Cultivated Tomato Varieties Research Articles

The effector-triggered immunity landscape of tomato against Pseudomonas syringae

Tomato (Solanum lycopersicum) is one of the world’s most important food crops, and as such, its production needs to be protected from infectious diseases that can significantly reduce yield and quality. Here, we survey the effector-triggered immunity (ETI) landscape of tomato against the bacterial pathogen Pseudomonas syringae. We perform comprehensive ETI screens in five cultivated tomato varieties and two wild relatives, as well as an immunodiversity screen on a collection of 149 tomato varieties that includes both wild and cultivated varieties. The screens reveal a tomato ETI landscape that is more limited than what was previously found in the model plant Arabidopsis thaliana. We also demonstrate that ETI eliciting effectors can protect tomato against P. syringae infection when the effector is delivered by a non-virulent strain either prior to or simultaneously with a virulent strain. Overall, our findings provide a snapshot of the ETI landscape of tomatoes and demonstrate that ETI can be used as a biocontrol treatment to protect crop plants.

Screening of some commonly cultivated tomato varieties against Fusarium wilt in Jama’are, Bauchi State, Nigeria

Fusarium wilt disease of tomato is caused by Fusarium oxysporum f.sp. lycopersici and is a limiting factor to tomato production in Nigeria. This research was conducted to assess the effect of Fusarium oxysporum on some tomato varieties cultivated in Jama’are, Bauchi state. The objectives of this research work were to isolate and identify pathogen (Fusarium oxysporum) from the soil, to determine the incidence and severity of Fusarium wilt on different varieties of Tomato grown in Jama’are, and to determine the most resistance variety among four different varieties. The experiment was laid in a Completely Randomized design (CRD) with four replications. The four tomato varieties (Roma Savanna, Rio Grande, UC82B and Tropimech) were inoculated at the root region by making shallow groove around the base of the plant in the root region and placing 3 g mycelia plug of 7 days old pure culture of F. oxysporum face-down close to the root of the seedling and covered with soil. At two weeks intervals after treatments the seedlings were then observed for symptoms of wilt infection. Data on disease incidence (%), were collected based on observation after which they were analyzed using Analysis of Variance (ANOVA) test. The Disease Incidence Percentage for Roma Savanna, Rio Grande, UC28B and Tropimech were evaluated to be 51.6%, 18.2 %,38.4 % and 43.3 % respectively while the Disease Severity Percentage were 72.1%, 24.8%, 40.9% and 62.3% respectively. The findings of this research reveals that; there is a significant effect of F. oxysporum on the tomato varieties, all the varieties were severely infected to some degree, and that of all species, Roma savanna was moderately resistant to F. oxysporum to some degree. This agrees with other findings in the literature, as Fusarium oxysporum affects different varieties of tomato at different growth stages. Also, it was observed that screening excises involving selecting of non-infected seedlings with Fusarium species and other fungi should be done prior to transplanting.

