Resynthesis of Brassica juncea for resistance to Plasmodiophora brassicae pathotype 3.

The oilseed crop Brassica juncea carries many desirable traits; however, resistance to clubroot disease, caused by Plasmodiophora brassicae , is not available in this species. We are the first to report the clubroot resistant resynthesized B. juncea lines, developed through interspecific crosses between a clubroot resistant B. rapa ssp. rapifera and two susceptible B. nigra lines, and the stability of the resistance in self-pollinated generations. The interspecific nature of the resynthesized B. juncea plants was confirmed by using A- and B-genome specific SSR markers, and flow cytometric analysis of nuclear DNA content. Self-pollinated progeny (S1 and S2 ) of the resynthesized B. juncea plants were evaluated for resistance to P. brassicae pathotype 3. The S1 and S2 progenies of one of the resynthesized B. juncea lines were resistant to this pathotype. However, resistance was lost in 6 to 13% plants of the S2 progenies derived from the second resynthesized B. juncea line; this apparently resulted from the loss of the genomic region carrying resistance due to meiotic anomalies.