Abstract
The utilization of diallel crosses for identification of superior combinations is a common practice in maize (Zea mays L.) breeding programs. This methodology allows the estimation of the combining ability of genotypes being evaluated. In this work, five inbred lines were evaluated as to their general (GCA) and specific (SCA) combining abilities, by using a complete diallel scheme. The single-crosses produced between these inbred lines were evaluated in seven environments, along with two checks, by using a randomized complete block design. Traits analized were: grain yield, plant height, ear height, ear placement, and prolificacy. A diallel analysis was carried out, following an adaptation of Griffing's method IV, in addition to hybrid stability and adaptability analyses. Significant differences were detected for entries and environments for all traits. The interaction genotype vs. environment was significant for all traits. GCA's were significant for all traits, while SCA's were non-significant only for ear placement. For grain yield, both additive (GCA) and non-additive (SCA) effects were important, while for the remaining traits additive effects were more important. The high yielding single-cross was obtained from the cross of lines L-08-05F and L-38-05D. Those inbred lines showed higher GCA's and their cross also had high SCA; also, it is responsive to environment improvements and reasonably stable. The second in rank high yielding single-cross, L-46-10D x L-08-05F, showed wide adaptability and stability.
Highlights
In addition to being an economically important crop, maize has genetic characteristics that allowed this species to be widely studied, contributing for an understanding of many questions of a genetic nature
general combining ability (GCA) is associated with additive effects of the genes, while specific combining ability (SCA) is related to dominance and epistatic effects of the genes
The lines were: L-3805D: is a yellow dent kernels inbred line extracted from the single-cross used as female for the commercial double-cross BR-201; L-46-10D: is a yellow dent kernels inbred line extracted from the BR-201; L-49-02D: is a yellow dent kernels inbred line extracted from the cross between populations BR-105 and BR-106; L-08-05F: is a orange flint kernels inbred line extracted from population IG1; L-36-07F: is a orange flint kernels inbred line extracted from the single-cross used as female for the commercial double-cross BR-201 .The ten singlecrosses possible from the crosses of these lines were obtained, following a complete diallel scheme; reciprocal crosses were not included
Summary
In addition to being an economically important crop, maize has genetic characteristics that allowed this species to be widely studied, contributing for an understanding of many questions of a genetic nature. Given the great economic importance of maize, genetic breeding in this crop is very intense, and mostly targeted at increasing grain yield. A very frequently method used in maize breeding is to obtain inbred lines that are later crossed in order to develop single-crosses, in which exhibit high heterosis when the inbred lines are complementary, and have high uniformity in the farms. The performance of a hybrid is related to the general (GCA) and specific (SCA) combining abilities of the inbred lines involved in the cross (Sprague & Tatum, 1942). The estimates of general (GCA) and specific (SCA) combining abilities of a group of inbred lines are obtained from the analysis of diallel crosses
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