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

Abstract

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.