Genetic diversity of Gibberella zeae isolates from Manitoba

Gibberella zeae (anamorph Fusarium graminearum) causes Fusarium head blight, one of the most important diseases of cereals in the Canadian prairies for the last decade. In 2002, 60 isolates of G. zeae were collected and single spored from naturally infected spikes of wheat from Carman and Winnipeg in Manitoba. These isolates were compared using vegetative compatibility analysis and polymerase chain reaction (PCR)-based sequence related amplified polymorphisms (SRAP). Sixteen vegetative compatibility groups (VCG) were found among the 50 isolates tested. Five VCGs were found in the two locations, five in Carman and six in Winnipeg. Eight SRAP primer pairs amplified 90 polymorphic DNA fragments from 60 isolates and identified 59 distinct haplotypes. Among seven pairs of isolates, each pair from a distinct spike, four had isolates with different VCGs and six comprised different SRAP haplotypes. Principal component analysis and UPGMA separated the dataset into two main groups, each with isolates from both locations. The analysis of molecular variance also revealed that 75 and 20% of the variance was associated with differences among individual isolates and varieties sampled, respectively. Geographic location was not a significant source of variation at P = 0.05 and accounted for only 4% of total variance. A low correlation between VCG and SRAP marker data was detected. This study showed that, although genetic diversity is high among G. zeae isolates, Carman and Winnipeg collections have a similar genetic makeup and are likely part of the same population. The significant proportion of variance accounted by the variety compared with the geographic origin of isolates suggests that seedborne inoculum might have contributed to the genetic diversity within the G. zeae collection under study.