Morphological Characterization of <i>Corticium koleroga</i>, Cause of Thread Blight on Arabica Coffee

Abstract

Coffee thread blight caused by Corticium koleroga is one of the fungal pathogens that cause severe damage to Coffea arabica in southwest Ethiopia. However, there are very few research findings on the features of the pathogen in Ethiopia. Therefore, the current work was designed with the objectives to characterize pathogen isolates and determine the pathogenicity of the Corticium koleroga isolates. For this purpose, diseased samples were collected from 11 districts of southwest Ethiopia during the 2017 cropping season. C. koleroga isolates were characterized using macroscopic and microscopic features. Eleven isolates of C. koleroga collected from southwest Ethiopia varied in their colony colour ranging from white to floral white, with circular to irregular form and filiform to entire in margin on PDA plates. Growth rate of the isolates was between 6 and 9 mm/day in diameter. Morphological variations in basidiospores length and basidial shape were also evident among the isolates. Average basidiospore size ranged from 10 to 13.75 x 3.75 to 5μ. All isolates were pathogenic to C. arabica (74110 susceptible variety), with significantly different (P<0.01) lesion size. The most aggressive isolate was Yayu isolate, followed by isolates from Andaracha and Mettu with average lesion size of 95.55, 94.49 and 93.29%, respectively. The current study revealed the identity of Corticium koleroga in southwest Ethiopia. Future research should be directed towards molecular characterization of the pathogen.