Identificação de QTL's e validação de marcadores na seleção de linhagens de feijão-comum para resistência à murcha-de-fusário

Abstract

Fusarium wilt, caused by the fungus Fusarium oxysporum f. sp. phaseoli, is a soil disease that causes lots of damage to the production of common beans (Phaseolus vulgaris L.). The use of resistant cultivars is the most recommended method, but there are few cultivars available on the market with resistance to the disease. Therefore, the objectives of this work were: a) to estimate genetic parameters and select common bean lines with commercial carioca standards and resistant to fusarium wilt and b) to study genetic control and to identify molecular markers associated with resistance alleles in the BRS Esplendor cultivar. In the first study, two experiments were conducted during the winter harvest, in the years 2019 and 2020, in an area with high natural infestation of the pathogen, located in Santo Antônio de Goiás, Goiás, Brazil. The design was in randomized blocks with plots of 3 rows of 3 meters and 3 replications. The 60 lines originating from a segregating population obtained from the parents BRS FC402 (resistant) and BRS FC406 (susceptible) and two controls were evaluated for reaction to fusarium wilt, productivity, mass of 100 grains (M100) and grain color after harvest. From individual and joint analyzes of variance, heritabilities and expected gains from selection (GS%), with an intensity of 25 for the four traits individually and simultaneously, and correlations were estimated. Significant differences were observed between the lines for all characters. The heritability estimates in the joint analysis were 74% for fusarium wilt, 73% for productivity, 91% for M100 and 52% for grain color, demonstrating that there is a great possibility of success with the selection. Fifteen lines were selected for the four traits simultaneously resulting in gains of 13.3%, 7.9%, 2.4% and 3.5% for fusarium wilt, productivity, M100 and grain color, respectively. Among these, CNFC20188, CNFC20134, CNFC20160 and CNFC20142 stand out. There was significant correlation for the reaction to fusarium wilt with productivity and M100.The second study was carried out using 103 progenies, resulting from the cross between BRS Esplendor (resistant) x BRS Horizonte (susceptible), and controls evaluated in a field naturally infested with the pathogen in Santo Antônio de Goiás, Goiás, Brazil. The experiments were conducted in the winter harvest of 2018 and 2019, using a randomized block design with plots of a three-meter row and three replicates. The reaction to fusarium wilt was evaluated with scales of scores ranging from 1, plants without symptoms, to 9, severely infected plants. The F2 progenies were genotyped using DArTseq technology, resulting in SNPs and SilicoDArTs markers, used in the construction of the linkage map and genetic mapping to identify regions of interest. Finally, the data obtained were validated by creating a hydrolysis probe and subsequent verification in progenies from the BRS Esplendor cultivar. Genetic variability was observed in the population, with heritability of 97% and genetic gains of 48% in the joint analysis, which indicates a high possibility of success with the marker selection. The linkage map was constructed with 2,189 markers, with a size of 2854.39cM. It was concluded that the inheritance of the character is poligenic, identifying a QTL with greater effect, located on the PV08 chromosome. This QTL showed stability in the different years tested and explained 66% of the phenotypic variation of the data in the joint analysis. The AN33KKZ probe, associated with the identified QTL, showed an efficiency of 97%, and could be an efficient tool to incorporate selection assisted by molecular markers (SAM).