Mycobiome Transplant Increases Resistance to Austropuccinia psidii in an Endangered Hawaiian Plant

Abstract

The accelerated global movement of plant pathogens has become a substantial threat to rare and endangered plants. Although application of synthetic pesticides on endangered plants is often necessary to control disease in greenhouse settings, these chemical treatments degrade the leaf microbiome. This reduction in diversity can eliminate foliar microbes that are essential for pathogen resistance, making plant hosts more susceptible to disease once outplanted in the wild. Beneficial microbes that naturally occur in plant tissue are a resource that is quickly gaining traction as a viable means to increase plant fitness and pathogen resistance in both agricultural and wild habitats. This is of particular interest for threatened and endangered wild plant populations with limited genetic variation where breeding for resistance is not possible. In this experiment, we tested the effectiveness of microbial inoculations to inhibit the fungal pathogen Austropuccinia psidii, which is currently threatening the critically endangered Hawaiian Eugenia koolauensis with extinction. Using molecular and culture-based methods, we characterize foliar fungal communities of Myrtaceous hosts resistant to A. psidii and introduced these diverse fungi into the microbiome of E. koolauensis leaves. Our results indicate that transplanting an intact mycobiome community is more effective at reducing foliar disease resistance when compared with single-fungal-species inocula. These findings demonstrate the potential of whole-microbiome transplants as a powerful tool to inducing disease resistance and enhancing plant health within a conservation context.