Development of phoma stem canker (Leptosphaeria maculans) and light leaf spot (Pyrenopeziza brassicae) on current and historical oilseed rape cultivars in 2003/04, 2004/05 and 2005/06 UK growing seasons

摘要

Winter oilseed rape (sown August, harvested July) field experiments at Rothamsted in successive growing seasons (2003/04,2004/05 and 2005/06) were monitored for phoma leaf spot and phoma stem canker (Leptosphaeria maculans) and light leaf spot (Pyrenopeziza brassicae). Each experiment included 42 current, historical or exotic Brassica napus cultivars/breeding lines.Weekly assessments examined leaf,stem and pod disease as % plants affected and % area affected. Significant differences were observed between cultivars for both diseases, suggesting that the cultivars ranged from susceptible (severely diseased) to resistant (little disease) to the pathogens. Many of the cultivars that were susceptible or resistant in one season gave similar responses in the other seasons. However, material gave a range of responses to the two pathogens; for example, cv. Aviso was very resistant to L.maculans in all seasons whilst Bronowski was the most susceptible cultivar in all seasons. For Pyrenopeziza brassicae, cv.Tapidor was consistently susceptible whilst the line PR45W05 was consistently resistant, when % leaf area affected was assessed.The results are discussed in relation to current knowledge of the reported oilseed rape resistance gene mediated response to L.maculans and the suggested oilseed rape resistance mechanism to P. brassicae.