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Origin 'Bwanjule', 'New Kawogo', 'Tanzania', and 'Wagabolige' are superior Ugandan farmers' cultivars selected from a collection of 380 landrace accessions assembled at Namulonge Agricultural and Animal Production Research Institute (NAARI) in 1987 and subsequently evaluated in trials at NAARI and elsewhere in Uganda. Pedigrees of these landrace cultivars are not known, but they are assumed to be chance seedlings selected by farmers. On the basis of numbers of landrace cultivars, and the adaptation of these cultivars to local conditions, including diseases and pests, eastern Africa is considered to be a secondary center of sweetpotato genetic diversity. 'Sowola', designated NIS/90/389a during testing, is a seedling selection from the sweetpotato breeding program at NAARI, and was selected from bulked seed from a polycross of 18 parents made from 1989 to 1990. The progenitors in this polycross block were popular farmers' cultivars from various parts of

"Sweetpotato weevils" Cylas puncticollis (Boheman) and Cylas brunneus F. (Coleoptera: Brentidae) are the most important biological threat to sweetpotato, Ipomoea batatas L. (Lam), productivity in sub-Saharan Africa. Sweetpotato weevil control is difficult due to their cryptic feeding behavior. Expression of Cylas-active Bacillus thuringiensis (Bt) Cry proteins in sweetpotato could provide an effective control strategy. Unfortunately, Bt Cry proteins with relatively high toxicity against Cylas spp. have not been identified, partly because no published methodology for screening Bt Cry proteins against Cylas spp. in artificial diet exists. Therefore, the initial aim of this study was to develop an artificial diet for conducting bioassays with Cylas spp. and then to determine Bt Cry protein efficacy against C. puncticollis and C. brunneus by using this artificial diet. Five diets varying in their composition were evaluated. The highest survival rates for sweetpotato weevil larvae were observed for diet E that contained the highest amount of sweetpotato powder and supported weevil development from first instar to adulthood, similar to sweetpotato storage roots. Seven coleopteran-active Bt Cry proteins were incorporated into diet E and toxicity data were generated against neonate C. puncticollis and second-instar C. brunneus. All Bt Cry proteins tested had toxicity greater than the untreated control. Cry7Aa1, ET33/34, and Cry3Ca1 had LC50 values below 1 microg/g diet against both species. This study demonstrates the feasibility of using an artificial diet bioassay for screening Bt Cry proteins against sweetpotato weevil larvae and identifies candidate Bt Cry proteins for use in transforming sweetpotato varieties potentially conferring field resistance against these pests.

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