To Tomato Leaf Curl Virus Research Articles

Characterisation of Tomato (Solanum lycopersicon Mill.) Genotypes for Morphological and Disease Resistance Traits through Cluster Analysis

The characterization of germplasm is crucial for breeding and developing improved seed varieties. In this study, seed material was collected from M/s. Noble Seeds Pvt. Ltd., Yelhanka, focusing on genotypes with varying resistance to Tomato Leaf Curl Virus (ToLCV). The research was conducted during the Kharif seasons of 2021 and 2022 in Kestur Village, Doddballapura. Morphological characterization was performed according to DUS guidelines set by PPV&FRA, assessing 20 qualitative and 22 quantitative traits. The genotypes were grown in a randomized complete block design for reliability. Multivariate cluster analysis was employed to group the genotypes based on the morphological traits assessed, enabling the identification of patterns and relationships among them. This analysis facilitated the formation of distinct clusters, highlighting the genetic diversity and similarities among the genotypes, which are crucial for targeted breeding strategies. Through multivariate cluster analysis, two main clusters (A and B) were identified, each further divided into two sub-clusters (C and D). Overall, 66.67% of the 30 genotypes (20 in total) were grouped in Cluster E, while 5 genotypes were placed in Cluster C, 3 in Cluster D, and only 2 in Cluster F. The analysis revealed that NBLTM-22 and NBLTM-11 exhibited the highest variation between them, while genotypes within clusters demonstrated greater similarity. These findings underscore the importance of genetic diversity in breeding programs, highlighting that closer proximity in clustering correlates with trait similarity among genotypes. This information can guide further breeding efforts aimed at developing ToLCV-resistant varieties.

Comparison of Post-transcriptional Gene Silencing (PTGS) Strategies for Developing Transgenic Plants Resistant to Tomato Leaf Curl Virus (ToLCV)

Tomato (Solanum lycopersicum L.), an economically important crop is host to many whitefly transmitted geminiviruses including tomato leaf curl virus (ToLCV). Genetically engineering resistance of pathogen through Post-transcriptional gene silencing (PTGS/RNAi) is a powerful strategy that can provide alternative to existing methods of producing virus resistant plants. We cloned and characterized ToLCV-replicase (TRP) gene from a local Dharwad, Karnataka, India ToLCV isolate for development of transgenic tomato plants. Plant expression vectors carrying viral replicase (rep) gene in sense, antisense, ihp (intron spaced hairpin) and HUTR (inverted repeats of heterologous 3΄-untranslated region) were constructed. Transgenic tomato plants carrying rep gene in different strategies when challenged with whiteflies carrying ToLCV showed varied degrees of resistance. Such plants were confirmed through PCR, GUS, Dot blot, Southern blot and semiquantitative PCR analysis. High degree of resistance was observed in the construct carrying both sense and antisense strand interrupted by intron (ihp). Our results demonstrate that, transgenic plants with simultaneous expression of sense and antisense strands are more efficient in gene silencing of ToLCV than those expressing either sense or antisense strand alone.

Molecular Characterization of a Begomovirus, α-Satellite, and β-Satellite Associated with Leaf Curl Disease of Parthenium hysterophorus in India.

Parthenium hysterophorus plants exhibiting severe leaf curl and stunting symptoms were observed near agriculture fields in Lucknow, India. The association of a begomovirus, β-satellite, and α-satellite with these symptoms of a Parthenium disease was investigated by sequence analyses of virus and satellite DNA amplified by rolling circle amplification and polymerase chain reaction. The highest sequence identities and closest phylogenetic relationships for the begomovirus, β-satellite, and α-satellite detected in P. hysterophorus plants were to Tomato leaf curl virus (ToLCV), papaya leaf curl β-satellite (PaLCuB), and Ageratum yellow vein India α-satellite (AYVIA), respectively. These findings identified the virus and satellites infecting the Parthenium sp. as ToLCV, PaLCuB, and AYVIA, respectively. P. hysterophorus and tomato seedlings infected with cloned ToLCV, PaLCuB, and AYVIA by agroinoculation developed leaf curl symptoms, whereas plants infected with ToLCV alone or with ToLCV and AYVIA developed mild yellowing. The results show that this complex infects and causes disease in P. hysterophorus and tomato. P. hysterophorus is an invasive weed commonly found around agricultural fields and along roadsides in India. These results indicate that P. hysterophorus plants infected with ToLCV and associated satellite DNA act as an alternate host (reservoir), and that could lead to increased incidence of tomato leaf curl disease.

