Browsing by Author "Nyaboga, Evans N."

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    Morpho-Physiological and Yield Traits for Selection of Drought Tolerant Urochloa Grass Ecotypes
    (AoB PLANTS, 2024-06) Ochola, Celestine Anyango; Ngugi, Mathew Pierro; Nyaboga, Evans N.; Njarui, Donald M. G.
    Drought has become more recurrent and causes a substantial decline in forage yields leading to strain on feed resources for livestock production. This has intensifed the search for drought-tolerant forages to promote sustainable livestock production. The objective of this study was to identify drought-tolerant Urochloa grasses and to discern their morpho-physiological and yield traits to water stress as well as the relationship between these traits and indices of drought resistance. The results showed that the ecotypes, water regimes and their interaction signifcantly infuenced all the studied morpho-physiological and yield traits. There was a signifcant decrease in plant height, number of leaves and tillers, dry matter yield, relative water content, photosystem II and effciency of photosystem II with an increase in non-photochemical quenching. The principal component analysis revealed that the performance of Urochloa grass ecotypes was different under water suffcient (WS) and water defcit conditions. Drought tolerance indicators (mean productivity, geometric mean productivity, tolerance index and stress tolerance index) were most effective in identifying Urochloa ecotypes with high biomass production under both water defcient and WS conditions. Ecotypes K17, K7, Kisii, Busia and Kakamega were the most drought tolerant, Basilisk, K6, K10, K19 and Toledo were moderately tolerant whereas, CIAT6385, CIAT16449, K13, K5 and K9 were drought sensitive. The fve drought-tolerant Urochloa ecotypes should be tested for sustainable biomass production under feld conditions and used in breeding programmes to develop high-yielding drought-tolerant varieties.
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    Overexpression of rice thaumatin-like protein (Ostlp) gene in transgenic cassava results in enhanced tolerance to Colletotrichum gloeosporioides f. sp. manihotis
    (Elsevier, 2018) Ojola, Patroba Odeny; Nyaboga, Evans N.; Njiru, Paul N.; Orinda, George
    Cassava (Manihot esculenta Crantz) is the most important staple food for more than 300 million people in Africa, and anthracnose disease caused by Colletotrichum gloeosporioides f. sp. manihotis is the most destructive fungal disease affecting cassava production in sub-Saharan Africa. The main objective of this study was to improve anthracnose resistance in cassava through genetic engineering. Transgenic cassava plants harbouring rice thaumatin-like protein (Ostlp) gene, driven by the constitutive CaMV35S promoter, were generated using Agrobacterium-mediated transformation of friable embryogenic calli (FEC) of cultivar TMS 60444. Molecular analysis confirmed the presence, integration, copy number of the transgene all the independent transgenic events. Semi-quantitative RT-PCR confirmed high expression levels of Ostlp in six transgenic lines tested. The antifungal activity of the transgene against Colletotrichum gloeosporioides pathogen was evaluated using the leaves and stem cuttings bioassay. The results demonstrated significantly delayed disease development and reduced size of necrotic lesions in leaves and stem cuttings of all transgenic lines compared to the leaves and stem cuttingss of non-transgenic control plants. Therefore, constitutive overexpression of rice thaumatin-like protein in transgenic cassava confers enhanced tolerance to the fungal pathogen C. gloeosporioides f. sp. manihotis. These results can therefore serve as an initial step towards genetic engineering of farmer-preffered cassava cultivars for resistance to anthracnose disease.