A New Leaf Spot of Sorghum Caused by Cochliobolus bicolor in Tamil Nadu, India. P. Lakshmanan, Department of Plant Pathology, Tamil Nadu Agricultural University, Coimbatore 641003, India. L. Mohan, S. Mohan, and R. Jeyarajan. Department of Plant Pathology, Tamil Nadu Agricultural University, Coimbatore 641003, India. Plant Dis. 71:651. Accepted for publication 11 March 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0651B.
During August 1985 and 1986, a previously undescribed leaf spot was
observed on the grain sorghum (Sorghum bicolor (L.) Moench) cultivar
KS 6312. Lesions were circular with alternating concentric, straw colored
bands and, in severe cases, coalesced on a large proportion of
the leaf surface. The pathogen was isolated and identified as
Cochliobolus bicolor Paul & Parberry (Herb. IMI No. 303555).
Pathogenicity was tested by spraying a conidial suspension (107/ ml) on
48-day-old KS 6312 plants. Ten inoculated plants were covered with
plastic bags for 24 hr. Typical zonation occurred 10 days after
inoculation. The pathogen is reported to cause zonate leaf spot on
Pennisetum cladestinum Hochst. ex Chiov. in Brazil (1). This is the first
report of C. bicolor causing leaf spot on S. bicolor.