Genetic and molecular characterisations of Tomato leaf curl virus resistance in tomato (Solanum lycopersicum L.)

SUMMARYFour different F2 populations were developed involving Solanum habrochaites accession ‘EC-520061’ that is highly resistant to Tomato leaf curl virus (ToLCV) disease and four ToLCV-susceptible cultivars of tomato (S. lycopersicum L.), ‘Punjab Chhuhara’ (PBC),‘H-24’, ‘H-86’, and ‘DVRT-2’.The segregation ratios of tomato leaf curl disease development in all four F2 populations were 13:3 (resistant:susceptible), indicating a dominant inhibitory gene for leaf curl disease resistance, and 3:1 (indeterminate:determinate) indicating a single dominant gene for plant growth habit. The patterns of inheritance were shown to be additive with dominant non-allelic gene interactions for the traits of ToLCV resistance and fruit yield. Using bulk segregant analysis (BSA) and one of the F2 populations (‘PBC’ X ‘EC-520061’) above, two SSR markers (SSR218170–145 and SSR304158–186) were identified for ToLCV resistance. The SSR marker SSR218170–145 was located at 15 cM on chromosome 10, and the marker SSR304158–186 was located at 35 cM on chromosome 7. This study will support the development of new ToLCV- resistant tomato varieties via breeding programmes.

English

This study was conducted to evaluate the comparison between the histological and histochemical changes in leaves of tomato due to tomato leaf curl virus (ToLCV) with or without plant growth-promoting rhizobacteria (PGPR) and chitosan treatments. The combined treatment of chitosan and Pseudomonas sp. induced a significant (P=0.05) increase in the activities of polyphenoloxidase (PPO), peroxidase (POD), chitinase, phenylammonialyase (PAL) and enhanced the content of phenolic compounds in tomato leaves. Furthermore, the combined application reduced the disease severity (%) of ToLCV in tomato plants. Although, the histopathological and histochemical studies revealed more destruction in the diseased plants, these changes could be reduced to the level of the healthy plants due to combined treatment of chitosan and Pseudomonas sp. Key words: Pseudomonas sp., Tomato leaf curl virus (ToLCV), induced systemic resistance, chitosan, biocontrol, Bemisia tabaci, histopathology.

Selection of tomato genotypes resistant to tomato leaf curl virus disease using biochemical and physiological markers

SUMMARYA total of 34 tomato genotypes (24 F1+10 parents) were tested for resistance to tomato leaf curl virus (ToLCV) disease by various whitefly inoculation techniques under field and insect-proof glasshouse (mass and cage) conditions. Of the ten tomato parental lines, two accessions [EC-520061 (Solanum habrochaites) and EC-521080 (Solanum pimpinellifolium)] were identified as highly resistant while four accessions (EC-520049, EC-528372, WIR-5032 and WIR-3957) of wild species were resistant to ToLCV. Out of the 24 F1 crosses, PBC×EC-520061, H-86×EC-520061, H-24×EC-520061 and DVRT-2×EC-520061 were found to be highly resistant against ToLCV disease. Biochemical (total phenol and total sugar concentration) and physiological (chlorophyll content and leaf area index) parameters were also used in healthy and disease-inoculated leaves of ten parents and six F1 hybrids to test the conformity of ToLCV-resistant and susceptible disease reactions. The results showed that among the 16 genotypes (10 parents+6 F1), EC-520061, EC-520049, PBC×EC-520061 and H-86×EC-520061 were stable for both biochemical and physiological markers while EC-521080 showed higher accumulations of total phenol and sugar concentrations and reduced leaf size between healthy and disease-inoculated leaves. The present study demonstrates the importance of the whitefly inoculation technique and biochemical and physiological markers in virus resistance screening programmes, and identifies a potential source of resistance to the ToLCV in Solanum species.