Functional diversification of miR172 isoforms in tomato under abiotic stress

Plant gene families have expanded many folds as opposed to animals to compensate for being sessile as well as having unique features like ability to photosynthesise. While different protein families are well characterised in plants, similar knowledge on miRNA families is still in its infancy. The MIR172 family plays important role in various plant development processes including vegetative to reproductive phase change, floral patterning, nodulation, and fruit ripening as well as also in response to different environmental cues. However, in-depth analysis of this family in tomato (Solanum lycopersicum) is limited. In this study, we identified four new MIR172 loci (Sly-MIR172a1/a2/e/f) and two new isoforms, other than those reported at the miRBase repository. The MIR172 family has expanded by segmental duplication events and is conserved between the wild (S. pennellii and S. pimpinellifolium) and the cultivated tomato varieties. However, phylogenetic analysis showed that S. pennellii formed the most divergent member within each clade and S. pimpinellifolium is closer to the cultivated varieties. Additionally, investigations in 42 plant species highlighted that miR172a/b is the most abundant form in the plant kingdom. In addition to the classical target Apetala2 (AP2), degradome analysis identified SEC14p-like phosphatidylinositol transfer family protein (SEC14p) as a novel target of Sly-miR172 that was validated using precursor:effector and target:reporter transient assays. Further, we report dual mode of Sly-miR172-mediated silencing of targets Sly-AP2 and Sly-SEC14p by post-transcriptional transcript cleavage as well as translational repression. Different members of Sly-MIR172s:Sly-AP2s and Sly-MIR172s:Sly-SEC14p exhibit inverse expression correlation in response to different abiotic stresses, suggesting their role in stress response. Functional investigation of MIR172 showed that tomato plants performed better in different abiotic stresses (heat, drought, and salt) upon MIR172 overexpression or target knock-down by virus-induced-gene-silencing. Conversely, when miRNA is chelated using short-tandem-target-mimic, the plants exhibit sensitivity to these stresses. Thus, Sly-miR172 acts as a positive regulator while its targets Sly-AP2a and Sly-SEC14p as negative regulators of different abiotic stresses.

Solanum elaeagnifolium and S. rostratum as potential hosts of the tomato brown rugose fruit virus.

Invasive weeds cause significant crop yield and economic losses in agriculture. The highest indirect impact may be attributed to the role of invasive weeds as virus reservoirs within commercial growing areas. The new tobamovirus tomato brown rugose fruit virus (ToBRFV), first identified in the Middle East, overcame the Tm-22 resistance allele of cultivated tomato varieties and caused severe damage to crops. In this study, we determined the role of invasive weed species as potential hosts of ToBRFV and a mild strain of pepino mosaic virus (PepMV-IL). Of newly tested weed species, only the invasive species Solanum elaeagnifolium and S. rostratum, sap inoculated with ToBRFV, were susceptible to ToBRFV infection. S. rostratum was also susceptible to PepMV-IL infection. No phenotype was observed on ToBRFV-infected S. elaeagnifolium grown in the wild or following ToBRFV sap inoculation. S. rostratum plants inoculated with ToBRFV contained a high ToBRFV titer compared to ToBRFV-infected S. elaeagnifolium plants. Mixed infection with ToBRFV and PepMV-IL of S. rostratum plants, as well as S. nigrum plants (a known host of ToBRFV and PepMV), displayed synergism between the two viruses, manifested by increasing PepMV-IL levels. Additionally, when inoculated with either ToBRFV or PepMV-IL, disease symptoms were apparent in S. rostratum plants and the symptoms were exacerbated upon mixed infections with both viruses. In a bioassay, ToBRFV-inoculated S. elaeagnifolium, S. rostratum and S. nigrum plants infected tomato plants harboring the Tm-22 resistant allele with ToBRFV. The distribution and abundance of these Solanaceae species increase the risks of virus transmission between species.

Morphological and biochemical resistance to Helicoverpa armigera (Lepidoptera: Noctuidae) in tomato

Tomato (Solanum lycopersicum L.) production in the tropics suffers from depredation by the tomato fruit borer, Helicoverpa armigera (Hübner), causing severe economic losses. Development of H. armigera resistant tomato cultivars in India is very limited due to lack of good sources of resistance for breeding. Use of insect resistant cultivars could reduce indiscriminate use of insecticides. A total of twenty-two tomato genotypes were assessed under field conditions for resistance to H. armigera during 2017–18 and 2018–19. Morphological and biochemical factors associated with the expression of resistance to this pest in tomato were estimated and considered as potential markers of resistance. The six genotypes, Kashi Sharad, Pb Barkha-1, DVRT-1, Pb Barkha-2, DVRT-2 and Pusa Rohit, were least infested by H. armigera with fruit weight loss ranging from 4.63 to 8.71 percent and were classified as resistant. Expression of resistance was associated with higher trichome density on leaves and calyxes, higher fruit pericarp thickness, higher phenol content in leaves and fruits, and lower soluble sugar and protein contents in leaves and fruits. Resistant genotypes of tomato with these factors may be used as sources of resistance in future breeding programs to enhance resistance to H. armigera in commercially cultivated tomato varieties.

