Severity of anthracnose and virus diseases of water yam (Dioscorea alata L.) in Nigeria I: Effects of yam genotype and date of planting

Abstract Anthracnose and virus diseases exert devastating impacts on yam production in many tropical regions of the world where the crop contributes to food security and income generation. The complexities in their epidemiology necessitate the use of integrated approaches in their management. Six genotypes of Dioscorea alata, planted on six dates (March–August) in each of 1998 and 1999 in Ibadan, Nigeria, were evaluated to determine the effects of planting date and genotype on severity of the two diseases. The date of planting had a profound influence on anthracnose severity, contributing 72% of the observed variation due to combined effects of planting date, genotype and their interactions. In contrast, the genotype effect was most dominant with respect to virus severity, accounting for 85% of the total observed variation. Planting in August supported least anthracnose development while April and May plantings resulted in the least severity of virus diseases. While selection of planting time could be used to manage anthracnose disease, its application could be influenced by the prevailing weather conditions in a particular location. Two of the genotypes (TDa 291 and TDa 297) had low severity values for both diseases across the different planting dates. Availability of such sources of multiple disease resistance and appropriate choice of planting date would be very useful in integrated management of the two major yam diseases.