Reaction of some tomato cultivars to tomato leaf curl virus and evaluation of the endophytic colonisation with Beauveria bassiana on the disease incidence and its vector, Bemisia tabaci

Tomato line LA1478 and Pusa Ruby were resistant to tomato leaf curl virus (TLCV) disease. They registered higher plant height, number of branches, total phenol content and yield per plant than the other cultivars. Variety Peto 86 was tolerant to the disease while the other popular tomato cultivars, i.e. Ace, Early Pack, Money Maker, Prichard and Strain B were highly susceptible to the disease. Plant height and number of branches per plant revealed significantly positive association with fruit yield per plant. The disease index of TLCV exhibited significant negative correlations with plant height, total phenol content and fruit yield per plant – 0–4 and 5–25 adult whiteflies were observed on resistant susceptible cultivars. In the case of epiphytically colonisation by Beauveria bassiana conidia, not all developing hyphae on the leaf surface penetrated the whitefly cuticle. Many of the germ tubes elongated to a short distance before terminating its growth. On the other hand, the rapid staining of tomato tissues injected with B. bassiana conidial suspension indicates that the entomopathogenic fungus was established inside tomato tissues until the end time of the trial. The direct injection with the spore suspension yielded high post-colonisation, where the fungus was recovered from sites distant from the point of inoculation. This indicates that the fungus has the potential to move throughout the plant tissues. Laboratory bioassay of tomato whitefly feeding on tomato tissues containing B. bassiana conidial spores indicates that plant endophytic colonisation with entomopathogenic fungi may reduce insect survival on these plants. LT50 values of the test diet were between three and four days. The mortality of Bemisia tabaci was high in the case of endophytically colonisation compared to epiphytically one (90.0% compared to 10.0% during three days) for whiteflies fed tomato tissues containing 1.5 × 107 B. bassiana spores/ml. Application of B. bassiana as an artificial endophyte inside tomato plants can be an important component in the integrated control of tomato whiteflies. The endophytic colonising can achieve biocontrol effect based on induced disease resistance in plant tissues. According the available references, this is the first report on B. tabaci controlling by plant endophytic treatment.

In silico analysis reveals that several tomato microRNA/microRNA∗ sequences exhibit propensity to bind to tomato leaf curl virus (ToLCV) associated genomes and most of their encoded open reading frames (ORFs)

Tomato leaf curl virus (ToLCV) is a member of family geminiviridae that constitute rapidly emerging group of phytopathogens posing threat to a large number of vegetable crops worldwide. Three different genomes are found to be associated with ToLCV viz., DNA-A, DNA-B and beta satellite DNA. MicroRNAs (miRs) are known to govern several fundamental processes in eukaryotes, including basal defense mechanisms. In animals, it has been demonstrated that certain host miRs prevent viral establishment by directly interfering with pathogen replication or by binding to viral transcripts. However, in spite of the existence of huge families of phytopathogenic viruses, no such mechanism has been observed in plants. In the present study, we performed in silico analysis to investigate whether tomato encoded miR/miR* sequences possess any potential to bind to viral genome and/or encoded ORFs. We observed that different sequences can bind to ToLCNDV DNA-A, ToLCNDV DNA-B and ToLCNDV associated DNA beta genomes and most of the encoded ORFs. Interestingly, our analysis revealed that several miR* species could similarly target genome and ORFs of ToLCNDV suggesting novel role of miR* in host defense response. This observation holds much importance as miR* molecules are presently thought to follow degradation pathway and are not assigned with any function. Moreover, we could predict targets for these miR* sequences that are generally involved in plant metabolism. Overall, these results shed light on new paradigm of intricate host-pathogen interactions via miRNA pathway.

Tomato Production in the Hot-wet Season using Grafting and Rainshelter Technology

Production of tomato (Lycopersicon esculentum) during the hot-wet season in the lowland humid tropics can be increased using grafted plants and rainshelter. This technology can reduce soil-borne diseases, improve the ability of tomato plants to tolerate high temperatures and flooding due to high rainfall, and protect the crop from the impact of heavy rains. AVRDC has developed tomato lines that are resistant to virus diseases and high temperatures. This experiment was conducted to evaluate the performance of these lines in the hot-wet season, with and without rainshelter protection. Tomato lines (CHT501, TLCV15, and FMTT847) were grafted onto eggplant (Solanum melongena cv. EG203) rootstock and grown under rainshelter and open field. Nongrafted plants of three lines were also grown under two rainshelter treatments. The experimental design was a split-plot with four replications. Plants were managed using AVRDC standard practices for summer tomato production. TLCV15 and FMTT847 were highly resistant to tomato leaf curl virus (ToLCV), whereas CHT501 was greatly infected by the virus disease. All nongrafted plants died from bacterial wilt, whereas grafted plants survived the disease and outyielded nongrafted plants by 233% in the open field and 143% under rainshelters. Plants under rainshelters had a slightly lower yield than in the open field, but the difference was nonsignificant. Due to lack of frequent high rainfall during the season, the benefit of rainshelter was not detected and realized. It was concluded that TLCV15 and FMTT847 are well suited for grafted tomato production during the hot-wet season.

