Phylogenetic Relationship to Study the Ploidy Status and Resistance to Karnal Bunt in Indian Wheat Cultivars Using RAPD Technique

Abstract

Tetraploid and hexaploid Indian wheat accessions were analyzed for genetic polymorphism using RAPD-PCR in order to study the gene rearrangements during polyploidization. Ten RAPD primers were employed to establish the evolutionary relationship amongst 10 tetraploid and 17 hexaploid wheat accessions. Tetraploid accession showed 75.7% polymorphism whereas hexaploid accessions showed 65.3% polymorphism. The Genetic Distance (GD) value of the tetraploid accessions ranged 0.400 to 0.966 was significantly higher than the GD values of the hexaploid accessions (0.630 to 0.952). RAPD primers clearly categorized tetraploid to hexaploid accessions in different groups according to similarity coefficient. Nearly all tetraploid accessions were grouped together. The same set of primers was also able enough to establish polymorphism amongst 20 Karnal bunt susceptible and resistant tetra and hexaploid wheat varieties. Like tetraploid accessions, susceptible varieties showed low genetic relationship. Some of the primers gave a distinct RAPD pattern for the discrimination between resistant and susceptible varieties but none of the primer was able to discriminate the resistant, susceptible and moderately susceptible wheat varieties. The phylogenetic polymorphism according to ploidy level and resistant status to KB is interpreted as the result of alteration in gene loci during polyploidization, genetic drift during inter and intra specific breeding andlor selection pressure for improved fertility.