Cultivable bacteriome dynamics in different Persian oak tissues and soil during Oak Decline Syndrome development in Iran

Abstract

Persian oak decline is a syndrome within the oak decline complex in Iran. Profuse stem bleed-ing and larval galleries of the native buprestid, Agrilus hastulifer characterize the disease. A systematic study comparing healthy with diseased trees was undertaken. This work reports the result of isolations from healthy trees and diseased tissue in affected trees, at eight sites in Iran. Culturable bacterial communities were identified using the 16S rDNA sequencing. A significantly higher proportion of symptomatic tissue pieces from diseased trees (Disease In-dex=5) yielded bacterial growth than other disease indexes (83.78%). Significantly higher yields were also obtained from bulk and rhizosphere compared with the root, leaf, and stem. Overall bacterial communities compositions varied at each site, but significant similarities were evident in diseased tissues at all sites. Enterobacteriaceae were dominated in diseased trees whereas Bacilluceae and Moraxellaceae were remarkable more abundant in healthy trees. Sig-nificant associations occurred between diseased tissues and certain bacterial species, implying that the cause of tissue necrosis was not due to random microbiota. Brenneria goodwinii, Ser-ratia marecescence, and Dickeya chrysanthemi were key species consistently isolated from diseased tissue; Campylobacter jejuni and an un-named Clostridium taxon were also frequent-ly isolated from both healthy and diseased trees. It was concluded that there was a shift in the cultivatable bacterial microbiome of diseased trees, with Enterobacteriaceae strongly repre-sented in symptomatic but not healthy tissues. No single dominated species was isolated from diseased tissues, so tissue degradation in oak likely have a polymicrobial cause.