Browsing by Author "Rubaihayo, P. R."

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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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    Genetic Diversity of Phytophthora infestans (Mont.) de Bary in the Eastern and Western Highlands of Uganda
    (Journal of Phytopathology, 2002-10-16) Ochwo, M. K. N.; Adipala, E.; Rubaihayo, P. R.; Olanya, M.
    Eight isolates of Phytophthora infestans were recovered from late blight infected samples collected from the districts of Mbale and Mbarara in the Eastern and Western highlands of Uganda in 2001 and analysed using mitochondrial deoxyribonucleic acid (DNA) haplotype and Amplified Fragment Length Polymorphism (AFLP) markers. Polymerase chain reaction amplification with the P2 primer followed by digestion with MspI yielded a three-fragment pattern characteristic of isolates belonging to the US-1 clonal lineage; the polymorphism was confirmed by DNA sequencing. AFLP analysis yielded 60 markers, analysis of which clustered the Ugandan isolates with reference to US-1 isolates (US930258 and US940501). These results suggest that the examined Ugandan isolates belong to the US-1 clonage lineage
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    Prevalence of viruses infecting cowpea in Uganda and their molecular detection
    (African Journal of Biotechnology, 2012-01-26) Amayo, R.; Arinaitwe, A. B.; Mukasa, S. B.; Kyamanywa, S.; Rubaihayo, P. R.; Edema, R.
    The main areas for cowpea cultivation in Uganda were surveyed in June and October 2006 for viruses affecting the crop. Seed and leaf samples from symptomatic and asymptomatic plants were collected from farmers’ fields and analysed for infecting viruses using double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). The viruses detected in the leaf and seed samples were: cucumber mosaic cucumovirus (CMV), cowpea mild mottle calarvirus (CPMMV), cowpea mottle carmovirus (CPMoV), Cowpea chlorotic mottle bromovirus (CCMV), Cowpea yellow mosaic comovirus (CYMV), cowpea severe mosaic comovirus (CPSMV), cowpea aphid-borne mosaic potyvirus (CABMV) and Southern bean mosaic sobemovirus (SBMV). CPMV was detected only in leaf samples. CMV and CABMV were later confirmed using reverse transcription polymerase chain reaction (RT-PCR). Of the viruses detected in leaf samples, 53.26% occurred as single infections, 24.46% dual and 22.28% multiple infections. Similarly, analysis of seed samples revealed infection of 40.6, 34.6 and 24.8% for single, dual and multiple infections, respectively. Multiple virus infections were associated with more disease severity and higher yield losses. The seed transmission levels of 23.0, 20.3 and 16.4% were recorded for CMV, CPMMV and CABMV, respectively. This study identified six more viruses in addition to what was previously reported in the country, of which eight were seed-borne. This necessitates the need for the production and use of virus-free seeds, development of virus resistant genotypes and adoption of efficient seed certification systems.