Browsing by Author "Steele K. A."

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    Molecular Characterization of Tomato Leaf Curl Disease-Causing Viruses in Uganda
    (African Journals Online, 2009) Ssekyewa Charles; Van Damme P.; Steele K. A.
    In this study, Tomato Leaf Curl Disease symptom-bearing samples were collected from dry savannah (Eastern and Northern) and wet equatorial/tall grass savannah (Central and Western) agro-climati c zones of Uganda. Their total DNA was extracted using a modifi ed Dellaporta protocol. Virus DNA was amplifi ed with fi ve diff erent primer pairs for Tomato yellow leaf curl virus (TYLCV), Tomato yellow leaf curl Sardinia virus (TYLCSV-Sic) and Tomato leaf curl Uganda virus (TLCUV) as well as their combinati ons. The results indicated that there is wide variati on in the tomato leaf curl viruses in the Country. The viruses were grouped into 24 categories and three (3) disti nct virus genomes, namely, Tomato leaf curl Uganda virus-Soroti , Tomato leaf curl Uganda virus- Iganga (Pallisa) and Tomato leaf curl Arusha virus-Mubende, were characterized. Parti al results indicated occurrence of viruses related to TYLCV and TYLCSV-Sic in wet agro-climati c zones. Genomic variati on was detected within isolates and recombinati on was suspected.
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    Relationship between Tomato Yellow Leaf Curl Viruses and the Whitefly Vector
    (African Journals Online, 2010) Ssekyewa C.; Van Damme P.; Nagawa F.; Kyamanywa Samuel; Steele K. A.
    Tomato yellow leaf curl is prevalent in tomato growing districts of Uganda. The disease is known to be spread by a whitefly (Bemisia tabaci) in a persistent manner. Some of its symptoms are leaf curl, marginal leaf yellowing, malformation of fruits, stunting and dieback (in case of primary infection at early seedling stage), so the disease is economically important. Therefore, this study delved into the relationship between the disease and the vector in selected agro-ecosystems in the Country. The influence of weather and seasonality on the incidence of the disease and the vector was also investigated through a series of field experiments across a period of two years. New methods for trapping the vector were developed and applied to estimate its populations on individual plants and in the overall field environment. The findings were that whereas incidence of the disease is low at seedling stage, the whitefly population is highest at this stage. It was also found that the vector population is favoured by drought, so rainy conditions reduced it tremendously.