Abstract:

Overview of sweet potato research and development in Uganda-this paper
summarizes the history of sweet potato 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 sweet potato and sweet potato-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 sweet potato 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
sweet potato clones and varieties for resistance to SPW. The American lines that were
tested at SAARI were those that had shown biochemical resistance Systerna spp,
Diabrotica 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 sweet potato 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. The practical