Variation among foliar isolates of Colletotrichum sublineolum of sorghum in Nigeria

Foliar anthracnose, caused by Colletotrichum sublineolum, is a major diseas e of sorghum in Nigeria. Pathogenic diversity was studied among foliar isol ates of C, sublineolum collected from sorghum cultivars in farmers fields i n the Sahel, Sudan, northern Guinea and southern Guinea zones of Nigeria du ring the 1997 crop season. For the study a total of 50 isolates were identi fied based on typical symptom types and cultural characteristics. On the ba sis of growth in culture and morphological characteristics, the isolates we re classified into nine morphological groups (MGs). Pathogenicity tests wer e done on a set of known sorghum differential lines by inoculating pot-grow n seedlings in a greenhouse. On the basis of disease reaction and disease s everity scores on the differential lines, the 50 isolates were classified i nto seven pathogenic groups (PGs). Sixteen representative isolates of the M Gs and the PGs were further evaluated for virulence and aggressiveness on t he differential lines and were classified into five distinct groups using t he centroid method of cluster analysis. The existence of five races of C. s ublineolum in major sorghum growing zones of Nigeria is suggested. (C) 2001 Elsevier Sciences B.V. All rights reserved.