Loss of salt tolerance during tomato domestication conferred by variation in a Na+ /K+ transporter.

Domestication has resulted in reduced salt tolerance in tomato. To identify the genetic components causing this deficiency, we performed a genome-wide association study (GWAS) for root Na+ /K+ ratio in a population consisting of 369 tomato accessions with large natural variations. The most significant variations associated with root Na+ /K+ ratio were identified within the gene SlHAK20 encoding a member of the clade IV HAK/KUP/KT transporters. We further found that SlHAK20 transports Na+ and K+ and regulates Na+ and K+ homeostasis under salt stress conditions. A variation in the coding sequence of SlHAK20 was found to be the causative variant associated with Na+ /K+ ratio and confer salt tolerance in tomato. Knockout mutations in tomato SlHAK20 and the rice homologous genes resulted in hypersensitivity to salt stress. Together, our study uncovered a previously unknown molecular mechanism of salt tolerance responsible for the deficiency in salt tolerance in cultivated tomato varieties. Our findings provide critical information for molecular breeding to improve salt tolerance in tomato and other crops.

Antioxidative response of tomato genotypes to late blight infection

Wild species are widely used as potential sources of resistance of tomato to late blight (LB) (causal agent Phytophthora infestans). The biochemical response of wild and cultivated tomato genotypes with different levels of resistance to P. infestans was assessed through the total phenolic and flavonoid content and antioxidative capacity. In total, six genotypes were included in the research ? three cultivated tomato varieties and three wild species. The wild genotypes Solanum pimpinellifolium S 220 and Solanum habrochaites had a significantly lower infection rate compared to the other tested genotypes. After disease assessment on the leaves, biochemical analyses were performed. Grouping of the wild accessions according to principal component analysis (PCA) analysis indicated similar reaction to LB infection. Furthermore, late blight trait is closer to cultivated genotypes. Although the phenolics and flavonoids have high importance in the reaction of tomato plants to late blight infection, these traits are not closely related to wild species and the disease. According to this study, the antioxidative tests that indicate a response of wild species to late blight infection are total antioxidant activity (TAA), ferric-reducing antioxidant power (FRAP) and radical cation scavenging activity (ABTS).

Resistance of Certain Wild Tomato (Solanum spp.) Accessions to Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) Based on Choice and No-Choice Bioassays

