Abstract:

Overview of sweetpotato research and development in Uganda-this paper summarises the history of sweetpotato introduction into Uganda and major research achievements made during the period. Twelve sweetpotato varieties with qualities of high yield, resistance to sweetpotato virus disease and Altemaria spp. and one variety, NASPOT 5, with high beta-carotene content were released officially by the Ministry of Agriculture. Production packages like appropriate seed-bed types, plant density, intercropping pattern for sweetpotato and sweetpotato-based cropping systems were developed for some agro-ecologies. Pheromones and pheromone traps were developed and used for monitoring weevil populations. Technology has been used to prove that Cylas brunneus and C. puncticollis or the African sweetpotato weevils (SPW) are the major weevil species in Uganda and African continent, and that C. formicarius is rare in the continent. Evaluation of sweetpotato clones and varieties for root quality and susceptibility to sweetpotato weevils- A number of studies revealed that there was differences among clones on important characteristics like yield, rooting depth, resistance to weevils, sweetpotato virus disease and Altemaria spp. In one study, sweetpotato clones were evaluated at preliminary yield trial stage at Serere Research Institute (SAARI), whereby the 951... American lines exhibited characteristics of having short maturation time of about 3 months, high yields, and high levels of beta-carotene. Offsprings from Tanzania, Sowola, Bwanjule and Wagabologe mothers had high yields, had aggressively growing vines, and seemed to be adaptable to the SAARI ecology. Some promising candidate clones were selected and were promoted to the next stage of evaluation. Deeply rooting varieties and those with plenty of latex, like line no. 523, had relatively little weevil attack when compared with those that lacked these qualities. A project for a MSc degree tested local varieties for resistance to weevils. Results revealed differences among varieties in terms of plant survival, tuber yield, marketable tubers and amount of soil cracking. Long-shaped tubers that protruded out of the soil suffered high weevil attack when compared with those that were buried deep in the soil. Biochemical resistance in weevil control-Collaborative work was conducted between NARO, USDA, CLP, Clemson and North Carolina Universities in screening sweetpotato clones and varieties for resistance to SPW. The American lines that were tested at SAARI were those that had shown biochemical resistance System aspp, spp., wireworms and C. formicarius, which are the major pests in the USA. Similar species, namely, wireworms, SPW and numerous beetles also occur in
4. Uganda. Also sweetpotato collection from CIP laboratory in Nairobi were being evaluated. The collections were the ones that had shown relative resistance to C. brunneus, C. puncticollis or C. formicarius in various parts of the world Relationship between vine injury, weevil infestation on tubers and pest counts from pheromone traps —Data analysis showed positive and significant association between weight of infested tubers and weevil damage score on vines, suggesting infestation can be monitored from the level of damage on vines.