Pathogenicity of Colletotrichum coccodes causing anthracnose disease and its effect on growth and yield of sweet potato [Ipomoea batatas (L.) Lam]

Abstract

The disease causing ability of Colletotrichum coccodes and the effect of anthracnose on growth and yield of sweet potato accessions were evaluated in a two-year field trial. Field layout was a randomized complete block design with 16 sweet potato accessions replicated thrice. Young leaves of sweet potato accessions were sprayed with an inoculum concentration of 2.1 × 107 in a two-split application in the field with growth, yield, and disease indices recorded. Pathogenicity of C. coccodes was significantly highest among four accessions; OW4, SE10, SE12 and SPK-004 with abundant necrosis on leaves and stems of inoculated plants. Disease incidence varied between 2.48% - 52.83%, and 2.77% - 50.73%, during the 2018 and 2019 planting seasons respectively, with host response ranging from being susceptible to resistant. Accessions OW5 and OS15 had significantly lower disease incidence and severity than other treatments (p = 0.031 and 0.28 respectively) and also produced the highest yield ranging between 15.84 - 17.29, and 14.88 - 15.72 t/ha-1, in 2018 and 2019, respectively. This study has shown that anthracnose causes significant reduction in expected yield in sweet potato cultivation and also identified two resistant sweet potato accessions that can be useful sources in breeding for resistance to the disease.