To Tomato Yellow Leaf Curl Virus Research Articles

The identification of the methylation patterns of tomato curly stunt virus in resistant and susceptible tomato lines.

Tomato curly stunt virus (ToCSV) is a monopartite begomovirus infecting tomatoes in South Africa, with sequence similarity to tomato yellow leaf curl virus (TYLCV). While there are numerous reports on the mechanism of TYLCV resistance in tomato, the underlying mechanisms in the tomato-ToCSV pathosystem is still relatively unknown. The main aim of this study was to investigate and compare the global methylation profile of ToCSV in two near-isogenic tomato lines, one with a tolerant phenotype (T, NIL396) and one with a susceptible phenotype (S, NIL395). Bisulfite conversion and PCR amplification, coupled with a next-generation sequencing approach, were used to elucidate the global pattern of methylation of ToCSV cytosine residues in T and S leave tissue at 35 days post-infection (dpi). The extent of methylation was more pronounced in tolerant plants compared to susceptible plants in all sequence (CG, CHG and CHH) contexts, however, the overall methylation levels were relatively low (<3%). Notably, a significant interaction (p < 0.05) was observed between the viral genomic region and susceptible vs. tolerant status for CG methylated regions where it was observed that the 3'IR CG methylation was significantly (p < 0.05) higher than CG methylation of other genomic regions in tolerant and susceptible plants. Additionally, statistically significant (EdgeR p < 0.05) differentially methylated cytosines were located primarily in the genomic regions V2/V1 and C4/C1 of ToCSV. The relative expression, using RT-qPCR, was also employed in order to quantify the expression of various key methylation-related genes, MET1, CMT2, KYP4/SUVH4, DML2, RDM1, AGO4 and AGO6 in T vs. S plants at 35dpi. The differential expression between T and S was significant for MET1, KYP4/SUVH4 and RDM1 at p<0.05 which further supports more pronounced methylation observed in ToCSV from T plants vs. S plants. While this study provides new insights into the differences in methylation profiles of ToCSV in S vs. T tomato plants, further research is required to link tolerance and susceptibility to ToCSV.

Characterization of tomato yellow leaf curl virus resistance genes and genetic variability in commercial tomato F1 hybrids

Tomato (Solanum lycopersicum L.) resistance to Tomato Yellow Leaf Curl Virus (TYLCV) is a major objective of breeding programs. Tomato breeders are now interested in the subsequent introgression of many resistance genes to increase resistance levels, expand resistance spectrum, and prolong the longevity of resistant cultivars. Many F1 hybrids are now multigene resistant. To select the best breeding materials, 15 commercial F1 tomato TYLCV-tolerant hybrids were evaluated for TYLCV resistance and productivity during the 2018 and 2019 fall seasons. Resistance genes were identified using gene-based molecular markers. Most hybrids have multiple heterozygous resistance genes. ‘Brivio’, ‘Dania’, ‘SV8320’, and ‘Tyrmes’ comprised resistance genes Ty-1/Ty-3, Ty-2, Ty-4, and ty-5. Thus, F1 hybrids exhibited moderate to mild symptoms, and viral replication was detected in their symptomless plants by PCR and qt-PCR. Genetic variability among hybrids, hybrid relationships, and inter-trait correlations were estimated based on phenotypes of TYLCV-tolerance, productivity, and fruit quality. Most traits had high estimates of genetic variance, genotypical coefficient of variance, and heritability. Genetic variability sufficed in selecting the best genotype. Based on multivariate analyses of principal components and hierarchical clusters, hybrids were highly diversified and divided into three clusters. Clusters 1 and 3 were better at TYLCV tolerance, yield, and fruit quality. Positive genotypical correlations were found between tolerance, total yield, and fruit quality (firmness, equatorial diameter, and TSS content). The use of ‘Brivio’, ‘Dania’, ‘SV8320’, and ‘Tyrmes’ will be very useful in TYLCV resistance breeding programs to pyramiding resistance genes by marker-assisted selection technique.

