Commercial Tomato Cultivars Research Articles

Implementation of an algorithm for automated phenotyping through plant 3D-modeling: A practical application on the early detection of water stress

High-throughput plant phenotyping requires integrated image-based tools for automated and simultaneous quantification of multiple morphological and physiological traits, which are valuable indicators of plant sensitivity to limiting environmental conditions. In this study, we proposed a novel segmentation algorithm for the automatic collection of plant structural parameters based on three-dimensional (3D)-modeling obtained through a phenotyping platform and a Structure from Motion (SfM) approach. The algorithm was initially tested on a 3D-reconstruction of four potted commercial tomato cultivars, namely “Saint Pierre” (S), “Costoluto Fiorentino” (C), “Reginella” (R), and “Gianna” (G) for the identification of the main phenotypic plant traits (heights, angles and areas). The results pointed out that the proposed algorithm was able to automatically detect and measure the plant height (R2¯ = 0.98, RMSE¯ = 0.34 cm, MAPE¯ = 3.12% and AIC¯ = 6.03), petioles inclination (R2¯ = 0.96, RMSE¯ = 1.35°, MAPE¯ = 3.64% and AIC¯ = 22.16), single-Leaf Area (R2¯ = 0.98, RMSE¯ = 0.95 cm2, MAPE¯ = 7.40% and AIC¯ = 14.91) and single-leaf angle (R2¯ = 0.84, RMSE¯ = 1.43°, MAPE¯ = 2.17% and AIC¯ = 15.83). As a study case, the algorithm was applied for monitoring plant’s dynamic responses to early water stress, measured according to Fraction of Transpirable Soil Water (FTSW), of the same tomato varieties, grown in pots, during 20 consecutive days under three treatments (full-irrigation, 50% deficit irrigation and no-irrigation). The results showed that for R and G cv., plant height was the phenotypic trait most sensitive to water stress (plant growth inhibition at 0.58 of FTSW value), while Total Leaf Area and transpiration rates started to be affected at lower FTSW (0.52 and 0.40, respectively). Conversely, S and C cv. did not exhibit any significant change in phenotypic traits under analysis, likely because these varieties exhibited a slow growth rate, allowing them to consume less water and therefore not reach a water stress threshold. The results indicated that plant height trait might be used in subsequent analyses to facilitate the rapid identification of tomato varieties resistant to water stress, thus enhancing crossbreeding programmes.

The Effective Role of Nano-Silicon Application in Improving the Productivity and Quality of Grafted Tomato Grown under Salinity Stress

This study aims to determine the influence of grafting and nano-silicon fertilizer on the growth and production of tomatoes (Solanumlycopersicum L.) under salinity conditions. A commercial tomato hybrid (cv. Strain B) was used as a scion and two tomato phenotypes were used as rootstocks: S. pimpinellifolium and Edkawy. The rootstock effect was evaluated by growing plants at two NaCl concentrations plus the control (0, 4000, and 8000 ppm NaCl). Nano-silicon foliar application (0.5 ppm) after 20, 28, and 36 days from transplanting was also used to mitigate salinity stress. Antioxidants, hormones, and proline were evaluated for a better understanding of the physiological changes induced by salinity and grafting. The results showed that grafting either on S. pimpinellifolium or Edkawy combined with nano-silicon application enhanced shoot and root growth, fruit yield, and fruit quality. The Edkawy rootstock was more effective than the S. pimpinellifolium rootstock in terms of counteracting the negative effect of salinity. Higher levels of mineral contents, GA3, ABA, and proline were detected in shoots that were subjected to grafting and nano-silicon application compared to the control treatment. This study indicates that grafting and nano-silicon application hold potential as alternative techniques to mitigate salt stress in commercial tomato cultivars.

