Identification and Comparative Analysis of Pathogenic Characteristics of Two Bacterial Diseases in Bananas Caused by...

Banana, a globally significant economic fruit, faces major production constraints due to pests and diseases. Recently, banana fruit rot and rachis rot have emerged in several banana plantations across Guangxi, China. This study aims to identify the pathogens of the diseases and investigate their potential interrelations. Pathogenicity tests were conducted on banana plants with eight representative strains isolated from the rachides and fruits of Cavendish (AAA) and Pisang Awak (ABB) banana cultivars. Pathogen identification was achieved through morphological, physiological, and biochemical tests coupled with phylogenetic analysis based on multigene sequences. Comparative analyses were then performed on growth and pathogenic virulence of the bacteria isolated from the fruits and rachides of the two banana cultivars. The pathogens causing fruit rot and rachis rot in Cavendish bananas were identified as Dickeya zeae, while those responsible for the same diseases in Pisang Awak bananas were identified as D. fangzhongdai. In addition, D. zeae strains exhibited optimal growth at pH 7.0, whereas D. fangzhongdai strains showed optimal growth at pH 7.5. Strains isolated from rachides exhibited higher motility and pectinase activity compared with those isolated from fruits of the same host. D. zeae exhibited significantly higher virulence toward Cavendish bananas, whereas D. fangzhongdai showed greater virulence toward Pisang Awak. This study provides the first evidence of D. zeae causing both rachis and fruit rot in bananas and D. fangzhongdai as a causal agent of banana fruit rot. Furthermore, each pathogen demonstrated distinct host preferences, with D. zeae predominantly infecting Cavendish cultivars and D. fangzhongdai targeting Pisang Awak. These findings offer new insights into the bacterial rot diseases of bananas caused by Dickeya spp.