Silencing of SlDRB1 gene reduces resistance to tomato yellow leaf curl virus (TYLCV) in tomato (Solanum lycopersicum)

ABSTRACT Double-stranded RNA-binding proteins are small molecules in the RNA interference (RNAi) pathway that form the RNAi machinery together with the Dicer-like protein (DCL) as a cofactor. This machinery cuts double-stranded RNA (dsRNA) to form multiple small interfering RNAs (siRNAs). Our goal was to clarify the function of DRB in tomato resistant to TYLCV. In this experiment, the expression of the SlDRB1 and SlDRB4 genes was analyzed in tomato leaves by qPCR, and the function of SlDRB1 and SlDRB4 in resistance to TYLCV was investigated by virus-induced gene silencing (VIGS). Then, peroxidase activity was determined. The results showed that the expression of SlDRB1 gradually increased after inoculation of ‘dwarf tomato’ plants with tomato yellow leaf curl virus (TYLCV), but this gene was suppressed after 28 days. Resistance to TYLCV was significantly weakened after silencing of the SlDRB1 gene. However, there were no significant expression differences in SlDRB4 after TYLCV inoculation. Our study showed that silencing SlDRB1 attenuated the ability of tomato plants to resist virus infection; therefore, SlDRB1 may play a key role in the defense against TYLCV in tomato plants, whereas SlDRB4 is likely not involved in this defense response. Taken together, These results suggest that the DRB gene is involved in the mechanism of antiviral activity.

Ty-5 Confers Broad-Spectrum Resistance to Geminiviruses.

The selection of resistant crops is an effective method for controlling geminivirus diseases. ty-5 encodes a messenger RNA surveillance factor Pelota with a single amino acid mutation (PelotaV16G), which confers effective resistance to tomato yellow leaf curl virus (TYLCV). No studies have investigated whether ty-5 confers resistance to other geminiviruses. Here, we demonstrate that the tomato ty-5 line exhibits effective resistance to various geminiviruses. It confers resistance to two representative begomoviruses, tomato yellow leaf curl China virus/tomato yellow leaf curl China betasatellite complex and tomato leaf curl Yunnan virus. The ty-5 line also exhibits partial resistance to a curtovirus beet curly top virus. Importantly, ty-5 confers resistance to TYLCV with a betasatellite. Southern blotting and quantitative polymerase chain reaction analyses showed that significantly less DNA of these geminiviruses accumulated in the ty-5 line than in the susceptible line. Moreover, knockdown of Pelota expression converted a Nicotiana benthamiana plant from a geminivirus-susceptible host to a geminivirus-resistant host. Overall, our findings suggest that ty-5 is an important resistance gene resource for crop breeding to control geminiviruses.

Performance Evaluation of Different Tomato Lines Grown Organically in Catarman, Camiguin, Philippines

Tomato (Solanum lycopersicum) is considered an important crop, but local producers face difficulties in choosing the appropriate variety due to its diversity and ecological adaptability. In an effort to provide an alternative option of varieties and selection of suitable varieties, this research was conducted to evaluate the comparative performance of sixteen tomato varieties (11 AVRDC lines, five check varieties) at Tangaro, Catarman, Camiguin from January to April 2014 using randomized complete block design with three replications under field conditions. It was found out that plant height, days to 50% flowering, days to first harvest, plant vigor, percent survival, fruit yield, number of fruits, fruit weight, marketable yield, and resistance to tomato yellow leaf curl virus (TYLCV) showed significant differences among the various tomato varieties under trial except for the fruit size. Maximum plant height (65.30 cm) at 60DAT was recorded in T11 (AVTO 1002) followed by T8 (AVTO 1130). Most check varieties produced first flowers earlier compared to AVRDC lines, with T15 (CV4 M) at 20.67 days and consequently mature early by having its first harvest (56DAT) at least two days earlier except for T1 (AVTO 1009), T2 (AVTO 1003) and T3 (AVTO 9803). T12 (CV1 TD) exhibited a vigorous plant stand compared to AVRDC lines T2 (AVTO 1003) and T8 (AVTO 1130), which showed a weak stand at the first harvest. Checked varieties T12 (CV1 TD) has the highest percentage of survival, while T7 (AVTO 0101) and T10 (AVTO 9001) showed a percent plant survival statistically comparable to other check varieties. T14 (CV3 MF1) produced the most number of fruits, while T5 (AVTO 1004) produced the least. The highest computed yield per hectare was observed from T14 (CV3 MF1), while the lowest yield was computed from AVRDC line T9 (AVTO 1008). AVRDC lines T1 (AVTO 1009), T2 (AVTO 1003), and T3 (AVTO 9803) are most susceptible to TYLCV, while checked varieties were more resistant. Considering the overall performance, it was found out that the checked varieties performed well. AVRDC lines T10 (AVTO 9001) and T4 (AVTO 1173) were also promising for their growth and yield performance and resistance to TYLCV. However, the potential of these varieties is needed to be further tested for verification under different growing seasons to elicit substantial conclusions.

