves’ length(cm), the number of inflorescences on the main stem and root’s weight (g) on average in all the seven tomato hybrids under the three cultivation conditions. The table also presents the average performance of the seven hybrids under low-input, low-input with PGPR, and high-input cultivation conditions in the last three rows.

Variety	Plant Height (cm) (65 DAT)	4th Inflorescence’s Height (cm)	Leaf Length (cm)	Number of Inflorescences	Root Weight (g)
Elpida F1	147.78 ± 27.73 ab	94.11 ± 14.19 b	39.67 ± 2.40 a	6.67 ± 0.50 c	119.76 ± 8.59 b
Formula F1	121.67 ± 17.01 c	82.89 ± 8.53 c	39.44 ± 2.76 a	7.22 ± 0.25 ab	138.64 ± 15.68 a
Ekstasis F1	124.00 ± 22.89 c	79.00 ± 10.73 c	39.33 ± 1.15 a	6.78 ± 0.38 bc	87.38 ± 13.40 c
Belladona F1	125.11 ± 19.81 c	82.44 ± 10.16 c	39.33 ± 2.14 a	7.67 ± 0.41 a	73.08 ± 15.98 c
Nissos F1	146.67 ± 27.47 ab	108.67 ± 17.94 a	38.89 ± 3.22 a	6.11 ± 0.35 d	142.33 ± 11.43 a
Finalist F1	154.44 ± 25.87 a	94.56 ± 9.42 b	42.22 ± 3.33 a	7.67 ± 0.58 a	52.53 ± 11.69 d
Bellfort F1	139.78 ± 26.96 b	90.78 ± 12.72 b	40.00 ± 2.65 a	7.33 ± 0.41 a	75.35 ± 6.88 c
Low input	163.43 ± 10.62 a	102.57 ± 8.41 a	36.57 ± 1.62 c	6.62 ± 0.34 b	89.93 ± 25.31 b
Low input and PGPR	164.19 ± 13.40 a	104.90 ± 7.69 a	38.86 ± 1.73 b	6.86 ± 0.49 b	87.97 ± 21.26 b
High input	83.57 ± 3.94 b	63.57 ± 3.31 b	44.10 ± 2.03 a	7.71 ± 0.45 a	115.9 ± 16.99 a

Statistically significant differences (p < 0.05) are indicated by different letters, as determined by Duncan’s multiple range test (DMRT).

). Noteworthy was the performance of the Ekstasis hybrid within the three distinct cultivation conditions. Unlike the other hybrids studied, Ekstasis exhibited reduced leaf size in the high-input conditions, transitioning from the leading position, in terms of leaf size under the low-input systems, to the lowest position under the high-input system (Figure 3).

Regarding the number of inflorescences in 65 days after transplanting, tomato hybrids under the high-input system exhibited approximately one additional inflorescence compared to those under the low-input systems (Table 2). In general, Belladonna F1, Finalist F1, and Bellfort F1 exhibit the highest number of inflorescences, while Elpida F1 recorded the most decreased number (Table 2). For the important trait of root weight, commercial tomato hybrids under the high-input cultivation system presented a significant advantage, with an increased root weight of 29–32% (Table 2). As demonstrated in Figure 3, Nissos F1 was the only hybrid that exhibited a lower root weight under the high-input system compared to the other cultivation systems, however, along with Formula F1 and Elpida F1, it demonstrated the highest root weight across all three cultivation systems (Table 2, Figure 4).

3.2. Yield Characteristics

For early yield measurements, the significantly higher average number of fruits of all experiments was presented in Elpida F1, Finalist F1, Ekstasis F1, and Belladona F1 with 12.21 to 13.45 fruits per plant, while the lowest average number of fruits was measured in Bellfort F1 (

Table 3. Early yield measurements regarding fruit number per plant, plant yield (g), and fruit weight (g) per plant, on average in all the seven tomato hybrids under the three cultivation conditions. The table also presents the average performance of the seven hybrids under low-input, low-input with PGPR, and high-input cultivation conditions in the last three rows.

Variety	Early Yield
	Fruit Number	Plant Yield (g)	Fruit Weight (g)
Elpida F1	13.45 ± 0.55 a	2379.77 ± 262.2 a	181.09 ± 21.59 a
Formula F1	12.19 ± 0.35 bc	2149.69 ± 137.08 a	175.16 ± 9.55 a
Ekstasis F1	12.90 ± 0.39 ab	2429.10 ± 171.79 a	187.05 ± 11.46 a
Belladona F1	12.21 ± 0.38 abc	2163.61 ± 141 a	176.90 ± 10.44 a
Nissos F1	11.88 ± 0.48 bc	2295.06 ± 305.92 a	184.46 ± 19.92 a
Finalist F1	13.13 ± 0.52 ab	2051.91 ± 149.84 a	161.64 ± 12.25 a
Bellfort F1	11.56 ± 0.74 c	2060.75 ± 204.75 a	172.66 ± 13.11 a
Low input	12.33 ± 0.88 a	1629.43 ± 263.26 a	128.90 ± 19.86 b
Low input and PGPR	12.62 ± 1.19 a	1566.00 ± 185.57 a	128.43 ± 10.30 b
High input	12.72 ± 0.46 a	3159.05 ± 259.26 a	250.01 ± 17.72 a

Statistically significant differences (p < 0.05) are indicated by different letters, as determined by Duncan’s multiple range test (DMRT).

). Yield per plant and fruit weight did not demonstrate any significant differences on average for the seven tested hybrids for the early yield measurements. Furthermore, early yield traits were also estimated separately for each farming system. Fruit number per plant and plant yield did not differ significantly in the three farming systems, while fruit weight was presented more increased in the high-input cultivation system compared to low-input and low-input with PGPR, which is a reasonable outcome, considering that hydroponic systems provide all the vital nutrients to the plants for achieving the maximum fruit size (Table 3).

Equally important as the total yield (TY), is the total commercial yield (TCY), which highlights the market value of the tested hybrids under the three experimental conditions. Bellfort F1 and Formula F1 demonstrated the highest fruit numbers per plant at the TCY measurements; however, the number of fruits in TY was also significantly higher in Elpida F1, Ekstasis F1, and Finalist F1 (

Table 4. Total commercial yield (TCY) measurements regarding fruit number per plant, plant yield (g), and fruit weight (g) per plant, on average in all the seven tomato hybrids under the three cultivation conditions. The table also presents the average performance of the seven hybrids under low-input, low-input with PGPR, and high-input cultivation conditions in the last three rows.