The development of cultivars resistant to tomato fruit borer, Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae), are very limited in Pakistan and other parts of the world because of the lack of good sources of resistance for breeding. Insect-resistant cultivars would be beneficial to decrease the indiscriminate use of pesticides on tomato crops. Seven wild tomato accessions, including Solanum galapagense Darwin & Peralta, Solanum pimpinellifolium L., Solanum cheesmaniae (Riley) Fosberg, and a susceptible check (Solanum lycopersicum L.) (all Solanaceae), were evaluated for resistance to tomato fruit borer based on oviposition preference and feeding in the choice and no-choice bioassays. In the oviposition preference test, S. cheesmaniae (VI037240) and S. galapagense (VI063174) recorded the lowest mean number of eggs, 4.40 and 7.00 per plant, respectively. The highest mortality of H. armigera larvae (90%) was recorded on S. pimpinellifolium (VI030462) compared to the susceptible check (15%). The lowest pupal weight (89.67 mg) resulted from S. galapagense (VI063174), but it was not significantly different from the S. pimpinellifolium and S. cheesmaniae accessions. Among all tested accessions, S. pimpinellifolium (VI030462) was found to be highly resistant to H. armigera based on larval mortality, pupal weight, and pupation percentage. These results can pave the way to enhance the resistance in cultivated tomato varieties to control this notorious fruit borer. Resumen El desarrollo de cultivares resistentes al barrenador de la fruta del tomate, Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae), es muy limitado en Pakistan y otras partes del mundo debido a la falta de buenas fuentes de variedades resistentes para el fitomejoramiento. Los cultivares resistentes a los insectos serian beneficiosos para disminuir el uso indiscriminado de pesticidas en los cultivos de tomate. Se evaluaron siete accesiones de tomates silvestres, incluyendo Solanum galapagense Darwin y Peralta, Solanum pimpinellifolium L., Solanum cheesmaniae (Riley) Fosberg y un control susceptible (Solanum lycopersicum L.) (todas Solanaceae), para determinar la resistencia al barrenador de la fruta del tomate en base de la preferencia de oviposicion y alimentacion en bioensayos de eleccion y no eleccion. En la prueba de preferencia de oviposicion, S. cheesmaniae (VI037240) y S. galapagense (VI063174) recibieron el numero promedio mas bajo de huevos, 4.40 y 7.00 por planta, respectivamente, en bioensayos de eleccion y de no eleccion. La mortalidad mas alta de larvas de H. armigera (90%) se registro en S. pimpinellifolium (VI030462) en comparacion con el control susceptible (15%). El peso pupal mas bajo (89,67 mg) resulto de S. galapagense (VI063174), pero no fue significativamente diferente de las accesiones de S. pimpinellifolium y S. cheesmaniae. Entre todas las accesiones analizadas, se encontro que S. pimpinellifolium (VI030462) es altamente resistente a H. armigera en funcion de la mortalidad de las larvas, el peso de las pupas y el porcentaje de pupacion. Estos resultados pueden ser un camino para mejorar la resistencia en las variedades de tomate cultivadas para controlar este notorio perforador de frutas. Key Words: tomato fruitworm; wild species; resistance; oviposition; antibiosis; mortality View this article in BioOne

Olfactory responses of adult Potato Tuber Moth, Phthorimaea operculella (Zeller) measured by attraction relative to the tomato leaf volatiles

Abstract The potato tuber moth (PTM) is an oligophagous herbivore and a severe pest of solanaceous crops in many countries of the world. Previously, we reported host expansion and damage potential of PTM on tomato, a congeneric crop of potato. Here we tested adult olfactory behaviour of PTM to leaves of five different cultivated tomato varieties including Moneymaker, Campari, Ailsa craig, LA3475 and E6203, and one wild species, Solanum pimpinellifolium. Tomato leaf hydro-distilled oils of Moneymaker, Campari, Ailsa craig, S. pimpinellifolium and E6203 showed strong attractiveness and LA3475 exhibited repulsiveness for adult PTM of both sexes in two-armed bioassays. Volatiles of Moneymaker, Campari, Ailsa Craig, S. pimpinellifolium and E6203 showed attractiveness for mated adult PTM of both sexes (> 70%). The extracted oil of all tomato leaves contains monoterpenes, sesquiterpenes, diterpenes and C6 alcohols as well as other components. Phytol is one of the common and major compounds in all tomato varieties. Phytol showed weak attractiveness: 60.8–63.6% and 57.6–60.6% for male and female PTM, respectively when tested at concentrations of 0.1–10 mg/mL. Therefore, the attractiveness of tomato leaf volatiles might be due to synergistic effects of plant volatile mixtures. Identification PTM attractant volatile in tomato leaf is important in its control in environmentally friendly manner.

