White rust of Australian canola quality Brassica juncea - resistance screening and pathotyping isolates

ABSTRACT Australian isolates of the white rust pathogen, Albugo candidia, were collected from Brassica juncea at 1 NSW and 7 Victorian canola-quality B. juncea (Juncea canola) trial sites during 2003. The pathogen was isolated from leaf pustules and stagheads and 29 single pustule isolates were prepared. Inoculation of the isolates on cultivars of B. juncea, B. rapa and B. napus showed that all 29 isolates were B. juncea specific, thus belonging to race 2. Further investigations are underway to identify which pathotypes of race 2 are present in Australia, as preliminary screening of the 29 single pustule isolates using differential hosts showed variation among the isolates in their ability to attack B. juncea cultivars. The advanced Juncea canola germplasm from the Victorian breeding program was screened with one A. candidia isolate and variation in infection was observed, indicating that white rust resistance is present in some of the advanced germplasm