Distribution of A and B-group isolates of Leptosphaeria maculans in oilseed rape plants

摘要

Leptosphaeria maculans is responsible for Blackleg of oilseed rape worldwide. L. maculans was divided at least in two main groups of isolates named A-group (responsible for crown canker) and B-group (responsible for weak symptoms and pith degradation) by Johnson & Lewis (1990, 1994). This latter group was identified as a new species : Leptosphaeria biglobosa (Shoemaker & Brun, 2001). Both groups induce leaf lesions (Johnson & Lewis, 1994) and can coexist in a single leaf lesion (Brun et al., 1997).In some situations varieties seem to differ at the leaf level for their susceptibility to each group (Brun et al., 1997). This work aimed to assess which groups of isolates were present at the crown and stem base levels in the internal symptoms of winteroilseed rape cultivars at the end of the cropping season, in France.