Suitability of tomato leaves for larval development of Potato Tuber Moth, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae)

AbstractThe potato tuber moth (PTM) is an important pest of the potato plant and its tuber. With the expansion of its geographic range, the PTM could be potential threat to the tomato (Solanum lycopersicum L.), a congeneric species of the potato. To assess that risk, we tested larval feeding and development of PTM on leaves of five cultivated tomato varieties namely Moneymaker, Campari, Ailsa Craig, LA3475, E6203 and one wild tomato variety S. pimpinellifolium. PTM larvae accepted all tested plant leaves and developed into adults. Larval development was fastest on the Ailsa Craig variety. Pupae developed fastest on the Moneymaker variety and slowest on LA3475. Host acceptance and survival were highest on Ailsa Craig and lowest on LA3475. The significantly highest male proportion occurred on LA3475 variety. The study showed that PTM could be a potential threat to tomato cultivation which is rapidly increasing in temperate regions owing to climate change.

Morphological Characterization of Root System Architecture in Diverse Tomato Genotypes during Early Growth.

Plant roots exploit morphological plasticity to adapt and respond to different soil environments. We characterized the root system architecture of nine wild tomato species and four cultivated tomato (Solanum lycopersicum L.) varieties during early growth in a controlled environment. Additionally, the root system architecture of six near-isogenic lines from the tomato ‘Micro-Tom’ mutant collection was also studied. These lines were affected in key genes of ethylene, abscisic acid, and anthocyanin pathways. We found extensive differences between the studied lines for a number of meaningful morphological traits, such as lateral root distribution, lateral root length or adventitious root development, which might represent adaptations to local soil conditions during speciation and subsequent domestication. Taken together, our results provide a general quantitative framework for comparing root system architecture in tomato seedlings and other related species.

Exploring morphological variation in tomato (Solanum lycopersicum): A combined study of disease resistance, genetic divergence and association of characters

Abstract Genetic variation of quantitative traits is a prevalent characteristic among cultivated tomato varieties. Twenty tomato genotypes comprising indigenous varieties and commercial cultivars, cultured in the Western Region of Cameroon were evaluated using fourteen quantitative traits for disease resistance, phenotypic divergence and heritability estimates. The experiment was carried out using a randomized completed blocks design with three replications. Data collections were disease characteristics, plant development features and yield attributes. The analysis of variance revealed significant variation among genotypes for all the experimental quantitative traits. Hybrid varieties had significantly more fruit yield (1066.00 g/plant), single fruit weight (57.28 g), fruit diameter (4.47 cm) and pericarp thickness (0.54 cm) compared to standard and indigenous varieties. These indigenous varieties were significantly more resistant to late blight, alternaria leaf spot and viral diseases. They also had significantly higher collar diameter (16.30 mm), number of primary branches per plant (8.45), number of fruit per plant (31.58) and plant height (88.33 cm) compared to standard and hybrid plants. The genotype local 2 was the third most productive (1576.39 g / plant) after Rio Semagri (1984.80 g/plant) and Sakato F1 (1691.69 g/plant). Heritability and genetic advance estimates were high for twelve of the fourteen studied quantitative traits. Fruit yield showed significant positive correlations with single fruit weight and number of fruit per plant. However, significant negative correlation was found between fruit yield and time to 50 % flowering, 50 % fruiting, 50 % maturity and viral disease. The first three and the first four components in the principal component analysis explained, respectively, 77.85 % and 88.38 % of the total variation observed among genotypes. The first component determined 41.42 % of the total variation, dominated by the collar diameter, the number of primary branches per plant and plant height. This study clearly indicated that indigenous varieties are the most disease resistant genotypes and are having substantial fruit yield (945.30 g/plant) similar to standard varieties and at a touching distance to hybrid cultivars.

