Defining the pathobiomes associated with drippy blight in Colorado and drippy nut in California

Drippy blight, an emergent bacterial disease of oaks, was described recently from urban oaks in the Front Range of Colorado, USA. This disease, which causes branch dieback and oozing of bacterial exudates from cankers, is caused by Lonsdalea quercina and primarily affects red oaks, with Northern red oak (Quercus rubra) the most susceptible. Drippy nut is a similar, less acute condition that exists in California, USA and affects acorns of interior live oak (Quercus wislizenii) and coastal live oak (Quercus agrifolia). The objective of this study was to compare the microbial communities of drippy blight in Colorado to those of drippy nut in California, and determine if other pathogenic fungal or bacterial taxa are associated with the diseases. Symptomatic and asymptomatic tissues were sampled in California and Colorado, and metagenomic analyses were performed to describe the fungal and bacterial communities. We found a suite of bacterial species, dominated by taxa within the genus Zymobacter, that were associated with symptomatic tissues for both drippy nut and drippy blight. L. quercina is the main pathogenic associate of both diseases. We found fungal yeasts associated with symptomatic tissues, and although not pathogens, these taxa were present in the pathobiome of drippy nut and drippy blight in California and Colorado. We did, however, identify taxa belonging to Gnomoniopsis, a known pathogen, associated with California symptomatic samples. Our study found an overlapping suite of bacterial associates of drippy blight and drippy nut, though more variation occurred within the fungal genera associated with these oak diseases.