Genetic Transformation Of Banana With Extracellular Secreted Plant Ferredoxinlike Protein (Es-Pflp) Gene

ABSTRACT

Banana Xanthomonas wilt (BXW) caused by Xanthomonas campestris pv. musacearum (Xcm) is the most devastating diseases of banana (Musa spp.) in East Africa. There are no effective control measures for this disease. All cultivars of bananas are susceptible for BXW disease. Most cultivated cultivars are triploids and difficult to improve through conventional breeding due to sterility and long generation life cycle. Genetic engineering offers an alternative and effective approach to control BXW disease. The objectives of this study were to express Extracellular secreted-Plant ferredoxin like protein (ES-Pflp) gene in banana and evaluate transgenic lines for resistance against Xcm. A signal peptide directs the Pflp to the cell‟s extracellular space. ES-Pflp has shown to offer bacterial resistance in Arabidopsis. It is therefore anticipated that over expression of ES-Pflp in banana would enhance resistance against Xcm. Embryogenic cell suspensions (ECSs) of cultivars Gross Michel and Sukali Ndizzi were co-cultivated with Agrobacterium strain EHA105 harboring a binary vector pBI-ES-Pflp followed by selection of kanamycin-resistant calli and regeneration of plantlets. Transgenic banana plants were generated expressing Extracellular secreted-Plant ferredoxin like gene driven by Cauliflower mosaic virus 35S constitutive promoter. Molecular analyses of transgenic lines performed by polymerised chain reaction (PCR), Southern blot hybridization analysis and reverse transcription polymerised chain reaction (RTPCR) revealed stable integration and expression of the transgene. Growth analysis revealed that most transgenic lines did not differ significantly (p>0.05) from the nontransgenic plants in growth under glass house conditions and were therefore advanced to screening for resistance to BXW disease. Agronomic data was taken on all lines screened in comparison with control lines. Screening of transgenic lines by artificial inoculation with Xanthomonas campestris pv. Musacearum confirmed enhanced resistance to banana Xanthomonas wilt disease. Development of banana cultivars resistant to banana Xanthomonas wilt, would improve banana production and contribute to food security of farmers that depend on banana as a staple food and cash crop.