Examination of pathogenic variation among Australian white rust (Albugo candida) isolates from Brassica juncea and implications for breeding resistant canola quality B. juncea

摘要

White rust of Brassica juncea, caused by the oomycete Albugo candida is a potential threat to the emerging canola quality B.juncea (juncea canola) industry in Austria. Isolates of A. candida that infect B. juncea are classified as race 2 and can be subdivided into two pathotype groups, 2A and 2V, based on their virulence to particular Canadian B. juncea differential cultivars.To determine which races and pathotypes of B. juncea-infectng A. candida are present in Australia, isolates were collected from infected juncea canola in 2003 and 2004 from 8 locations in Australia, and tested against a set of Canadian differentials. All isolates were classified as race 2 pathotype 2A, thus, further surveying is underway to determine if pathotype 2V is present in Australia. An Australian 2A isolate was subsequently used to assess the resistance of Australian advanced breeding lines ofjuncea canola and in addition, the same Australian juncea canola lines were screened in Canada using Canadian pathotypes 2A and 2V.There was a significant correlation between white rust disease ratings for the lines using the Australian and Canadian 2A isolates (Pearson's correlation coefficient = 0.87) and resistance to pathotype 2A was observed in some of the advanced juncea canola breeding lines. However, no Australian breeding lines exhibited resistance to the Canadian 2V pathotype. Although pathotype 2V is yet to be identified in Australia attempts are underway to incorporate resistance to 2V into an Australian canola quality B. juncea background with the aim of releasing juncea canola cultivars resistant to 2V in the future.