Exploring morphological variation in tomato (Solanum lycopersicum): A combined study of disease resistance, genetic divergence and association of characters

Abstract Genetic variation of quantitative traits is a prevalent characteristic among cultivated tomato varieties. Twenty tomato genotypes comprising indigenous varieties and commercial cultivars, cultured in the Western Region of Cameroon were evaluated using fourteen quantitative traits for disease resistance, phenotypic divergence and heritability estimates. The experiment was carried out using a randomized completed blocks design with three replications. Data collections were disease characteristics, plant development features and yield attributes. The analysis of variance revealed significant variation among genotypes for all the experimental quantitative traits. Hybrid varieties had significantly more fruit yield (1066.00 g/plant), single fruit weight (57.28 g), fruit diameter (4.47 cm) and pericarp thickness (0.54 cm) compared to standard and indigenous varieties. These indigenous varieties were significantly more resistant to late blight, alternaria leaf spot and viral diseases. They also had significantly higher collar diameter (16.30 mm), number of primary branches per plant (8.45), number of fruit per plant (31.58) and plant height (88.33 cm) compared to standard and hybrid plants. The genotype local 2 was the third most productive (1576.39 g / plant) after Rio Semagri (1984.80 g/plant) and Sakato F1 (1691.69 g/plant). Heritability and genetic advance estimates were high for twelve of the fourteen studied quantitative traits. Fruit yield showed significant positive correlations with single fruit weight and number of fruit per plant. However, significant negative correlation was found between fruit yield and time to 50 % flowering, 50 % fruiting, 50 % maturity and viral disease. The first three and the first four components in the principal component analysis explained, respectively, 77.85 % and 88.38 % of the total variation observed among genotypes. The first component determined 41.42 % of the total variation, dominated by the collar diameter, the number of primary branches per plant and plant height. This study clearly indicated that indigenous varieties are the most disease resistant genotypes and are having substantial fruit yield (945.30 g/plant) similar to standard varieties and at a touching distance to hybrid cultivars.

Twenty Years of Tomato Breeding at EPSO-UMH: Transfer Resistance from Wild Types to Local Landraces—From the First Molecular Markers to Genotyping by Sequencing (GBS)

In 1998, the plant breeding team at the School of Engineering of Orihuela (EPSO), part of the Miguel Hernández University (UMH) in Elche, commenced a tomato breeding program. Marker-assisted selection and backcrossing were used to simultaneously introduce three genes (Tm-2a, Ty-1, and Sw-5) that confer resistance to relevant viruses, such as tomato mosaic virus (ToMV), tomato yellow curl virus (TYLCV), and tomato spotted wilt virus (TSWV), to traditional varieties of local tomatoes, specifically the “Muchamiel” and the “De la pera” types. After each backcross, cleaved amplified polymorphic sequence (CAPS) molecular markers were used to select the plants with the resistance genes of interest. A previously described marker was used for TSWV, and new markers were designed for ToMV, and TYLCV using available sequences in the National Center for Biotechnology Information (NCBI) database. In parallel to the breeding program, several molecular markers—Sequence Related Amplified Polymorphism (SRAP), Simple Sequence Repeats (SSRs), Amplified Fragment Length Polymorphisms (AFLPs), Single Nucleotide Polymorphisms (SNPs), and (GATA)4 probes—were used to study genetic variability, and to identify a collection of Spanish and Italian traditional tomato varieties. The results showed a limited genetic variability among cultivated tomato varieties. The breeding lines Muchamiel UMH 1200, and De la pera 1203 (both with homozygous resistance to the three viruses) were the first new varieties that were obtained. They were included in the Register of Protected Plant Varieties in 2013. Lines without a resistance to TYLCV were also developed, and protected in 2017. We have begun to use SNP massive genotyping for studies of genetic association, and for selecting plants with the Ty-1 gene with less linkage drag. Molecular markers have been extremely useful in identifying the different steps of the tomato breeding program at EPSO-UMH.

