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Poster: Epidemiology: Cropping Systems/Sustainability


Changes in frequency of Leptosphaeria maculans avirulence genes in North Dakota.
S. Mansouripour (1), K. Chittem (1), Z. Liu (1), L. del Rio Mendoza (1) (1) North Dakota State University, U.S.A.

Blackleg, caused by Leptosphaeria maculans is resurging as a threat to North Dakota canola industry. A shift in the virulence profile of L. maculans populations is thought to be responsible for it. Estimating the prevalence of specific avirulence genes in L. maculans populations could be used to infer the relative value of its interacting resistance genes for a plant breeding program. The objective of this study was to determine the frequency of avirulence genes in L. maculans isolates from North Dakota. Single-spore cultures of L. maculans isolates collected from commercial grower’s fields in 2004, 2007 and 2014 were used. Presence of avirulence genes AvrLm1, AvrLm6, AvrLm4-7 and AvrLm11 was determined using PCR assays. The results indicated that the frequency of AvrLm1 increased from 3% among isolates collected in 2004 to 45% among isolates collected in 2014 while the frequencies of AvrLm6 and AvrLm11 remained unchanged (91 to 100% and 91 to 95%, respectively) between the same two periods. AvrLm4 and AvrLm7 alleles were present in 90 and 100% of the isolates, respectively in 2014. Determination of frequencies of AvrLm4 and AvrLm7 in 2004 and 2007 is underway. The higher frequency of isolates carrying avrLm1 in 2014 suggests its corresponding resistance gene, Rlm1, can no longer provide effective protection. In contrast, the high prevalence of avirulence genes Avrlm4, AvrLm6, AvrLm7, and AvrLm11 indicates their interacting resistance genes could be safely used.