School of Agricultural Sciences (SAS)

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Browsing School of Agricultural Sciences (SAS) by Author "Adipala, E."
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    Characterization and distribution of a Potyvirus associated with passion fruit woodiness disease in Uganda
    (The American Phytopathological Society, 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.
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    Early screening of cassava for resistance to root-knot nematodes
    (Organization of Tropical American Nematologists, 1997) Talwana, L.A.H. ; Speijer, P.R. ; Adipala, E. ; Maslen, N.R.
    A method was developed for early screening of cassava for resistance to root-knot nematodes. One­ node cassava cuttings were planted in plastic disposable beverage cups filled with sterile 1:1 (by vol­ume) sand-soil mixture. Two weeks after planting, the plantlets were infested with a 10 ml suspension containing approximately 1000 Meloidogyne spp. eggs. One month after inoculation, the cassava root systems were evaluated for damage and rated for gall index. Densities of Meloidogyne females in the roots were established by differential staining, followed by counting of the female root-knot nema­todes under a stereomicroscope. Significant differences in gall index and number of established females, but not in reduction in fresh root weight, were observed among varieties. While some confirmatory field surveys are still required, findings from preliminary surveys carried out in two areas of Uganda suggest that the relative susceptibility of a variety in the field can adequately be predicted by using one-node cuttings.
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    Effect of crop protection management practice on yield of seven cowpea varieties in Uganda
    (Taylor & Francis, 1996) Edema, R. ; Adipala, E.
    Field experiments were conducted during the first and second rainy seasons of 1994 to evaluate the seed yield potential of two commonly grown cowpea varieties and five introduced lines under different pest and disease situations. The highest yields (4654.7 kg/ha, 2083.5 kg/ha and 974.6 kg/ha, respectively) were obtained from the lines IT82D-522-1, IT85F-1987 and Katumani-80, and the least yield was from Icirikukwai, a local line. Between 32.5% to 70.7% yield depression was obtained in plots where pests were not controlled, whereas 9.2% to 16.0% yield depression was attributed to fungal diseases. These results indicate that insect pests are the most important biotic constraint to cowpea production in Uganda.
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    Efficacy of manual seed sorting methods in reduction of transmission of rice and cowpea seed-borne diseases
    (African Crop Science Society, 2005) Kawube, G. ; Kanobe, C. ; Edema, R. ; Tusiime, G. ; Mudingotto, P. J. ; Adipala, E.
    The production of rice and cow pea in Uganda is increasing in acreage rather than productivity. This is attributed to a number of factors, mainly seed-borne diseases. The farmers in Uganda mainly use farm saved seeds for planting. These seed are infected with a wide range of seed-borne pathogens, which result into diseases in the field. The objective of this study was to evaluate the effectiveness of sorting rice and cowpea seed by 15% salt solution density and by hand in reduction of transmission of seed-borne diseases, improvement of germination and yield in the field. Seed dressing with mancozeb (2%) and unsorted seed were included as control. Results indicate that the treatment methods used significantly (P<0.05) improved rice and cowpea seed germination, with the highest germination recorded in seed dressed with fungicides and sorted by 15% salt solution density than in those which are hand sorted. Rice blast and brown leaf spot were recorded on rice, while on cowpea, Cercospora leaf spots (Cercospora cruenta and C. canescens), septoria leaf spots (S. vignae and S. vignicola), brown blotch and sphaceloma scab (Elsinoe phaseoli) were recorded. The lowest disease incidences were recorded in plots planted with seeds sorted by salt solution (15%) density and seeds dressed with mancozeb than hand sorted seeds. Similarly, rice and cowpea yield was improved by seed dressing and 15% salt solution density, compared to hand sorted and unsorted seed. Therefore, 15% salt solution density can be used as an alternative to seed dressing in reducing transmission of rice and cowpea seed-borne diseases and improving rice germination and yield. This should be popularized among the farmers to improve rice yield in the farm.
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    Influence of season and cropping system on occurrence of cowpea diseases in Uganda.
    (American Phytopathological Society, 1997) Edema, R. ; Adipala, E. ; Florini, D.A.
