Occurrence of Ergot (Sugary Disease) Incited by a Sphacelia sp. on Sorghum in Mississippi in 1997

A Reevaluation of the Host Range and Geographical Distribution of Claviceps Species in the United States

A listing of host and state reports and distribution maps for 11 taxa of Claviceps occurring in the United States, including C. africana, C. cinerea, C. grohii, C. nigricans, C. paspali, C. pusilla, C. purpurea var. purpurea and var. spartinae, C. tripsaci, C. yanagawensis, and C. zizaniae, was prepared based on literature citations and examination of specimens from herbaria. The occurrence of C. ranunculoides is questioned based on examination of conidia and sclerotia from archived specimens. Collections of C. purpurea var. purpurea from grasses in the Pani-coideae were referred to other Claviceps spp. based on occurrence of macroconidia and micro-conidia. C. purpurea var. purpurea was found on 165 grass species within the continental United States and Alaska. The size of conidia of C. purpurea var. purpurea was found to be relatively stable across host and geographical regions. However, conidia of C. purpurea var. purpurea from hosts in the Aveneae and Meliceae (generally associated with wet habitats) were more variable in size and generally larger than those from other tribes in the Pooideae. Claviceps spp. in the continental United States occurred in diverse habitats, including temperate grasslands of the middle to northern latitudes (C. purpurea var. purpurea, C. nigricans) to the middle to southern latitudes (C. pusilla), coastal habitats (C. purpurea var. spartinae, C. ziza-niae), northern wetlands (C. grohii), southern temperate to subtropical grasslands (C. africana, C. paspali, C. tripsaci, C. yanagawensis), and arid southwestern grasslands (C. cinerea).

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

ABSTRACT 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.