Melhoramento genético do feijoeiro (Phaseolus vulgaris L.) para alto teor de proteínas

Abstract

The common bean is one of the most important component of the brazilian diet, in addition, is an agricultural product of great economic and social importance. In this sense, to attend the consumers exigencies, the breeding programs start to give attention for quality traits of the grain. This work is part of the quality bean breeding program being developed by BIOAGRO/UFV in partnership with Embrapa - Rice and Bean center and aims to increase the common bean protein content by means of backcrosses assisted by molecular markers. There were used the varieties Baliza, Laranja, Gaurama and PVA as gene donors for high protein content and the CNFC 7827 as recurrent genitor. To achieve this goal, specific steps were reached: (a) crossings high protein content genotypes with an elite cultivar (b) analysis of protein content of 400 F 2 seeds from each cross by using non-destructive method; (c) selection of seeds with high protein content from each cross (selection intensity of 10%); (d) fingerprinting the F 2 selected plants with RAPD markers; (e) backcrosses the selected F 2 plants with the recurrent genitor; (f) confirmation the protein content in the F 2:3 seeds by the Kjeldahl method; (g) selection and planting the RC1F1 based on genetic distances, obtained with molecular markers, and protein content of the F 2 plants selected and confirmed in the F2:3. All the populations had a high heritability varying from 58 to 77%, which suggested that they are adequate for selection or protein mapping loci. The general gains varied from - 0.95 to 4.26%, which indicates that the selection in F 2 has low efficiency when used isolated. However, the wide variation of protein content in F 2:3 and the gains observed (13,66 to 25,84% considering the five F 2:3 of high protein contents) demonstrate that the genes transfer process for high protein content by backcrosses is efficient when based on pre-selection of F 2 seeds and posterior selection of the best F 2:3 families . The selection gains for protein using molecular markers varied from 15.65 to 9.92%. The F 2 plants of the different populations had genetic distances regarding the recurrent genitor highly variable. It was possible to obtain similarity gains, regarding the similarity average found in the F 2 populations, varying from 12 to 16%. With the utilization of selected individuals of high protein content and genetically closer to the recurrent progenitor the number of backcrosses necessary to recover the genome of the recurrent should be smaller.