Abstract

Banana Xanthomonas wilt is a devastating disease of cultivated banana in East and Central Africa, manifesting as initial leaf wilting, premature fruit ripening and eventual death of all infected plants leading to total yield loss. In order to contribute towards development of effective disease control options, hrpf expression by Xanthomonas campestris pv musacearum (Xcm) during establishment of Xanthomonas wilt infection was determined. To successfully initiate infection, plant pathogenic bacteria deliver effector proteins into host cells using specialized protein transport system such as the Type III secretion system (TTSS). It is a syringe needle-like translocation apparatus essential for delivery of effector proteins into the host cells and hypersensitive response and pathogenicity gene f (hrpf) encodes one of the structural proteins for effector protein delivery. In this study, hrpf expression by Xcm during establishment of Xanthomonas wilt infection was determined in minimal medium amended with extracts from susceptible banana genotypes and banana host plants. Total RNA was isolated from Xcm recovered from inoculated plants and also from minimal medium amended with banana extracts; cDNA synthesised and hrpf amplified by PCR using gene specific primers. Findings showed that Xcm multiplied in susceptible host banana and minimal medium amended with their extracts but not in resistant M. balbisiana and its extract. hrpf gene was thus amplified from cDNA samples of susceptible banana genotypes and their extracts suggesting its expression and involvement in the successful establishment of Xanthomonas wilt disease by Xcm.

Key words: Xanthomonas campestris pv. musacearum (Xcm), Type three secretion system (TTSS), hypersensitive response and pathogenicityf (hrpf) gene, banana.