Browsing by Author "Sengooba, T."

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Characterization and Distribution of a Potyvirus Associated with Passion Fruit Woodiness Disease in Uganda
    (Plant Disease, 2012) Ochwo-Ssemakula, M.; Sengooba, T.; Hakiza, J. J.; Adipala, E.; Edema, R.; Redinbaugh, M. G.; Aritua, V.; Winter, S.
    This article describes the incidence and etiology of a viral disease of passion fruit in Uganda. Symptoms, including those characteristic of passion fruit woodiness disease (PWD), were observed on 32% of plants in producing areas. Electron microscopic observations of infected tissues revealed flexuous filaments of ca. 780 nm. Enzymelinked immunosorbent assays indicated a serological relationship with Cowpea aphid-borne mosaic virus (CABMV) and Passion fruit ringspot virus (PFRSV). In host range studies, only species in the families Solanaceae and Chenopodiaceae were susceptible, and neither Vigna unguiculata nor Phaseolus vulgaris became infected. Coat protein (CP) gene sequences of eight isolates exhibited features typical of potyviruses and were highly similar (88 to 100% identity). However, the sequences had limited sequence identity with CP genes of two of the three potyviruses reported to cause PWD: East Asian Passiflora virus and Passion fruit woodiness virus (PWV). Deduced amino acid sequences for the CP of isolates from Uganda had highest identity with Bean common mosaic necrosis virus (BCMNV) (72 to 79%, with evolutionary divergence values between 0.17 and 0.19) and CABMV (73 to 76%, with divergence values between 0.21 and 0.25). Based on these results and in accordance with International Committee for Taxonomy of Viruses criteria for species demarcation in the family Potyviridae, we conclude that a previously unreported virus causes viral diseases on passion fruit in Uganda. The name “Ugandan Passiflora virus” is proposed for this virus.
  • Thumbnail Image
    Item
    Metalaxyl resistance, mating type and pathogenicity of Phytophthora infestans in Uganda
    (Crop Protection, 2001) Mukalazi, J.; Adipala, E.; Sengooba, T.; Hakiza, J.J.; Olanya, M.; Kidanemariam, H.M.
    A total of 81 isolates of Phytophthora infestans (Mont.) de Bary were recovered from late blight infected samples collected from different areas of Uganda in 1998/1999. They were analyzed for their resistance to metalaxyl fungicide, mating types, and cross infection between potato and tomato hosts. Sensitivity to metalaxyl was determined by growing isolates on 10% V8 medium amended with 0, 5 and 100μg/ml metalaxyl. Overall 44.4% of the isolates tested were resistant to metalaxyl, 23.5% were intermediate and 31.2% were sensitive. Mating type was determined on 80 isolates using an A1 (1724) isolate and by growing the same isolates in pure culture (selfing). Fifty percent of the isolates produced oospores by matings and selfings, 22.5% by mating only and 10% by selfing only; 18% did not produce oospores in the two tests. Twenty seven of the P. infestans isolates from potato-infected tomato. The majority of these isolates were highly resistant to metalaxyl and produced oospores by either mating or selfing or both.
  • Thumbnail Image
    Item
    Potential for soybean rust tolerance among elite soybean lines in Uganda
    (Crop protection, 2009) Oloka, Herbert K.; Tukamuhabwa, P.; Sengooba, T.; Adipala, E.; Kabayi, P.
    Soybean rust, (Phakopsora pachyrhizi), currently the most devastating disease of soybeans worldwide, is known to challenge single resistance genes deployed against it and therefore, disease tolerance is indisputably the most viable measure in controlling the pathogen. Studies were conducted at Namulonge in Central Uganda to assess the level of tolerance to soybean rust among selected elite soybean lines. Seven elite lines together with three local checks were tested in a split-plot design where some plots were protected with fungicide to estimate the level of tolerance to soybean rust. The experimentwas conducted for three cropping seasons beginning second rains of 2005. A rust tolerance index (RTI) was computed for each test line as the ratio of yield from unprotected plots to yield from protected plots. The study showed that high levels of tolerance to soybean rust were present in the test lines. The soybean lines that showed high levels of tolerance included MNG 10.3 and MNG 3.26 all showing RTIs higher than 0.93. These lines also out-yielded the local checks by about 400 kg ha 1 and are recommended for multi-location testing.
  • Thumbnail Image
    Item
    Reaction of Exotic Soybean Germplasm to Phakopsora pachyrhizi in Uganda
    (Plant Disease, 2008) Oloka, H. K.; Tukamuhabwa, P.; Sengooba, T.; Shanmugasundram, S.
    Host plant resistance is the best long-term strategy for managing soybean rust (Phakopsora pachyrhizi) in endemic areas. Resistance breeding efforts are hampered by the presence of several races of the pathogen that often overcome single resistance genes deployed against them. In Uganda, only two soybean cultivars show moderate resistance to Phakopsora pachyrhizi, but this is likely to break down given the aggressive nature of the pathogen. A total of 25 rust tolerant or resistant accessions were imported from the Asian Vegetable Research and Development Centre and screened at Namulonge, in central Uganda. Only 10 accessions, G 33, G 8527, G8586, G 8587, GC 60020-8-7-7-18, GC 87016-11-B-2, GC 87021-26-B-1, SRE-D-14A, SRE-D-14B, and SS 86045-23-2, showed no rust symptoms at growth stage R6 during the three seasons of testing. Soybean rust resistance genes Rpp1, Rpp3, and Rpp4 did not confer resistance at Namulonge; gene Rpp2 was effective.