Genetic diversity analysis of Brassica juncea mutants through morphological and molecular characterization

Mutation breeding is a tool to strengthen the germplasm and is being exploited for crop improvement. Mutations for morphological, yield, and yield attributes were isolated from parent variety Bio902 using g-radiation and Ethyl Methane Sulphonate (EMS). Their morphological and molecular diversity analyses were performed. Morphological diversity was assessed using PCA analysis and the result revealed six principal components with Eigen values greater than one and altogether explained 74.34% of total accumulated variability. Varimax rotation was applied since the analysis without rotation of axes failed to load all the variables. The UPGMA-based cluster analysis showed the formation of 8 clusters. Thirty mutants were grouped in cluster VIII and this cluster did not contain any of the checks including Pusa bold and BIO 902 hence these mutants were diverse from the checks. For the molecular marker study, 20 SSR primers were used out of which eight primers showed polymorphism. The percent polymorphism varied from 66.67 to 100% with an average of 77%. Polymorphism Information Content (PIC) values ranged from 0.08 to 0.48 with an average of 0.34 per primer combination. Distance-based cluster analysis and dendrogram showed the presence of three major clades. The first clade consists of Bio902 along with five mutants derived from g-irradiation. The second clade consists of five mutant’s viz. ACNMM 23, ACNMM13, ACNMM 22, ACNMM 14, and ACNMM 7 without any checks, while the third clade consists of two genotypes viz. Kranti and ACNMM15. The findings of this study shall be useful in a breeding program to recombine desirable traits. Out of the 10 superior high-yielding mutants selected for molecular analysis, mutant ACNMM9 was similar to checks both in morphological as well as molecular studies. Mutants ACNMM 4, ACNMM 17, ACNMM 19, and ACNMM 15 were found in distinct clusters as of checks morphologically but in the same cluster as that of checks in molecular analysis.