Relations among sorghum ergot isolates from the Americas, Africa, India, and Australia

Sorghum ergot, initially restricted to Asia and Africa, was recently found in the Americas and Australia. Three species causing the disease have been reported: Claviceps sorghi in India, C. sorghicola in Japan, and C. african a in all ergot-positive countries. The objective of our study was to study the intraspecific variation in C. africana isolates in the Americas, Africa , India. and Australia. We confirmed C. africana, C. sorghi, and C. sorghic ola as different species using differences in nucleotide sequences of inter nal transcribed spacer 1 and 5.8S rDNA regions. Sequences of this region ob tained from the representative American, Indian, and Australian isolates of C. africana were identical. In addition, random amplified polymorphic DNA (RAPD) banding patterns of sorghum ergot pathogen isolates from the United States, Mexico, Puerto Rico, Bolivia, Australia, and India were evaluated w ith nearly 100 primers. A total of 65 primers gave identical patterns for a ll isolates, which confirmed that all were C. africana. The identity of RAP D pattern and rDNA sequence of Indian isolates with those of C. africana co nfirmed that the species is now present in India. Only 20 primers gave smal l pattern differences and 7 of them were used for routine testing. All of t he American isolates were identical and three isolates of the same type wer e also found in South Africa, suggesting Africa as the origin of the invasi on clone in the Americas. Australian and Indian isolates were distinguishab le by a single band difference; therefore, migration from the Asian region to Australia is suspected. Another distinct group was found in Africa. Clus ter analysis of the informative bands revealed that the American and Africa n group are on the same moderately (69%) supported clade. Isolates from Aus tralia and India belonged to another clade.