    An on-farm survey was conducted for two seasons (first and second rains of 1994) to determine influence of season and cropping systems on occurrence of cowpea (Vigna unguiculata) diseases in Uganda. Viral diseases were widespread in both seasons but were more severe in the intercropped than in the nonintercropped cowpea. In contrast, scab, rust, and powdery mildew were less common and less severe when cowpea was grown in intercrops. High plant populations favored scab and anthracnose, but viral diseases were more severe under low plant populations. Higher incidence and severity of viral diseases, anthracnose, and scab were recorded during the first (wetter) season than during the second (drier) season. Disease level varied considerably among the common cultivars, but these differences may have been influenced by environmental differences.
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    Inheritance of root dry matter content in sweet potato.
    (African Crop Science Society, 2014) Shumbusha, D. ; Tusiime, G. ; Edema, R. ; Gibson, P. ; Adipala, E. ; Mwanga, R.O.M.
    There has been much emphasis on breeding for increased sweet potato storage root yield, but less on dry matter yield, and its inheritance. High dry matter content (DMC) is associated with consumer preferences, and is important for the processing industry. This study was conducted to determine the type of gene action controlling DMC and to assess genotype by environment (G x E) interaction effect on DMC in sweetpotato. Five parental clones varying in DMC were hand-crossed in a half-diallel design to generate ten families. Ten genotypes of each family were planted in a trial at Namulonge (swamp and upland environments) and Serere in Uganda in 2009 and 2010. Highly significant (P<0.001) differences were found both between genotypes and between families for DMC. High significant general combining ability (GCA) (P<0.001) and specific combining ability (SCA) (P<0.01) were obtained, meaning that the differences among families for high DMC were due to both GCA and SCA. The relative importance of GCA and SCA was 0.59, indicating that additive gene action was slightly more predominant than non-additive gene action in predicting progeny performance for high DMC. Broad sense heritability (H) estimates for DMC were 0.70 and 0.73, respectively on genotype and family means across environments basis, suggesting that DMC was moderately influenced by the environment. Rapid selection for best genotypes would be possible, since progenies can be predicted from the phenotype of the parents. Parent SPK (GCA = 1.02) was the best combiner. The effect of location was less significant compared to seasons, suggesting the need to evaluate genotypes for several seasons, but in few locations to save resources.
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    Pests and diseases on cowpea in Uganda: Experiences from a diagnostic survey.
    (African Crop Science Society, 1999) Adipala, E. ; Omongo, C.A. ; Sabiti, A. ; Obuo, J.E. ; Edema, R. ; Bua, B. ; Atyang, A. ; Nsubuga, E.N. ; Ogenga-Latigo, M.W.
    diagnostic survey (DS) using a questionnaire covering 525 farm households was conducted in 1993/94 to determine the status of cowpea (Vigna unguiculata L. Walp) and its production constraints in Uganda. Subsequent on-farm assessments were made during the two rainy seasons of 1994 to verify and quantify the survey information. Additionally, on-station trials were conducted to address issues arising from the information. Insect pests, low plant population densities, poor weed management and labour bottlenecks are the most important constraints to cowpea production in Uganda. Insect pest damage, particularly by bruchids, is most important. Research to develop integrated pest management (IPM) strategies based on the finding of this study are in progress.
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    A preliminary analysis of diversity among East African sweet potato landraces using morphological and simple sequence repeats (SSR) markers
    (International Society for Hoticultural Science, 2006) Gichuru, V. ; Aritua, V. ; Lubega, G.W. ; Edema, R. ; Adipala, E. ; Rubaihayo, P.R.
