Antagonistic activity of phyllosphere bacteria from pineapple leaves against bacterial heart rot disease (BHR) in pineapple

Abstract

Pineapple (Ananas comosus) is one of the most important fruit crops in tropical and subtropical regions. Bacterial heart rot (BHR), caused by the pathogenic bacterium Dickeya zeae, has emerged as a major threat to pineapple production worldwide. Phyllosphere bacteria, which inhabit the aerial surfaces of plants, have shown potential as biological control agents (BCAs) against BHR due to their antagonistic activity. In this study, the causal agent of BHR was isolated from diseased pineapple plants which exhibiting water-soaked and rotting basal tissues. Meanwhile, phyllosphere bacteria were recovered from asymptomatic pineapple leaves, morphologically characterized, and subjected to an in vitro bioassay using the well-diffusion method to assess their antagonistic potential against BHR pathogenic bacteria. The isolated bacteria were Gram-positive, rod-shaped, with circular in shape, with surface features ranging from convex to flat or undulated, and margins that were either entire or slightly irregular, and cream white color colony. In the well-diffusion assay, the phyllosphere isolates successfully inhibited the growth of the BHR pathogen, forming clear inhibition zones. These findings suggest that phyllosphere bacteria could serve as promising BCAs for managing BHR in pineapple production.