Assessment of resistance of Ty-1 and ty-5 genes in Solanum lycopersicum plants infected with tomato yellow leaf curl virus (TYLCV)

Abstract

A group of viruses within the Begomovirus genus is responsible for tomato yellow leaf curl virus disease (TYLCVD). The genus Begomovirus belongs to the family Geminiviridae, which is divided into 14 genera. TYLCV is a virus that since its emergence in 1939 continues to severely affect tomato crops worldwide, partly due to its ease of recombination and emergence of new mutations. The virus is transmitted by the whitefly (Bemisia tabaci), and since measures to control B. tabaci populations are not fully effective and there is always a risk of infection, the best defence mechanism is genetic resistance. Two sets of breeding lines with different homozygous combinations of the Ty-1 and ty-5 genes (Ty-1 lines, ty-5 lines, Ty-1/ty-5 lines and susceptible lines) were studied. A priori, this is the first study of TYLCV inoculation under controlled conditions in lines carrying the Ty-1 and ty-5 genes. The aim of the study was to evaluate the behaviour of tomato breeding lines carrying these two genes and test their level of tolerance to TYLCV. All plants showed a homogeneous response depending on the genotype studied. The results of the breeding lines studied with all homozygous combinations of the Ty-1 and ty-5 genes were consistent with those of the controls. Susceptible genotypes (ss/SS) showed severe symptoms and high viral accumulation, and resistant genotypes (Ty-1/ty-5, ty-5 and Ty-1) showed very mild symptoms and low viral accumulation. The phenotypic responses to TYLCV can be classified into two groups: the susceptible genotypes (ss/SS) for the two genes and the resistant genotypes (Ty-1, ty-5 and Ty-1/ty-5), presenting Ty-1, ty-5 or both. In this study, we have demonstrated that both Ty-1 and ty-5, whether used together or individually, provide a similarly high level of resistance