Improvement of Sclerotinia sclerotiorum resistance in Brassica napus by using B. oleracea

Sclerotinia stem rot is one of the most serious diseases in rapeseed (Brassica napus) due to the lack of resistance sources. A high level of resistance was reported in Brassica oleracea cytodeme, one of parental species of rapeseed. In this study, a panel of 55 resynthesized lines of B. napus (RS lines) derived from seven wild and two cultivated types of B. oleracea was evaluated for Sclerotinia resistance over 2 years. Relative to ‘Zhongyou 821’, a cultivar of B. napus with partial resistance against S. sclerotiorum, RS lines exhibited stronger stem resistance. Although the resistant level of RS lines was lower than that of corresponding parental B. oleracea, a moderate correlation between resistance of RS line and corresponding parental B. oleracea type was found both for leaf (r = 0.74, P = 0.02) and stem (r = 0.69, P = 0.04). Our data suggests that the RS lines are important resources to improve Sclerotinia resistance of current rapeseed. A breeding strategy is discussed to enhance the Sclerotinia resistance of rapeseed by using B. oleracea.