Browsing by Author "Alajo, Agnes"

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    Combining ability and heritability analysis of sweetpotato weevil resistance, root yield, and dry matter content in sweetpotato
    (Frontiers Media S.A., 2022-09) Mugisa, Immaculate; Karungi, Jeninah; Musana, Paul; Odama, Roy; Alajo, Agnes; Chelangat, Doreen M; Anyanga, Milton O; Oloka, Bonny M.; Gonçalves dos Santos, Iara; Talwana, Herbert; Ochwo-Ssemakula, Mildred; Edema, Richard; Gibson, Paul; Ssali, Reuben; Campos, Hugo; Olukolu, Bode A; Guilherme; Yencho, Craig; Yada, Benard; da Silva Pereira, Guilherme; Yencho, Craig
    Efficient breeding and selection of superior genotypes requires a comprehensive understanding of the genetics of traits. This study was aimed at establishing the general combining ability (GCA), specific combining ability (SCA), and heritability of sweetpotato weevil (Cylas spp.) resistance, storage root yield, and dry matter content in a sweetpotato multi-parental breeding population. A population of 1,896 F1 clones obtained from an 8 × 8 North Carolina II design cross was evaluated with its parents in the field at two sweetpotato weevil hotspots in Uganda, using an augmented row-column design. Clone roots were further evaluated in three rounds of a no-choice feeding laboratory bioassay. Significant GCA effects for parents and SCA effects for families were observed for most traits and all variance components were highly significant (p ≤ 0.001). Narrow-sense heritability estimates for weevil severity, storage root yield, and dry matter content were 0.35, 0.36, and 0.45, respectively. Parental genotypes with superior GCA for weevil resistance included “Mugande,” NASPOT 5, “Dimbuka-bukulula,” and “Wagabolige.” On the other hand, families that displayed the highest levels of resistance to weevils included “Wagabolige” × NASPOT 10 O, NASPOT 5 × “Dimbuka-bukulula,” “Mugande” × “Dimbuka-bukulula,” and NASPOT 11 × NASPOT 7. The moderate levels of narrow-sense heritability observed for the traits, coupled with the significant GCA and SCA effects, suggest that there is potential for their improvement through conventional breeding via hybridization and progeny selection and advancement. Although selection for weevil resistance may, to some extent, be challenging for breeders, efforts could be boosted through applying genomics-assisted breeding. Superior parents and families identified through this study could be deployed in further research involving the genetic improvement of these traits.
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    Factors influencing diversity of farmers' varieties of sweet potato in Uganda: implications for conservation
    (Economic Botany, 2014) Zawedde, Barbara M.; Harris, Craig; Alajo, Agnes; Hancock, Jim; Grumet, Rebecca
    Factors Influencing Diversity of Farmers’ Varieties of Sweet Potato in Uganda: Implications for Conservation. There is increasing concern that agricultural intensification is causing loss of crop biodiversity due to displacement of traditional farmers’ varieties by a small number of improved cultivars. Using ethnobotanical surveys, we assessed the implication of adoption of new sweet potato (Ipomoea batatas) cultivars on the maintenance of farmers’ varieties in Uganda. Other factors influencing varietal diversity were also assessed. A total of 102 farmer households distributed in the top three sweet potato production agro-ecological zones were interviewed. With the exception of released cultivars, very few varieties appeared in more than one region. The majority of the respondents indicated that they continue to plant some of the existing varieties when they adopt new cultivars. Loss of planting materials due to drought was a major constraint to maintaining varietal diversity for this vegetatively propagated crop. Limited land and lack of access to best management practices were also key constraints to maintenance of farmers’ varieties. The primary criteria for adopting new cultivars were higher yield, taste, and duration to maturity. Yield stability, tolerance to native biotic and abiotic stresses, and good taste were important for maintenance of currently grown varieties. Overall, criteria for variety selection varied with household characteristics including farmer age and gender, uses of the crop, micro-climatic conditions in the farmers’ fields, and level of access to agricultural extension. The observed heterogeneity in selection criteria, influence of social ties, and the role of environment in varietal maintenance have important implications for establishing breeding priorities and preservation of crop diversity.
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    Factors influencing diversity of farmers' varieties of sweet potato in Uganda: implications for conservation.
    (The New York Botanical Garden Press, Bronx, NY 10458-5126 U.S.A., 2014) Zawedde, Barbara M.; Harris, Craig; Alajo, Agnes; Hancock, Jim; Grumet, Rebecca
    There is increasing concern that agricultural intensification is causing loss of crop biodiversity due to displacement of traditional farmers’ varieties by a small number of improved cultivars. Using ethnobotanical surveys, we assessed the implication of adoption of new sweet potato (Ipomoea batatas) cultivars on the maintenance of farmers’ varieties in Uganda. Other factors influencing varietal diversity were also assessed. A total of 102 farmer households distributed in the top three sweet potato production agro-ecological zones were interviewed. With the exception of released cultivars, very few varieties appeared in more than one region. The majority of the respondents indicated that they continue to plant some of the existing varieties when they adopt new cultivars. Loss of planting materials due to drought was a major constraint to maintaining varietal diversity for this vegetatively propagated crop. Limited land and lack of access to best management practices were also key constraints to maintenance of farmers’ varieties. The primary criteria for adopting new cultivars were higher yield, taste, and duration to maturity. Yield stability, tolerance to native biotic and abiotic stresses, and good taste were important for maintenance of currently grown varieties. Overall, criteria for variety selection varied with household characteristics including farmer age and gender, uses of the crop, micro-climatic conditions in the farmers’ fields, and level of access to agricultural extension. The observed heterogeneity in selection criteria, influence of social ties, and the role of environment in varietal maintenance have important implications for establishing breeding priorities and preservation of crop diversity.