Screening tomato genotypes for resistance and tolerance to Tomato chlorosis virus

Tomato chlorosis virus (ToCV) is an emerging crinivirus in Brazil that causes an economically important disease in tomato (Solanum lycopersicum) and other solanaceous species. ToCV is transmitted predominantly by the whitefly Bemisia tabaci Middle East‐Asia Minor 1 (MEAM1, formerly biotype B), in a semipersistent manner. As all cultivated tomato varieties and hybrids are susceptible to this crinivirus, the main alternatives for the control of the disease are the use of healthy seedlings for transplanting and the chemical control of the insect vector. The objective of this work was to evaluate the responses of tomato genotypes to infection with this crinivirus and their tolerance to the disease in order to support the development of other alternatives for disease control. Resistance to infection was evaluated by ToCV inoculation with viruliferous B. tabaciMEAM1 followed by virus detection by RT‐PCR and RT‐qPCR. To measure tolerance to the disease, plant development and fruit yield of ToCV‐infected and healthy plants were compared. Among 56 genotypes, only the lineage IAC‐CN‐RT (S. lycopersicum ‘Angela Gigante’ × S. peruvianum ‘LA 444‐1’) was highly resistant to infection with ToCV. Tolerance to the disease over two trials with different genotypes showed variable results. The effect of ToCV on plant development varied from 2.9% to 71.9% reduction, while yield loss varied from 0.2% to 51.8%. The highly ToCV‐resistant lineage IAC‐CN‐RT, which is also resistant to a Spanish isolate of ToCV, might be useful for tomato breeding programmes.

Identification and expression profiling of microRNAs involved in the stigma exsertion under high-temperature stress in tomato

BackgroundAutogamy in cultivated tomato varieties is a derived trait from wild type tomato plants, which are mostly allogamous. However, environmental stresses can cause morphological defects in tomato flowers and hinder autogamy. Under elevated temperatures, tomato plants usually exhibit the phenotype of stigma exsertion, with severely hindered self-pollination and fruit setting, whereas the inherent mechanism of stigma exsertion have been hitherto unknown. Numerous small RNAs (sRNAs) have been shown to play significant roles in plant development and stress responses, however, none of them have been studied with respect to stamen and pistil development under high-temperature conditions. We investigated the associations between stigma exsertion and small RNAs using high-throughput sequencing technology and molecular biology approaches.ResultsSixteen sRNA libraries of Micro-Tom were constructed from plants stamen and pistil samples and sequenced after 2 d and 12 d of exposure to heat stress, respectively, from which a total of 110 known and 84 novel miRNAs were identified. Under heat stress conditions, 34 known and 35 novel miRNAs were differentially expressed in stamens, and 20 known and 10 novel miRNAs were differentially expressed in pistils. GO and KEGG pathway analysis showed that the predicted target genes of differentially expressed miRNAs were significantly enriched in metabolic pathways in both stamen and pistil libraries. Potential miRNA-target cleavage cascades that correlated with the regulation of stigma exsertion under heat stress conditions were found and validated through qRT-PCR and RLM-5′ RACE.ConclusionOverall, a global spectrum of known and novel miRNAs involved in tomato stigma exsertion and induced by high temperatures were identified using high-throughput sequencing and molecular biology approaches, laying a foundation for revealing the miRNA-mediated regulatory network involved in the development of tomato stamens and pistils under high-temperature conditions.

In vitro Screening of Salt Tolerent Genotypes in Tomato (Solanum lycopersicum L.)

Soil salinity is one of the most important abiotic stress that limit crop production. Tomato (Solanum lycopersicum L.) is moderately tolerant to salinity and is typically cultivated in regions that are exposed to soil salinization. The aim of the study was to characterize phenotype response to salt stress under in vitro conditions of fourteen tomato genotypes. The shortest root length was observed entries BD-7260 at 250 mM. Longer roots (11.6 cm) were developed by the plants from the solutions containing 50 mM NaCl in entries BD-7302. NaCl concentration in the medium significantly affected the root length and plant weight of tomato. Genotypic distribution of weight LS means revealed that genotypes BARI-2 and the Line BD-7292 is the highest performed and the Line BD-7762 is the lowest performed. These findings indicated some salt tolerant tomato genotypes which will be promising for future hybridization program. Analysis of novel genes as well as some previously identified genes such as PIPs, LTPs, AGPs, PRPs, GRPs etc. which showed protective roles in different abiotic stresses to other crops is quiet necessary and the presence and expression pattern of those genes in these screened genotypes of tomato will provide powerful information for over-expression of those genes in transgenic plants those will confer salt tolerances to the cultivated tomato varieties.

