Reciprocal recurrent selection effects on the genetic structure of tropical maize populations assessed at microsatellite loci

Abstract

A modified reciprocal recurrent selection (RRS) method, which employed one cycle of high-intensity selection, was applied to two tropical maize (Zea mays L.) populations, BR-105 and BR-106, originating the improved synthetics IG-3 and IG-4, respectively. In the present study the effects of this kind of selection on the genetic structure of these populations and their synthetics were investigated at 30 microsatellite (SSR) loci. A total of 125 alleles were revealed. A reduction in the number of alleles was observed after selection, as well as changes in allele frequencies. In nearly 13% (BR-105) and 7% (BR-106) of the loci evaluated, the changes in allele frequencies were not explained, exclusively due to the effects of genetic drift. The effective population sizes estimated for the synthetics using 30 SSR loci were similar to those theoretically expected after selection. The genetic differentiation (G ST ) between the synthetics increased to 77% compared with the original populations. The estimated R ST values, a genetic differentiation measure proper for microsatellite data, were similar to those obtained for G ST . Despite the high level of selection applied, the total gene diversity found in the synthetics allows them to be used in a new RRS cycle.

Assessment of Genetic Diversity of NIFOR Oil Palm Main Breeding Parent Genotypes Using Microsatellite Markers

“…However, genetic diversity evaluation based on agromorphological information alone is no longer sufficient because of low polymorphism, long juvenile phase, and vulnerability to environmental effects [17]. An additional and objective measure of genetic variation which will permit the monitoring of genetic variability within and between populations, efficient selection of parents to maximize heterosis among populations and sustained genetic progress in the RRS programme is compulsory [18] [19].…”

Functional molecular markers (EST-SSR) in the full-sib reciprocal recurrent selection program of maize (Zea mays L.)

“…The use of molecular markers in recurrent selection programs initially aimed to investigate changes in allele frequencies resulting from the selection inherent in this method (Labate et al, 1997;De Koeyer et al, 2001;Pinto et al, 2003a). However, the use of this molecular tool to assist the breeder during the implementation steps of recurrent selection was observed from the study of Tardin et al (2007), where the authors used molecular information to identify the most divergent genotypes in two corn populations in a full-sib reciprocal recurrent selection (FSRRS) program, seeking to maximize the genetic gains through exploration of heterosis.…”

Comparative analysis of genetic diversity among the maize inbred lines (Zea mays L.) obtained by RAPD and SSR markers

“…The genetic diversity evaluation by the means of the molecular markers presents some advantages over other methods because, in addition to identifying the high polymorphism, they do not present interactions with the environment, and can be evaluated at any stage of development (Williams et al, 1990). PCR-based techniques such as RAPD (Random Amplified Polymorphic DNA) and microsatellites have been widely used in the corn genetic studies (Heun and Helentjaris, 1993;Gupta et al, 1994;Taramino and Tingey, 1996;Senior et al, 1998 andPinto et al, 2003). The RAPD consists in the random amplification of the DNA fragments with a single primer with an arbitrary sequence, resulting in the final synthesis of several DNA fragments, with different sizes.…”