Browsing by Author "Paparu, Pamela"

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    Beauveria bassiana (Balsamo) Vuillemin as an endophyte in tissue culture banana (Musa spp.)
    (Journal of invertebrate pathology, 2007) Akello, Juliet; Dubois, Thomas; Gold, Clifford S.; Coyne, Daniel; Nakavuma, Jessica; Paparu, Pamela
    Beauveria bassiana is considered a virulent pathogen against the banana weevil Cosmopolites sordidus. However, current field application techniques for effective control against this pest remain a limitation and an alternative method for effective field application needs to be investigated. Three screenhouse experiments were conducted to determine the ability of B. bassiana to form an endophytic relationship with tissue culture banana (Musa spp.) plants and to evaluate the plants for possible harmful effects resulting from this relationship. Three Ugandan strains of B. bassiana (G41, S204 and WA) were applied by dipping the roots and rhizome in a conidial suspension, by injecting a conidial suspension into the plant rhizome and by growing the plants in sterile soil mixed with B. bassiana-colonized rice substrate. Four weeks after inoculation, plant growth parameters were determined and plant tissue colonization assessed through re-isolation of B. bassiana. All B. bassiana strains were able to colonize banana plant roots, rhizomes and pseudostem bases. Dipping plants in a conidial suspension achieved the highest colonization with no negative effect on plant growth or survival. Beauveria bassiana strain G41 was the best colonizer (up to 68%, 79% and 41% in roots, rhizome and pseudostem base, respectively) when plants were dipped. This study demonstrated that, depending on strain and inoculation method, B. bassiana can form an endophytic relationship with tissue culture banana plants, causing no harmful effects and might provide an alternative method for biological control of C. sordidus.
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    Genetic variation, Heritability estimates and GXE effects on yield traits of Mesoamerican common bean (Phaseolus vulgaris L) germplasm in Uganda
    (Plant Genetic Resources, 2018) Okii, Dennis; Mukankusi, Clare; Sebuliba, Sulaiman; Tukamuhabwa, Phinehas; Tusiime, Geoffrey; Talwana, Herbert; Odong, Thomas; Namayanja, Annet; Paparu, Pamela; Nkalubo, Stanley; Otim, Michael; Ugen, Michael; Buah, Stephen; Gepts, Paul
    Germplasm of common beans from the Mesoamerican gene pool races: Durango, Jalisco, Mesoamerica and Guatemala have highest genetic variation for the crop’s improvement. The objective was to assign 50 common bean germplasm in Uganda into its gene pool races based on analyses of population structure. Secondly, to estimate heritability and effects of genotype environment (GXE) interaction on common bean agronomic and yield traits in space and time. Sample genomic DNA was amplified in 2011 with 22 Simple sequence repeat markers (SSRs) and alleles separated using capillary electrophoresis. Field evaluations were conducted in 2010 and 2011 at NaCRRI and 2015 at CIAT – Kawanda. Multivariate analyses of SSRs data identified four subgroups within the germplasm: K4.1–K4.4, with corresponding Wrights fixation indices (FST) as 0.1829 for K4.1, 0.1585 for K4.4, 0.1579 for K4.2 and least for K4.3 at 0.0678. Gene pool race admixtures in the population (14%) were notable and attributed to gene flow. Four superior parents currently used in improving resistance to major diseases grouped as; Jalisco for MLB49-89A; Mesoamerica for MCM5001 and G2333; Durango for MEXICO 54. Heritability values for yield traits estimated using phenotypic data from above fixed parents, was above 0.81. Season and location had significant effect (P < 0.05) on numbers of: flower buds per inflorescence, pod formation and weight of 100 seeds. The findings will improve understanding of co-evolutionary relationships between bean hosts and pathogens for better disease management and will broaden the germplasm base for improving other tropical production constraints.