Behavior of new entries and developed tomato hybrids carrying Ty-2 genes

Tomato yellow leaf curl disease (TYLCD) is a serious problem hampering tomato production worldwide. In the Mediterranean Basin, disease incidence and severity are higher in the dry season increasing whitefly (Bemisia tabaci) populations. Effectiveness of resistance to Tomato yellow leaf curl virus (TYLCV) depends on both tomato host resistance and TYLCV complex species. So far, six different Ty tomato resistance genes have been identified. Two main TYLCV complex species, Tomato yellow leaf curl virus-Israel (TYLCV-Is) and Tomato yellow leaf curl Sardinia virus (TYLCSV), have been identified in Tunisia. The present work aimed to evaluate entries heterozygous for Ty-2 gene to help predict hybrid performance. Two tomato entries homozygous for the Ty-2 TYLCV resistance gene, one tomato hybrid homozygous for Ty-2 and two heterozygous hybrids were included, besides two susceptible tomato entries. Resistance response to TYLCD was recorded based on disease incidence and severity levels. Data analysis was performed according to presence/absence of Ty-2 gene and taking into account homozygosity and heterozygosity of Ty-2. Generalized linear model analysis was applied to check significance of individual factors' effects (i.e. effect of tomato entries or tomato groups of entries based on presence or absence of homozygous/heterozygous Ty-2 gene, block unit within the field trial and the year of the trial) on the dependent variables (disease incidence and severity). Further multicomparison tests gave evidence on significant effect of Ty-2 homozygous gene tomato entries on TYLCD incidence and severity levels. The results were discussed with special focus on the relevance use of heterozygous hybrid tomato varieties.

Small RNA Profiling of Susceptible and Resistant Ty-1 Encoding Tomato Plants Upon Tomato Yellow Leaf Curl Virus Infection.

Ty-1 presents an atypical dominant resistance gene that codes for an RNA-dependent RNA polymerase (RDR) of the gamma class and confers resistance to tomato yellow leaf curl virus (TYLCV) and other geminiviruses. Tomato lines bearing Ty-1 not only produce relatively higher amounts of viral small interfering (vsi)RNAs, but viral DNA also exhibits a higher amount of cytosine methylation. Whether Ty-1 specifically enhances posttranscriptional gene silencing (PTGS), leading to a degradation of RNA target molecules and primarily relying on 21–22 nucleotides (nts) siRNAs, and/or transcriptional gene silencing (TGS), leading to the methylation of cytosines within DNA target sequences and relying on 24-nts siRNAs, was unknown. In this study, small RNAs were isolated from systemically TYLCV-infected leaves of Ty-1 encoding tomato plants and susceptible tomato Moneymaker (MM) and sequence analyzed. While in susceptible tomato plants vsiRNAs of the 21-nt size class were predominant, their amount was drastically reduced in tomato containing Ty-1. The latter, instead, revealed elevated levels of vsiRNAs of the 22- and 24-nt size classes. In addition, the genomic distribution profiles of the vsiRNAs were changed in Ty-1 plants compared with those from susceptible MM. In MM three clear hotspots were seen, but these were less pronounced in Ty-1 plants, likely due to enhanced transitive silencing to neighboring viral genomic sequences. The largest increase in the amount of vsiRNAs was observed in the intergenic region and the V1 viral gene. The results suggest that Ty-1 enhances an antiviral TGS response. Whether the elevated levels of 22 nts vsiRNAs contribute to an enhanced PTGS response or an additional TGS response involving a noncanonical pathway of RNA dependent DNA methylation remains to be investigated.

