Browsing by Author "Mwanga, R. O. M."

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    Genetic Diversity in White- and Orange-Fleshed Sweetpotato Farmer Varieties from East Africa Evaluated by Simple Sequence Repeat Markers
    (Crop Science, 2011-05-01) Tumwegamire,S.; Rubaihayo, P. R.; Kapinga, R.; Mwanga, R. O. M.; Grüneberg, W. J.
    Sweetpotato [Ipomoea batatas (L.) Lam] farmer varieties are still the backbone of production and breeding programs in Sub-Sahara Africa. Usually, farmer varieties in Sub-Sahara Africa are white- or cream-fleshed sweetpotato (WFSP), but recently orange-fleshed sweetpotato (OFSP) were found in East Africa. The objective of the study was to characterize WFSP and OFSP germplasm from East Africa. Eighty-five East African farmer varieties (29 OFSPs and 56 WFSPs) and seven varieties of non-African origin as check clones were analyzed for diversity using 26 simple sequence repeat (SSR) markers. A total of 158 alleles were scored with an average of 6.1 alleles per SSR loci. The mean of Jaccard's similarity coefficients was 0.54. The unweighted pair group method analysis (UPGMA) revealed a main cluster for East Africa germplasm at a similarity coefficient of 0.52. At a similarity coefficient of about 0.55 subclusters within the East African germplasm were observed, but these were neither country nor flesh color specific. Analysis of molecular variance (AMOVA) found a significant difference between East African and non-African germplasm and a nonsignificant difference between OFSP and WFSP germplasm. In conclusion, the East African germplasm appears to be distinct from non-African germplasm, and OFSP and WFSP farmer varieties from East Africa are closely related. Orange-fleshed sweetpotato farmer varieties from East Africa might show similar adaptation to Sub-Sahara African environments as WFSP and a big potential in alleviating vitamin A deficiency.
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    Morphological Characterization of Ugandan Sweetpotato Germplasm
    (Crop Science, 2010-11-01) Yada, B.; Tukamuhabwa, P.; Alajo, A.; Mwanga, R. O. M.
    Sweetpotato [Ipomoea batatas (L.) Lam] is a widely grown and consumed root crop in Uganda. A total of 1303 accessions of sweetpotato germplasm collected from 21 districts of Uganda were planted for morphological characterization. Forty morphological descriptors were scored on 1256 accessions 90 to 100 d after planting. Stepwise discriminant analysis showed that the discriminating power of 20 morphological traits was sufficient to differentiate the accessions. The level of morphological variation for the 40 traits estimated using the Shannon Weaver diversity index (H') ranged from 0.10 to 0.99, with an overall mean of 0.71 ±0.03, suggesting a highly diverse collection. Cluster analysis using the unweighted pair-group method using arithmetic averages grouped the 1256 accessions into 20 major clusters, with the number of accessions per cluster ranging from 15 to 166. The general leaf outline was highly correlated with leaf lobe type (r = 0.79) and leaf lobe number (r = 0.80) and were the predominant characters in grouping the accessions to clusters. No grouping of accessions based on region of origin was observed, suggesting movement of germplasm between regions. Approximately 70% of the accessions were morphologically distinct and a collection of 946 accessions was selected to represent Ugandan sweetpotato landrace diversity. The complete passport data for this collection is available at: http://www.viazivitamu.org/ugasp_db/gis.htm