Resistance to bacterial spot (Xanthomonas gardneri) on foliage and fruit of commercial processing tomato cultivars

Bacterial spot of tomato (Xanthomonas gardneri Šutić) is an economically important disease of processing tomatoes in Ontario, Canada, resulting in premature defoliation and fruit damage. Breeding efforts for host resistance focus on assessments of foliar health as opposed to fruit health but anecdotal reports from industry suggest a poor relationship between fruit and foliar resistance. To investigate this, nine commercial cultivars were inoculated at the vegetative (foliar experiment) or reproductive (fruit experiment) stages in replicated field experiments from 2016 to 2018. In the foliar experiment, the standardized area under the disease progress curve (sAUDPC) for defoliation was 51% to 54% higher for ‘TSH18’ than ‘H9706’, ‘Hypeel 696’, and ‘H3406’, but equivalent to ‘CC337’. Fruit disease incidence was 49% and 47% lower for ‘CC337’ than ‘TSH18’ and ‘H9706’, but equivalent to ‘H3406’ and ‘Hypeel 696’. Fruit disease severity was 63% and 60% lower for ‘CC337’ than ‘H9706’and ‘H3406’, respectively, but equivalent to ‘TSH18’ and ‘Hypeel 696’. However, in the fruit experiment, fruit disease incidence was equivalent among cultivars, while the disease severity index for ‘H9706’ (3.4) was higher than ‘Hypeel 696’ (0.7). Furthermore, rank correlation analysis between sAUDPC and fruit disease variables failed to meet the criteria for a significant and strong relationship (r ≥ 0.8 or ≤ −0.8 and P ≤ 0.05). Additional research is needed to better understand the mechanisms of fruit infection by X. gardneri. In the meantime, scientists should consider the limitations of assessing only foliar damage as an evaluation method for bacterial spot management tools in tomato.

Effect of grafting on yield of commercial tomato cultivars grown under bacterial wilt (Ralstonia solanacearum) infested soil

Effect of grafting on yield of commercial tomato cultivars grown under bacterial wilt (Ralstonia solanacearum) infested soil

Italian Tomato Cultivars under Drought Stress Show Different Content of Bioactives in Pulp and Peel of Fruits.

Background: This study aims to evaluate the performance, in terms of accumulation of antioxidant compounds in fruits, of nine local and three commercial Italian tomato cultivars subjected to drought stress. The same local cultivars had been previously studied at morpho-physiological level. Methods: The present manuscript analyzes drought stress as a tool to increase the amount of secondary metabolites that can enhance fruit quality. Nutraceutical characterization of the fruits was performed by analyzing the content of antioxidants, phenols, flavonoids, lycopene, ascorbic acid (vitamin C), rutin, caffeic acid, and naringenin. At the same time, plant sensitivity to stress during the reproductive phase was monitored in terms of flower abscission, fruit drop, and seed germination. Results: Perina turns out to be the tomato cultivar with the best nutraceutical properties in the absence of stress while the Quarantino cultivar is so for flavonoid content (control plants) and lycopene and vitamin C content (stressed plants). Perina and Quarantino are the cultivars with the best response to drought and Perina has the highest concentrations of bioactives. Quarantino responds most effectively to stress in the reproductive phase. Conclusions: data confirm that drought stress increases bioactive production in some local cultivars of tomato, which produce higher quality fruits.

Modification of tomato breeding traits and plant hormone signaling by target-AID, the genome-editing system inducing efficient nucleotide substitution.

