Potential for using host resistance to reduce production of pseudothecia and ascospores of Leptosphaeria maculans, the blackleg pathogen of Brassica napus

Abstract

Pseudothecial density of the blackleg fungus Leptosphaeria maculans and discharge of ascospores was measured from stubble of a range of Brassica species, including Brassica napus (canola) cultivars, with a range of blackleg resistance. Since ascospores are the primary inoculum, these parameters reflect inoculum potential for blackleg. Stubble from a representative line of each of B. carinata, B. nigra, Sinapis alba and B. napus cv. Surpass 400 (incorporates blackleg resistance from B. rapa ssp. sylvestris) had lower pseudothecial density and discharged fewer ascospores than stubble of other B. napus cultivars (Karoo, Oscar, Emblem, Dunkeld and Columbus). These latter B. napus cultivars and a..