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Predicting the inbreeding and the outcrossing potential of soybean (Glycine max (l.) merrill) varieties

José Francisco Ferraz de Toledo

Empresa Brasileira de Pesquisa Agropecuária. Centro Nacional de Pesquisa de Soja, EMBRAPACNPSo, Caixa Postal 1061, 86001 Londrina, PR, Brasil

ABSTRACT

Predicting the outcome of a breeding program in its initial stages is a challenging but a feasible task facing the breeder. Means and variances of the parental varieties and of their F3 generation are required for making predictions on .the potential of a single cross for producing superior inbred lines (first cycle inbred lines). Means and variances of the parents and their F2 generation are required for the predictions of the hybrids we can produce by crossing those first-cycle inbred lines (second cycle hybrids). The early selection of the most promising material allows the breeders to allocate more efficiently their resources. The theoretical developments made are exemplified with data from soybean (Glycine max (L.) Merrill). The proportion of the first cycle inbred lines and second cycle hybrids maturing and flowering earlier, later, or within given standards were calculated from the F₂ and F₃ generations obtained from 28 crosses between eight soybean varieties (Pérola, Paraná, IAS 4, Davis, BR-5, Bragg, BR-1 and Bossier) grown in Londrina, PR, Brazil,. in the years of 1980/81 and 1981/82. The selection power of this approach of discriminating between potent and non-potent crosses was discussed.

Keywords: inbreeding; outcrossing; soybean; Glycine max.

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