Genetic similarity of sweet corn inbred lines in correlation with heterosis

The narrowness of sweet corn genetic base limited to the great extent its genetic improvement. This is associated to the fact that sweet corn does not have well defined heterotic groups such as those important in field corn breeding, and therefore application of marker assisted selection becomes a necessity. The objective of this study was to determine genetic similarity (GS) of six sweet corn inbred lines selected at Maize Research Institute Zemun Polje, based on SSR markers and to compare it with data of specific combining ability (SCA) and heterosis for fresh ear yield, obtained in a diallel study. SSR markers showed that all genotypes had specific genetic pattern. Estimates of GS varied from 0.422 (L4 - L2) up to 0.756 (L6 - L5). Cluster analysis and PCA showed clear groupings of inbreds into two subclusters, with inbred L3 less related to the others. Results of diallel analysis showed that data of heterosis and SCA were in concurrence with the data of GS based on SSR markers. Hybrid combinations with higher estimates of SCA and heterosis expressed less genetic similarity with each other (such in hybrids L2 x L1; L6 x L2; L3 x L2 and L5 x L2), while inbreds that were genetically most similar L5 and L6 expressed low heterosis and SCA in their hybrid combination. That was confirmed by rank correlation coefficients, whose estimates were negative and in most cases significant, indicating that more similar inbreds produced less expressed effects of heterosis and SCA.