Browsing by Author "Macharia, Sarah Wanjiku"

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    Genetic transformation of banana with extracellular secreted plant ferredoxin-like protein (es-pflp) gene
    (2014-08-15) Macharia, Sarah Wanjiku
    Banana Xanthomonas wilt (BXW) and fusarium wilt, caused by Xanthomonas campestris pv. Musacearum and Fusarium oxysporum f. sp. cubense, respectively, are the most devastating diseases of banana (Musa spp.). Apart from resistant cultivars, there are no effective control measures for these diseases. Most cultivated cultivars are triploids and difficult to improve through conventional breeding due to sterility and long generation life cycle. As such, genetic engineering offers an alternative and effective approach to control BXW and Fusarium wilt diseases. Therefore, the aim of this study will be to express Es-Pflp gene in banana and evaluate transgenic lines for resistance against BXW and Fusarium wilt diseases. Es-Pflp is plant ferredoxin like amphipathic protein (Pflp) gene that has a signal peptide that directs it to the cell's extracellular space. Es-Pflp has shown increase in bacterial wilt resistance compared to Pflp gene. It is therefore anticipated that over expression of Es-pflp would create broad spectrum resistance to bacterial and fungal pathogens in banana. Embryogenic cell suspensions (ECSs) of cultivars 'Gross Michel' and 'Sukali Ndizzi' will be co-cultivated with Agrobacterium strainEHAI05 harboring a binary vector pBI-espflp followed by selection of kanamycin-resistant calli and regeneration of plantlets. The presence and integration of the nptII and Es-Pflp genes in the transgenic lines will be confirmed by PCR and Southern blot analysis, respectively. The transgenic lines of both cultivars will be screened for resistance against BXW and Fusarium wilt diseases. Development of banana cultivars resistant to BXW and fusarium wilt diseases would improve banana production and contribute to food security of farmers depending on banana as a staple food and cash crop.
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    Overexpression of Musavicilin Gene for Disease Resistance in Banana.
    (Frontiers in Plant Science, 2026-03) Macharia, Sarah Wanjiku; Tripathi, Jaindra Nath; Ntui, Valentine Otang; Kariuki, Samwel Muiruri; Tripathi, Leena
    Banana Xanthomonas wilt (BXW) disease, caused by Xanthomonas vasicola pv. musacearum, is a major constraint to banana production in East and Central Africa. All cultivated banana varieties are susceptible, with the wild progenitor Musa balbisiana being the only known source of complete resistance. Limitations in classical breeding have prompted the exploration of molecular genetic tools, such as genetic modification, to develop resistant cultivars. Comparative transcriptomic analyses revealed a five-fold upregulation of MusaVicilin gene in M. balbisiana (BB genome) compared to the BXW- susceptible ‘Pisang Awak’ at early infection stage with the pathogen, suggesting its role in defense. This study investigated whether constitutive overexpression of the MusaVicilin gene cloned from M. balbisiana could enhance resistance to BXW in the susceptible ‘Sukali Ndiizi’ cultivar (AAB genome). Transgenic lines were developed overexpressing the MusaVicilin gene under the control of the constitutive CaMV 35S promoter. Agrobacterium-mediated transformation of embryogenic cell suspension of ‘Sukali Ndiizi’ generated 52 independent transgenic lines. These transgenic lines were confirmed via PCR and Southern blot analysis. The transgenic lines showed reduced disease severity and significantly lower disease severity index compared with non-transgenic controls. MusaVicilin overexpression (∼400 - 1300 folds) showed moderate correlation with disease resistance (r=0.68, p