Genetic diversity analysis in cytoplasmic male sterile ‘A’ lines and restorer ‘R’ lines of Indian mustard using SSR markers

Indian mustard (Brassica juncea L. Czern & Coss.) is a highly economically important oilseed crop of India. An accurate estimation of genetic diversity inherent in breeding material is a pre-requisite for the success of any hybrid breeding programme, as it leads to identification of genetically divergent parents for exploiting high heterotic levels. In the present study, 200 genome-wide spanned simple sequence repeat (SSR) markers were used for estimation of genetic diversity and identification of genetically divergent parental combinations in a panel of 28 parental lines of Indian mustard comprising of 21 cytoplasmic male sterile (CMS) ‘A' lines and 7 restrorer ‘R' lines. A total of 179 SSR markers resulted in positive amplification with 155 (81.57 %) SSRs producing polymorphic amplicons and 24 (13.41 %) SSRs resulted into monomorphic products. Allele number varied from 2 to 6 with a mean value of 3.27 alleles per SSR marker. PIC values ranged from 0.23 to 0.7 with a mean value of 0.38 per SSR marker. Gene diversity values were in the range of 0.27–0.75 with average value of 0.47, inferring the presence of a moderate level of genetic diversity in the plant material. Neighbor-Joining dendrogram could not exactly differentiate ‘A' and ‘R' lines into different groups. This study led to identification of few genetically diverse A and R lines, suitable for making crosses for heterotic hybrid development in Indian mustard. On the basis of Euclidean distances, various cross-combinations viz. MJA10 & MJR3/EC597313, MJA 14 & MJR3/EC597313, and MH 12–12/EC597313S & MJR9 were designated as genetically diverse genotypes. These cross-combinations may be used in hybrid breeding program to exploit heterosis in Indian mustard improvement.