Phylogenetic Analysis and Homologies of the Replicase of Tomato Leaf Curl Geminiviruses: Implications for Obtaining Pathogen Derived Resistance

Geminiviruses encode a replication initiator protein, Rep, which binds to iterated DNA motifs functioning as essential elements for virus specific replication. Rep protein gene of three isolates of whitefly transmitted geminivirus causing leaf curl disease of tomato in India were amplified, cloned and sequenced. Nucleotide sequence and the derived amino acid sequence for the replicase gene of these isolates was determined and included in an analysis with the published sequences. Phylogenetic relationship clearly indicates two subsets, one belonging to Tomato leaf curl virus (ToLCV) having bipartite genome and the other having the monopartite genome. Comparisons of various functional domains and motifs involved in specificity determinants, DNA-binding and catalysis were discussed. The implications of the sequence analysis were discussed with respect to the strategy for the generation of engineered resistance having wide spectrum applications.

Transfer of Tomato Leaf Curl Virus Resistance from Lycopersicon hirsutum f. glabratum to L. esculentum

AbstractSix lines, i.e., H‐2, H‐11, H‐17, H‐23, H‐24, and H‐36, resistant to Tomato Leaf Curl Virus (TLCV) have been developed with controlled introgression of L. hirsutum f. glabratum into Lycopersicon esculentum. The disease incidence, 120 days after inoculation, of those lines derived from L. hirsutum f. glabratum ranged from 8.3 to 35.0 %, whereas in susceptible varieties it ranged from 95.0 to 100 %. The coefficient of infection (CI) values in the resistant lines were very low, ranging from 0.25 to 4.55, whereas in susceptible varieties CI values ranged from 60.56 to 88.96. Line H‐2 had the highest resistance by showing the least disease incidence and CI values. The fruit size and days to maturity in resistant lines were close to those of cultivated susceptible varieties. These lines have the scope for being used as varieties in the TLCV infested areas or as foundation lines for further genetic improvement.

Sources and inheritance of resistance to leaf curl virus in Lycopersicon

One hundred and twenty-two varieties, lines and wild accessions of Lycopersicon were screened under three different regimes during the autumn/winter season of 1982-83 and 1983-84 for resistance to tomato leaf curl virus (TLCV). L. hirsutum f. glabratum ('B6013') and L. hirsutum f. typicum ('A1904') proved to be highly resistant to TLCV in all three environments. Various accessions of L. peruvianum were also highly resistant. L. pimpinellifolium ('A1921') exhibited no TLCV symptoms within 90 days. Of the cultivated varieties, 'Acc 99' exhibited the minimim score for susceptibility; 'AC 142', 'Collection No. 2', 'Kalyanpur Angurlata' and 'HS 101' had a low rating for virus incidence. The inheritance of resistance was studied in the interspecific crosses between a TLCV resistant line of L. pimpinellifolium ('A1921') and five ('HS 101', 'HS 102', 'HS 110', 'Pusa Ruby' and 'Punjab Chhuhara') susceptible cultivars of L. esculentum. Parents, F1, F2 and backcross progenies were artificially inoculated with local strains of TLCV using vector the viruliferious whitefly, Bemisia tabaci (Genn.). Data indicated that the resistance of L. pimpinellifolium ('A 1921') is monogenic and incompletely dominant over susceptibility.

Inheritance of tomato leaf curl virus resistance in Lycopersicon hirsutum f. glabratum

Inheritance of resistance to tomato leaf curl virus (TLCV) was studied in the progenies derived from interspecific crosses between TLCV resistant Lycopersicon hirsutum f. glabratum line B 6013 and five susceptible cultivars (HS 101, HS 102, HS 110, Pusa Ruby and Punjab Chhuhara) of L. esculentum. P1, P2, F1, F2, B1 and B2 progenies of the five crosses were artificially inoculated with local strains of TLCV by means of the vector whitefly, Bemisia tabaci (Genn.). and the disease reaction was studied in all the crosses. Reaction of parents, F1, F2 and backcrosses suggests that resistance derived from L. hirsutum f. glabratum B 6013 is based on two epistatic genes, one from the wild parent and one from the cultivated one, resulting in a 13:3 segragation in the F2.