Complete resistance to leaf and staghead disease in AustralianBrassica junceagermplasm exposed to infection byAlbugo candida(white rust)

Abstract

White rust (Albugo candida) can be a highly destructive disease of Brassica juncea. Identification ofnewsources of host resistance to A. candida is a key priority in Australia for the B. juncea breeding program.Afew genotypes from China and Australia have been recently identified with useful levels of resistance to A. candida. In this study, a line of B. juncea (JM06011) from Australia showed complete resistance to white rust disease during the whole growing season and overall performed better than three Chinese genotypes (CBJ-001, CBJ-003, CBJ-004) and one other Australian genotype (JR049) that were previously reported to be promising and that were used as resistant controls. JM06011 showed no symptoms of the disease on leaves and a total absence of stagheads, and this is the first report of complete resistance to white rust among Australian B. juncea germplasm. More Australian genotypes, JM06010, JM06021, JM06004 and JM06013, showed a lower but still useful level of resistance to A. candida based on both incidence and severity of disease on leaves when screened under the natural environmental conditions existing in Western Australia. Overall, genotypes from China were relatively more susceptible than those from Australia with the exception of the three resistant controls. There was no relationship between foliar disease and staghead incidence across the genotypes tested.