Procedimentos para a identificação de progênies superiores em gerações sucessivas de avaliação na cultura do feijoeiro

Abstract

Bulk within progenies derived from F2 or S0 plants is one of the most used breeding methods for common bean. When using this method in Brazil the progenies are evaluated in experiments with replications from F2:3 or S0:1. This assessment continues for four or five generations. Usually, the selection made by generation is done based only on previous generation information. However, some papers published recently show that if the evaluation is performed considering all the generations, the selection gain can be greater, especially when using an index that involves the original population information. What is not known is if using field data the advantage of the selection index remains in future generations, what is the difference when only the progenies means are used and when an index that considers the heritability among populations and the heritability among progenies within populations is applied. Thus, the aim with this study was to compare three selection procedures among successive generations of evaluation and to verify the coincidence in the rank of the progenies identified as the best ones in past generations and the same progenies in future generations. Additionally, we discuss the progenies x environments interaction implications selection success. Progenies of the XV cycle of Universidade Federal de Lavras common bean recurrent selection program were used. S0:1 progenies from 19 populations were evaluated, with approximately 23 progenies by population, in a total of 439 progenies. 322 S0:2 and S0:3 progenies and 79 S0:4 progenies were evaluated. The experiments were carried out in Lavras, MG, Brazil, in the period of 2015 and 2016. The evaluated traits were grain yield, plant architecture and grain type. With the data obtained, by generation or set of generations, we performed the analysis of variance using the least squares method and estimated the means and the components of genetic and phenotypic variance. The same analyzes were performed using mixed models, considering in the model the effect of populations to obtain the BLUP's. A selection index (ISP) was also weighted by heritability among populations and heritability within populations. The correlations between the progeny rank were estimated using the three procedures: means, BLUP's and ISP, in the same generation and in successive generations. The coincidence of the best progenies evaluated in S0:4, with the same progenies in previous generations by the three procedures was also estimated. It was found that the progenies rank by BLUP's and the ISP did not differ significantly from the means only, even when considering several generations in the selection. Any of the procedures used did not effectively mitigate the effect of interaction progenies x environments, because the coincidence in the selection efficiency of one or more generations with a future generation was small and there was a little variation between the adopted procedures.