Sweetpotato, with a global annual planting area of approximately 9 million ha, is the second most important tropical root crop. It is widely adapted, being grown in more than 110 countries. Early maturing varieties grow in 3-4 months. It is hardy and has multiple uses. Both roots and foliage are edible and provide energy and nutrients in diets. Distinct quality types have different uses, with orange-fleshed sweetpotato being valued for its extremely high provitamin A content, and other types used in varied fresh and processed forms. Sweetpotato is easily bred, as true seed is easily obtained and generation cycles are short. There are five objectives of this review. The first objective is to briefly describe recent production and utilization trends by region; the second is to review knowledge about the origin and genetic nature of sweetpotato; the third is to review selected breeding objectives. The fourth objective is to review advances in understanding of breeding methods, including: (i) generation of seed through polycross nurseries and controlled cross breeding; (ii) a description of a new accelerated breeding approach; (iii) recent efforts to systematically exploit heterosis; and (iv) new approaches of genomic selection. The fifth objective is to provide information about variety releases during the past 20 years in West, East and Southern Africa, South Asia, East and South-east Asia, China and the Pacific.

Seven resistant varieties of sweetpotato were compared with three susceptible varieties in field trials and laboratory bioassays and showed that resistance was an active process rather than an escape mechanism, as field resistant varieties also had reduced root damage and oviposition compared with susceptible varieties in the laboratory. Liquid chromatography-mass spectrometry (LC-MS) of root surface and epidermal extracts showed significant variation in the concentration of hexadecyl, heptadecyl, octadecyl, and quinic acid esters of caffeic and coumaric acid, with higher concentrations correlated with resistance. All compounds were synthesized to enable their positive identification. Octadecyl coumarate and octadecyl caffeate applied to the surface of susceptible varieties in laboratory bioassays reduced feeding and oviposition, as observed on roots of resistant varieties, and therefore are implicated in weevil resistance. Segregating populations from breeding programs can use these compounds to identify trait loci for resistance and enable the development of resistant varieties.

The changes in content of total carotenoid at each stage of processing cassava storage roots were investigated with three improved yellow-fleshed cassava varieties (TMS 94 ⁄ 0006, TMS 01 ⁄ 1235 and TMS 01 ⁄ 1371) grown in 2005 ⁄ 2006 in a randomised complete block design with two replications at Ibadan, Nigeria. When the cassava roots were grated to a mash, results obtained indicate that there was a significant reduction in total carotenoid content for all the genotypes. The reduction was highest for TMS 01 ⁄ 1235 (1.20 lg g )1 ), intermediate for TMS 01 ⁄ 1371 (0.78 lg g )1 ) and least for TMS 94 ⁄ 0006 (0.35 lg g )1 ). In most cases, we observed higher total carotenoid concentration, especially when the intermediate step involved pressing to remove excess water, and during roasting compared with the initial concentration in the raw cassava storage roots. In conclusion, grating, drying and cooking to a paste resulted in reduction of total carotenoid content, while roasting and pressing resulted in higher carotenoid concentration. A change in total carotenoid content during processing depends on variety, processing method, especially unit operation and the initial total carotenoid content of the variety.

Additional index words. Ipomoea batatas, sweetpotato virus disease, alternaria bataticola blight, provitamin A Two sweetpotato [Ipomoea batatas L. (Lam.)] cultivars, NASPOT 12 O (Namulonge sweetpotato 12 orange-fleshed) and NASPOT 13 O (Namulonge sweetpotato 13 orange-fleshed) were approved for release by the Ugandan Plant Variety Release Committee (UPVRC) in Nov. 2013(Ssemakula et al., 2013. This brings to 22, the number of sweetpotato cultivars officially released between 1999 and 2013 by the National Sweetpotato Program in Uganda (Mwanga et al., 2011;Ssemakula et al., 2013). The two cultivars herein described and released in 2013, have high average storage root yields, 43.1 t • ha -1 ('NASPOT 12 O') and 27.8 t • ha -1 ('NASPOT 13 O') on station, and 14.9 t • ha -1 ('NASPOT 12 O') and 9.7 t • ha -1 ('NASPOT 13 O') on farm compared with the national on-farm average for Uganda of 4.5 t • ha -1 (FAOSTAT 2010;Low et al., 2009). The cultivars have acceptable root shape, high dry matter content (DMC) (>30%) with

Uganda is the world's second largest producer of sweetpotato after China. About 43 million children in sub-Saharan Africa (SSA) are at risk of vitamin A deficiency (VAD); in Uganda 20 per cent of children and 19 per cent of women are vitamin A deficient. VAD can be addressed using orange-fleshed sweetpotato (OFSP) varieties with high b-carotene content. The Uganda National Sweetpotato Program (UNSP) and its partners developed and released two OFSP landrace varieties in 2004. Another two improved OFSP varieties with desirable traits and resistance to the devastating diseases Alternaria bataticola blight and sweetpotato virus disease were released in 2007. The four released OFSP varieties have been deployed in Uganda and several other countries to alleviate VAD. The lessons drawn from the UNSP receiving steady support clearly show that it takes a long time to develop technologies, and to disseminate and commercialize them. It requires commitment by the partners for effective commercialization of the developed technologies. The programme used a partnership approach to engage different stakeholders in the value chain to speed up dissemination and commercialization of OFSP varieties and other technologies. Compelling evidence exists of the potential contribution of OFSP to improved nutrition in Uganda and SSA.