Genetic Transformation of Bananas for Resistance to Xanthomonas Wilt Disease

Banana Xanthomonas wilt (BXW), caused by the bacterium Xanthomonas campestris pv. musacearum, is the most devastating disease of banana  in East Africa, where banana  is a major staple crop produced mostly by smallholder subsistence farmers. Uganda is the world’s second leading grower with a total annual production of about 10.5 million tons. All banana varieties in Africa are vulnerable to BXW. Overall economic losses were estimated at $2 billion over a decade, arising from price increases and significant reductions in production. BXW can be managed by following cultural practices; however, the adoption of these practices has been inconsistent as these techniques are labor intensive. Given the rapid spread and devastation of BXW across the continent, genetic improvement through the use of modern biotechnology tools offers an effective and viable way to develop resistant varieties. In the absence of natural host plant resistance among banana cultivars, researchers at the International Institute of Tropical Agriculture (IITA) and the National Agricultural Research Organization (NARO), in partnership with the African Agricultural Technology Foundation (AATF), have developed hundreds of transgenic lines expressing the Hypersensitive Response Assisting Protein (Hrap) or Plant Ferredoxin Like Protein (Pflp) gene originated from sweet pepper. These transgenic lines have exhibited strong resistance to BXW in the laboratory and glasshouse tests. The best 65 resistant lines were planted in a confined field trial (CFT) in Uganda for further evaluation. All transgenic lines tested had significantly higher (P≤0.05) resistance in comparison to control non-transgenic plants under field conditions. Twelve of these transgenic lines had shown absolute resistant to BXW with both mother and progenies plants in CFT. Currently, these lines are under evaluation for 3^rd generation progenies. Aside from full resistance to BXW, the transgenic lines also showed flowering and yield (bunch weight and fruit size) characteristics comparable to non-transgenic plants, indicating there are no observable unintended impacts. This study is a significant step toward development of transgenic bananas resistant to BXW, which will boost the available arsenal to fight this epidemic disease and save livelihoods in Africa.