Target activation-induced cytidine deaminase (Target-AID), a novel CRISPR/Cas9-based genome-editing tool, confers the base-editing capability on the Cas9 genome-editing system. It involves the fusion of cytidine deaminase (CDA), which catalyzes cytidine (C) to uridine (U) substitutions, to the mutated nickase-type nCas9 or deactivated-type dCas9. To confirm and extend the applicability of the Target-AID genome-editing system in tomatoes (Solanum lycopersicum L.), we transformed the model tomato cultivar "Micro-Tom" and commercial tomato cultivars using this system by targeting SlDELLA, which encodes a negative regulator of the plant phytohormone gibberellic acid (GA) signaling pathway. We confirmed that the nucleotide substitutions were induced by the Target-AID system, and we isolated mutants showing high GA sensitivity in both "Micro-Tom" and the commercial cultivars. Moreover, by successfully applying this system to ETHYLENE RECEPTOR 1 (SlETR1) with single sgRNA targeting, double sgRNA targeting, as well as dual-targeting of both SlETR1 and SlETR2 with a single sgRNA, we demonstrated that the Target-AID genome-editing system is a promising tool for molecular breeding in tomato crops. This study highlights an important aspect of the scientific and agricultural potential of the combinatorial use of the Target-AID and other base-editing systems.

Tomato mottle mosaic virus: Characterization, resistance gene effectiveness, and quintuplex RT-PCR detection system

Tomato mottle mosaic virus (ToMMV), an economically important species of the genus Tobamovirus, causes significant loss in yield and quality of tomato fruits. Here, we identified the Shandong isolate of ToMMV (ToMMV-SD) collected from symptomatic tomato fruits in Weifang, Shandong Province of China. ToMMV-SD caused symptoms such as severe mosaic, mottling, and necrosis of tomato leaves, yellow spot and necrotic lesions on tomato fruits. The obtained full genome of ToMMV-SD was 6 399 nucleotides (accession number MW373515) and had the highest identity of 99.5% with that of isolate SC13-051 from the United States of America at the genomic level. The infectious clone of ToMMV-SD was constructed and induced clear mosaic and necrotic symptoms onto Nicotiana benthamiana leaves. Several commercial tomato cultivars, harboring Tm-22 resistance gene, and pepper cultivars, containing L resistance gene, were susceptible to ToMMV-SD. Plants of Solanum melongena (eggplant) and Brassica pekinensis (napa cabbage) showed mottling symptoms, while N. tabacum cv. Zhongyan 100 displayed latent infection. ToMMV-SD did not infect plants of N. tabacum cv. Xanthi NN, Brassica rapa ssp. chinensis (bok choy), Raphanus sativus (radish), Vigna unguiculata cv. Yuanzhong 28-2 (cowpea), or Tm-22 transgenic N. benthamiana. A quintuplex RT-PCR system differentiated ToMMV from tomato mosaic virus, tomato brown rugose fruit virus, tobacco mosaic virus, and tomato spotted wilt virus, with the threshold amount of 0.02 pg. These results highlight the threat posed by ToMMV to tomato and pepper cultivation and offer an efficient detection system for the simultaneous detection of four tobamoviruses and tomato spotted wilt virus infecting tomato plants in the field.

Novel Sources of Resistance to Fusarium oxysporum f. sp. lycopersici Race 3 Among Solanum pennellii Accessions

Fusarium wilt of tomato (Solanum lycopersicum), caused by fungal pathogen Fusarium oxysporum f. sp. lycopersici (Fol), is one of the most important diseases in tomato production. Three races of the pathogen are described, and race-specific resistance genes have been applied in commercial tomato cultivars for controlling the disease. Race 3 (Fol3) threatens tomato production in many regions around the world, and novel resistance resources could expand the diversity and durability of Fol resistance. The wild tomato species, Solanum pennellii, is reported to harbor broad resistance to Fol and was the source of two known Fol3 resistance genes. In this study, we evaluated 42 S. pennellii accessions for resistance to each fusarium wilt race. F1 plants, developed from crossing each accession with the Fol3 susceptible line ‘Suncoast’, were evaluated for Fol3 resistance, and BC1F1 plants were screened to determine the likelihood that Fol3 resistance was based on a novel locus (loci). Nearly all accessions showed resistance to Fol3, and many accessions were resistant to all races. Evaluation of F1 plants indicated a dominant resistance effect to Fol3 from most accessions. Genetic analysis indicated 24 accessions are expected to contain one or more novel Fol3 resistance loci other than an allele near the I-3 locus. To investigate genetic structure of the S. pennellii accessions used in this study, we genotyped all 42 accessions using genotyping by sequencing. Approximately 20% of the single nucleotide polymorphism (SNP) loci were heterozygous across accessions, likely due to the outcrossing nature of the species. Genetic structure analysis at 49,120 unique SNP loci across accessions identified small but obvious genetic differentiations.

