STUDIES ON ANTHRACNOSE ON SORGHUM AMD MAIZE CAUSED BY COLLETOTRICHUM GRAMINICOLA (Ces.) Wils. AND ON A MIDRIB SPOT ON MILLET

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STUDIES ON ANTHRACNOSE ON SORGHUM AMD MAIZE CAUSED BY COLLETOTRICHUM GRAMINICOLA (Ces.) Wils. AND ON A MIDRIB SPOT ON MILLET

Abstract:

Field observations on the anthracnose on sorghum and maize in Nigeria had shown variations in the type of symptoms and the location of the symptoms. Confusion existed as to whether a midrib lesion on millet in Nigeria is caused by anthracnose. Because it was not known whether these various symptoms were caused by the one and same fungus, Colletotrichum graminicola, the causal agent of cereals anthracnose, this project was undertaken to clear the doubts or confusions. Isolates of the pathogen(s) were obtained from sorghum, maize and millet showing the typical various symptoms observed in the field. To determine extent of similarities and/or differences among the isolates morphological features of conidia and setae were studied with the aid of microscopes,. Cultural characteristics on artificial growth media were also studied. Pathogenicity tests of the different isolates using different crop cultivars under glass house conditions were conducted. Colletotrichum graminicola was readily isolated from a maize and sorghum leaf specimens and never at all from the millet leaf specimens which yielded mainly Curvularia eragrostidis and Phoma sorghina. Statistical analyses of the morphological parameters of the conidia and setae of the different isolates did not show significant differences among the isolates. Various cultural forms were detected but none being specific to a particular isolate. Pathogenicity tests proved that the millet midrib lesion, a hitherto undescribed millet disease, is not caused by Colletotrichum graminicola but by Curvularia eragrostidis and Phoma sorghina. Two formae speciales were identified from the isolates of C. graminicola; one form specializing on maize and another specializing on sorghum. Two pathotypes were separated, based on symptoms produced on sorghum, from the form that specialises on sorghum. The work demonstrated that the same fungus species, Colletotrichum graminicola, is responsible for anthracnose on maize and sorghum in Nigeria.

STUDIES ON ANTHRACNOSE ON SORGHUM AMD MAIZE CAUSED BY COLLETOTRICHUM GRAMINICOLA (Ces.) Wils. AND ON A MIDRIB SPOT ON MILLET

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