An in vitro detached leaf assay for pre-screening resistance to anthracnose disease in cassava (Manihot esculenta Crantz)

Abstract

Cassava anthracnose disease (CAD), caused by Colletotrichum gloeosporioides f. sp. manihotis is one of the most important fungal infections that affects cassava yield in many countries especially in Africa and including Thailand. In this study, a rapid screening method to identify cassava varieties that are resistant to CAD based on a detached leaf assay was developed. Three different varieties of cassava commonly grown in Thailand, Hanatee, Huay Bong 60 and Kasetsart 50 were used. Agar plugs (0.8 cm diameter) with mycelia of C. gloeosporioides f. sp. manihotis were applied to the centre of the middle lobe of the cassava leaves, while sterile potato dextrose agar plugs were used as controls. Lesions on the inoculated samples were measured on the fourth day after inoculation. The size of the lesions on each variety was compared using ANOVA and the results revealed that Huay Bong 60 showed the highest resistance to CAD whereas Hanatee was the most susceptible variety. The screening method developed in this study can be undertaken within a short time and without contamination of the pathogen into the environment. This methodology will be useful for identification of cassava varieties with resistance to CAD. © 2010 Australasian Plant Pathology Society.