    East Africa is known to have a wide range of sweet potato landraces and, therefore, is considered to be a secondary center of diversity. In this study, we assessed the diversity among sweet potato landraces from Kenya, Uganda and Tanzania using morphological and simple sequence repeats (SSR) markers. Two hundred and sixty-six landraces collected from agro-ecologically-distinct locations were screened for morphological characters using the CIP Research Guide. Morphological characters were recorded and phylogenetic analysis using UPGMA showed a close relatedness amongst the East African sweet potato landraces with the majority having a 0.1-0.5 range of Nei’s genetic distance from each other. The landraces, however, formed two major sub-clusters, irrespective of geographical origin. Based on the morphological analysis, 57 landraces that were fairly distant were further analysed using four SSR primers specific for sweet potato. Each primer pair was able to generate between two and five polymorphic and clearly scorable fragments. Phylogenetic analysis using UPGMA revealed similar results for the morphological characters. However, in each analysis, landraces from Tanzania tended to cluster together, suggesting that they are morphologically and genetically distinct from the Kenyan and Ugandan accessions. AMOVA, performed to further examine the relationships, indicated greater diversity than revealed by phylogenetic analysis suggesting that SSR markers are more reliable in assessing genetic diversity.
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    Response of improved cassava varieties in Uganda to cassava mosaic disease (CMD) and their inherent resistance mechanisms
    (Academic Journals, 2011) Adriko, J. ; Sserubombwe, W.S. ; Adipala, E. ; Bua, A. ; Thresh, J.M. ; Edema, R.
    Field based trials were setup to evaluate response and inherent resistance mechanisms to cassava mosaic disease (CMD) of four improved varieties; Nase 9, Nase 11, 00036 and 00057 together with Nase 4 and Bao as resistant and susceptible standards, respectively. These were grown in a CMD epidemic hotspot at Namulonge in Central Uganda. There were differences in sensitivity to CMD and whitefly populations among tested varieties. The improved varieties were less affected by CMD than the susceptible standard Bao. Three resistance mechanisms were exhibited by the varieties tested, namely; low infectibility (00036), recovery (Nase 9 and Nase 11) and reversion. Two of the varieties, that is, Nase 4 and 00057 showed all three resistance mechanisms. High whitefly populations characterized Bao, Nase 4 and 00057. Most of the varieties had a higher infestation of whiteflies on healthy than diseased plants. Results also showed that growth and yield parameters depended on the variety, growth stage at infection and health status of the cuttings used with improved varieties recording lower yield losses than the susceptible Bao. Also, plants infected earlier in the growth period suffered higher yield losses. Furthermore, plots planted from diseased cuttings recorded higher yield losses compared to those planted from healthy cuttings.
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    Response of local cassava varieties in Uganda to cassava mosaic virus disease
    (SCIENCEDOMAIN International, 2012) Adriko, J. ; Sserubombwe, W.S. ; Adipala, E. ; Bua, A. ; Edema, R.
    Cassava mosaic disease (CMD) resistant varieties have been used to manage CMD in Uganda. In spite the availability of a number of CMD resistant cultivars, several local landraces are continually grown in Uganda because they possess certain desirable traits, which may not have been fully met by the resistant varieties. Field based trials were setup to evaluate the response to CMD of some landraces that became prominent after the 1990s CMD pandemic. Experiments were located in areas where CMD is reported to have subsided namely, Mukono (Central Uganda) and Bulindi (Western Uganda). Three landraces were evaluated per site along with resistant (Nase 4) and susceptible (Bao) standards. Plots were planted with materials obtained from either diseased or healthy fields. The results showed differences in sensitivity to CMD among varieties tested, with landraces consistently having higher CMD incidences than Nase 4. The landraces tested in Mukono were more susceptible to CMD than even the Bao, while at Bulindi on the other hand, only Sibampale proved to be more resistant than Bao. There were differences in the whitefly populations among the cassava varieties and locations. High whitefly populations characterized all landraces and Nase 4. In most tested varieties, there was a higher infestation of whiteflies on healthy than diseased plants. Low spread of CMD among local landraces was observed in Bulindi as would be expected in areas where CMD has almost subsided (low pressure areas). However, in Mukono, disease spread among landraces was very rapid and high CMD incidences reaching 100% were recorded regardless of whether plots were planted with healthy or diseased cuttings suggesting it to be a CMD hot-spot. Thus, the use of clean planting materials as an effective phytosanitary method can only be employed under low disease pressure while high disease pressure areas need use of resistant varieties.