Enhancement of biological control of anthrurium blight caused by Xanthomonas axonopodis pv. dieffenbachiae

Abstract

Anthuriums are Hawaii's signature cut flower, and optimal growth and protection of anthurium plants are crucial to the Hawaiian floriculture industry. Anthurium blight, caused by Xanthomonas axonopodis pv. dieffenbachiae (Xad), is the most destructive disease of anthurium worldwide. Beneficial bacteria have been identified for use as biological control agents (BCAs) against Xad and these strains have also been shown to stimulate growth of micro-propagated plants. Optimization of transplanted microplant growth was examined. Anthurium microplants grew better with the combination of inorganic fertilizer combined with BCAs than when grown in either fertilizer or BCAs alone. Biostimulation was observed on all anthurium cultivars treated with the beneficial strains. Populations of beneficial bacteria decline after foliar application on anthurium plants. Studies were focused on improving the efficacy of the BCAs with carbon sources that sustain beneficial bacterial populations on plant surfaces without stimulating pathogen growth. Valine and isoleucine were identified as amino acids that enabled growth of beneficial bacteria while inhibiting growth of the pathogen in vitro. In greenhouse and field studies, treatments with valine combined with the BCAs reduced disease incidence by 12 to 21 % compared to treatments with BCAs alone.