Mycoflora Of Dioscorea Rotundata Tubers In Calabar Metropolis And Their Effect On The Nutrient Composition Of The Tubers

Abstract

Dioscorea rotundata Poir is a primary source of carbohydrate in most African homes, where it is consumed in various forms. This research focuses on the identification of the prevalent fungal isolate responsible for the rot of yam in Calabar metropolis and the effect of these fungi on the nutritional composition of white yam. A survey of the major markets (Akim, Marian, Mbukpa and Watt) showed that the major fungi responsible for the soft rot of yam included Aspergillus flavus, A. niger, Fusarium oxysporium, Penicillium notatum and Rhizopus stolonifer. Aspergillus niger recorded the highest incidence, occurring in all the samples from various locations. The result of the pathogenicity test, proved that Aspergillus niger, Penicillium notatum and Rhizopus stolonifer were the major causes of rot in Calabar metropolis. The proximate analysis of the healthy tubers and those inoculated with Aspergillus niger, Penicillium notatum and Rhizopus stolonifer showed that the infection by these fungal isolates caused significant changes in the nutrient composition of the tubers. The total moisture content of the inoculated tubers increased within a range of 65.43±0.35 – 70.01±0.05% as compared to 59.59±0.12% in the control experiment. The carbohydrate content decreased significantly from 27.87±0.50% to a range of 18.11±0.36 – 22.68±0.28%.