Disease Note.

Occurrence of Cochlioholus carbonum Race 3 on Corn in China, Nigeria, and Germany. H. G. Welz, University of Hohenheim, Institute of Plant Breeding, Seed Science and Population Genetics (350), 70593 Stuttgart, Germany. H. H. Geiger, University of Hohenheim, Institute of Plant Breeding, Seed Science and Population Genetics (350), 70593 Stuttgart, Germany. Plant Dis. 79:424. Accepted for publication 15 February 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0424B.

Five different races (0 through 4) have been described in Cochlioholus carbonum R. R. Nelson, the incitant of Carbonum Com Leaf Spot Race 3 causes long, narrow lesions on most corn inbred lines and hybrids. It was first described in 1973 in Pennsylvania and is prevalent in the southeastern US. In 1981 it occurred on corn in Japan and was subsequently identified there as a foliar pathogen of rice (1). We observed C. carbonum race 3-type lesions on dried maize leaves collected in China, established C. carbonum isolates from these leaves and leaves obtained from other countries, and tested them on a differential set of corn inbreds (Pr, Prl, A632. W64A, B37Ht, Mol7Ht) as described previously (2). Lesions typical of race 3 were obtained with two isolates from China (Shandong and Hebei province, leaves collected 1990 and 1991, respectively), one from Nigeria (Ibadan, 1990) and one from Germany (Emmendingen, 1991) Race 2 occurred two (l + l), one, and five times in the respective samples. In a sample from Switzerland (Cadenazzo, 1993) comprising three isolates, all were race 2. The German race-3 isolate mated successfully with a MAT-l/race 2 US tester isolate (2). The mating capacity of the other isolates has not been investigated.