GENETIC VARIABILITY AMONG THE BROWN RUST RESISTANT AND SUSCEPTIBLE GENOTYPES OF SUGARCANE BY RAPD TECHNIQUE

Abstract

Brown leaf rust in sugarcane is caused by Puccinia melanocephala (Syd. & P. Syd.), which is a major cause of cultivar withdrawal. We attempted to analyze the RAPD diversity of two discrete phenotypic classes, i.e., rust resistant (R) and rust susceptible (S) of six commercially available sugarcane elite genotypes in Pakistan. DNA samples were extracted from these cultivars. The genomic DNA was amplified with 160 decamer primers and 33 of them generated 216 trackable loci with the range of 150-2500 bp. The total polymorphic bands were 164 (76%) and these were used to cluster rust resistant and susceptible cultivars. UPGMA (Unweighted Pair Group Method with Arithmetic Mean) based on Nei’s genetic distance was analyzed by NTSYSpc and showed that 6 genotypes were clustered into 3 groups with the range from 63% to 73% genetic distances. This observation indicated the significant correlation between genetic distance and disease. Ten of 33 decamers (30%) had shown 100% polymorphism with three polymorphic bands/loci, which were generated in two different discrete groups rust resistant and rust susceptible. In this study we have found 17 cultivars specific loci generated by 11 RAPD primers and cluster analysis revealed three main groups and two subgroups against rust susceptible genotypes to develop characterization of genotypes at molecular level. Additionally, this explored the genetic basis of discrete phenotypic classes in sugarcane genome for marker development.