Browsing by Author "Kumakech, Alfred"

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    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.
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    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.