National Root Crops Research Institute, Umudike, PMB 7006, Umuahia, Nigeria; International Institute of Tropical Agriculture, Oyo Road, PMB 5320, Ibadan, Nigeria; Department of Crop Protection and Environmental Biology, University of Ibadan, Ibadan, Niger
Egesi, C.N., National Root Crops Research Institute, Umudike, PMB 7006, Umuahia, Nigeria, National Root Crops Research Institute, Umudike, Umuahia, Nigeria; Odu, B.O., International Institute of Tropical Agriculture, Oyo Road, PMB 5320, Ibadan, Nigeria, National Root Crops Research Institute, Umudike, Umuahia, Nigeria; Ogunyemi, S., Department of Crop Protection and Environmental Biology, University of Ibadan, Ibadan, Nigeria, National Root Crops Research Institute, Umudike, Umuahia, Nigeria; Asiedu, R., International Institute of Tropical Agriculture, Oyo Road, PMB 5320, Ibadan, Nigeria, National Root Crops Research Institute, Umudike, Umuahia, Nigeria; Hughes, J., Department of Crop Protection and Environmental Biology, University of Ibadan, Ibadan, Nigeria, Asian Vegetable Research and Development Center (AVRDC), PO Box 42, Shanhua, Tainan 74199, Taiwan, National Root Crops Research Institute, Umudike, Umuahia, Nigeria
Use of genetic resistance is the most practical and economic way to manage major diseases of yams. In a search for sources of resistance, 40 water yam (Dioscorea alata L.) accessions from Benin, Ghana, Nigeria and Puerto Rico were screened under natural disease infection conditions in Ibadan, Nigeria. The accessions were evaluated at 1, 3 and 6 months after planting (MAP) for severity of yam anthracnose and viral diseases. The effect of the pathogens on yield was also evaluated at harvest 9 MAP. There were significant differences (P < 0.001) between accessions for severities of anthracnose and viral diseases. Eight (20%) of them had lower anthracnose area under disease progress curves (AUDPC) values than the resistant check while 10 (25%) had AUDPC values below the trial mean. There were significant variations (P < 0.001) in yield components among the accessions. There was significant negative correlation of anthracnose severity with fresh tuber yield (r = -0.51) and with number of tubers per plot (r = -0.40). Similarly, significant negative correlations were observed of virus disease severity with fresh tuber yield (r = -0.78) and number of tubers per plot (r = -0.65). Linear regression models also showed that the fresh yield had significant negative relationships with anthracnose (R 2 = 0.26) and viral (R2 = 0.62) diseases. The accessions identified as resistant constitute a valuable resource for breeding of resistant germplasm.