Variety	Total Commercial Yield
	Fruit Number	Plant Yield (g)	Fruit Weight (g)
Elpida F1	20.03 ± 1.82 c	4022.29 ± 650.99 c	166.36 ± 14.51 a
Formula F1	23.56 ± 1.39 a	4522.63 ± 500.28 ab	175.57 ± 10.13 a
Ekstasis F1	22.71 ± 2.02 b	4924.65 ± 725.05 a	181.98 ± 13.89 a
Belladona F1	20.32 ± 1.96 c	4178.57 ± 599.90 c	177.43 ± 12.45 a
Nissos F1	20.28 ± 1.69 c	4162.50 ± 588.93 bc	174.41 ± 12.47 a
Finalist F1	20.47 ± 1.59 c	3920.53 ± 531.53 c	165.82 ± 11.65 a
Bellfort F1	24.66 ± 1.48 a	4843.38 ± 572.54 ab	178.16 ± 13.32 a
Low input	14.14 ± 1.99 c	1675.81 ± 349.85 c	120.33 ± 12.83 b
Low input and PGPR	15.76 ± 1.75 b	1966.05 ± 289.64 b	123.52 ± 6.47 b
High input	32.6 ± 1.02 a	8298.68 ± 492.76 a	254.80 ± 8.25 a

Statistically significant differences (p < 0.05) are indicated by different letters, as determined by Duncan’s multiple range test (DMRT).

and

Table 5. Total yield (TY) measurements regarding fruit number per plant, plant yield (g), and fruit weight (g) per plant, on average in all seven tomato hybrids under the three cultivation conditions. The table also presents the average performance of the seven hybrids under low-input, low-input with PGPR, and high-input cultivation conditions in the last three rows.

Variety	Total Yield
	Fruit Number	Plant Yield (g)	Fruit Weight (g)
Elpida F1	28.03 ± 1.03 a	4945.48 ± 570.87 ab	165.69 ± 14.83 a
Formula F1	26.25 ± 1.09 ab	4662.44 ± 486.19 b	165.83 ± 11.33 a
Ekstasis F1	27.77 ± 1.37 ab	5554.23 ± 643.14 a	182.52 ± 13.85 a
Belladona F1	24.43 ± 1.42 c	4740.68 ± 521.97 b	178.57 ± 11.25 a
Nissos F1	25.50 ± 1.20 bc	5051.19 ± 570.10 ab	183.14 ± 16.11 a
Finalist F1	27.16 ± 0.83 ab	4579.13 ± 464.59 b	159.27 ± 12.28 a
Bellfort F1	27.50 ± 1.38 ab	5029.75 ± 557.32 b	171.83 ± 13.80 a
Low input	22.33 ± 1.46 b	2555.19 ± 429.23 b	115.90 ± 17.77 b
Low input and PGPR	22.86 ± 1.54 b	2801.86 ± 246.88 b	123.33 ± 8.49 b
High input	33.17 ± 1.04 a	8402.26 ± 491.43 a	253.32 ± 8.45 a

Statistically significant differences (p < 0.05) are indicated by different letters, as determined by Duncan’s multiple range test (DMRT).

). Yield per plant demonstrated a significant increase in Ekstasis F1, Bellfort F1, and Formula F1 in TCY, while in total yield Ekstasis F1, Nissos F1, and Elpida F1 performed higher. The only tested hybrid that ranks first both in TCY and in TY in all three cultivation systems is Ekstasis F1 (Table 4 and Table 5). Regarding fruit weight measurements, the seven hybrids did not discriminate significant differences in TCY or TY (Table 4 and Table 5).

In Figure 5, the performance of the seven genetic materials within each cultivation system is presented. The results demonstrate that TY and TCY exhibit similar trends, indicating comparable performance of the hybrids for these two yield characteristics. However, this is not the case for the low-input system and the low-input system with the addition of PGPR. Regarding TCY, Ekstasis F1 stood out in the high-input system, while Bellfort F1 and Formula F1 were prominent in the low-input systems. For TY, the hybrid Ekstasis F1 excelled under the high-input system, whereas all hybrids showed similar performance across the low-input systems.

Referring to the number of commercial fruits per plant, Bellfort F1 excelled at the low-input system. In the low-input system with PGPR, Bellfort F1, Formula F1, and Finalist F1 were prominent, while in the high-input system, Ekstasis F1 was distinct. Regarding the weight of commercial fruits, significant differences were observed only in the high-input system, where Ekstasis F1, Nissos F1, and Elpida F1 stood out with weights ranging from 258.17 to 275.39 g per fruit.

Overall, it is observed that the performance of the genetic materials across the three cultivation systems for the number of fruits per plant is more related to those of total yield compared to the results for fruit weight. This is likely due to the stronger correlation between yield and the number of fruits than between yield and fruit weight.

All three yield-related characteristics presented the highest values in high-input systems in all three experimental conditions (Table 4 and Table 5). However, in TCY measurements, the addition of rhizobacteria in the soil seemed to affect positively the fruit number and yield. Therefore, the low-input system with PGPR presented significantly higher fruit number and plant yield compared to the low-input treatment (Table 4 and Table 5).

3.3. Leaf Nutrient Diagnostics

Leaf sampling was conducted toward the end of the cultivation period to assess the condition of the plants following the stress of fruit development and substantial vegetative growth. Regarding micronutrients, the high-input environment presented statistically significantly higher values compared to the other two environments (

Table 6. Micronutrients (Fe, Mn, Cu, and Zn in ppm; P, K, Ca, and Mg in percentage (%)) measurements on average in all the seven tomato hybrids under the three cultivation conditions. The table also presents the micronutrient average of the seven hybrids under low-input, low-input with rhizobacteria, and high-input cultivation conditions in the last three rows.