Breeding of New Tomato Cultivar ‘TY Sun’ with Resistance to Tomato Yellow Leaf Curl Virus (TYLCV)

Breeding of New Tomato Cultivar ‘TY Sun’ with Resistance to Tomato Yellow Leaf Curl Virus (TYLCV)

Genome-Wide Analysis of Lectin Receptor-Like Kinases in Tomato (Solanum lycopersicum) and Its Association with the Infection of Tomato Yellow Leaf Curl Virus

Lectin receptor-like kinases (LecRLKs) are crucial factors in response to plant biotrophic pathogens. This study aimed to systemically analyze the effect of tomato LecRLKs on the responses to tomato yellow leaf curl virus (TYLCV) infection. A total of 93 tomato SlyLecRLK genes, including 69 G-type LecRLKs, 23 L-type LecRLKs, and one C-type LecRLK, were identified using genome-wide analysis and were clustered into three subfamilies using phylogenetic analysis. These SlyLecRLK genes were localized on the 12 tomato chromosomes with some gene duplication events. Transcriptomic analysis showed most of SlyLecRLKs were modulated by phytohormones and TYLCV infection. Gene ontology (GO) enrichment analysis showed all SlyLecRLK genes were associated with receptor protein kinase activity and protein modification. Quantitative RT-PCR (qRT-PCR) and gene interference validation showed SlyLecRLKs007, SlyLecRLKs036, and SlyLecRLKs044 genes were inhibited by TYLCV infection, and silencing of them were accompanied by accumulation of TYLCV DNA content. Subcellular localization of LecRLKs023 and LecRLKs044 on cell membranes was determined using a SlyLecRLK-containing A. tumefaciens strain GV3101. These results showed SlyLecRLK genes were key factors for TYLCV resistance, and also provided crucial information uncovering the protective effects of SlyLecRLKs on resisting TYLCV infection in tomato.

SlMAPK3 enhances tolerance to tomato yellow leaf curl virus (TYLCV) by regulating salicylic acid and jasmonic acid signaling in tomato (Solanum lycopersicum).

Several recent studies have reported on the role of mitogen-activated protein kinase (MAPK3) in plant immune responses. However, little is known about how MAPK3 functions in tomato (Solanum lycopersicum L.) infected with tomato yellow leaf curl virus (TYLCV). There is also uncertainty about the connection between plant MAPK3 and the salicylic acid (SA) and jasmonic acid (JA) defense-signaling pathways. The results of this study indicated that SlMAPK3 participates in the antiviral response against TYLCV. Tomato seedlings were inoculated with TYLCV to investigate the possible roles of SlMAPK1, SlMAPK2, and SlMAPK3 against this virus. Inoculation with TYLCV strongly induced the expression and the activity of all three genes. Silencing of SlMAPK1, SlMAPK2, and SlMAPK3 reduced tolerance to TYLCV, increased leaf H2O2 concentrations, and attenuated expression of defense-related genes after TYLCV infection, especially in SlMAPK3-silenced plants. Exogenous SA and methyl jasmonic acid (MeJA) both significantly induced SlMAPK3 expression in tomato leaves. Over-expression of SlMAPK3 increased the transcript levels of SA/JA-mediated defense-related genes (PR1, PR1b/SlLapA, SlPI-I, and SlPI-II) and enhanced tolerance to TYLCV. After TYLCV inoculation, the leaves of SlMAPK3 over-expressed plants compared with wild type plants showed less H2O2 accumulation and greater superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) activity. Overall, the results suggested that SlMAPK3 participates in the antiviral response of tomato to TYLCV, and that this process may be through either the SA or JA defense-signaling pathways.

