This paper reports analysis of 7 × 7 diallel crosses using a genotype main effect plus genotype-by-environment interaction biplot for determining cold tolerance at the germination stage in rice. ANOVA indicated that there were highly significant differences among the replications, genotypes, general combining ability (GCA) and specific combining ability (SCA) for percentage of reduction in radicle length (RL), coleoptile length (CL) and germination percentage (GP). The hybrid Neda × Hassani had the highest mid-parent heterosis for RL, CL and GP (–58.84, –68.47 and –80.77%, respectively). This result indicated that the reduction of three traits in crosses of Neda × Hassani was lower than their parents. The graphical representation by biplot analysis allowed a rapid and effective overview of GCA and reveals that Deilamani was an ideal general combiner for all traits and this parent is a superior variety for these three traits. Three potential heterotic groups are suggested for RL reduction. Four potential heterotic groups were identified for the two other traits, in the biplot. The first two principal component (PC) axes in the biplot for reduction in GP explained 85% of the variation with first and second principal components (PC1 and PC2, respectively). An important inference that can be drawn from these results is that cross combinations involving Hassani and Deilamani as one of the parents recorded desirable SCA effects for all or most of the studied traits. The information obtained from this experiment can facilitate the identification of hybrids that combine cold resistance traits in rice.
COMBINING ABILITY FOR SOME YELLOW MAIZE INBRED LINES BY DIALLEL CROSSES