Differential modulation of the bacterial endophytic microbiota of Festuca arundinaceae (tall fescue) cultivars by the plant-growth promoting strain Streptomyces albidoflavus UYFA156

Aims The bacterial endophyte Streptomyces albidoflavus UYFA156 was isolated from seeds of tall fescue, Festuca arundinaceae cultivar SFRO Don Tomas, promoting growth specifically in its host cultivar. Under the hypothesis that along with the growth promotion effect by UYFA156, a shift of the endophytic bacterial community occurs, we aimed to explore the effect of inoculation of this strain on the endophytic bacterial microbiota in F. arundinaceae cultivars SFRO Don Tomas and in cultivar Tacuabe, in which no growth promotion has been observed. Methods Initially, growth inhibition of fourteen bacterial endophytes from both cultivars was tested in vitro, and then endophytic microbiota of plants and seeds were explored through high throughput sequencing of 16S rRNA. Results Diversity and composition in the seeds, along plant development, and in response to inoculation were examined in both cultivars, finding significant differences between them. In 7 days old uninoculated plants, endophytic bacterial diversity was lower in cultivar SFRO Don Tomas than in cv. Tacuabe. However, upon inoculation, Simpson's diversity index in the cultivar in which growth promotion was observed increased significantly, approximately two-fold in inoculated plants with respect to uninoculated plants. However, no differences were observed in cultivar Tacuabe. In addition, microbiota composition was significantly altered in plants of the cultivar SFRO Don Tomas, whereas in Tacuabe plants, changes by inoculation did not reach statistical significance. Conclusion Our results show that growth promotion by UYFA156 is accompanied by an early effect in endophytic diversity and composition and encourage further explorations in the relationship between the observed community modulation and plant growth promotion.