Obtaining advanced generations from Solanum peruvianum PI 126944 in the genetic background of S. lycopersicum by immature seed culture

The accession Solanum peruvianum PI 126944 has been reported as resistant to different biotic and abiotic stresses. In previous works of the group, advanced generations were derived from two interspecific hybrids, including up to pseudo-F6 generations and backcrosses to the cultivated species of some of the pseudo-Fn generations. Moreover, resistance to Tomato yellow leaf curl virus (TYLCV) and Tomato spotted wilt virus (TSWV) was confirmed in some of the plant materials obtained. Here we describe the development of some advanced backcross generations between the cultivated tomato and S. peruvianum. Three backcross assays were carried out. In the first assay, 16 plants belonging to pseudo-F4, pseudo-F5 and pseudo-F6 generations were backcrossed as male parents to cultivated tomato. Immature seeds from the 408 fruits obtained were platted and 77 plants were regenerated. A total of 21 descendants obtained in the first assay were backcrossed as male parents in the second assay, which allowed the obtaining of 599 fruits and regeneration of 365 plants. The 19 male parents used in the third assay were obtained either in the first or in the second one. Seventeen of them were obtained in the first assay and two in the second. A total of 339 plants were regenerated from 519 fruits. A high number of the plants obtained in these assays has been acclimated. Some plants set fruits with viable seeds.

Aplikasi Teknik Rekayasa Genetik dalam Perbaikan Sumber Daya Genetik Tanaman untuk Ketahanan Cekaman Biotik

&lt;p&gt;The main constraint encountered in the&lt;br /&gt;utilization of plant genetic resources (PGR) in agriculture are&lt;br /&gt;biotic stresses such as insect pests, plant diseases, and plant&lt;br /&gt;parasitic nematodes. The application of genetic engineering&lt;br /&gt;techniques create a great opportunity for crops improvements&lt;br /&gt;particularly for insect and plant diseases resistance. Through&lt;br /&gt;genetic engineering, genetically engineered (GE) crops have&lt;br /&gt;been developed, of which having the new traits such as resistance&lt;br /&gt;to insect pests, plant diseases, and herbicide tolerance.&lt;br /&gt;GE crops are already widely grown and marketed in many&lt;br /&gt;countries. Globally, GE crops that are commercialized consists&lt;br /&gt;of four categories of traits, which are insect resistance (IR),&lt;br /&gt;herbicide tolerance, (HT), the combined traits of IR and HT&lt;br /&gt;(stacked genes), and virus resistance. Initially, GE crops had&lt;br /&gt;been commercialized globally covering 1.7 million ha in 1996,&lt;br /&gt;and the cropping area increased rapidly to reach about 134&lt;br /&gt;million ha in 2009. Indonesia is known as a country rich in&lt;br /&gt;PGR, that have very high value. One of environmentally&lt;br /&gt;friendly technologies that can be applied in the utilization of&lt;br /&gt;PGR in Indonesia, is genetic engineering. In Indonesia,&lt;br /&gt;research on plant genetic engineering had started since 1997.&lt;br /&gt;Commodities that are being researched to develop GE plants&lt;br /&gt;limited on rice, potatoes and tomatoes. GE rice resistant to&lt;br /&gt;stem borer (Scirpophaga incertulas), GE potato resistant to&lt;br /&gt;late blight (Phytophthora infestans), and GE tomato resistant&lt;br /&gt;to tomato yellow leaf curl virus (TYLCV) and cucumber&lt;br /&gt;mosaic virus (CMV) have been successfully developed by&lt;br /&gt;Research Center for Biotechnology of Indonesian Institute of&lt;br /&gt;Science and Indonesian Center for Agricultural Biotechnology&lt;br /&gt;and Genetic Resources Research and Development&lt;br /&gt;(ICABIOGRAD). Those GE crops have been tested for their&lt;br /&gt;resistance at the screenhouses, green houses of the biosafety&lt;br /&gt;containment, and confined field trial.&lt;/p&gt;

Eugenol confers resistance to Tomato yellow leaf curl virus (TYLCV) by regulating the expression of SlPer1 in tomato plants

