Variability and inbreeding in semiexotic maize populations

Abstract

ABSTRACT. Three semiexotic populations (CRE-01, CRE-02, CRE-03) obtained by incorporation of exotic germplasm (lines from CIMMYT, Colombia; selected for resistance to corn stunt complex) were evaluated in two cycles of recurrent selection with half-sib families. In cycle-I, samples comprising 50, 70, and 50 half-sib families were evaluated at Jataí (GO) and traits analyzed were ear yield, plant height, and ear height. For yield (t/ha), populations means were 5. 86, 6.19, and 5.31, representing approximately 73% of hybrid check. Sets of parameters estimates representing the three populations were: [237, 485, and 608] for the additive genetic variance ( In cycle-II, materials analyzed included 60 non-inbred (half-sib) and 60 inbred (S 1 ) families from each population, evaluated at Anhembi (SP) with two replications; traits analyzed included ear yield plus ear weight and grains weight of four ears, two plant traits (plant height and ear height), two ear traits (length and diameter), two tassel traits (branch number and length), and resistance to corn stunt complex. Means of half-sib families for ear yield (t/ha) were [10.614, 10.419, 10.842], representing 83 to 86% of the hybrid check. The same pattern of variation was observed for ear Variability and inbreeding in maize weight and grain weight of four ears. Means of S 1 families were [6.465, 5.527, 5.925] and the inbreeding depression in percent of the non-inbred families were [39.1, 46.9, 45.3]. Estimates for other traits are also shown.

Inbreeding depression and performance of partially self-fertilized maize progenies in a top cross

“…In the analysis of inbreeding depression, we used the inbred families (S1) and plots that were representative of the base population (random pollination), from the same population, which allowed us to estimate the population parameters. We used the basic model adopted by Oliveira et al (2015) for population mean, as follows: m0 = u + a * + d * = A + d * where u is half of the difference between the genotypic values of homozygotes for all loci; a * is the contribution of homozygotes to the mean; d * is the contribution of heterozygotes to the mean.…”

“…However, in the evaluation of genetic material, it is important to consider both the additive effect, which is estimated when all loci are homozygous, and the dominance effect, which is related to the level of inbreeding depression. Oliveira et al (2015) studied three semiexotic populations of maize (CRE-1, CRE-2, and CRE-3). They found depression by inbreeding with one generation of self-fertilization, indicating that the phenotypic mean value of the three populations under inbreeding reduced in comparison with the random-mating population.…”

Genetic variability and breeding potential of Flintisa Composite of maize in two levels of technology

“…Over the selection cycles, this procedure helps in the checking, from time to time, of the evolution of genetic variability and the need for changes in the selection process (Freitas Júnior et al 2009). Large ranges of values in the genetic parameter estimates are reported for the traits studied in this work, as well as other traits that make part of yield components in Brazilian maize populations (Candido and Andrade 2008, Andrade and Miranda Filho 2008, Faluba et al 2010, Reis et al 2014 and semi-exotic populations (Oliveira et al 2015, Souza et al 2018).…”

Evaluation of diallel crosses of maize at multilocation (Zea mays L.) for saline tolerance

“…Such great changes justify the interest for new sources of germplasm to increase the chances of success of breeding programs to attend the new and expanding demands for adapted and outstanding genotypes. Recently, there has been an increasing interest for new sources of germplasm, particularly focusing the resistance or tolerance to several kinds of stresses (Basso and Miranda, 2001;Oliveira et al, 2015) like soil salinity.…”