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Field evaluation of eight cultivars of Dioscorea for possible resistance to yam beetle damage in Oshimili Area of Delta State, Nigeria.
Abstract
Trials to evaluate 8 cultivars of yam (Dioscorea species) for possible resistance to yam beetle (Heteroligus sp) damage was conducted at Anwai and Ugbolu in 2004 and 2005 planting seasons in a yam monocrop system. The two sites were located in Oshimili South and North LGA respectively in Delta State. Trials were laid out in a randomized completely block design (RCBD) with three replications. Results showed that all the cultivars tested were susceptible to the yam beetles damage. The two-year results consistently indicated that Dioscorea rotundata were the most susceptible. It was observed that D. alata and D. cayenensis had tuber yields significantly higher (P0.05) than other cultivars. This ranged from 20tha and above, irrespective of locations and year of cropping. Least yields were obtained from D. rotundata cv akwukwu-ukpa 7.36, ekpe 11.0, in Anwai in 2004 while 6.50 and 8.26tha were recorded at the same location in 2005 respectively for the two cultivars. At Ugbolu location, D. dumetorum and D. cayenensis showed some degree of resistance and tolerance to the beetle with 'mild' damage irrespective of time and location. This may be due partly to the bitter taste and alkaloid properties in D. dumetorum while the late tuber initiation in D. cayenensis may be responsible for the tolerance. Attacked tubers by the beetle were highest in ekpe cultivar which ranged between 77% to 80% at both locations and the periods under investigation.
Keywords: evaluation, cultivar, resistance yam beetle damage.