Tomato yellow leaf curl virus (TYLCV) is one of the most devastating plant diseases, and poses a significant agricultural concern because of the lack of an efficient control method. Eugenol is a plant-derived natural compound that has been widely used as a food additive and in medicine. In the present study, we demonstrated the potential of eugenol to enhance the resistance of tomato plants to TYLCV. The anti-TYLCV efficiency of eugenol was significantly higher than that of moroxydine hydrochloride (MH), a widely used commercial antiviral agent. Eugenol application stimulated the production of endogenous nitric oxide (NO) and salicylic acid (SA) in tomato plants. The full-length cDNA of SlPer1, which has been suggested to be a host R gene specific to TYLCV, was isolated from tomato plants. A sequence analysis suggested that SlPer1 might be a nucleobase-ascorbate transporter (NAT) belonging to the permease family. The transcript levels of SlPer1 increased markedly in response to treatment with eugenol or TYLCV inoculation. The results of this study also showed that SlPer1 expression was strongly induced by SA, MeJA (jasmonic acid methyl ester), and NO. Thus, we propose that the increased transcription of SlPer1 contributed to the high anti-TYLCV efficiency of eugenol, which might involve in the generation of endogenous SA and NO. Such findings provide the basis for the development of eugenol as an environmental-friendly agricultural antiviral agent.

Control of Tomato yellow leaf curl virus disease by Enterobacter asburiaeBQ9 as a result of priming plant resistance in tomatoes

Enterobacter asburiae BQ9, a plant-growth-promoting rhizobacterium, was shown to promote tomato plant growth and induce resistance to Tomato yellow leaf curl virus (TYLCV) under greenhouse conditions. Compared with mock-treated tomato plants, plants that were pretreated with BQ9 had increased fresh mass and significantly reduced disease severity and 52% biocontrol efficacy was achieved 30 days after inoculation. The expression of defense-related genes PR1a and PR1b and the H 2 O 2 burst were quickly induced in BQ9 pretreated plants. Antioxidase activity analysis showed that the activities of phenylalanine ammonia lyase, peroxidase, catalase, and superoxide dismutase increased significantly in BQ9 pretreated plants. Our results suggest that the plant-growth-promoting rhizobacterium BQ9 induced a priming of the plant defense responses to TYLCV by increasing the expression of defense response genes, and the induced resistance was mechanistically connected to the expression of antioxidant enzymes and the production of H 2 O 2 .

COMBINATIONS OF TY RESISTANCE GENES GENERALLY PROVIDE MORE EFFECTIVE CONTROL AGAINST BEGOMOVIRUSES THAN DO SINGLE GENES

Begomoviruses are a major threat to tropical and subtropical tomato production, worldwide. Host resistance provides an effective strategy for reducing yield losses associated with these viruses. Resistance has been introgressed into cultivated tomato (Solanum lycopersicum L.) primarily from a number of wild tomato relatives, and the major resistance genes available to breeders today include Ty-1 (and its allele, Ty-3), Ty-2, Ty-4, ty-5, and a recently-identified gene tentatively named “Ty-6”. Important to the effective and efficient deployment of resistant cultivars is an understanding of each resistance allele’s effect when used alone and when combined with other resistance genes. Ty-1 and Ty2 are both dominant and, where effective, provide a high level of resistance; whereas the other genes provide partial resistance and are additive to partially dominant or recessive as with ty-5. Two- and three-gene combinations of Ty-3, Ty-4, and ty-5 in semi-isogenic backgrounds provided high levels of resistance to Tomato yellow leaf curl virus (TYLCV). Tomato mottle virus (ToMoV) trials in Florida using the same materials were severe, but indicated that Ty-3 and Ty-4 had small but significant effects in lowering ToMoV disease severity but, ty-5 did not. In two additional populations segregating for both ty-5 and “Ty-6” that were inoculated with ToMoV, ty-5 had no significant effect on resistance. Combining “Ty-6” and ty-5 homozygously provided a high level of resistance to TYLCV while the combination of homozygous ty-5 with heterozygous “Ty-6” was also good, but not as resistant as the former.

Water Balance, Hormone Homeostasis, and Sugar Signaling Are All Involved in Tomato Resistance to Tomato Yellow Leaf Curl Virus.

