72 15 th Triennial ISTRC Symposium Release and diffusion orange sweetpotato cultivars, ‘NASPOT 9 O’, ‘NASPOT 10 O’ in Uganda R.O.M. Mwanga 1 , G. Ssemakula 1 , C. Niringiye 1 , A. Alajo 1 , B. Kigozi 1 , R. Makumbi 1 , E. Lugwana 1 , J. Namakula 1 , and I. Mpembe 1 , R. Kapinga 2 , B. Lemaga 2 , J. Nsumba 2 , S. Tumwegamire 2 , and G.C. Yencho 3 1 National Agricultural Research Organization (NARO), National Crops Resources Research Institute (NaCRRI), Namulonge, P.O. Box 7084, Kampala, Uganda (Emails: r.mwanga@cgiar.org ; gssemakula@naro-ug.org ; nankinga@yahoo.com ; csniringiye@gamil.com ; agnesalajo@yahoo.com ; bkigozi@naro-ug.org ; rose_makumbi@yahoo.com ; elugwana@naro-ug.org ; jnamkula@naro-ug.org ; impembe@naro-ug.org ) 2 International Potato Center (CIP), Box 22274, Kampala, Uganda (reginakapinga@gatesfoundation.org ; b.lemaga@cgiar.org ; nsumba@cipuganda.co.ug ; s.tumwegamire@cgiar.org ) 3 Department of Horticultural Science, North Carolina State University, Rm. 214A Kilgore Hall, Box 7609, Raleigh, NC 27695-7609, USA (Email: Craig_Yencho@ncsu.edu) Corresponding author: r.mwanga@cgiar.org Abstract Two orange-fleshed sweetpotato (Ipomoea batatas L. (Lam.) cultivars, NASPOT 9 O (Namulonge Sweetpotato 9 orange-fleshed) and NASPOT 10 O were approved for release by the Ugandan Plant Variety Release Committee in July 2007. The two cultivars were evaluated for five seasons, on-station at Namulonge in seedling, observation, preliminary, and intermediate trials, between 2002 and 2004 to confirm field resistance to sweetpotato virus disease (SPVD). They were further evaluated for three seasons, on-station and on-farm between 2004 and 2006 in replicated, standardized, multi-location yield trials. The root yields of the cultivars fluctuated across agroecologies in both on-station and on-farm trials (5.3-35.4 t•ha -1 ), but were above the national average of 4.0 t•ha -1 . The yield of the two cultivars were similar to the local check cultivars in most sites on-station and on-farm. The two cultivars have acceptable storage root shapes when grown in light soils. They also have high average dry matter content (about 30%), and good to excellent consumer acceptance. NASPOT 9 O and NASPOT 10 O have high pro-vitamin A, hence potential to alleviate widespread vitamin A deficiency. However, the cultivars were susceptible to sweetpotato weevils in no choice laboratory tests and under dry season field conditions but have moderate field resistance to Alternaria stem blight. The cultivars have moderate field resistance to SPVD which is the most devastating disease of sweetpotato in Uganda. Since their release, they have spread widely, promoted by government, non-government organizations, and farmer groups. Keywords: Alternaria bataticola blight, Cylas puncticollis, Cylas brenneus, selection. Introduction Two orange-fleshed sweetpotato (Ipomoea batatas L. (Lam.) cultivars, NASPOT 9 O and NASPOT 10 O were approved for release by the Uganda Plant Variety Release Committee in July 2007 (Mwanga et al., 2007a). The cultivars were part of the fourth group of sweetpotato cultivars to be officially released by the Sweetpotato Program in Uganda. The first three groups were released in different years; six in 1995 (Mwanga et al., 2001), six in 1999 (Mwanga et al., 2003), and two in 2004 (Mwanga et al., 2007c). The two orange-flehed cultivars described herein are pro-vitamin A (beta-carotene) rich. They have acceptable storage root shapes when grown in light soils. They also have high dry matter content (about 30%), and good to excellent consumer acceptance, particularly among women and children below six years (Wamaniala, 2008; Potts and Nagujja, 2007; Mwanga et al, 2007b, Odongo et al. 2002). The cultivars have moderate levels of field resistance to sweetpotato virus disease (SPVD) and Alternaria bataticola blight, and high storage root yields compared to the average national storage root yield of 4.0 t•ha -1 (International Potato Center, 1999). The release of these cultivars provides consumers and farmers with high quality sweetpotatoes with storage roots that are high in pro-vitamin A content. The high pro- vitamin A content in the two cultivars presents potential to alleviate widespread vitamin A deficiency in Uganda and other developing countries (Low et al. 2007; Jaarsveld et al. 2005; Ruel, 2001; UDHS, 2001).