Optimization of Agrobacterium-mediated transformation and regeneration for CRISPR/ Cas9 genome editing of commercial tomato cultivars

Tomato (Solanum lycopersicum) is the second most important horticultural crop worldwide that is widely used as a model plant in genetic manipulation of Solanaceae. CRISPR/Cas9 system has been successfully utilized in several studies for genome edition of model tomato cultivars. However, these genome editing systems should be also optimized for commercial tomato cultivar for direct application of genome editing in field conditions. In this study, we have optimized an Agrobacterium-mediated gene transfer and regeneration system for CRISPR/Cas9 genome editing in two commercial tomato cultivars for the first time. The effect of explant type, genotype, pre-transformation time, Agrobacterium concentration, infection time, and different co-culture periods of bacteria were evaluated to optimize the regeneration and transformation parameters. The highest regeneration capacity of 83% was obtained from cotyledons of Crocker incubated in a medium supplemented with BA (3 mg/L) and IAA (0.1 mg/L). The maximum transformation frequency was obtained by using the following parameters: cotyledon explants of commercial Crocker cultivar that were left for 2 days of pre-transformation incubation, infected with Agrobacterium for 10 min at a concentration of OD600 of 0.6 and co-cultivated with Agrobacterium cells for 48 h. CRISPR/Cas9 system was tested with two gRNAs targeting the phytoene desaturase gene. Fully albino and chimeric plants were successfully produced with optimized transformation and culture conditions in up to 71% of all regenerated plants. In the current study, we optimized the implementation of the CRISPR/Cas9 technique in a commercial tomato cultivar and our method will enable breeders to make necessary changes in traits of interest to improve tomato crops for commercial applications.

The synthetic elicitors 2,6-dichloro-isonicotinic acid (INA) and 2,4-dichloro-6-{(E)-[(3-methoxyphenyl)imino]methyl}phenol (DPMP) enhances tomato resistance against bacterial canker disease with different molecular mechanisms

Clavibacter michiganensis ssp. michiganensis (Cmm) causes bacterial canker disease in tomato and causes significant economic losses. Since there are no commercial tomato cultivars fully resistant against Cmm, alternative approaches need to be applied for plant protection. 2,6-dichloro-isonicotinic acid (INA) and 2,4-dichloro-6-{(E)-[(3-methoxyphenyl)imino]methyl}phenol (DPMP) are two of the potent synthetic elicitors that induce plant immune responses, and protect plants against several diseases or reduce the severity of such diseases. The objective of this study was, to determine the effects of INA and DPMP application on tolerance to Cmm in tomato for the first time at disease incidence and molecular levels. 100 μM INA and 10 μM DPMP were applied to plants two days before Cmm inoculation. Disease severity, lesion lengths, and impact of Cmm on plant growth were determined. Relative expression of some marker defense genes was determined. According to the results, INA and DPMP applied plants had 42% and 30% reduced lesion lengths. Gene expression analyses indicated that while both synthetic elicitors reduced the disease severity of the Cmm, INA and DPMP induced molecular defense mechanisms differently. While both are related to the Salicylic acid defense pathway, INA induced gene expressions of PR-5, WRKY33b, PAL, and WRKY70, however, DPMP induced PR-1 and WRKY70. Taken together, our results indicated that both INA and DPMP reduced the severity of the disease with different mode-of-action and DPMP has reduced the severity of disease at a much lower concentration compared to INA.

