Genetic Diversity Analysis in Sugarbeet (Beta vulgaris L.) Using Isozymes, RAPD and ISSR Markers

Abstract

Four elite diploid populations of sugarbeet viz. IISR Comp-1, LKC-11, LS-6 and Ramonskaya-06 were examined using isozymes and molecular markers. Seventy-one bands consisting of 28 isomorphs of 6 isozyme systems viz. superoxide dismutase, guaiacol peroxidase, malate dehydrogenase, amylase, esterase and aspartate amino transferase were resolved. Molecular analysis was performed using 28 RAPD (random amplification of polymorphic DNA) and 4 inter simple sequence repeat (ISSR) primers. Highly polymorphic band profiles with 327 RAPD markers (11.67/primer) of 162–2862 bp and 39 ISSR markers (9.75/primer) of 160–1884 bp were obtained. Mean value of Polymorphic Information Content (PIC) for RAPD and ISSR primers was 0.41 and 0.44 respectively. Based on the binary matrix of presence/absence of bands, Dice coefficient of genetic similarity (GS) matrix was computed for each marker system, which ranged from 0.62–0.76 (mean value 0.726), 0.10–0.74 (mean value 0.27) and 0.12–0.86 (mean value 0.35) for isozyme, RAPD and ISSR markers. There was significant correlation (r=0.908) between the RAPD-GS and ISSR-GS matrices, however, the correlation of isozyme matrix vs. RAPD and ISSR pattern was low. GS coefficients of isozyme, RAPD and ISSR were used to cluster the genotypes based on the UPGMA method and the dendrograms obtained were compared to develop consensus phylogenetic trees using NTSYSpc. The X-axis contained IISR Comp-1 and R-06, and the Y-axis contained LS-6 and LKC-11. The much lower values of average genetic similarity based on RAPD (0.27) and ISSR (0.35) indicated the ability of DNA based markers to detect high degree of polymorphism among these populations suggesting thereby, the possibility of screening a higher number of anonymous loci in sugarbeet using these molecular markers as compared to isozymes to enable the selection of the best parents in order to obtain new genetic combinations.