Abstract

Cassava Mosaic Disease (CMD) was found for the first time in Southeast Asia in Ratanakiri Province Cambodia in 2015 and spread to Thailand in 2018. The disease is caused by Sri Lankan cassava mosaic virus (SLCMV), resulting in a reduction of 80-100% in cassava yields. The severity of the disease depends on the species of cassava Viruses and cultivar of cassava The objective of this experiment was to test the severity of cassava mosaic disease in commercial cassava cultivars and cassava hybrids total of 13 cultivars. In the greenhouse using a grafting tool, CRD (Completely randomized design) trials were rated disease severity on a scale of 1-5 of 8 weeks after inoculation according to the IITA (1975) method. Calculating the average severity score, disease incidence, and disease index showed that cassava cultivars C33 47-27 and TK4 have the least symptoms. The disease index was 20 percent, at level 1 (Highly resistant), the percentage of disease incidence was 50 percent, and the average severity score was 1.57, 2.12, and 2.00 respectively, with the C33 being significantly less virulent. The results of this experiment can be used as information in cultivar selection to improve cassava cultivars resistant to cassava mosaic disease in the future.