Browsing by Author "Kumakech, Alfred"

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    Azadirachta indica reduces black sigatoka in east african highland banana by direct antimicrobial effects against Mycosphaerella fijiensis without inducing resistance
    (Journal of Agricultural Science, 2017) Kumakech, Alfred; Jørgensen, Hans Jørgen Lyngs; Collinge, David B.; Edema, Richard; Okori, Patrick
    Black Sigatoka is a major disease of East African highland cooking bananas in Uganda. Aqueous extracts of Azadirachta indica, Cinnamomum zeylanicum and Capsicum annuum have shown the potential to reduce Black Sigatoka in banana plantlets. The mechanisms by which plant extracts confer protection against plant pathogens has previously been reported to involve activation of defence and direct antimicrobial activity. In the current study, both antimicrobial activities of selected extracts were studied as well as expression of three defence-related genes using quantitative real-time PCR. Gene expression was compared in susceptible (cv. Musakala, genomic group AAA-EA) and resistant (cv. Kayinja, genomic group ABB) banana cultivars. Additionally, Musakala treated with A indica extract at 1 day before inoculation (DBI) was tested for induction of defence-related genes at 0, 10 and 20 days after inoculation (DAI). Pathogenesis-related genes (PR-1 and PR-3) and non-expressor of PR-genes (NPR1B) were up-regulated in the resistant cultivar. The genes analysed responded at late time points to M. fijiensis inoculation in both extract-treated and control plants in the susceptible cv. Musakala. On the other hand, A. indica and C. annuum completely inhibited mycelial growth of M. fijiensis at 30% (w/v). These findings suggest that the effect of plant extracts on Black Sigatoka is strongly associated with the direct antimicrobial effects.
  • Thumbnail Image
    Item
    Cassava Brown Streak Disease Prevalence in Smallholder Cassava Cropping Systems in Northern Uganda: The Case of Acholi Sub-region
    (East African Nature and Science Organization, 2024-04-16) Kumakech, Alfred; Tekkara, Allan; Turyagyenda, Laban F.
    Cassava brown streak disease (CBSD) is a devastating disease of cassava in Uganda.  Limited information exists on the incidence and severity of CBSD in Northern Uganda. The prevalence of CBSD in the eight (8) districts in the Acholi sub-region is also unknown.  Therefore, the current study intended to: a) determine the prevalence and severity of CBSD in the Acholi sub-region, and b) identify the drivers of CBSD epidemics in smallholder cassava cropping systems in Acholi. An assessment of 120 cassava fields was conducted in the 2018b season. CBSD field incidence was highest in Nwoya District (51.3%) and lowest in Kitgum (6.4%), with severity ranging from 2.1 to 3.4 in the sub-region. CBSD prevalence was also highest in Nwoya (76.2%) and lowest in Kitgum and Pader Districts (30.8%). The use of CBSD-susceptible varieties (TME 14, TME 204, and NASE 12) was identified as the main driver of the epidemic. The result of the current study highlights the need for a wide-scale CBSD awareness creation and community-based cassava seed multiplication and distribution system in the Acholi sub-region to promote the up-take of CBSD-tolerant cassava varieties
  • Thumbnail Image
    Item
    Effect of Two Years of Conservation Agricultural Practices on Weed Seed Banks Evaluated Using Three Techniques
    (East African Nature and Science Organization, 2024-07-06) Otim, Godfrey Anyoni; Ocan, David; Kumakech, Alfred; Tumwebaze, Susan; Obia, Alfred
    Understanding the soil seed bank is very important when developing integrated weed management technologies and detecting the influence of crop management practices on weeds. In conventional weed control, farmers tend to focus on the above-ground, yet the above-ground vegetation is related to the below-ground soil seed bank. Several soil seed bank estimation methods have been used to estimate the soil seed bank, but varying results have been obtained under different field management practices and soil depths. In this study, we compared three methods for estimating the soil seed bank: seedling emergence method and two direct seed extraction methods (floatation and cloth bag) for determining weed seed density and diversity from different soil depths under conservation farming practices. The three methods had significant differences in estimating weed densities from the soil seed bank (p<0.001). The greenhouse seedling emergence method had a mean number of 5.06, cloth bag had 4.07 while floatation method had the lowest number of 3.38 per 300g of soil. The mean highest weed density was obtained from soil depth of 0-15 cm (5 weeds/300g vs 1.6 weeds/300g of soil from 15-30 cm depth). For soil seed bank diversity, cloth bag method had the highest mean value followed by greenhouse emergence and lastly floatation method