AUTHOR=del Barrio-Duque Alejandro , Ley Johanna , Samad Abdul , Antonielli Livio , Sessitsch Angela , Compant Stéphane 

TITLE=Beneficial Endophytic Bacteria-Serendipita indica Interaction for Crop Enhancement and Resistance to Phytopathogens

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.02888

DOI=10.3389/fmicb.2019.02888

ISSN=1664-302X

ABSTRACT=<p><italic>Serendipita</italic> (=<italic>Piriformospora</italic>) <italic>indica</italic> is a fungal endophytic symbiont with the capabilities to enhance plant growth and confer resistance to different stresses. However, the application of this fungus in the field has led to inconsistent results, perhaps due to antagonism with other microbes. Here, we studied the impact of individual bacterial isolates from the endophytic bacterial community on the <italic>in vitro</italic> growth of <italic>S. indica</italic>. We further analyzed how combinations of bacteria and <italic>S. indica</italic> influence plant growth and protection against the phytopathogens <italic>Fusarium oxysporum</italic> and <italic>Rhizoctonia solani</italic>. Bacterial strains of the genera <italic>Bacillus, Enterobacter</italic> and <italic>Burkholderia</italic> negatively affected <italic>S. indica</italic> growth on plates, whereas <italic>Mycolicibacterium, Rhizobium, Paenibacillus</italic> strains and several other bacteria from different taxa stimulated fungal growth. To further explore the potential of bacteria positively interacting with <italic>S. indica</italic>, four of the most promising strains belonging to the genus <italic>Mycolicibacterium</italic> were selected for further experiments. Some dual inoculations of <italic>S. indica</italic> and <italic>Mycolicibacterium</italic> strains boosted the beneficial effects triggered by <italic>S. indica</italic>, further enhancing the growth of tomato plants, and alleviating the symptoms caused by the phytopathogens <italic>F. oxysporum</italic> and <italic>R. solani</italic>. However, some combinations of <italic>S. indica</italic> and bacteria were less effective than individual inoculations. By analyzing the genomes of the <italic>Mycolicibacterium</italic> strains, we revealed that these bacteria encode several genes predicted to be involved in the stimulation of <italic>S. indica</italic> growth, plant development and tolerance to abiotic and biotic stresses. Particularly, a high number of genes related to vitamin and nitrogen metabolism were detected. Taking into consideration multiple interactions on and inside plants, we showed in this study that some bacterial strains may induce beneficial effects on <italic>S. indica</italic> and could have an outstanding influence on the plant-fungus symbiosis.</p>