Physiological and Biochemical Responses of Tomato Plants Grafted onto Solanum pennellii and Solanum peruvianum under Water-Deficit Conditions.

Grafting using suitable rootstocks mitigates the adverse effects caused by environmental stresses such as water deficit in the tomato crop. Solanum pennellii and Solanum peruvianum, the wild relatives of tomato, are used as rootstocks due to their tolerance to water deficit and soil-borne diseases. This study focused on evaluating physiological and biochemical responses of tomato plants grafted onto S. pennellii and S. peruvianum rootstocks during water deficit. The commercial tomato cultivar ‘HM 1823’ (HM) either self-grafted (HM/HM) or grafted onto S. pennellii (HM/PN), S. peruvianum (HM/PR), and ‘Multifort’ (HM/MU) rootstocks were subjected to water-deficit stress by withholding irrigation for eight days. The performance of the grafted plants under water deficit was evaluated using physiological and biochemical parameters in vegetative tissues of the grafted plants. Plants grafted using S. pennellii (PN) and S. peruvianum (PR) rootstocks showed higher values of water potential (Ψw), relative water content (RWC), net photosynthetic rate (A), and leaf water use efficiencies (WUE) compared to HM, HM/HM, and HM/MU. Plants grafted onto tomato wild relatives showed the lowest malondialdehyde (MDA) and proline content. This study demonstrated that the rootstocks of wild tomato relatives reduced the effect of water deficit to a greater extent through better physiological, metabolic, and biochemical adjustments than self-grafting plants.

Effects of the sliaa9 Mutation on Shoot Elongation Growth of Tomato Cultivars.

Tomato INDOLE-3-ACETIC ACID9 (SlIAA9) is a transcriptional repressor in auxin signal transduction, and SlIAA9 knockout tomato plants develop parthenocarpic fruits without fertilization. We generated sliaa9 mutants with parthenocarpy in several commercial tomato cultivars (Moneymaker, Rio Grande, and Ailsa Craig) using CRISPR-Cas9, and null-segregant lines in the T1 generation were isolated by self-pollination, which was confirmed by PCR and Southern blot analysis. We then estimated shoot growth phenotypes of the mutant plants under different light (low and normal) conditions. The shoot length of sliaa9 plants in Moneymaker and Rio Grande was smaller than those of wild-type cultivars in low light conditions, whereas there was not clear difference between the mutant of Ailsa Craig and the wild-type under both light conditions. Furthermore, young seedlings in Rio Grande exhibited shade avoidance response in hypocotyl growth, in which the hypocotyl lengths were increased in low light conditions, and sliaa9 mutant seedlings of Ailsa Craig exhibited enhanced responses in this phenotype. Fruit production and growth rates were similar among the sliaa9 mutant tomato cultivars. These results suggest that control mechanisms involved in the interaction of AUX/IAA9 and lights condition in elongation growth differ among commercial tomato cultivars.

Effects of para-aminobenzoic acid on bacterial speck symptom development and Pseudomonas syringae pv. tomato populations in tomato leaves

Para-aminobenzoic (PABA) is reported to induce resistance against a range of plant pathogens in different crops in a salicylic acid-dependent manner. However, factors affecting its efficacy are not well understood. Foliar PABA applications on tomato seedlings reduced lesion incidence caused by Pseudomonas syringae pv. tomato (Pst) in a dose-dependent manner in distal leaves up to 18 mM under controlled environment conditions, but only three out of six commercial processing tomato cultivars tested showed a response to PABA. Leaves in direct contact with 9 and 18 mM PABA of both PABA-responsive and PABA-nonresponsive cultivars showed phytotoxicity. In a PABA-responsive cultivar, one, two and three PABA applications were equally effective at reducing lesion incidence in distal leaves, but the duration of control only persisted for approximately 7 days. Although PABA application reduced lesion incidence in distal leaves, the Pst population in leaves was unaffected. Lesions on PABA-treated plants were larger than nontreated plants, and thus the proportion of leaf surface area with lesions was unaffected by PABA treatment. In in vitro assays, 18 and 72 mM PABA produced zones of inhibition against Pst 15 and 50% larger than the ethanol control, demonstrating direct antimicrobial effects of PABA. PABA application did not affect symptom development in a mixed infection of Pst or Xanthomonas spp. in one field experiment with a PABA-responsive cultivar. Further research is needed to understand why PABA was unsuccessful in the field before it is to be used as a practical disease management tool for foliar bacterial diseases of tomato.

