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Assessment of Diversity in Claviceps africana and Other Claviceps Species by RAM and AFLP Analyses

Genetic diversity among isolates of Claviceps africana, the sorghum ergot pathogen, and isolates of other Claviceps spp. causing ergot on sorghum or other hosts, was analyzed by random amplified microsatellite (RAM) and amplified fragment length polymorphism (AFLP) analyses. Of the RAM primer sets tested, one revealed polymorphism in C. africana isolates, with Australian and Indian isolates possessing a unique fragment. AFLP analysis, in addition to clearly distinguishing Claviceps spp., revealed polymorphisms in C. africana. A group of isolates from the United States, Puerto Rico, and South Africa exhibited 95 to 100% similarity with one another. Several isolates from Isabela, Puerto Rico were 100% similar to an isolate from Texas, and another isolate from Puerto Rico was identical with one from Nebraska. Australian and Indian isolates showed greater than 90% similarity with isolates from the United States., Puerto Rico, and South Africa. A number of polymorphisms existed in the United States group, indicating that the recently introduced population contains multiple genotypes. Isolates of C. sorghicola, a newly described sorghum pathogen from Japan, were very distinct from other species via RAM and AFLP analyses, as were isolates from outgroups C. purpurea and C. fusiformis. Both RAM and AFLP analysis will be useful in determining future patterns of intercontinental migration of the sorghum ergot pathogen, with the AFLP method showing greater ability to characterize levels of intraspecific variation.