Melhoramento molecular do feijão-comum para resistência múltipla a viroses
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2021-06-14
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Universidade Federal de Goiás
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Among the diseases that affect the common bean (Phaseolus vulgaris L.), viruses deserve to be highlighted, since they are difficult to control and cause partial or total yield and grain quality losses. In Brazil, the main viruses of beans are: the common mosaic, caused by the Bean common mosaic virus (BCMV), the golden mosaic, whose causal agent is the Bean golden mosaic virus (BGMV) and the soybean stem necrosis disease, caused by Cowpea mild mottle virus (CPMMV). The symptoms of CPMMV emerged in common beans more recently in agronomic performance tests with the transgenic cultivar BRS FC 401 RMD, which presents effective resistance to BGMV (event Embrapa 5.1). The symptoms of CPMMV were confused or hidden by the more severe symptoms of BGMV, and both viruses occur simultaneously in the field and are transmitted by the whitefly (Bemisia tabaci), mainly in Central region Brazil. Thus, two studies were carried out with the objectives of: i) develop, evaluate and select transgenic common bean progenies, second generation, with carioca market class, good agronomic performance and with multiple resistance to viruses BCMV, BGMV and CPMMV, and ii) to investigate genetic inheritance of the CPMMV and to genetically map loci of resistance to CPMMV in the carioca seeded cultivar BRS Sublime. In the first study, elite progenies were developed from crosses using the carioca seeded cultivars BRS Estilo and BRS Sublime (both showing resistance to CPMMV and BCMV), with the transgenic line CNFCT 16206 (event Embrapa 5.1; effective resistance to BGMV) and resistant to BCMV. The recovery of elite progenies with a greater proportion of parents was performed through the analysis of backcrosses assisted by SSR and SNP markers. Thus, 39 elite progenies were evaluated in field condition, in the rainy (2016) and dry (2017) growing seasons, and in an insect-proof screenhouse. The evaluated traits were the seed yield and mass of 100 seeds, plant architecture and tolerance to lodging, seed appearance, and virus disease severity (VS). The elite progenies in addition to the controls were mechanical inoculated at eight days after planting with the strain (CPMMV: BR:GO:14 – GenBank MK202583), and were evaluated, at 35 days after inoculation, for severity of CPMMV. These progenies and the controls were also evaluated for the presence of the event Embrapa 5.1 (marker Ahas) and gene I (marker SCAR SW13). The result of the joint analysis showed variability between the progenies for all characters evaluated, especially SV, except for ARQ, considering the two environments, with P × E interaction (P ≤ 0.01). All elite progenies showed effective resistance to BCMV and BGMV, with the exception of progeny 336-3.1 (BGMV), whereas the conventional controls were susceptible to BGMV, and the transgenic control (cv. BRS FC401 RMD,) and the progenies were susceptible to CPMMV. Thus, the severity of CPMMV was assessed in progenies and transgenic controls. Twelve elite progenies showed mean scores ≤ 3.0 for VS. Of these, the progenies 184-12.1, 356-5.1, 398-3.1, 417-22.1 and 422-39.1 showed resistance to BCMV, BGMV and CPMMV. Therefore, the use of conventional breeding strategies and marker-assisted selection (SAM) enabled the development and selection of elite transgenic carioca-seeded cultivars, second-generation, with carioca-seeded market class, better plant architecture and allowing direct mechanical harvest, with multiple resistance to viruses and presenting potential to be evaluated in agronomic performance tests. In the second study, the genotyping of SNP and SilicoDArT markers was performed using the DArTseq technology, in a mapping population in the F2 generation obtained from the crossing between the cultivar BRS Sublime (resistant) e transgenic line CNFCT 16207 (susceptible). All F1 plants were tested with molecular marker linked to the event Embrapa 5.1 to confirm the hybrid nature. The plants were conducted in an insect-proof screenhouse. Thus, a total of 180 F2 individual plants and 180 F2:3 progenies (2160 seedlings; 12 seedlings/progeny), in addition to the parents, were mechanically inoculated with the same CPMMV isolate, at eight days after planting. At 35 days after inoculation, the plants were evaluated for severity of CPMMV. The phenotypic data were subjected to the chi-square test (ꭕ2) (P ≤ 0.05), considering the expected mendelian segregation ratio for each generation. The complete genetic map was obtained with 1.695 markers segregated according to the expected frequency and distributed in the 11 chromosomes of the bean, with total length of 2.864 cM and average distance between marks of 1.8 cM. The results indicated that a single dominant gene controls the inheritance of CPMMV resistance in the cultivar BRS Sublime. The QTL – single Gene (CPMMV. Pv08) was identified in the final region of chromosome 8, associated with resistance to CPMMV and explaining ~77% of the phenotypic variation. This is the first report to study genetic inheritance and genetically map locus to CPMMV resistance in BRS Sublime. The construction of the genetically map and the QTL analysis approach generates new perspectives for common bean breeding programs, with the potential for development and validation of molecular markers to be used through SAM for reaction to CPMMV in common bean genotypes.
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SILVA, R. S. Melhoramento molecular do feijão-comum para resistência múltipla a viroses. 2021. 100 f. Tese (Doutorado em Genética e Melhoramento de Plantas) - Universidade Federal de Goiás, Goiânia, 2021.