Assessment of Genetic Variation in Indian Mustard ( Brassica juncea L.) Using PCR Based Markers

Indian mustard ( Brassica juncea L.) is an important oilseed crop with oil content ranging from 30 to 48 percent. However, presence of high erusic acids, glucosinolates and saturated fatty acids and also narrowed genetic base of existing varieties confines its use. The present investigation was undertaken to explore the diversity among Indian mustard genotypes (varieties) using molecular markers. We used RAPD and EST based SSRs as the markers for assessment of genetic variation among 23 genotypes of Brassica juncea L. cultivated in North India.  In order to be sure about the authenticity of primers especially RAPDs, four other genotypes of different Brassica species were also considered for this investigation. To determine the discriminatory power of the RAPD primers, polymorphism percentage, PIC, MI and Rp were calculated. Finally the cluster analysis was done to determine the genetic diversity among the 27 genotypes, which includes 4 genotypes of other Brassica species. The polymorphism percentage of more than 91% and 86.66% was observed using the fifteen reproducible RAPDs and three EST SSRs respectively. Moreover the PIC values observed corresponds to 0.303, with 4.44 marker index and 6.89 resolving power for RAPDs, however, SSRs showed the PIC value of 0.281, with 0.94 marker index and 0.269 resolving power. The parameters calculated to estimate the discriminatory power presented a significant correlation and their high values depict the potential of primers for distinguishing the genotypes. The cluster analysis based on UPGMA separated the genotypes in two major groups. To the best of our expectations, all the genotypes of Brassica juncea are grouped in one major cluster and genotypes of other Brassica species are grouped in different cluster. Based on these preliminary results, the diverse genotypes can be used as a genetic stock for improvement of this crop in future breeding programs.