Heterotic grouping of late-maturing maize inbred lines based on combining ability and molecular marker studies

Aim: To examine concurrence between yield based and SSR marker based heterotic grouping of late-maturing maize inbred lines. Methodology: A total of 45 F1 crosses derived from 10x10 diallel mating scheme were evaluated along with their parents and hybrid checks across two locations (New Delhi and Dharawada). To group the inbred lines at molecular level, 35 polymorphic SSR primers were used for PCR amplification of repeat sequences from the genomic DNA of each inbred isolated by CTAB method. Cluster analysis was carried out by using NTSYS-pc- 2.02. Results: Analysis of variance revealed significant (P<0.01) variation among the parents and their hybrids across two locations for all the traits. The yield SCA classified 10 late-maturing maize inbred lines into three heterotic groups. Similarly, molecular genetic diversity analysis also categorized the inbred lines into three major clusters. However, correlations between SCA effects and genetic distance were low (r=0.161) for grain yield. Interpretation: Heterosis prediction with the help of molecular markers alone was not found effective. Further, field-testing can be complimented with molecular markers for the elimination of inferior crosses.

Genetic distance estimates among single cross hybrids and correlation with specific combining ability and yield in corn double cross hybrids

The objective of the present study was to correlate the genetic distances (GD) of single cross hybrids with yield, heterosis and specific combining ability (SCA) in the double cross hybrid synthesis. For this, 10 single cross commercial hybrids were used from different companies, and all the possible double hybrids were synthesized by a complete dialell. The hybrids were assessed in 15 locations in the 2005/2006 agricultural season, using the randomized complete block design with three repetitions. DNA was extracted from the single cross hybrids and 20 simple sequence repeat primers were used, nine of which were linked to the quantitative trait loci. It was ascertained that the single hybrids were superior in general to the double cross hybrids and that yield was highly correlated with heterosis and SCA (r = 0.75 and 0.82, respectively). There was no significant correlation between yield and GD (r = 0.25), but this index was at the limit of significance. There was a medium correlation between GD and heterosis (r = 0.40) and GD and SCA (r = 0.38). The intergroup hybrids placed by genetic grouping were generally more productive than intragroup hybrids, and the hybrids with GD greater than 0.84 had the maximum heterosis and SCA. It was concluded that the markers were efficient in placing hybrids in different heterosis groups and were also useful in eliminating the most negative heterosis and SCA.