Tomato R2R3-MYB Proteins SlANT1 and SlAN2: Same Protein Activity, Different Roles.

Anthocyanins are water-soluble polyphenolic compounds with a high nutraceutical value. Despite the fact that cultivated tomato varieties do not accumulate anthocyanins in the fruit, the biosynthetic pathway can be activated in the vegetative organs by several environmental stimuli. Little is known about the molecular mechanisms regulating anthocyanin synthesis in tomato. Here, we carried out a molecular and functional characterization of two genes, SlAN2 and SlANT1, encoding two R2R3-MYB transcription factors. We show that both can induce ectopic anthocyanin synthesis in transgenic tomato lines, including the fruit. However, only SlAN2 acts as a positive regulator of anthocyanin synthesis in vegetative tissues under high light or low temperature conditions.

Expression of heterosis in floral traits and fruit size in tomato (<i>Solanum lycopersicum</i>) hybrids

The present research was prompted by lack of improved tomato cultivars adapted to the humid tropical. Tomato hybrids were developed by crossing wild and cultivated tomato varieties. The average fruit size of the tomato hybrids generated did not meet the level of acceptability in the local market. A modified three way cross between the advanced generation of the tomato hybrids and an exotic variety with giant fruit size was initiated. The resulting hybrids were evaluated to determine the magnitude of heterosis in floral traits and fruit size. Highly significant differences were observed among the genotypes in all the traits studied. Highly significant heteroses were found for flower length which ranged from 2.7 to 13.4% and 7.2 to 21.9%, style length 2.6 to 14.5% and 6.8 to 43%, fruit length 1.9 to 5.1% and 4.6 to 27.4% over the better and mid parents, respectively. Similarly, a significant positive heterosis was recorded for ovary area which ranged from 1.2 to 6.2%, ovary perimeter 1.6 to 6.2%, ovary length 4.8 to 15.3%, fruit diameter 5.7 to 6.5% and number of fruits per plant 14.56 to 55.195% over mid parents only. Key words : Heterosis, floral traits, modified three way cross, tomato, Solanum spp

Analysis of natural and induced variation in tomato glandular trichome flavonoids identifies a gene not present in the reference genome.

Flavonoids are ubiquitous plant aromatic specialized metabolites found in a variety of cell types and organs. Methylated flavonoids are detected in secreting glandular trichomes of various Solanum species, including the cultivated tomato (Solanum lycopersicum). Inspection of the sequenced S. lycopersicum Heinz 1706 reference genome revealed a close homolog of Solanum habrochaites MOMT1 3'/5' myricetin O-methyltransferase gene, but this gene (Solyc06g083450) is missing the first exon, raising the question of whether cultivated tomato has a distinct 3' or 3'/5' O-methyltransferase. A combination of mining genome and cDNA sequences from wild tomato species and S. lycopersicum cultivar M82 led to the identification of Sl-MOMT4 as a 3' O-methyltransferase. In parallel, three independent ethyl methanesulfonate mutants in the S. lycopersicum cultivar M82 background were identified as having reduced amounts of di- and trimethylated myricetins and increased monomethylated myricetin. Consistent with the hypothesis that Sl-MOMT4 is a 3' O-methyltransferase gene, all three myricetin methylation defective mutants were found to have defects in MOMT4 sequence, transcript accumulation, or 3'-O-methyltransferase enzyme activity. Surprisingly, no MOMT4 sequence is found in the Heinz 1706 reference genome sequence, and this cultivar accumulates 3-methyl myricetin and is deficient in 3'-methyl myricetins, demonstrating variation in this gene among cultivated tomato varieties.