Development and validation of CAPS and AFLP markers for white rust resistance gene in Brassica juncea.

White rust, caused by Albugo candida, is a very serious disease in crucifers. In Indian mustard (Brassica juncea), it can cause a yield loss to the extent of 89.9%. The locus Ac2(t) controlling resistance to white rust in BEC-144, an exotic accession of mustard, was mapped using RAPD markers. In the present study, we developed: (1) a more tightly linked marker for the white rust resistance gene, using AFLP in conjunction with bulk segregant analysis, and (2) a PCR-based cleaved amplified polymorphic sequence (CAPS) marker for the closely linked RAPD marker, OPB06(1000). The data obtained on 94 RILs revealed that the CAPS marker for OPB06(1000) and the AFLP marker E-ACC/M-CAA(350) flank the Ac2(t) gene at 3.8 cM and 6.7 cM, respectively. Validation of the CAPS marker in two different F(2) populations of crosses Varuna x BEC-144 and Varuna x BEC-286 was also undertaken, which established its utility in marker-assisted selection (MAS) for white rust resistance. The use of both flanking markers in MAS would allow only 0.25% misclassification and thus provide greater efficiency to selection.