Genetic variation, genetic distance and population structure of the blackleg pathogen Leptosphaeria maculans of canola/rapeseed

摘要

Leptosphaeria maculans causes blackleg disease in canola (Brassica napus L.). The isolates can be identified into different pathogenicity groups based on the interaction phenotype on differential cultivars. PG-3, PG-4 and PGT strains were recently found in Western Canada and North Dakota (ND), USA. Genetic diversity and population structure of L. maculans population collected from a single field in La Riviere, Manitoba, Canada and other regions in ND, USA, Brazil, Australia and United Kingdom was investigated using the sequence-related amplified polymorphism (SRAP) marker technique. High number of polymorphic loci was found based on 91 polymorphic fragments and high number of genotypes was detected in each of those populations,suggesting that L. maculans is extensively diverse in genetics and each population consists of isolates with high number of unique genotypes. Phylogenic analysis indicated that all populations were clustered together. Indirect estimation of gene flow showed that high rate of gene flow existed among all populations with the greatest rate between La Riviere and ND (Nm = 15.96) as they are geographically close to each other. AMOVA revealed that a major genetic variance source came from the genetic variation among isolates within populations regardless of the origin and pathogenicity.