Tissue-specific elucidation of lycopene metabolism in commercial tomato fruit cultivars during ripening

Lycopene is a naturally occurring chemical compound that gives fruits and vegetables a red/orange color. As an intermediate metabolite of β-carotene biosynthesis, lycopene represents one of the major carotenoids. This work studies the gene expression pattern of lycopene biosynthesis/catabolism transcripts and the accumulation pattern of lycopene/β-carotene/chlorophyll contents at three developmental stages and three tissues in five widely consumed, commercial tomato cultivars (cvs. ‘Cherry Ninolino F1’, ‘Elpida F1’, ‘Daphne F1’, ‘Eliseo Plum F1’, and ‘Oxheart’). These contents were correlated with in vitro antioxidant activity. Higher levels of lycopene were observed in the peel than other tissues and in the fully ripe stage, with ‘Oxheart’ displaying the highest content. Differential regulation of lycopene biosynthetic genes (SlZDS and SlCRTISO) was demonstrated in all cultivars. Interestingly, a gene implicated in lycopene catabolism (SlLCYB) demonstrated a general induction in the tested tissues. High lycopene content correlates with significant induction of both SlZDS and SlCRTISO in ‘Oxheart’. Significantly increased antioxidant activity was observed in the peel of ‘Cherry Ninolino F1’ and ‘Elpida F1’ cultivars compared with other tested tissues across all cultivars. The exploration of lycopene activity in different cultivars and the consumption of ripe tomatoes including the peel could be useful for the protection of human health.

Resistance to Bemisia tabaci (Hemiptera: Aleyrodidae) Mediterranean (Q Biotype) in Landrace and Wild Tomato Populations from Mexico

Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) Mediterranean (Q biotype) is a major pest of tomato (Solanum lycopersicum L.; Solanaceae) globally. To our knowledge, no whitefly resistant cultivar has been released commercially, and breeding programs are hampered by the lack of resistance sources to this insect which are related closely to the cultivated tomato. Two non-free-choice experiments on B. tabaci with 22 landrace (S. lycopersicum) and wild tomato (S. lycopersicum var. ‘cerasiforme') populations from Mexico were performed to find sources of antibiosis resistance to this insect. Plants were infested with 20 insects per 1 leaflet of each plant using plastic micro-cages. In both assays, the number of adults and eggs were counted at 4 d post infestation, the number of nymphs (12 d post infestation), new adults, and non-glandular trichomes at 28 d post infestation. The highest B. tabaci resistance was detected in the UTC-SV13 population followed by UTC-SV12, UTC-SV1, and UTC-SV3 with a range of 15.0 to 20.0 dead adults, 0.0 to 16.5 eggs, 0.0 to 12.6 nymphs, 0.0 to 9.7 new adults per leaflet, and with a reproduction index of 0.0 to 21.7. Ten populations showed an intermediate level of resistance significantly lower in the number of dead adults, eggs, nymphs, new adults, and reproduction index compared to the commercial cultivar (‘Bonny Best') used as the standard. The remaining 8 genotypes and the commercial cultivar were fully susceptible to B. tabaci. The number of non-glandular trichomes correlated significantly with the number of eggs, nymphs, and new adults emerging from the infested plants, suggesting that the density of non-glandular trichomes is favorable for whitefly reproduction. Those genotypes with moderate to high levels of resistance to B. tabaci are potential candidates for developing commercial tomato cultivars with some resistance levels to this insect.

