Physicochemical alteration of tissues of white yam (dioscorea rotundata poir) tubers incited by botryoiplodia theobromae pat

Investigations on the anatomical aberrations and biochemical alterations of white yam incited by Botryodiplodia theobromae was carried out. Inoculated and uninoculated head, middle and tail portions of white yam were treated, sectioned weekly for five weeks and photomicrographs taken. The plates revealed massive cell wall macerations and depletion of starch grains in the three portions of yam assessed. Less damage was evident in the head portion especially after one week of infection compared with the middle and tail portions. However, there was general progressive tissue destruction and starch grains depletion with weeks. Inoculated and uninoculated yam samples were also analyzed for the carbohydrate content weekly for five weeks. Results showed that there was a reduction for carbohydrate with increase in weeks of infection. Values of 24.60 mg, 25.1 mg and 23.9 mg carbohydrate per 100 g of edible portion of white yam were recorded after one week of infection for the head, middle and tail portions respectively. About 16.90 mg and 16.80 mg carbohydrate per 100 g edible portion of white yam tuber were recorded in the fifth week compared with 20.10 mg and 20.09 mg recorded in the second week of infection in the middle and tail portions respectively. From the third week, there was no tangible reduction in the carbohydrate content especially in the head portion, though appreciable tissue maceration was evident from the photomicrograph sections, particularly, in the tail portions where there was total breakdown and collapse of cell wall boundaries.