Prevalence of Green Gram Fungal Diseases in the Eastern Part of Kenya

Abstract

Green gram (Vigna radiata L.), also known as Mung bean, is an annual legume crop that is grown all over the world. Green gram yield in the arid and semi-arid lands of Kenya is still low due to various factors including plant diseases and poor soils. The objective of this study was to evaluate prevalence of green gram fungal diseases and the effects of soil factors on their occurrence in Tharaka-Nithi and Kitui Counties in Kenya. The study was conducted in Kitui Central and Kyangwithya wards in Kitui County, and Mukothima and Nkondi wards in Tharaka-Nithi County. Household surveys were conducted using a semi-structured questionnaire. Farm surveys were carried out using transects to evaluate disease incidence and severity. Symptomatic green gram samples were collected for isolation of pathogens. Isolates were identified based on morphological features and cultural characteristics. Soil samples were collected from farms and analyzed for physicochemical properties. Eight fungal diseases with diverse morphological and cultural characteristics were identified. The diseases were Downy mildew, Powdery mildew, Cercospora leaf spot, Macrophomina rot, Anthracnose, Late blight, Corynespora spot and Angular spot. Disease severity and incidences ranged from 6.13 to 32.2% and 16.67 to 67.79%, respectively. Powdery mildew, caused by Erysiphe polygoni DC, was the most prevalent disease with an incidence and severity mean of 59.09% and 30.92%, respectively. This could be attributed to susceptibility of the local cultivar, soil conditions and crop management practices. Soil physicochemical properties also varied among the wards and had a significant correlation with incidence and severity of diseases. These results could be useful in mapping green gram diseases and developing sustainable management options.