Development of processing tomato lines resistant to Xanthomonas gardneri: From screening to breeding

摘要

Bacterial spot of tomato is caused by four species of Xanthomonas: X. euvesicatoria, X. vesicatoria, X. perforans and X. gardneri. The disease causes lesions on tomato leaves and black spot on fruits, leading to yield loss and nonmarketable tomatoes. The bacterial species X. gardneri has been recently implicated in outbreaks of bacterial spot in processing tomato fields in Brazil, Canada and the Mid-West United States. As chemical solutions are currently not reliable to control bacterial spot, the development of varieties resistant to X. gardneri and to the other Xanthomonas species is of primary interest. This project sought to identify sources of resistance to X. gardneri, to describe the genetic basis of the trait, and to develop strategies to improve selection for bacterial spot of tomato and for agronomic and fruit quality traits.;To identify sources of resistance to X. gardneri, wild and cultivated tomato accessions were evaluated for Hypersensitive Response (HR) and tested under inoculated field conditions. Both evaluation methods showed phenotypic variation explained by genetics. The results of the two assays were not significantly correlated. Field evaluation mimics natural epidemics, thus this method was the most reliable to identify sources of resistance to X. gardneri. Five S. pimpinellifolium and Four S. lycopersicum var cerasiforme accessions showed low disease levels in the field. S. pimpinellifolium LA2533 and S. lycopersicum var cerasiforme LA1545 were selected as sources of resistance. (Abstract shortened by ProQuest.).