Mutations Found in the Asc1 Gene That Confer Susceptibility to the AAL-Toxin in Ancestral Tomatoes from Peru and Mexico.

Tomato susceptibility/resistance to stem canker disease caused by Alternaria alternata f. sp. lycopersici and its pathogenic factor AAL-toxin is determined by the presence of the Asc1 gene. Several cultivars of commercial tomato (Solanum lycopersicum var. lycopersicum, SLL) are reported to have a mutation in Asc1, resulting in their susceptibility to AAL-toxin. We evaluated 119 ancestral tomato accessions including S. pimpinellifolium (SP), S. lycopersicum var. cerasiforme (SLC) and S. lycopersicum var. lycopersicum “jitomate criollo” (SLJ) for AAL-toxin susceptibility. Three accessions, SP PER018805, SLC PER018894, and SLJ M5-3, were susceptible to AAL-toxin. SLC PER018894 and SLJ M5-3 had a two-nucleotide deletion (nt 854_855del) in Asc1 identical to that found in SLL cv. Aichi-first. Another mutation (nt 931_932insT) that may confer AAL-toxin susceptibility was identified in SP PER018805. In the phylogenetic tree based on the 18 COSII sequences, a clade (S3) is composed of SP, including the AAL-toxin susceptible PER018805, and SLC. AAL-toxin susceptible SLC PER018894 and SLJ M5-3 were in Clade S2 with SLL cultivars. As SLC is thought to be the ancestor of SLL, and SLJ is an intermediate tomato between SLC and SLL, Asc1s with/without the mutation seem to have been inherited throughout the history of tomato domestication and breeding.

Comparing the Flavor Characteristics of 71 Tomato (Solanum lycopersicum) Accessions in Central Shaanxi.

Flavor is an important quality of mature tomato fruits. Compared with heirloom tomatoes, modern commercial tomato cultivars are considerably less flavorful. This study aimed to compare the flavor of 71 tomato accessions (8 pink cherry, PC; 11 red cherry, RC; 15 pink large-fruited, PL; and 37 red large-fruited, RL) using hedonism scores and odor activity values. Taste compounds were detected using high-performance liquid chromatography. Volatiles were detected using gas chromatography–olfactometry–mass spectrometry. The flavor of tomato accessions can be evaluated using the DTOPSIS analysis method. According to the results of DTOPSIS analysis, 71 tomato accessions can be divided into 4 classes. Tomato accessions PL11, PC4, PC2, PC8, RL35, RC6, and RC10 had better flavor; accessions PC4, PC8, RC10, RL2, and RL35 had better tomato taste; and accessions PL11, PC2, and RC6 had better tomato odor. The concentrations of total soluble solids, fructose, glucose, and citric acid were shown to positively contribute to tomato taste. Tomato odor was mainly derived from 15 volatiles, namely, 1-hexanol, (Z)-3-hexen-1-ol, hexanal, (E)-2-hexenal, (E)-2-heptenal, (E)-2-octenal, (E,E)-2,4-decadienal, (Z)-3,7-dimethyl-2,6-octadieal, 2,6,6-timethyl-1-cyclohexene-1-carboxaldehyde, (2E)-3-(3-pentyl-2-oxiranyl)acrylaldehyde, 6-methyl-5-hepten-2-one, (E)-6,10-dimetyl-5,9-undecadien-2-one, methyl salicylate, 4-allyl-2-methoxyphenol, and 2-isobutylthiazole. Significant positive correlations (P < 0.05) were detected between the compound concentrations and flavor scores. The above-mentioned compounds can be used as parameters for the evaluation of flavor characteristics and as potential targets to improve the flavor quality of tomato varieties.

