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Genetic Structure and Temporal Dynamics of a Colletotrichum graminicola Population in a Sorghum Disease Nursery

October 1998 , Volume 88 , Number  10
Pages  1,087 - 1,093

U. L. Rosewich , R. E. Pettway , B. A. McDonald , R. R. Duncan , and R. A. Frederiksen

First, second, third, and fifth author: Department of Plant Pathology, Texas A&M University, College Station 77840; and fourth author: Department of Crop and Soil Sciences, University of Georgia, Georgia Station, Griffin 30223

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Accepted for publication 30 June 1998.

Restriction fragment length polymorphisms (RFLPs) were used to study the population genetics of Colletotrichum graminicola (= C. sublineolum), the causal agent of sorghum anthracnose. Screening of 80 anonymous probes from a genomic library detected polymorphisms in 81% of 299 probe-enzyme combinations among nine international isolates. Seven single- or low-copy probes were used to study a collection of 411 isolates sampled during 1991 to 1993 from a sorghum disease nursery in Georgia. Nei's gene diversity was moderately high, with = 0.215 on average, while genotypic diversity was extremely low with an average genotypic diversity value of Ĝ = 1.513. Only nine multilocus haplotypes were identified, with one haplotype being present at a frequency of approximately 80% each year. Two other haplotypes were found at significant frequencies (4 to 10%). Allele and haplotype frequencies did not differ over the 3 years, indicating that this population was stable. Our findings suggest that genetic drift and gene flow were not major contributors to genetic structure, while asexual reproduction had a significant effect.

© 1998 The American Phytopathological Society