with Simpsons diversity index of 2.72, 1.79 and 1.31, respectively. Shannon Weiner diversity index followed the same pattern for the three methods. The methods had different sensitivity to density and diversity and therefore greenhouse emergence method should always be combined with cloth bag method. The greenhouse emergency method detected a total of 26 weed species, cloth bag detected 22 weed species and Floatation method detected 18 weed species. Despite, the greenhouse emergence method detecting more species than the cloth bag at 26 and 22 weed species, respectively, it had a lower Simpson’s diversity index than the cloth bag method due to lower species evenness. Sampling of the entire soil plough layer of 0-30 cm depth for disturbed agricultural soils may produce the best results. Seasons significantly influenced soil seed bank diversity and not soil seed bank density where second season (B) significantly increased soil seed bank diversity. Soil cover practice through intercropping maize with soybean significantly reduced soil seed bank density and not diversity in both minimum and conventional tilled plots. This positive influence on weed density and diversity is a good indicator for integration into a weed management program
  • Thumbnail Image
    Item
    Re-Fining Citrus Leaf and Fruit Spot Disease Control Options in Northern Uganda
    (East African Nature and Science Organization, 2024-03-05) Kumakech, Alfred; Turyagyenda, Laban F.
    Citrus leaf and fruit spot disease, caused by Pseudocercospora angolensis has, since 2010, come about as the most dreadful disease of citrus in Northern Uganda. Over the last few years, feedback from citrus farmers has helped in re-fining management strategies. In the first years of citrus leaf and fruit spot disease outbreak in Northern Uganda, chemical treatment was promoted as part of a control package, in addition to the destruction of heavily diseased plants and buckthorn to remove inoculum. Buck horning and destruction of diseased plants is labour-intensive and time-consuming, especially when many infected citrus trees have to be taken out, or buck horned. Research findings indicate citrus leaf and fruit spot disease fungus can be weakened with fungicide sprays to the extent that even when disease symptoms are present on leaves, it does not automatically lead to infection of fruits. This gave rise to a new control strategy where only infected plants in an orchard are pruned, and all the citrus trees in the orchard are treated with fungicides. The pruning of visibly infected plants in an orchard will lessen the inoculum load, and the fungicide sprays will stop pathogen replication. This method is not labour intensive and takes less time when equated to severe buck horning of all the trees in the orchard. However, pruning and fungicide treatment need to move together with the control of new infections that can happen via unrestricted entry during harvesting
  • Thumbnail Image
    Item
    Yield and Disease Responses of Improved Groundnut Genotypes Under Natural Disease Infection in Northern Uganda: Implication for Groundnut Disease Management
    (Journal of Agricultural Science, 2022) Kumakech, Alfred; Otim, Godfrey A.; Opio, Tonny; Komakech, Alfred; Turyagyenda, Laban F.
    Groundnut production in Uganda is constrained by groundnut rosette disease (GRD), the main cause of yield loss experienced by farmers. We conducted the current study to assess the responses of improved groundnuts to diseases (rosette and late leaf spot) and yield under local conditions. Four released groundnut genotypes (Serenut 5R, Serenut 8R, Serenut 9T and Serenut 14R) were evaluated in four locations in northern Uganda for two seasons in 2019. We established the experiment following randomised complete block design with three replications. GRD severity (harvest) and late leaf spot (LLS) severity (harvest) on the four genotypes were not significantly (P > 0.05) different but positively correlated with the Area Under Disease Progress Curve (AUDPC). Genotype-by-location interaction for LLS AUDPC, GRD AUDPC and dry pod yield were significant (P < .001). Season-by-genotype interaction was not significant (P = 0.367). Days to 50% flowering were also not significant (P > 0.05). Highest and lowest yields were recorded for Serenut 9T in the Omoro district (1,291 kg/acre) and the Amuru district (609 kg/acre), respectively. Dry pod yield was significantly (P < 0.001) negatively correlated with GRD severity and GRD AUDPC. Yield performance of the four genotypes was not significantly (P < 0.05) different in the districts, except for Kitgum, where yields of Serenut 9T and Serenut 8R were significantly (P < 0.05) higher. These genotypes could be used to manage GRD by smallholder farmers in Northern Uganda. Special consideration should therefore be given to these four groundnut genotypes for GRD management in the Acholi sub-region.