AUTHOR=Kandel Shyam L. , Firrincieli Andrea , Joubert Pierre M. , Okubara Patricia A. , Leston Natalie D. , McGeorge Kendra M. , Mugnozza Giuseppe S. , Harfouche Antoine , Kim Soo-Hyung , Doty Sharon L. 

TITLE=An In vitro Study of Bio-Control and Plant Growth Promotion Potential of Salicaceae Endophytes

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.00386

DOI=10.3389/fmicb.2017.00386

ISSN=1664-302X

ABSTRACT=<p>Microbial communities in the endosphere of Salicaceae plants, poplar (<italic>Populus trichocarpa</italic>) and willow (<italic>Salix sitchensis</italic>), have been demonstrated to be important for plant growth promotion, protection from biotic and abiotic stresses, and degradation of toxic compounds. Our study aimed to investigate bio-control activities of Salicaceae endophytes against various soil borne plant pathogens including <italic>Rhizoctonia solani</italic> AG-8, <italic>Fusarium culmorum, Gaeumannomyces graminis</italic> var. <italic>tritici</italic>, and <italic>Pythium ultimum</italic>. Additionally, different plant growth promoting traits such as biological nitrogen fixation (BNF), indole-3-acetic acid (IAA) biosynthesis, phosphate solubilization, and siderophore production were assessed in all bio-control positive strains. <italic>Burkholderia, Rahnella, Pseudomonas</italic>, and <italic>Curtobacterium</italic> were major endophyte genera that showed bio-control activities in the <italic>in-vitro</italic> assays. The bio-control activities of <italic>Burkholderia</italic> strains were stronger across all tested plant pathogens as compared to other stains. Genomes of sequenced <italic>Burkholderia</italic> strains WP40 and WP42 were surveyed to identify the putative genes involved in the bio-control activities. The <italic>ocf</italic> and <italic>hcnABC</italic> gene clusters responsible for biosynthesis of the anti-fungal metabolites, occidiofungin and hydrogen cyanide, are present in the genomes of WP40 and WP42. Nearly all endophyte strains showing the bio-control activities produced IAA, solubilized tricalcium phosphate, and synthesized siderophores in the culture medium. Moreover, some strains reduced acetylene into ethylene in the acetylene reduction assay, a common assay used for BNF. Salicaceae endophytes could be useful for bio-control of various plant pathogens, and plant growth promotion possibly through the mechanisms of BNF, IAA production, and nutrient acquisition.</p>