Variety	Fe (ppm)	Mn (ppm)	Cu (ppm)	Zn (ppm)
Elpida F1	61.36 ± 7.57 bc	79.43 ± 7.48 bc	10.40 ± 1.29 bc	20.20 ± 1.49 c
Formula F1	58.65 ± 3.94 c	87.74 ± 8.36 ab	12.00 ± 0.97 a	21.05 ± 2.06 c
Ekstasis F1	67.72 ± 5.08 ab	85.32 ± 6.28 ab	11.36 ± 0.97 abc	25.55 ± 2.20 a
Belladona F1	64.42 ± 5.02 bc	91.02 ± 5.07 a	10.02 ± 1.02 c	20.06 ± 1.95 c
Nissos F1	72.96 ± 7.44 a	84.21 ± 7.82 abc	11.82 ± 1.25 ab	24.78 ± 1.96 ab
Finalist F1	58.72 ± 4.31 c	74.69 ± 6.40 cd	11.70 ± 0.73 ab	23.44 ± 1.77 b
Bellfort F1	74.05 ± 7.60 a	69.33 ± 6.67 d	11.25 ± 0.64 abc	23.23 ± 1.50 b
Low input	61.13 ± 8.01 b	78.81 ± 8.93 b	10.45 ± 0.96 b	20.29 ± 1.72 b
Low input and PGPR	61.69 ± 4.78 b	75.50 ± 6.77 b	11.02 ± 0.75 b	21.38 ± 1.08 b
High input	73.42 ± 4.26 a	90.73 ± 4.13 a	12.2 ± 1.14 a	25.97 ± 1.83 a
	P (%)	K (%)	Ca (%)	Mg (%)
Elpida F1	0.18 ± 0.12 a	1.17 ± 0.28 ab	1.27 ± 0.23 b	0.15 ± 0.02 a
Formula F1	0.10 ± 0.04 a	0.78 ± 0.18 c	1.62 ± 0.25 a	0.16 ± 0.03 a
Ekstasis F1	0.11 ± 0.02 a	1.17 ± 0.36 ab	1.61 ± 0.13 a	0.09 ± 0.01 b
Belladona F1	0.11 ± 0.04 a	0.90 ± 0.10 bc	1.64 ± 0.13 a	0.16 ± 0.02 a
Nissos F1	0.09 ± 0.02 a	1.41 ± 0.22 a	1.78 ± 0.22 a	0.14 ± 0.03 a
Finalist F1	0.11 ± 0.01 a	0.98 ± 0.10 bc	1.95 ± 0.21 a	0.13 ± 0.02 a
Bellfort F1	0.07 ± 0.01 a	1.10 ± 0.10 abc	1.85 ± 0.18 a	0.14 ± 0.02 a
Low input	0.10 ± 0.05 a	0.90 ± 0.19 b	1.54 ± 0.16 b	0.13 ± 0.03 a
Low input and PGPR	0.08 ± 0.01 a	1.09 ± 0.19 ab	1.63 ± 0.21 b	0.15 ± 0.02 a
High input	0.14 ± 0.07 a	1.23 ± 0.27 a	1.85 ± 0.26 a	0.14 ± 0.03 a

Statistically significant differences (p < 0.05) are indicated by different letters, as determined by Duncan’s multiple range test (DMRT).

). The overall evaluation across the three cultivation systems demonstrated that Bellfort F1, Nissos F1, and Ekstasis F1 significantly outperformed iron (Fe) content; Belladona F1, Formula F1, Ekstasis F1, and Nissos F1 in manganese (Mn) content; Formula F1, Nissos F1, Finalist F1, and Ekstasis F1 in copper (Cu) content; and Ekstasis F1 and Nissos F1 in zinc (Zn) content (Table 6).

For macronutrients, no significant differences were observed among the three cultivation systems for phosphorus (P) and magnesium (Mg) (Table 6). However, plants exhibited higher potassium (K) content in the high-input and low-input systems with PGPR and higher copper (Cu) content in the high-input system. When comparing the hybrids across the three cultivation systems, no significant differences were observed for phosphorus (P). However, Elpida F1 presented lower calcium (Ca) content, and Ekstasis F1 exhibited lower magnesium (Mg) content (Table 6). Lastly, for potassium (K), the hybrids Nissos F1, Elpida F1, Ekstasis F1, and Bellfort F1 significantly outperformed the others.

Studying the seven commercial tomato hybrids within each cultivation system, it was observed that, regarding potassium (K) concentration in leaves, the hybrids Ekstasis F1, Nissos F1, and Elpida F1 demonstrated superior performance in the high-input system; Bellfort F1 and Ekstasis F1 at the low-input system; and Nissos F1 and Elpida F1 at the low-input system with the addition of PGPR. Belladona F1 presented the least influence across cultivation systems for this trait, followed by Bellfort F1 and Finalist F1. Regarding calcium (Ca), consistently good performance across all three cultivation systems was observed in Finalist F1, Bellfort F1, and Nissos F1, while Elpida F1 constantly ranked last (Figure 6).

3.4. Fruit Quality and Nutritional Value Characteristics

Total soluble solids (TSS) and resistance of flesh to pressure were determined to estimate fruit quality. Ekstasis F1 and Finalist F1 presented the most significantly increased levels of TSS (6.07 and 5.20, respectively) average of all the experimental treatments. At the same time, Bellfort F1, Nissos F1, and Finalist F1 demonstrated the highest resistance of flesh to pressure (1.12, 1.06, and 1.03, respectively). Regarding the performance of these two traits in the three different experimental conditions, no statistically significant differences were observed for the resistance of flesh to pressure, while TSS presented more increases in high-input conditions (

Table 7. Total soluble solids (TSS) and resistance of flesh to pressure measurements on average in all the seven tomato hybrids under the three cultivation conditions. The table also presents the average performance of the seven hybrids under low-input, low-input with PGPR, and high-input cultivation conditions in the last three rows.

Variety	Total Soluble Solids (Brixo)	Resistance of Flesh to Pressure
Elpida F1	5.76 ± 0.29 b	0.90 ± 0.09 d
Formula F1	4.80 ± 0.14 c	0.95 ± 0.05 bcd
Ekstasis F1	6.07 ± 0.28 a	0.94 ± 0.04 cd
Belladona F1	5.51 ± 0.12 bc	0.88 ± 0.06 d
Nissos F1	5.27 ± 0.29 bc	1.06 ± 0.07 ab
Finalist F1	5.20 ± 0.38 a	1.03 ± 0.09 abc
Bellfort F1	5.52 ± 0.16 bc	1.12 ± 0.12 a
Low input	5.46 ± 0.25 b	1.00 ± 0.06 a
Low input and PGPR	5.57 ± 0.26 b	0.97 ± 0.07 a
High input	6.05 ± 0.29 a	0.98 ± 0.13 a

Statistically significant differences (p < 0.05) are indicated by different letters, as determined by Duncan’s multiple range test (DMRT).

