Submitted to: Plant Disease
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/1/2004
Publication Date: 8/11/2005
Citation: Viji, G., Uddin, W., Oneill, N.R., Mischke, B.S., Saunders, J.A. 2004. Genetic diversity of sclerotinia homoeocarpa isolates from turfgrasses from various regions in north america and canada. Plant Disease. 88:1269-1276. Interpretive Summary: Little is known about the genetic diversity among strains of plant pathogenic fungi within a single species. New technologies are being developed to investigate the biological, geographical, and host specificity of strains and correlate these characteristics with the genetic make-up of the fungus. It is important to accurately identify pathogens in as much detail as possible so that appropriate disease control methods can be implemented and epidemics can be predicated and controlled. The genetic diversity within a species of fungus, Sclerotinia homoeocarpa, was investigated. The fungus causes diseases in a wide range of grasses and is difficult to identify because the species does not produce spores. Some investigators have suggested that S. homoecarpa represents more than one species. Strains of the fungus were collected in different years, from different hosts, and from diverse geographic regions in North America. We determined that with the exception of two strains, Sclerotinia homoeocarpa represented one species but was genetically diverse and was categorized into 11 groups based on their physical and biochemical interactions. A DNA fingerprinting test was developed that established DNA profiles corresponding with the same groups. The research will be used by breeders, seed companies, APHIS, and research scientists concerned with controlling diseases caused by strains of this pathogen.
Technical Abstract: Sixty-seven isolates of Scleroinia homoeocarpa, the causal agent of dollar spot in golf greens, collected from various geographical regions in the U.S. and Canada between 1972 and 2001, were characterized by vegetative compatibility and genetic diversity using Amplified Fragment Length Polymorphism (AFLP) and pathogenicity. Eleven vegetative compatibility groups (VCG A to K) were identified among the isolates tested in this study, and five of them (VCG G to K) were new. Among the eleven groups identified, VCG B was the most predominant group, which was represented by 33 (51%) of the isolates tested. A low VCG diversity (0.17) was observed among the sixty-seven isolates tested. Two isolates were incompatible when paired in all possible combinations, and could not be grouped into any known VCG. Genetic analyses by AFLP showed polymorphisms among isolates, indicating that the population consisted of multiple genotypes. Comparision of AFLP groups and VCGs showed two distinct groups (designated as major and minor groups) among the isolates of S. homoeocarpa. The major group comprised all of the isolates except two from Florida which formed a minor group. Pathogenicity assays on Penncross creeping bentgrass showed significant differences (P=0.05) in virulence among isolates. The close similarity among the archival and contemporary isolates collected from different geographic locations suggests that isolates of the same genetic group could be involved in the simultaneous outbreaks of dollar spot epidemics in various regions of the U.S.