Vacuolar water movement is largely controlled by membrane channels called tonoplast-intrinsic aquaporins (TIP-AQPs). Some TIP-AQP genes, such as TIP2;2 and TIP1;1, are up-regulated upon exposure to biotic stress. Moreover, TIP1;1 transcript levels are higher in leaves of a tomato (Solanum lycopersicum) line resistant to Tomato yellow leaf curl virus (TYLCV) than in those of a susceptible line with a similar genetic background. Virus-induced silencing of TIP1;1 in the tomato resistant line and the use of an Arabidopsis (Arabidopsis thaliana) tip1;1 null mutant showed that resistance to TYLCV is severely compromised in the absence of TIP1:1. Constitutive expression of tomato TIP2;2 in transgenic TYLCV-susceptible tomato and Arabidopsis plants was correlated with increased TYLCV resistance, increased transpiration, decreased abscisic acid levels, and increased salicylic acid levels at the early stages of infection. We propose that TIP-AQPs affect the induction of leaf abscisic acid, which leads to increased levels of transpiration and gas exchange, as well as better salicylic acid signaling.

Comparative metabolomics and transcriptomics of plant response to Tomato yellow leaf curl virus infection in resistant and susceptible tomato cultivars

In order to understand resistance to Tomato yellow leaf curl virus (TYLCV) we have performed a combined analysis of the metabolome and transcriptome of resistant (R) and susceptible (S) tomato plants both prior to and following TYLCV infection. Metabolites detected by gas chromatography–mass spectrometry (GC–MS) and liquid chromatography–mass spectrometry analysis, in leaves of R and S plants, at 1, 3, 7 and 14 days post infection and control plants, were used for the reconstruction of four independent metabolic networks. Measuring the network parameters revealed distinctive systemic metabolic responses to TYLCV infection between the R and S plants. Notably, the GC–MS metabolic network indicated that, following infection, the R plant exhibited tight coordination of the metabolome than the S plant. Clear differences in the level of specialized metabolites between the S and R plants were revealed; among them, substantial alteration in the abundance of amino acids and polyamines, phenolic and indolic metabolites, all leading to the synthesis of defense compounds. Integrating metabolome and transcriptome data highlighted differently regulated pathways in the R and S plants in response to TYLCV, including the phenylpropanoid, tryptophan/nicotinate and urea/polyamine pathways. Salicylic acid biosynthesis was additionally distinctively activated in R plants upon infection. Comparing the expression of genes of the urea and phenylpropanoid pathways in S, R and Solanum habrochaites, the resistance genitor wild species tomato, indicated a time-shift in the expression patterns, before and following infection, which on one hand reflected the genetic similarity between these plants, and on the other hand demonstrated that the resistant phenotype is intermediate between that of S and S. habrochaites.

