Interactions between putatively endophytic bacteria and tall fescue (Festuca arundinacea): plant growth promotion and colonization in host and non-host cultivars

Abstract

Tall fescue (Festuca arundinacea) is a forage grass highly used in prairies. Cultivar SFRO Don Tomas has excellent drought and cold resistance, characteristics which are influenced by the native endophytic bacterial community. The aims of this work were to deepen the characterization of a selected group of putatively endophytic strains with different plant growth promoting (PGP) traits and to analyze the relationship between colonization and PGP abilities. PGP with single inoculations in pots containing a mixture of sterile sand and field soil and with paired inoculations in field soil cores were carried out. Colonization of plants inoculated singly or co-inoculated under gnotobiotic conditions was quantified. Confocal laser microscopy was used to visualize the colonization and infection processes of strain Streptomyces sp. UYFA156 in cultivars SFRO Don Tomas and Tacuabe. Tall fescue cultivars displayed different responses to single bacterial inoculation. Inoculation with two strain pairs which included UYFA156 were successful in promoting growth in soil cores. Higher bacterial densities did not correspond to higher PGP. Strain UYFA156 was observed colonizing both fescue cultivars. UYFA156 is a true endophyte of tall fescue. Its PGP activity is cultivar-specific and may be related to the modulation of other endophytes.