).

The nutritional value in the tested varieties was determined by measuring important chemical compounds in the peel and the flesh of the fruits. Phenols, flavonoids, and antioxidant capacity (FRAP) were estimated for the seven hybrids. Formula’s F1 and Finalist’s F1 peel phenols concentrations were presented as the highest followed by Ekstasis F1 and Belladona F1, while peel flavonoid content did not present any significant differences on average in any of the tested hybrids. Peel’s antioxidant capacity, measured with the FRAP method, presented significantly increased values in Finalist F1 and Ekstasis F1, followed by Elpida F1 and Nissos F1. Noteworthy is the fact that at the three different experimental environments peel’s phenols and antioxidant capacity demonstrated significantly decreased values at high-input cultivation systems (16.5 for phenols and 48.25 for antioxidant capacity) compared to the low-input and PGPR and the low-input systems (17.45 and 17.39 for phenols and 57.65 and 57.94 for antioxidant capacity, respectively) (

Table 8. Fruit peel’s total phenols (mg/100 g FW), flavonoids (mg/g FW), and antioxidant capacity (mmol/Fe²⁺ FW) estimated with FRAP (ferric-reducing antioxidant power) method, on average in all the seven tomato hybrids under the three cultivation conditions. The table also presents the average performance of the seven hybrids for these traits under low-input, low-input with PGPR, and high-input cultivation conditions in the last three rows.

Variety	Fruit Peel
	Phenols (mg/100 g FW)	Flavonoids (mg/g FW)	FRAP (mmol/Fe2+ FW)
Elpida F1	16.13 ± 1.37 e	57.61 ± 4.68 a	54.89 ± 5.22 b
Formula F1	18.16 ± 0.68 a	57.04 ± 1.90 a	53.01 ± 4.14 cd
Ekstasis F1	17.36 ± 0.56 bc	58.73 ± 5.85 a	57.81 ± 2.55 a
Belladona F1	17.07 ± 0.51 bcd	60.27 ± 2.06 a	51.21 ± 3.83 d
Nissos F1	16.80 ± 0.21 cd	61.07 ± 2.31 a	54.57 ± 1.78 bc
Finalist F1	17.62 ± 0.61 ab	58.70 ± 1.89 a	58.06 ± 1.30 a
Bellfort F1	16.67 ± 0.59 de	58.36 ± 1.43 a	52.73 ± 2.52 cd
Low input	17.39 ± 0.44 a	58.21 ± 2.13 b	57.94 ± 1.47 a
Low input and PGPR	17.45 ± 0.50 a	55.43 ± 3.03 c	57.65 ± 2.20 a
High input	16.50 ± 1.11 b	62.84 ± 2.88 a	48.25 ± 2.90 b

Statistically significant differences (p < 0.05) are indicated by different letters, as determined by Duncan’s multiple range test (DMRT).

), indicating that low-input systems can effectively enhance the concentration of important nutritional compounds.

Measurements of important chemical compounds in fruit flesh were also conducted to estimate the nutritional value of the seven hybrids on average under the three experimental conditions. Phenols’ concentrations were significantly increased in Formula F1, Belladona F1, and Nissos F1, while lycopene content presented its highest concentration in Finalist F1 followed by Formula F1. Flesh antioxidant capacity was determined with two methods. DPPH method discriminated hybrids Nissos, Belladona, Ekstasis, and Finalist as the varieties with the most significant higher flesh antioxidant capacity, while the TEAC method distinguished hybrids Finalist and Formula as the outstanding varieties. Formula F1 was also rated first regarding its carotenoid accumulation followed by Nissos F1 and Finalist F1. Additionally, ascorbic acid concentrations were observed significantly higher in Formula F1 and Finalist F1 followed by the rest five varieties (

Table 9. Fruit flesh’s total phenols (mg/g FW), lycopene (mg/g FW), antioxidant capacity estimated with DPPH (2,2-diphenyl-1-picrylhydrazyl) (%) and TEAC (Trolox equivalent antioxidant capacity) (μM/g FW) methods, total carotenoids (μg/100 g DW) and ascorbic acid (mg/g), on average in all the seven tomato hybrids under the three cultivation conditions. The table also presents the average performance of the seven hybrids for these traits under low-input, low-input with PGPR, and high-input cultivation conditions in the last three rows.

Variety	Fruit Flesh
	Phenols (mg/g FW)	Lycopene (mg/g FW)	DPPH (%)	TEAC (μM/g FW)	Carotenoids (μg/100 g DW)	Ascorbic Acid (mg/g FW)
Elpida F1	501.44 ± 75.77 c	531.99 ± 16.97 c	50.14 ± 4.16 bc	6.83 ± 0.70 d	118.17 ± 7.66 e	2789.88 ± 145.63 c
Formula F1	588.21 ± 8.43 a	593.70 ± 18.73 b	49.73 ± 1.58 bc	7.67 ± 0.19 a	194.16 ± 1.76 a	3493.68 ± 222.69 a
Ekstasis F1	564.33 ± 17.88 b	440.30 ± 8.79 d	50.88 ± 4.98 ab	7.29 ± 0.19 bc	159.34 ± 9.43 d	2855.52 ± 159.07 c
Belladona F1	584.37 ± 44.01 a	385.49 ± 21.93 f	52.20 ± 1.70 ab	7.38 ± 0.20 b	168.00 ± 12.86 c	2558.74 ± 165.31 d
Nissos F1	569.30 ± 10.08 ab	374.74 ± 18.81 f	52.97 ± 1.95 a	7.21 ± 0.24 bc	182.00 ± 4.55 b	2916.36 ± 83.38 c
Finalist F1	555.33 ± 44.93 b	651.06 ± 13.49 a	50.43 ± 1.49 ab	7.76 ± 0.31 a	178.01 ± 3.92 b	3416.60 ± 127.53 a
Bellfort F1	513.33 ± 55.74 c	402.28 ± 36.26 e	47.90 ± 2.44 c	7.09 ± 0.22 c	170.66 ± 1.29 c	3148.34 ± 111.04 b
Low input	581.90 ± 16.45 a	489.91 ± 51.26 a	50.54 ± 1.85 b	7.57 ± 0.19 a	170.33 ± 12.97 a	3028.29 ± 113.07 ab
Low input and PGPR	593.40 ± 20.84 a	483.95 ± 51.02 ab	48.14 ± 2.63 c	7.51 ± 0.24 a	173.85 ± 12.38 a	2945.58 ± 198.05 b
High input	485.99 ± 56.63 b	474.51 ± 82.56 b	53.14 ± 3.40 a	6.87 ± 0.47 b	157.39 ± 17.28 b	3102.90 ± 335.35 a

