Development and selection of transgenic advanced lines of carioca seeded common bean with multiple resistance to viruses

The most important viruses infecting common bean ( Phaseolus vulgaris L.) in Brazil are BCMV, BGMV and CPMMV, the last two transmitted by the whitefly Bemisia tabaci occurring simultaneously and causing severe yield losses. Embrapa has previously developed a genetically modified common bean cultivar carrying the 5.1 transgenic event for resistance to BGMV, which is commercially available. This cultivar also carries the gene I , which confers resistance to BCMV. Recently, sources of natural resistance to CPMMV were identified in common bean cultivars from the carioc a market class. So, the objective of the present work was to develop new commercial carioca breeding lines with multiple resistance to viruses (BCMV, BGMV and CPMMV), using conventional breeding and molecular tools. Agronomic performance and virus disease severity (VS) were evaluated in two field trials, allowing the selection of 39 superior progenies out of 477 row-progenies tested. Molecular analyses identified the presence of BCMV and BGMV resistance alleles in individual plants. CPMMV resistance was screened by mechanical inoculation of plants. Five progenies showed resistance to BCMV, BGMV and CPMMV, in addition to upright plant architecture, tolerance to plant lodging and carioca market class grains, presenting therefore potential to be a new transgenic cultivar with multiple virus resistance. Additionally, the resistant progenies may also contribute to reduce virus spread in the field, as they were a less efficient inoculum source of CPMMV as shown by insect transmission assays.