APS Homepage

Poster: Biology & Disease Mgmt: Genetics of Resistance


Identification of Brassica napus plant introductions with resistance to pathogenicity group 4 of Leptosphaeria maculans
S. MANSOURIPOUR (1), L. del Rio Mendoza (1) (1) North Dakota State University, U.S.A.

Blackleg caused by Leptosphaeria maculans (Desmaz) Ces. & de Not is a serious disease of canola (Brassica napus L.) worldwide. In North Dakota, L. maculans isolates that overcome resistance genes Rlm1, Rlm2, and Rlm3 are the most prevalent and have been classified in pathogenicity group (PG) 4 using a set of three differentials. The objective of this study was to identify sources of resistance against PG-4. Replicated greenhouse trials using mixtures of five PG-4 isolates were used to evaluate the reaction of B. napus plant introductions (PI) at the seedling stage. Twenty one PI materials identified as resistant were evaluated in field trials in 2014 and 2015 using a randomized complete block design with four replications. Cultivar “Westar” and two commercial canola hybrids were used as controls. Seedlings were inoculated repeatedly with a mixture of spores from the same five isolates used in the greenhouse and supplemented with naturally infested residues. Disease severity was estimated at harvest as percentage of internal stem crown tissue discoloration. Five PIs were considered highly resistant and behaved consistently better (P < 0.05) than the hybrids in both field trials with an average disease severity < 4% compared to 25% of the hybrids. Crosses between these PIs and canola breeding lines have been made to transfer the resistance into advanced germplasm. In addition, efforts to produce doubled haploid mapping populations from these sources are under way.