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Etiology

Isozyme Comparisons for Identification of Colletotrichum Species Pathogenic to Strawberry. M. R. Bonde, Research plant pathologist, USDA, Agricultural Research Service, Foreign Disease-Weed Science Research, Fort Detrick, Bldg. 1301, Frederick, MD 21702; G. L. Peterson(2), and J. L. Maas(3). (2)Support scientist, USDA, Agricultural Research Service, Foreign Disease-Weed Science Research, Fort Detrick, Bldg. 1301, Frederick, MD 21702; (3)Research plant pathologist, USDA, Agricultural Research Service, Fruit Laboratory, BARC-West, Beltsville, MD 20705. Phytopathology 81:1523-1528. Accepted for publication 6 August 1991. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1991. DOI: 10.1094/Phyto-81-1523.

Presently there is uncertainty about the appropriate taxonomic classification of species of Colletotrichum infecting strawberry. Some workers consider C. fragariae part of the highly variable species C. gloeosporioides, whereas others feel they should be separate. The strawberry pathogens C. acutatum, C. fragariae, and C. gloeosporioides were successfully distinguished by means of comparing isozymes for 12 enzymes and 14 putative isozyme loci. The intraspecific coefficients of similarity (CS) based on the 12 enyzmes and 14 loci were 1.00 for C. acutatum (maximum possible = 1.00), 1.00 for C. fragariae, and 0.80 for C. gloeosporioides. Intraspecific CS values indicated little variation in C. acutatum and C. fragariae; however there was considerable variation in C. gloeosporioides. The interspecific CS comparing C. fragariae and C. gloeosporioides was relatively low (0.42), suggesting C. fragariae and C. gloeosporioides are distinct species. The considerably higher CS of 0.77 when comparing C. acutatum and C. gloeosporioides suggests that they are more closely related. C. coccodes (= C. atramentarium) and C. trifolii also were included in the comparison. Neither exhibited intraspecific isozyme variation and further demonstrated the great potential for isozyme analysis to identify Colletotrichum species.