Resynthesis of <i>Brassica juncea</i> for resistance to <i>Plasmodiophora brassicae</i> pathotype 3

Abstract

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