Relationship between isozyme diversity of parental clones and progeny performance in sugarcane (Saccharum spp.)

Abstract

Isozyme marker based estimation of genetic diversity among 49 parental clones used in sugarcane varietal development was carried out using peroxidase, esterase and phosphorylase systems. Based on similarity index values, all 1176 possible parental combinations were categorized into high, medium and low diversity groups. Maximum number of combinations showed medium diversity (51 = 0.60 to 0.80) reflecting the existence of moderate genetic diversity in sugarcane parental clones. Selection percent per cross, based on H.R. Brix, cane diameter and single cane weight, calculated in 14 crosses belonging to all the three groups in the 1st clonal trial, was correlated with similarity index. A significant negative correlation (-0.6221) was observed between them. Selection percent was lower in the combinations with high 51 values (above 0.80) compared to the other two groups indicating the importance of diversity information in indirectly identifying less productive combinations. Moderate levels of diversity. were sufficient to generate a higher proportion of selectable types, as selection % did not improve with increasing diversity. Thus isozyme analysis of parental clones provided useful information in identifying and thereby avoiding genetically more similar combinations, which would otherwise lead to close breeding. Use of more efficient marker systems is needed to identify heterotic cross combinations and to predict progeny performance in sugarcane.