Temporal genetic structure patterns in tropical maize populations under reciprocal recurrent selection

Abstract

In order to investigate the effect of long term recurrent selection on the pattern of gene diversity, thirty randomly-selected individuals from the progenitors (p) and four selection cycles (C0, C3, C6 and C11) were sampled for DNA analysis from the tropical maize (Zea mays L.) breeding populations, Atherton 1 (AT1) and Atherton 2 (AT2). Fifteen polymorphic Simple Sequence Repeat markers amplified a total of 284 and 257 alleles in AT1 and AT2 populations, respectively. Reductions in the number of alleles were observed at advanced selection cycles. About 11 and 12% of the alleles in AT1 and AT2 populations respectively, were near to fixation. However, a higher number of alleles (37% in AT1 and 33% in AT2) were close to extinction. Fisher's exact test and analysis of molecular variance (AMOVA) showed significant population differentiations. Gene diversity estimates and AMOVA revealed increased genetic differentiations at the expense of loss of heterozygosity. Population differentiations were mainly due to fixation of complementary alleles at a locus in the two breeding populations. The estimates of effective population at an advanced selection cycle were close to the population size predicted by the breeding method.

Long‐term on‐farm participatory maize breeding by stratified mass selection retains molecular diversity while improving agronomic performance

“…() and Solomon et al. (), in which the authors detected a loss of genetic diversity in maize population subjected to few as 11 and 12 cycles of reciprocal recurrent selection, no significant differences in genetic diversity levels were identified in the current study. According to Hoban et al.…”

“…() and Solomon et al. (). In addition, the results presented here concur with the results previously described for the Portuguese Pigarro maize population (Vaz Patto et al., ) where stratified mass selection demonstrated to be an effective way to conserve diversity on‐farm, and at the same time allowed relevant phenotypic improvements to be achieved.…”

“…(), in which the authors used molecular markers to access the genetic variability of cotton populations of a participatory breeding program and, as a direct result, farmers were advised to use another breeding methodology to increase the efficiency of the selection. Molecular markers have been also used to assess the temporal variation on maize genetic diversity due to human selection (Labate, Lamkey, Lee, & Woodman, and Solomon, Martin, & Zeppa, ). In Labate et al.…”

“…In Solomon et al. (), using other types of molecular markers to study the effects of reciprocal recurrent selection on tropical maize breeding populations, the authors reported a loss of 33%–37% of the alleles detected initially after 11 cycles of selection. Nevertheless, as reviewed by Rauf, Teixeira da Silva, Khan, and Naveed (), different plant breeding methods have shown different impacts on plant genetic diversity.…”

Combining ability, genetic diversity and heterosis in relation to F1 performance of tropically adapted shrunken (sh2) sweet corn lines

“…These heterotic populations were often developed through a long‐term recurrent selection programme, which results in fixation of complementary alleles (Labate et al. 1999, Solomon et al. 2010).…”