Breeding strategies for recurrent selection of maize

José Marcelo Soriano Viana

doi:10.1590/s0100-204x2007001000003

Abstract

The objectives of this work were to analyze theoretical genetic gains of maize due to recurrent selection among full-sib and half-sib families, obtained by Design I, Full-Sib Design and Half-Sib Design, and genotypic variability and gene loss with long term selection. The designs were evaluated by simulation, based on average estimated gains after ten selection cycles. The simulation process was based on seven gene systems with ten genes (with distinct degrees of dominance), three population classes (with different gene frequencies), under three environmental conditions (heritability values), and four selection strategies. Each combination was repeated ten times, amounting to 25, 200 simulations. Full-sib selection is generally more efficient than half-sib selection, mainly with favorable dominant genes. The use of full-sib families derived by Design I is generally more efficient than using progenies obtained by Full-Sib Design. Using Design I with 50 males and 200 females (effective size of 160) did not result in improved populations with minimum genotypic variability. In the populations with lower effective size (160 and 400) the loss of favorable genes was restricted to recessive genes with reduced frequencies.

Highlights

Half-sib and full-sib families have been used and proved effective in the improvement of maize populations (Hallauer & Miranda Filho, 1988)
The lowest values were the result of half-sib selection in populations with intermediate gene frequency or improved populations
The gains in grain yield in a single cycle, estimated by Granate et al (2002) with half-sib families, by Pereira & Amaral Júnior (2001) with progenies of half-sibs and of full-sibs derived by the use of Design I, and by Daros et al (2002) with full-sib families obtained by Full-Sib Design were 4.22, 6.26 and 9.42, and 4.70%, respectively

Summary

Introduction

Half-sib and full-sib families have been used and proved effective in the improvement of maize populations (Hallauer & Miranda Filho, 1988). Full-sib selection is more efficient than half-sib selection, due to the better parental control. Predicted gains due to selection are higher. Owing to the possibility of exploiting a greater effective population size with greater ease of operation, half-sib selection is the common procedure. A recent exception is the work of Gonçalves et al (2007) with yellow passion fruit. Their objective was to evaluate alternative strategies of progeny selection for obtaining the best predicted genetic gain.

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Conclusion