Alternatives for selection of common bean with upright plant type and Carioca grain type

Abstract

In common bean (Phaseolus vulgaris L.), upright plant type and light cream with brown stripe grain color – Carioca type – are important phenotypes in the cultivars to assure their acceptance by the growers. However, it has been some trouble to associate those phenotypes. So, it were obtained segregant populations with different allelic frequencies, aiming to check which one is better for improving the efficiency of selection of both traits. It were used the lines H-4 and H-15 that have the desired grain type, and the Carioca MG cultivar, that has upright plant type. Three segregant populations were obtained from each cross, with 50% of the alleles of Carioca MG (F₂ generation), 25% of the alleles of Carioca MG (F₁generation from backcross with H-4 or H-15) and 75% of the alleles of Carioca MG (F₁ generation from backcross with Carioca MG). Thirty two families from each population with a particular allelic frequency were evaluated based on those two traits, using a note scale, during two years, 1995 and 1996. The highest frequency of families with upright plant type and acceptable grain type was selected from the population with 25% of Carioca MG allelic frequency. So the best strategy is to perform cross with the cultivar with the best grain type. However, even with that strategy it was verified that the frequency of families bearing the desired phenotypes was very low.