Statistically significant differences (p < 0.05) are indicated by different letters, as determined by Duncan’s multiple range test (DMRT).

). Summarizing the measurements of peel and flesh, in an overall estimation, it can be claimed that Formula and Finalist present as the most outstanding candidate hybrids for further study regarding their nutritional value characteristics (Table 9). Referring to the three different experimental environments, flesh’s measurements presented promising results under the two low-input cultivation systems. More specifically, phenols and lycopene content, antioxidant capacity (TEAC method), and carotenoids demonstrated significantly decreased values at the high-input cultivation system compared to the low-input and PGPR and the low-input systems (Table 9). These results are in accordance with the measurements referring to fruit peel (Table 8) enhancing the claim that low-input systems can effectively contribute to increasing the accumulation of critical nutritional compounds in the cultivated tomato hybrids.

In Figure 7, commercial hybrids are compared across cultivation environments for selected nutritional quality traits. Regarding peel’s total phenols, the genetic materials Formula F1 and Ekstasis F1 excelled at the high-input hydroponic system, while Finalist F1 and Elpida F1 were prominent in the low-input system with rhizobacteria. In the low-input system without rhizobacteria, no significant differences were observed among the hybrids (Figure 7a). Regarding peel’s total antioxidant capacity, as measured by the FRAP method, the hybrids Finalist F1, Ekstasis F1, and Nissos F1 excelled at the high-input system. Under the low-input system, Ekstasis F1 and Elpida F1 performed best, while under the low-input system with rhizobacteria, Elpida F1 was distinct as the best hybrid (Figure 7b). Two hybrids, Nissos F1 and Ekstasis F1, exhibited consistent total phenolic values in the peel across all cultivation systems. Similarly, Finalist F1 displayed stability for the antioxidant capacity of the peel, regardless of the cultivation system (Figure 7a,b).

Regarding the total carotenoids in the fruit flesh, the results indicated a strong correlation across the three cultivation systems, with the hybrid’s concentration increasing or decreasing depending on the cultivation system. Formula F1 and Nissos F1 demonstrated exceptional values across all systems, with Belladona F1 joining the top-performing hybrids in the low-input system. Overall, many hybrids showed considerable stability for this trait, regardless of the cultivation system, with Bellfort F1 and Formula F1 demonstrating the greatest homeostasis (Figure 8a). Referring to the total antioxidant capacity in the fruit flesh, estimated by the TEAC method, the hybrids Formula F1 and Ekstasis F1 presented remarkably higher values in the high-input system (Figure 8b). In the low-input system, the top-performing hybrids were Finalist F1, Belladona F1, and Elpida F1, while in the low-input system with rhizobacteria, Finalist F1 and Elpida F1 excelled. Ekstasis F1 exhibited stable total antioxidant values for this trait, despite the cultivation system (Figure 8a,b).

The present study evaluated the clustering and differentiation among seven tomato hybrid varieties based on all measured traits related to descriptive factors, yield, quality, and nutritional value. The analysis was conducted using Hierarchical Cluster Analysis (HCA) and Principal Component Analysis (PCA), providing complementary insights into the patterns of variation and grouping among the varieties (Figure 9).

In the Hierarchical Cluster (HCA) dendrogram, the hybrids were categorized into two main groups, A and B. Hybrids, Ekstasis, and Bellfort formed a compact subgroup (A1), indicating their close relationship based on the full set of traits. Finalist F1 joined group A (subgroup A2) at a higher hierarchical level, signifying partial similarities with the former but considerable differentiation. Another distinct cluster (B1) included hybrids Belladona, Nissos, and Formula, showing high within-group homogeneity. Elpida F1 was loosely associated with this cluster, suggesting it shares certain traits with the group but retains a higher degree of dissimilarity (subgroup B2).

The Hierarchical Cluster Analysis (HCA) dendrogram corroborated the PCA results while providing additional insights into the hierarchical relationships among the varieties. The Principal Component Analysis (PCA) reduced the dimensionality of the dataset while retaining 70% of the total variation in the first three principal components (PCs). PCA scores revealed distinct clustering among the varieties, with certain overlaps and separations. The hybrids Belladona Formula and Nissos were closely clustered, indicating their similarities in the measured traits. Elpida F1 was situated slightly apart from this group, indicating a moderate degree of differentiation. Hybrids Ekstasis and Bellfort were situated near one another, indicating their shared characteristics and forming a distinct group. Finalist F1 appeared relatively isolated, showing considerable differentiation from all other varieties. This dual approach provided strong evidence for the grouping and differentiation of the varieties, offering valuable insights for breeding programs or targeted cultivation strategies.

The heatmaps in Figure 10, Figure 11 and Figure 12 demonstrate the comparative performance of the seven commercial hybrids studied across thirty-one traits, including yield, nutritional value, fruit quality, descriptive traits, root weight, and leaf element concentration. The overall score for each commercial hybrid within each cultivation system is represented in each heatmap using a color spectrum ranging from red to blue. The best-performing hybrids are ranked from 1 to 7, with the highest performance depicted in red. As performance decreases, the colors transition gradually toward blue, with the lowest-ranked hybrids appearing in an intense blue shade. To count the overall score of each hybrid, a scale was created from one to seven. More specifically, the hybrids that ranked with 1 (red color) took seven points, with 2 (light red) took six points and the scaling continued, respectively, up to 7 (blue color) with one point. According to that scaling method, the results for the low-input cultivation system, from the best to worst performance of the tested traits, were configured as follows: Finalist F1 (150 points), Bellfort F1 (141 points), Nissos F1 (139 points), Ekstasis F1 (130 points), Formula F1 (126 points), Belladona F1 (121 points), and Elpida F1 (102 points) (Figure 10).

