Molecular mapping of the downy mildew resistance genePpa3in cauliflower (Brassica oleraceavar.botrytisL.)

Abstract

The present study aimed to construct a linkage map for the downy mildew resistance gene, Ppa3, in cauliflower. Ppa3 is a dominant, single locus gene in cauliflower which confers downy mildew resistance. Out of 190 markers screened, 13 were found to be polymorphic between the two parental lines, ‘BR-2’ and ‘Pusa Himjyoti’. Among these 13 polymorphic markers, six were random amplified polymorphic DNA (RAPD) markers (OPB181276, OPB201174, OPC141186, OPC1850, OPF1960, and OPE141881) and the remaining seven were inter-simple sequence repeat (ISSR) markers (ISSR5525, ISSR81125, ISSR11550, ISSR121050, ISSR231103, ISSR30575, and ISSR35620). Furthermore, bulked segregant analysis identified only three markers (OPC141186, OPE141881, and ISSR231103) as being polymorphic. An F2 mapping population consisting of 120 plants was analysed using the latter three polymorphic markers and a linkage map was constructed for Ppa3. OPC141186 was located 22.3 cM from the Ppa3 gene on the top-arm end, with OPE141881 and ISSR231103 at 10.6 cM and 26.4 cM, respectively on the other side of the Ppa3 gene on the linkage map. This information may be useful for further studies to identify more closely-linked markers for the Ppa3 gene.