Heterotic grouping of tropical early-maturing maize inbred lines based on combining ability in Striga-infested and Striga-free environments and the use of SSR markers for genotyping

Heterotic Patterns of IITA and CIMMYT Early‐Maturing Yellow Maize Inbreds under Contrasting Environments

“…Mean values (± SE) for grain yield of hybrids within and between heterotic groups based on HSGCA, HGCAMT, and single nucleotide polymorphism-based genetic distance (SNP-based GD) methods under drought, low soil nitrogen (low-N), in optimal conditions and across the three research environments. DISCUSSION In the present study, significant mean squares were detected for G, E, and GEI for most measured traits under drought stress, low N, and in optimal growing conditions and across environments indicating that the test environments were unique and that there was adequate genetic variability among the early yellow hybrids to allow good progress from selection for improvements in most of the traits (Badu-Apraku et al, 2011b;Akinwale et al, 2014). Furthermore, the significant GEI suggested differential responses of the genotypes and the need to identify high-yielding and stable genotypes across test environments (Sabaghnia et al, 2008;Moghaddam and Pourdad, 2009).…”

“…This implied that significant breeding progress could be made using inbreeding, hybridization, backcrossing, and recurrent selection methods for the development of hybrids and synthetics as well as in population improvement. Moreover, these results suggested that the inbreds could be classified into distinct heterotic groups under each research environment, and that superior inbreds with good combining abilities as well as those that can serve as outstanding testers could be identified under the contrasting environments (Akinwale et al, 2014). The presence of significant mean squares for both GCA × E and SCA × E for all measured traits under all research environments with the exception of the SCA × E mean squares for ear height and husk cover under drought, plant and ear heights, EPP, and stay-green characteristic under low-N, plant and ear heights under optimal growing environments and across research environments, confirmed that the parental inbreds exhibited differential performances in hybrid combinations under the contrasting environments in this study.…”

“…However, it appears that the choice of the type of molecular markers used for grouping maize inbred lines influences the results. Akinwale et al (2014) used SSR markers and the groups identified were more closely related in their pedigree than those identified by HSGCA, SCA of grain yield, and MP. This may suggest that SSR markers are better for classifying tropical maize genotypes than SNPs but may require further studies to confirm this conclusion.…”

“…The method was comparable to the groupings based on SSR markers but superior to the traditional method of grouping inbreds using the SCA effects of grain yield. Furthermore, Akinwale et al (2014) compared the efficiency of the groupings based on the SCA of grain yield, HSGCA, and microsatellite markers, and concluded that the HSGCA method was the best, followed by the molecular marker method. However, no such comparison has been made in the efficiency of the HGCAMT, HSGCA, and SNP marker methods in grouping inbreds.…”

“…One of such methods is the HSGCA method that combines both SCA and GCA effects for assigning inbred lines into heterotic groups. Studies have so far proved this method to be more effective than the use of SCA effects of grain yield alone or molecular markers for classifying inbred lines into distinct groups (Fan et al, 2004;Badu-Apraku et al, 2013b, 2013cAkinwale et al, 2014). A grouping method using the GCA of multiple traits (designated HGCAMT) was proposed for grouping inbred lines (Badu-Apraku et al, 2013b).…”