토마토 황화잎말림바이러스(TYLCV) 저항성 품종 선발 및 원예특성 분석

본 연구는 외국 종자 회사의 토마토 <TEX>$F_1$</TEX> 품종들을 대상으로 토마토황화잎말림바이러스(TYLCV) 저항성 분자마커 분석과 포장병리검정을 통해 각 품종의 저항성 유전자형과 내병성 수준을 분석하고, 원예형질 특성평가를 통해 TYLCV 저항성 품종보급과 분리육종에 적절한 품종선발을 위해 수행되었다. 40개 공시품종의 분자마커 및 병리검정 결과, 대부분 저항성으로 표기된 품종들이 TYLCV 저항성 유전자인 Ty-1, Ty-3, 또는 Ty-3a유전자를 이형접합 또는 동형접합으로 지니고 있으며, 표현형에서도 매우 낮은 발병률을 보였다. 반면, 중간 저항성으로 표기된 4 품종 중 3 품종은 18.1-33.3%의 발병률을 보였으며, 마커형이 이병성이었다. 내병성이 확인된 <TEX>$F_1$</TEX>품종들을 대상으로 원예형질 특성조사 결과, 유럽형 TYLCV 저항성 대과종 품종은 국내 선호 대비종보다 비교적 수량이 높고 당도 및 당산도도 크게 떨어지지 않아 국내용 품종 육성재료로 적합하였지만, 높은 과실경도의 문제점이 있었다. 반면, 소과종 품종들은 수량, 당도 등에서 국내 선호 품종보다 낮고 절간장도 길어 이들을 활용한 고품질 TYLCV 저항성 품종 육성을 위해서는 대과종에 비해 많은 시간과 노력이 소요될 것으로 판단되었다. This study was conducted to evaluate imported tomato <TEX>$F_1$</TEX> cultivars as breeding materials for the resistance to Tomato yellow leaf curl virus (TYLCV) by molecular markers and bioassay. From marker genotyping and disease evaluation of 40 <TEX>$F_1$</TEX> cultivars, most of the cultivars declared as TYLCV-resistance carried heterozygous marker genotype for the TYLCV resistance genes Ty-1, Ty-3, or Ty-3a, and showed low disease rates. Whereas, 4 of 5 <TEX>$F_1$</TEX> cultivars declared as intermediate resistance showed marker genotype for susceptibility and disease rates ranged 18.1-33.3%. However, the xx cultivars showed inconsistency in marker genotype and disease rate. Characterization of horticultural traits of the <TEX>$F_1$</TEX> cultivars with TYLCV-resistance indicated that large-size fruit cultivars were higher in yield and similar in sugar contents and solid-acid ratio compared to a control cultivar preferred in the domestic market, although hardness remained to be a problem. On the other hand, cherry tomato cultivars showed lower yield and brix, but longer internode compared to a control cultivar, indicating that breeding for TYLCV-resistance using these cultivars will require more efforts and time compared to large-sized.

Initial development of a set of introgression lines from Solanum peruvianum PI 126944 into tomato: exploitation of resistance to viruses

Resistance to Tomato yellow leaf curl virus (TYLCV) and Tomato spotted wilt virus (TSWV), among other diseases, has been reported in Solanum peruvianum PI 126944. Introgression lines (ILs) from S. peruvianum PI 126944 into the genetic background of cultivated tomato (S. lycopersicum) are being developed. Several generations were derived from three interspecific hybrids previously obtained. A lot of crosses and embryo rescue were required until the third backcross, due to the high degree of incompatibility existing between tomato and PI 126944. Crosses between F1 plants were made to obtain a pseudo-F2 generation. The same procedure was followed up to the pseudo-F6 generation. Additional crosses between plants of different generations were made in order to increase progeny. Of 263 molecular markers tested, 105 were polymorphic between tomato and PI 126944. This set of polymorphic markers consisted of 90 simple sequence repeats (SSR) and 15 cleaved amplified polymorphic sequences (CAPS). The amount of the S. peruvianum genome was reduced in advancing generations and this was coupled in some cases with a reduction of incompatibility. However, the S. peruvianum genome was almost completely represented among the different plants of the most advanced generations. ILs will be basically developed from them. Some of the generations developed were resistant to TYLCV and TSWV.

Fontes de resistência em tomateiro aos begomovírus bissegmentados Tomato yellow spot virus e Tomato severe rugose virus

Os begomovírus causam doenças de grande importância econômica em diversas culturas, principalmente em regiões tropicais e subtropicais. Juntamente com outras famílias de vírus, os begomovírus têm causado grande prejuízo para os produtores de tomate in natura e para processamento industrial. O objetivo deste trabalho foi avaliar o comportamento de 11 genótipos resistentes ao Tomato yellow leaf curl virus (TYLCV) frente à infecção pelos begomovírus Tomato yellow spot virus (ToYSV) e Tomato severe rugose virus (ToSRV) em condições de casa-vegetação. A inoculação das plantas foi realizada via biobalística no estádio de duas folhas verdadeiras. A infecção viral confirmou-se pelo desenvolvimento dos sintomas e pela técnica de hibridização dot blot. Selecionaram-se como promissores os genótipos STY2, STY5, STY6 e L7, por não apresentarem sintomas e por terem concentrações virais muito baixas para os dois vírus. O espectro de resistência dos genes Ty-1 e Ty-2 não resultaram efetivos ante as espécies virais empregadas no estudo. As linhagens TY52, H24 e CLN2116B, portadoras destes genes, foram suscetíveis aos vírus ToYSV e ToSRV.