Evaluation of cassava varieties for cassava mosaic disease resistance jointly by agro-inoculation screening and molecular markers

摘要

The whitefly-transmitted cassava mosaic disease (CMD) has become a potential threat to cassava (Manihot esculenta?Crantz) cultivation in ASEAN countries because of its devastating impact on cassava and overgrowth of whitefly vector regionally. To reduce the risk caused by the disease, it is necessary to evaluate the capacity of major cassava germplasms for CMD resistance to guide local farmers in adopting CMD-resistant cultivars once CMD epidemics occur. After agro-inoculation mediated infection of plantlets of collected cassava cultivars from China, Thailand and other ASEAN countries, the 18 cultivars tested developed various levels of CMD symptoms, indicating a lack of resistance to CMD. There was a positive association between symptom severity scores and accumulation levels of viral DNA in the different cultivars tested. The molecular markers RME1, SSRY28 and/or NS158, which link with the CMD resistance loci CMD2 in cassava, were found in only three cultivars (11Q, T7 and N13) with moderate resistance to CMD. Our study suggests that CMD-resistance germplasms should be introduced from Africa.