Regarding the low-input system with the PGPR, according to the same method, the scaling has undergone changes, signifying that bacterial presence significantly affects the observed traits of the hybrids. The scaling was developed as follows: Finalist F1 (146 points), Formula F1 (143 points), Bellfort F1 (134 points), Nissos F1 (129 points), Elpida F1 (127 points), Ekstasis F1 (120 points), and Belladonna F1 (119 points). It has been observed that Finalist F1, Bellfort F1, and Nissos F1 consistently attain top rankings, irrespective of bacterial addition. Nonetheless, the hybrids Formula and Elpida exhibit a positive response to the presence of rhizobacteria (Figure 11).

In the high-input hydroponic cultivation system, the scaling of hybrids showed variation. The hybrids were arranged in descending order based on their scores as follows: Ekstasis F1 (157 points), Nissos F1 (155 points), Formula F1 (143 points), Finalist F1 (132 points), Elpida F1 (116 points), Belladonna F1 (101 points), and Bellfort F1 (98 points). The hybrids Ekstasis F1, Nissos F1, and Formula F1 seem to respond exceptionally well to the high inputs provided by the hydroponic system, outperforming the other hybrids in total scoring (Figure 12).

Analyzing the distinct categories of previously discussed traits, the following trends emerge: In relation to yield components, the prominent hybrids include Bellfort, Nissos, and Ekstasis within the low-input cultivation system, Formula and Ekstasis in the rhizobacteria-enhanced system (PGPR), and Ekstasis, Elpida, and Nissos in the high-input hydroponic system. Concerning the nutritional value traits of the fruit peel, the leading hybrids are Finalist and Belladonna for the low-input system. Elpida, Formula, and Finalist excelled in the rhizobacteria-enhanced system, while Ekstasis, Nissos, and Finalist in the high-input system. Regarding other nutritional value and fruit quality traits, the dominant hybrids were Finalist, Formula, and Belladonna in the low-input system, Finalist and Formula in the low-input with PGPR system, and Formula, Finalist, and Ekstasis in the hydroponic cultivation system (Figure 10, Figure 11 and Figure 12).

Referring to the descriptive characteristics, Finalist F1 was the best or one of the best hybrids, regardless of the cultivation system. Regarding root weight, Nissos F1 and Formula F1 ranked among the top two in all cultivation systems. Concluding, concerning the elements’ concentrations in leaves, the Nissos hybrid consistently exhibited the highest concentrations across all cultivation systems. Additionally, the highest total concentrations were observed in Ekstasis, Bellfort, and Finalist under low-input conditions, in Bellfort and Finalist under PGPR treatments, and in Ekstasis in the hydroponic system.

The economic feasibility and efficiency of tomato production under the three input systems were also determined in the present study (

Table 10. Techo-economic analysis of tomato hybrids according to the input cultivation system.

	Low-Input System	Low-Input and RGPR System	High-Input System
Production (kg/acre)	5.110	5.603	16.804
Price (€)	0.70	0.70	0.50
Gross Revenue	3.570	3.922	8.402
Variable costs
Fertilizers (€/acre)	80	80	740
Plant Protection (€/acre)	60	60	340
Plant Capital (€/acre)	500	500	500
Irrigation (€/acre)	70	70	130
Hired labour (€/acre)	900	900	450
Other (€/acre)	180	200	250
Interest in operating capital (€/acre)	95	95	130
Total variable cost	1.885	1.905	2.540
Gross Margin	1.685	2.017	5.862

Source: survey data.

). In agriculture, gross margin is a useful tool for evaluating the economic importance of a production line, as it includes only the production value and variable costs. Gross margin provides the most accurate overview over time by calculating the result based on the investment made to produce the quantity in question [43]. Results unraveled that Gross Revenue was 3.570 €/acre for the low-input system, with a yield of 5.110 kg/acre and a price of 0.7 €/kg. In the low-input with the PGPR system, the yield presented increased to 3.922 kg/acre, and the selling price was found to be slightly higher (0.70 euro per kilogram), resulting in gross revenue of 3.922 € per acre. Having the highest yield (16.804 kg/acre) and price of 0.5€/kg, the high-input system (hydroponics) generates the highest Gross Revenue of 8.402 €/acre. Additionally, fertilizers, plant protection, and irrigation costs increased with higher input levels. The cost increase, however, is relatively small compared to the increase in revenue. Despite higher costs, the high-input system provides the highest returns. Compared to the low-input system, the low-input with PGPR system offered moderate improvements in productivity. This is likely due to the beneficial influence of the PGPR inoculation.

4. Discussion

Tomato hybrid cultivation has largely replaced traditional varieties, particularly for fresh-market production, with hybrids now dominating nearly 100% of production in many countries [44]. Breeders from major seed companies develop hybrids to thrive under high-input conditions, including intensive fertilization and pesticide use [45]. Nevertheless, their adaptability and efficacy in low-input cultivation systems have not been thoroughly examined, thereby raising significant inquiries regarding their appropriateness for sustainable organic low-input agriculture [46,47]. The inquiries pertain to both the attributes of plants, such as yield components and fruit quality, as well as their economic viability. Specifically, the assessment focuses on whether the profitability derived from cultivating such hybrids substantiates their application in low-input agricultural systems. The cost of purchasing hybrid tomato seeds constitutes a substantial part of the overall production expenses, making it a crucial factor in assessing the economic feasibility of hybrid cultivation under low-input conditions [48]. Furthermore, the shift towards eco-friendly and sustainable farming practices has resulted in a greater use of beneficial microorganisms. PGPR are widely used in tomato cultivation to improve nutrient absorption from the soil, especially in low-input conditions [10,49,50,51].

