Prophylactic phage biocontrol prevents <i>Burkholderia gladioli</i> infection in a quantitative <i>ex planta</i> model of bacterial virulence

Agricultural crop yield losses and food destruction due to infections by phytopathogenic bacteria such as <i>Burkholderia gladioli</i>, which causes devastating diseases in onion, mushroom, corn, and rice crops, pose major threats to worldwide food security and cause enormous damage to the global economy. Biocontrol using bacteriophages has emerged as a promising strategy against a number of phytopathogenic species but has never been attempted against <i>B. gladioli</i> due to a lack of quantitative infection models and a scarcity of phages targeting this specific pathogen. In this study, we present a novel, procedurally straightforward, and highly generalizable fully quantitative <i>ex planta</i> maceration model and an accompanying quantitative metric, the <i>ex planta</i> maceration index (<i>x</i>PMI). In utilizing this model to test the <i>ex planta</i> virulence of a panel of 12 strains of <i>B. gladioli</i> in <i>Allium cepa</i> and <i>Agaricus bisporus</i>, we uncover substantial temperature-, host-, and strain-dependent diversity in the virulence of this fascinating pathogenic species. Crucially, we demonstrate that <i>Burkholderia</i> phages KS12 and AH2, respectively, prevent and reduce infection-associated onion tissue destruction, measured through significant (<i>P</i> < 0.0001) reductions in <i>x</i>PMI, by phytopathogenic strains of <i>B. gladioli</i>, thereby demonstrating the potential of agricultural phage biocontrol targeting this problematic microorganism.IMPORTANCEAgricultural crop destruction is increasing due to infections caused by bacteria such as <i>Burkholderia</i> gladioli, which causes plant tissue diseases in onion, mushroom, corn, and rice crops. These bacteria pose a major threat to worldwide food production, which, in turn, damages the global economy. One potential solution being investigated to prevent bacterial infections of plants is "biocontrol" using bacteriophages (or phages), which are bacterial viruses that readily infect and destroy bacterial cells. In this article, we demonstrate that <i>Burkholderia</i> phages KS12 and AH2 prevent or reduce infection-associated plant tissue destruction caused by strains of <i>B. gladioli</i>, thereby demonstrating the inherent potential of agricultural phage biocontrol.