Symptom types of Colletotrichum graminicola cesati Wils. of Sorghum in the Northern Guinea Savanna of Nigeria

Abstract

A study of symptom types of Colletotrichum graminicola Cesati Wils. of Sorghum was carried out at Samaru, Nigeria using four sorghum varieties, maize and millet. Morphological and cultural characteristics in addition to the pathogenicity studies under screen house conditions were carried out. The occurrence of three symptomatic groups (patchy, midrib and isolated lesions) in Sorghum anthracnose was confirmed. Conidia measurement showed that the symptoms with isolated spots produced the largest conidia (24.0-30.4x8.4-9.4 μm) among the sorghum cultivars. Maize isolates produced larger conidia (22.5-35.0x5.0-8.5 μm) than those of sorghum. Maize produced only one symptom group (patchy). Pathogenicity test in the screen house revealed that all the three isolates from sorghum could only infect sorghum varieties and neither infected maize nor millet. Maize isolates infected both maize and millet, but not sorghum. C. graminicola was found to be host-specific. Based on findings in the pathogenicity test studies, it was concluded that isolates of C. graminicola from maize were highly pathogenic to both maize and millet, but not virulent on sorghum, while isolates from susceptible sorghum cultivars were highly pathogenic to sorghum varieties, but did not infect maize and millet. Investigation of the host range using more cereals and grasses is recommended.