The current study aims to evaluate whether commercially available tomato hybrids can provide a feasible solution for low-input agriculture. By 2030, 25% of agricultural production in Europe must be organic as part of the European Green Deal, leading to vigorous scientific discussions about the most suitable genetic material for these cultivation systems [52]. This study also evaluates the effects of PGPR on the growth and productivity of tomato hybrids under low-input conditions. To attain this objective, seven commercially cultivated large-fruited fresh-market tomato hybrids were selected to be cultivated in three distinct cultivation systems: (i) a low-input system, (ii) a low-input system supplemented with PGPR, and (iii) a high-input hydroponic system.

Scientists explore various strategies to enhance crop yields sustainably, including the use of phytomicrobiome members, which are now being recognized as a “fresh” green revolution [53]. The application of beneficial microorganisms on food crops has been extensively studied, yet their use in the field remains limited. Introducing phytomicrobiome members into agricultural systems as a sustainable approach for managing diseases and providing nutrients could help reduce the negative effects of excessive chemical inputs, such as fertilizers and pesticides [54]. Moreover, constituents of the phytomicrobiome have been employed as an efficacious strategy to mitigate particular biotic and abiotic challenges that may hinder crop growth and productivity [55,56]. PGPR uses both direct and indirect methods to promote plant growth. These mechanisms are essential for increasing nutrient availability, supporting hormonal balance, and strengthening plants against various stresses. It contributes to plants’ growth, development, and overall health through various mechanisms such as nitrogen fixation, nutrient solubilization, and disease suppression [57]. The results in this experiment demonstrated that PGPR conferred a significant advantage over the traditional low-input system in terms of leaf length (considering all descriptive traits) as well as in the number of fruits and yield per plant for commercial production (considering all yield components). This can be explained by the high and significant Pearson correlation coefficient between the trait of leaf length and the number of marketable fruits (0.63), which is greater than the correlation with the total number of fruits per plant (0.52). This ultimately contributes to an increase in marketable yield. The positive correlation between leaf length and marketable yield can be attributed to larger leaves having a greater surface area for photosynthesis, leading to increased production of photosynthetically derived substances (e.g., sugars) that are transported to the fruits. This can result in a higher number and larger size of marketable fruits. In another tomato study, inoculation of tomato roots with B. subtilis BEB-lSbs (BS13) significantly improved yield and fruit quality [58]. Previous studies have shown the positive effects of other Bacillus strains on tomato growth and yield and physiological performance under salinity conditions [59]. Another PGPR, Serratia marcescens, promoted tomato plant growth for tomato [60]. PGPRs have been demonstrated to improve plant growth through various mechanisms, such as phytohormones, enhanced nutrient uptake, and protection against pathogenic microorganisms. These benefits can lead to larger leaves and increased productivity. Gashash et al. [50] also reported a significant increase in the number of fruits per tomato plant after applying PGPRs, with improvements reaching up to 76%. As more is discovered about the plant growth-promoting mechanisms of PGPR, tomato production is expected to increase while chemical inputs decrease. Studies in greenhouse conditions have shown that PGPR can significantly influence root, stem, and leaf development, with the greatest variability observed in leaf dry weight. Additionally, their application has been associated with increased fresh and dry biomass, contributing to improved growth rates, fruit production, and nutrient availability, and new standards for crop productivity [61]. Since its discovery, PGPR has shown great promise as a major contributor to sustainable agriculture development [62].

Furthermore, the high-input system surpassed both the low-input system and low-input system with the added PGPR, in all morphological characteristics, including plant height, height of the fourth inflorescence, leaf length, number of inflorescences, and root weight. Moreover, no statistically significant differences in earliness were observed among the three cultivation systems. All yield-related components were significantly higher in the high-input system when considering total production, which includes both commercial and no commercial yield. Additionally, under high-input conditions, both the number of fruits and the total fruit weight nearly doubled, resulting in a four-fold increase in marketable yield. In terms of total production, the weight of the fruit was observed again doubled under high-input conditions compared to low-input systems. The number of fruits per plant in low-input systems only reached two-thirds of the high-input system. Consequently, this resulted in an overall increase that was nearly threefold in yield. These findings highlight the importance of hydroponic cultivation, at least in terms of productivity-related characteristics. However, for short-duration crops, possibly due to unfavorable conditions or higher market prices during early production, high-input cultivation does not appear to be advantageous. Moreover, when considering the high costs associated with hydroponic production, organic cultivation may ultimately prove to be more cost-effective. In another study, Pseudomonas fluorescens strain 63–28, significantly enhanced tomato fruit yield and quality in greenhouse production, particularly under suboptimal environmental conditions [63].

Findings from similar studies reinforce the role of PGPR in enhancing crop productivity and soil health in sustainable cultivation systems. Research on organic tomato production highlights the positive effects of PGPR on yield and quality parameters, emphasizing specific application methodologies [64]. PGPR offers promising avenues for sustainable agriculture and ecosystem health, yet they come with inherent challenges. They hold the potential to enhance plant growth, nutrient uptake, and disease resistance through mechanisms such as nitrogen fixation, phosphate solubilization, and production of growth-promoting substances. Regarding leaf nutrient concentrations, hybrids grown in the hydroponic system displayed significantly higher values compared to those in the low-input systems, which was anticipated due to the continuous supply of optimal fertilizer concentrations. However, potassium levels in the low-input system with PGPR addition were similar to those in the high-input system, indicating a potential positive effect of rhizobacteria on potassium uptake. This is particularly significant given the crucial role of potassium in enhancing fruit quality and nutritional value, including improvements in flavor, color, and shelf life of tomatoes. Harnessing these benefits could lead to reduced reliance on chemical fertilizers and pesticides, fostering environmentally friendly agricultural practices [65]. Phosphorus is an essential macro-nutrient for plant growth, playing a key role in metabolism, signal transduction, macromolecule biosynthesis, and photosynthesis. However, over 90% of available phosphorus is insoluble, making plant absorption difficult. Phosphate-solubilizing PGPR, abundant in the rhizosphere, release phosphorus through organic acids and phosphatase enzymes [65]. Sharafzadeh in 2012 revealed that tomato hybrids’ (F1 Hybrid, Delba, and F1 Hybrid, Tivi) root inoculation with PGPR has shown promising results in greenhouse-grown tomatoes [66]. Pseudomonas fluorescens 92rk was found to act as a mycorrhiza helper bacterium, promoting root architecture modifications that enhance phosphorus uptake. In other studies, an increase in phosphorus concentration has been observed under the influence of PGPRs. However, in the present study, the specific rhizobacteria used resulted in the opposite effect, namely a slight decrease in phosphorus concentration.

