Verticillium dahliae inoculation and in vitro propagation modify the xylem microbiome and disease reaction to verticillium wilt in a wild olive genotype

Abstract

Host resistance is the most practical, long-term, and economically efficient disease control measure for Verticillium wilt in olive caused by the xylem-invading fungus Verticillium dahliae (Vd), and it is at the core of the integrated disease management. Plant’s microbiome at the site of infection may have an influence on the host reaction to pathogens; however, the role of xylem microbial communities in the olive resistance to Vd has been overlooked and remains unexplored to date. This research was focused on elucidating whether in vitro olive propagation may alter the diversity and composition of the xylem-inhabiting microbiome and if those changes may modify the resistance response that a wild olive clone shows to the highly virulent defoliating (D) pathotype of Vd. Results indicated that although there were differences in microbial communities among the different propagation methodologies, most substantial changes occurred when plants were inoculated with Vd, regardless of whether the infection process took place, with a significant increase in the diversity of bacterial communities when the pathogen was present in the soil. Furthermore, it was noticeable that olive plants multiplied under in vitro conditions developed a susceptible reaction to D Vd, characterized by severe wilting symptoms and 100% vascular infection.