Tomato Brown Rugose Fruit Virus (ToBRFV): A Potential Threat for Tomato Production in Florida

Tobamoviruses are mechanically transmitted plant viruses that cause severe economic damage to vegetable and ornamental crops in Florida and worldwide. While certain tomato cultivars have genetic resistance to the most common tobamoviruses, no commercial tomato cultivars are resistant to tomato brown rugose fruit virus (ToBRFV), a recently described tobamovirus that also infects pepper and eggplant. It is currently unknown how ToBRFV may affect tomato production in Florida. This new 5-page publication of the UF/IFAS Plant Pathology Department describes symptoms of the virus, how it is different from other tobamoviruses, and how it is transmitted, as well as what to do if you think you have ToBRFV in your field. Written by Ozgur Batuman, Salih Yilmaz, Pamela Roberts, Eugene McAvoy, Samuel Hutton, Kishore Dey, and Scott Adkins.https://edis.ifas.ufl.edu/pp360

Development of a Mutant Population of Micro-Tom Tomato Using Gamma-Irradiation

Knowledge of genetic resources is essential for breeders to create new crop varieties with improved characteristics. In this respect, mutant populations may conveniently provide a powerful tool for identifying new functional genes. Therefore, we used the Micro-Tom tomato variety, which has a reduced size and a relatively short life-cycle compared to other commercial tomato cultivars, to construct a mutant population using gamma-ray radiation as a mutagen. To determine the optimal mutagenic intensity of gamma rays for tomato, dry seeds of Micro-Tom were irradiated with gamma-ray intensities from 0 to 1000 gray (Gy) with increments of 100 Gy. The germination rate of mutagenized seeds (M1 seeds) on MS media was not affected by the tested gamma-ray intensity range. However, seedling growth was severely reduced with increasing irradiation. Seedling growth rate at eight days after germination showed that the median gamma-ray doses for hypocotyl and root elongation were 600 and 300-400 Gy, respectively. The survival test for 300, 400, and 500 Gy-treated M1 seeds showed that survival rates significantly decreased with increasing irradiation. The survival rate of 400 Gy-radiated seeds was 48%, while that of 500 Gy-radiated seeds was only 25%, compared with the control treatment. Therefore, we concluded that gamma-ray irradiation at 300-400 Gy is best for tomato mutagenesis. To find new mutants, M2 seeds produced by M1 plants were grown. We found several mutants, including plants with varying cotyledon number, variegated or red leaves, and green hypocotyls.

Cultivar Variation in Tomato Seed Coat Permeability Is an Important Determinant of Jasmonic Acid Elicited Defenses Against Western Flower Thrips.

Induction of defenses is one of the most widely accepted eco-friendly approaches for management of pests and diseases. Seeds are receptive to resistance-inducing chemicals and could offer broad-spectrum protection at the early stages of development. However, seed treatment with elicitors has previously been shown to differentially influence induced defense responses among cultivars and thus, could hamper commercial exploitation. In this context, the objective of the present study was to evaluate the genotype-dependent ability of jasmonic acid (JA) to induce resistance against western flower thrips (WFT) at the seed stage. We examined the variation in inducibility of resistance in eight commercial tomato cultivars. Causal factors accounting for discrepancies in JA-induced responses at the seed stage were phenotypically and biochemically evaluated. Seed receptivity to exogenous JA appeared to be cultivar dependent. Thrips associated silver damage was only reduced in JA seed-treated plants of cultivar Carousel. Enhancement of resistance, was not associated with activation of defense-related traits such as polyphenol oxidase activity (PPO), trichomes or volatiles. Sulfuric acid scarification, prior to JA seed incubation, significantly augmented the embryonic responsiveness to JA in cv. Moneymaker without an adverse effect on growth. Hence, these results support the hypothesis that seed coat permeability is a key factor for successfully inducing JA mediated thrips defenses. The outcome of our study is of translational value as it creates opportunities for the seed industry to perform pre-treatments on non-responsive cultivars as well as for tomato breeding programs to select for genetic traits that affect seed permeability.