Marcador microssatélite associado ao alelo Ty-1 que confere resistência a begomovírus em tomate

Abstract

The tomato crop is plagued by many pests and diseases. Whiteflies (Bemisia spp.) are considered a major tomato pest because of their action as a vector of geminivirus diseases. Geminivirus diseases caused by species of the genus Begomovirus are of major economic significance. Resistant cultivars are the most promissing means of disease control, but few resistance sources have been deployed in the development of begomovirus resistant cultivars. The most widely deployed resistance source available in commercial hybrids is the resistance allele Ty-1. The objective of this work was to associate a microsatellite marker to the Ty-1 allele, and to verify its efficiency in the selection of begomovirus resistant lines. The microsatellite markers SSR-47 and SSR-48 were initially tested in isogenic lines with constrasting genotypes for the presence of the Ty-1 allele. The SSR-47 was polymorphic, and was the only marker used subsequently. The association between SSR-47 and the Ty-1 allele was further tested in the selection of advanced tomato genotypes. In order to test the efficiency of the selection, plants with contrasting band patterns were tested for their reaction to begomovirus. All plants with a single 191 bp band were found to be begomovirus resistant following a graft inoculation with the virus, and all plants with a single 180 bp band were found to be susceptible. Plantas with both bands were also rated as resistant. Reaction of plants to begomovirus infection was consistant with the results expected from selection with the SSR-47 marker. The maximum estimated distance between the begomivirus resistant allele Ty-1 and the SSR-47 marker was 2,7 cM, and the marker was therefore considered efficient as a tool for selection for begomovirus resistance.