Referring to TSS content, it presented the highest values in the hydroponic system. Regarding nutritional composition, the results varied based on the examined parameters. Phenolic compounds of the peel, peel antioxidants (FRAP method), flesh phenolics, lycopene, antioxidants (TEAC method), carotenoids, and ascorbic acid content were observed significantly higher in the low-input systems. This is in agreement with other scientific studies [67,68] where ascorbic acid, lycopene, and total phenolic content in fruits are found in higher concentrations in organically grown plants compared to hydroponically cultivated ones. In contrast, peel flavonoids and flesh antioxidants (DPPH method) were more pronounced under the high-input system, indicating that different cultivation practices may selectively influence specific bioactive compounds. A study by [69] revealed that applying plant growth-promoting rhizobacteria (PGPR) as biofertilizers to tomato plants under water stress improved fruit quality and strengthened antioxidant defenses. Specifically, PGPR treatment resulted in a notable increase in sugar (24%) and protein (177%) content, alongside a significant decrease in polyphenol content (42%).

Analyzing the performance of each hybrid individually, it was revealed that the same hybrids did not excel in both high-input and low-input cultivation systems regarding yield. Since almost the whole production in the high-input system was marketable, the commercial and total yield curves almost overlapped, with the hybrids Ekstasis, Bellfort, and Nissos standing out. In contrast, the commercial and total production curves did not align in low-input cultivation systems (Figure 5). The presence of the PGPR seemed to offer at least a slight advantage to all genetic materials under low-input conditions, enhancing both marketable and total yield. Regarding marketable yield, Bellfort F1 and Formula F1 demonstrated superior performance under low-input conditions, with or without rhizobacteria. Notably, Bellfort F1 consistently ranked among the top hybrids for marketable yield across all cultivation systems, indicating stability and resilience to stress. The two hybrids that showed the greatest improvement in total yield due to rhizobacteria application were Elpida F1 and Nissos F1. However, the positive effect of PGPR on commercial yield was minimal and nearly uniform across all hybrids. Findings on Solanaceae species suggest that the exploitation of PGPR can enhance soil health and crop productivity, offering sustainable cultivation practices in enhancing tomato productivity under low-input conditions, while also highlighting their broader benefits for soil health and disease suppression, reinforcing their role in the transition toward more sustainable agricultural systems [70,71]. However, successful implementation faces hurdles such as variability in PGPR effectiveness across different plant species [62], varieties, and environments.

In terms of overall hybrid performance, considering the sum of rankings across all measured traits, hybrids Finalist and Bellfort excelled in the low-input system, while Finalist, Bellfort, and Formula performed best in the low-input with PGPR system, and Ekstasis and Nissos stood out in the high-input system (Figure 10, Figure 11 and Figure 12). Consequently, different genetic materials are preferred depending on the level of input.

Hybrids are favored in commercial tomato cultivation due to their enhanced productivity, earlier maturity, and improved fruit quality, which contribute to greater revenue for growers [72]. However, it is uncertain whether hybrids could be a suitable choice when the target cropping environment is a low-input farming system [16]. Breeders developing commercial tomato hybrids work with only a narrow genetic base of the total genetic variability available within the species [73]. To streamline and expedite the breeding process, they often select already improved genetic materials. Estimates suggest that the genetic variation within tomato cultivars constitutes less than 5% of that observed in their wild progenitors [74]. As Bai and Lindhout [75] say, breeders are continuously improving their breeding lines, by using the cultivars of their competitors. This resulted in a market dominated by genetically similar hybrids. In the present study, a comprehensive analysis of all measured traits revealed that Ekstasis F1 is genetically very similar to Bellfort F1, while another distinct group of related hybrids includes Belladonna F1, Nissos F1, and Formula F1. Conversely, Finalist F1 and Elpida F1 appear to represent genetically distinct materials, indicating a different genetic background. The economic analysis shows that commercial tomato hybrids specifically developed for high-input cultivation are unsuitable for low-input farming systems. These findings highlight the need for tailored breeding programs to develop hybrids optimized for sustainable, resource-efficient agricultural practices.

5. Conclusions

As tomato hybrids are bred and selected for high-input cultivation systems, their performance under low-input systems remains largely unknown. The challenges posed by climate change, along with the need for more sustainable agricultural practices and the economic constraints of high-input systems, highlight the importance of breeding and adapting varieties for low-input conditions. However, the adaptability of tomato commercial hybrids under these conditions has been less extensively studied. Therefore, this study aims to characterize and evaluate the adaptability of seven popular tomato hybrids in Greece, under low-input cultivation conditions, as well as low-input conditions supplemented with PGPR. The outcomes indicated that commercial tomato hybrids exhibit excellent yield performance only under high-input cultivation systems. Certain characteristics, especially those pertaining to the nutritional value of fruits, seem to exhibit advantages arising from low-input agricultural systems. Additionally, noteworthy is the fact that different hybrids performed better under low-input conditions than in high-input systems, with Bellfort F1 emerging as one of the top-performing hybrids. Furthermore, the application of the specific PGPR tested did not provide many benefits to the hybrids except some like commercial production, number of fruits, and phosphorus uptake. In that point, it is important to note that the development of hybrids under high-input conditions appears to be neither a viable nor efficient or profitable strategy when addressing low-input farming systems. Avdikos et al. [7,16,44] found that breeding under low-input conditions could produce tomato cultivars, inbred lines, or hybrids suitable for organic and low-input agriculture. This may be a viable solution involving the breeding of varieties specifically for low-input conditions, thereby ensuring their suitability for these agricultural practices. This method is likely to more effectively meet the increasing demands of organic farming, especially considering climate change and the growing need for environmental sustainability.

Moreover, to ensure the economic viability and sustainability of farms, indexed production costs must be developed [76]. Using techno-economic and comparative analysis between the most widely cultivated commercial tomato hybrids in Greece is an effective way to profile agriculture systems since this method helps policy formulators present sustainable development in different ways. The findings of our study demonstrate, in economic terms, the unsuitability of cultivating commercial tomato hybrids in low-input systems, even when supplemented with the use of beneficial rhizobacteria.