Limits in recurrent selection. I. Factors affecting the increment in allelic frequencies

• Autor(a) principal: Pereira, Mauricio B.
• Data de Publicação: 2014
• Outros Autores: Vencovski, Roland
• Tipo de documento: Artigo
• Idioma: por
• Título da fonte: Pesquisa Agropecuária Brasileira (Online)
• Texto Completo: https://seer.sct.embrapa.br/index.php/pab/article/view/13961
• topic: selection limits; gene fixation; effective size; maize; Zea mays; limites da seleção; fixação de genes; tamanho efetivo; milho; Zea mays

The limit of intrapopulational recurrent selection and the main factors affecting it were investigated, through the total change in allelic frequency, until total depletion of genetic variability, and was computed through the probability of ultimate fixation of favorable alleles. Half mass selection was considered as reference selection scheme, in a panmitic species. For different combinations of the main factors 360 values of the total change were calculated. Despite the restrictions, it was concluded that selection limit is strongly unfavored when we combine: a low coefficient of heritability (h2), small effective population size (Ne), weak selection intensity, low initial frequency of favorable alleles and a trait controlled by loci with small effects. When one of these factors is at an inadequate level, it can be compensated through changes in the others. High Ne values, during selection cycles, can be chosen for such compensation, provided k is not reduced correspondingly, since, in this case, immediate progress will be reduced. Low experimental precision reduces h2, so a high Ne is needed. The product Neh is a good measure of how much Ne a should be increased if h2 is reduced. The model was applied to corn yield data, and the use of local populations for breeding purposes, which have as only advantage its adaptations, was commented. It was also verified that 80% to 85% of the total change in allelic frequency variation is due to factors under the control of the breeder. This indicates that schemes can be chosen not only to assure adequate immediate progress but also appropriate selection limits.