Genetic variability in a canker pathogen fungus Gremmeniella abietina (Lagerb.) Morelet. I. Contribution of sexual vs. asexual reproduction

Xiao-Ru Wang

Mycological Research (1997) 101(10): 1195-1201.

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Genetic variation of the haploid canker pathogen fungus Gremmeniella abietina (Lagerb.) Morelet was investigated with RAPD markers. A total of 126 single pycnidia isolates of G. abietina were sampled from one Pinus contorta (Dougl.) plantation in northern Sweden. Average Nei´s gene diversity over 32 putative RAPD loci was 0.29. Multilocus genotype analysis revealed 85 different genotypes in the 126 isolates sampled, of which 66 genotypes were detected only once. 41 isolates were members of 19 different genotypes that were detected more than once, representing 32.5% of clonal fraction of the sampled population. Gametic disequilibrium tests in the sampled population revealed 29.6% (147 of 496) of significant associations between RAPD loci. When the clonal fraction was removed from the data set, the number of significant pairwise combinations decreased from 147 to 73 (14.7%), indicating a high degree of random mating. These results are consistent with the previous field observations suggesting that sexual fruiting bodies of G. abietina were common in northern Scandinavia. The high genetic variability detected in the investigated population also suggests that the population was founded by a relative large number of unrelated genotypes.
Key words: Gremmeniella abietina, genetic structure, RAPD

by Alfred E. Szmidt