ProporÃÃo alÃlica e eficiÃncia da seleÃÃo em populaÃÃes do cruzamento entre feijÃes andinos x mesoamericanos / Allelic proportion and selection efficiency in cross populations of andean and mesoamerican common bean

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Common bean (Phaseolus vulgaris L.) was domesticated in at least two distinct regions, in the Andes and the Mexican and Central American highlands. Andean and mesoamerican common beans, along the evolution process, developed clearly different phenotypic expressions for some traits. To increase genetic variability, improvement programs have focused on crossings between plants from both domestication centers. However, incompatibility barriers make most crosses unfeasible and when crosses are possible the performance of the segregating population is poor. The present study aimed to propose strategies that could enhance the efficiency in using the two gene pools. For this purpose, an andean parent, âBRS-Radianteâ, was crossed with a mesoamerican, âCarioca-MGâ. Populations with 12.5%, 25%, 50%, 75% and 87.5% of the allelic proportion from âCarioca-MGâ were established through backcrosses. From each population, 44 progenies of F2:3 and F2:4 generations were evaluated, sown in February 2006 and July 2006, respectively. The 220 progenies plus the two parents and three controls were evaluated in each generation in a 15 x 15 lattice design. Each plot consisted of one two-meter row. The evaluated traits were the number of days to flowering, weight of 100 grains and grain yield (g/plot). Concerning variability release, there was no tendency of consistent alteration in the populations with different frequencies of parental alleles. In general, they all presented sufficient genetic variance among progenies to allow selection gains. The population means differed according to allele frequency of parents. For grain yield, the lowest mean was observed in the populations with 50% of alleles from each parent. The ideal allelic proportion to be obtained has to be defined according to the target grain type. If large grains are desired, one or two backcrosses to the andean parent are recommended, prior to selection.

ASSUNTO(S)

gene pool phaseolus vulgaris agronomia retrocruzamento conjuntos gÃnicos phaseolus vulgaris backcrossing

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