Morphological, anatomical and biochemical changes associated with the infection processes of Sclerotinia sclerotiorum in a resistant cultivar of Brassica napus

Owing to a large diversity of S. sclerotiorum reported under field conditions, the selected B. napus genotypes identified in the initial screening experiment were further evaluated across a range of morphologically different S. sclerotiorum isolates. Out of the eight isolates collected from the different regions of Western Australia, three darkly pigmented isolates were identified and this is the first report of the occurrence of such isolates in Australia. Significant differences were observed between different isolates (P≤ 0.001) in two separate experiments in relation to pathogenicity. Differences were also observed between the different Brassica genotypes (P ≤ 0.001) in their responses to different isolates of S. sclerotiorum and there was a significant host x pathogen interaction (P ≤ 0.001) in both experiments. Responses of some genotypes (e.g., cv. Charlton) were relatively consistent irrespective of the isolates, whereas highly variable responses were observed in certain other genotypes (e.g., Zhongyou-ang No. 4, Purler) against the same isolates. Results indicate that the unique genotypes which show relatively consistent resistant reaction (e.g., cv. Charlton) across different but highly pathogenic isolates are suitable for commercial exploitation in oilseed Brassica breeding programmes...