Overexpression of MusaVicilin gene for disease resistance in banana

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<0.01), with transgenic line (S2) demonstrating complete resistance under greenhouse conditions. These results suggest that the overexpression of MusaVicilin can confer enhanced resistance to BXW and highlight its potential as a candidate gene for genetic engineering resistance to BXW in susceptible cultivars. Moreover, MusaVicilin could serve as a valuable component in gene stacking strategies aimed at developing durable, disease-resistant banana varieties.