Natural selection and the breederâs decision about the best moment to extract families in common bean. / SeleÃÃo natural e a decisÃo do melhorista sobre o melhor momento de abrir o Bulk na cultura do feijoeiro

AUTOR(ES)
DATA DE PUBLICAÇÃO

2003

RESUMO

The âbulkâ method presents some advantages, including the versatility in extracting families at any moment. Theoretically there is no justification in delaying line extraction beyond the F5 generation, but if there is action of natural selection in the direction required by the breeders, a question of whether delaying line extraction would increase the chance of obtaining families with greater grain yield. This study was carried out to investigate this issue. For this, a segregant population derived from the single cross between the Carioca MG cultivar and the ESAL 686 lineage was used. The Carioca cultivar has upright stand, normal cycle and small grains and ESAL 686 has upright stand, early cycle and large grains. The F2 generation was obtained by selfing and a portion of the seeds was stored. The remnant seed was conducted by the bulk method to F8, when again a portion was stored and the process repeated to F24. The three segregant F2, F8 and F24 populations were sown in March 2001 and at harvest 108 families from the F2 plants, 107 from the F8 and 107 from the F24 plants were obtained. These families and their parents were assessed for grain yield (kg/ha) in Lavras-MG in three growing seasons, winter (July 2001), wet season (November 2001) and the dry season (March 2002) in an 18 x 18 lattice design with two replications in the first sowing and three in the other two. Estimates of the genetic and phenotypic parameters were obtained for the individual and joint analyses using variance components. The largest mean yield, regardless of growing season, was among the families derived from the F24 plants, which was 20% greater than those of the families derived from F2 plants. The frequency of superior families increased when line extraction was delayed to more advanced generations, and hence the chance of extracting superior lines was increased.

ASSUNTO(S)

"bulk" mÃthods seleÃÃo natural melhoramento vegetal mÃtodo "bulk" segregant population avaliaÃÃo de famÃlias common bean-phaseolus vulgaris populaÃÃo segregante progenies evaluation natural selection plant breeding melhoramento genÃtico vegetal feijÃo-phaseolus vulgaris

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