Lolium perenne (perennial ryegrass) is a common temperate pasture grass species and is favored by dairy farmers. Commercially, the known association with the mutualistic endophytic fungus Epichloë festucae subsp. lolii is used to enhance insect resistance of host plants. Knowledge of other members of the microbiome and their functions are limited. Sequencing of the V4 region of the 16S ribosomal RNA gene was used to examine the bacterial microbiome of perennial ryegrass (Alto) seed (generation 1 [G1]), subsequent mature plants grown in soil and sand, and seed (generation 2 [G2]) from crosses of these mature plants. The G1 microbiome was dominated by the class Gammaproteobacteria. The mature plant microbiomes were far more diverse, comprising up to 37 classes inclusive of Gammaproteobacteria. Different growth media yielded different microbiome profiles in mature plants. The G2 microbiome, similar to the G1 microbiome, was dominated by Gammaproteobacteria as the primary constituent, with additional supplementation from class Bacilli. This suggests the continuation of a core microbiome which persists from seed through plant maturation to seed. This study sheds new light on the hereditability of perennial ryegrass bacterial microbiomes and has identified some operational taxonomic units of potential commercial significance due to their seed transmissibility, and their roles are currently being explored.

Research into the bacterial component of the seed microbiome has been intensifying, with the aim of understanding its structure and potential for exploitation. We previously studied the intergenerational seed microbiome of one cultivar of perennial ryegrass with and without one strain of the commercially deployed fungal endophyte Epichloë festucae var. lolii. The work described here expands on our previous study by exploring the bacterial seed microbiome of different commercial cultivar/Epichloë festucae var. lolii combinations in collections of single seeds from the harvest year 2016. In this dataset, a cultivar effect could be seen between the seed microbiomes from cultivars Alto and Trojan. The bacterial component of the seed microbiome from pooled seeds from a single cultivar/E. festucae var. lolii combination harvested from 13 seed production farms around Canterbury in the year 2018 was also studied. This dataset allows the effect of different production locations on the bacterial seed microbiome to be examined. By comparing the two sets of data, bacteria from the genera Pantoea, Pseudomonas, Duganella, Massilia, and an unknown Enterobacteriaceae were observed to be in common. This core bacterial microbiome was stable over time but could be affected by supplemental taxa derived from the growth environment of the parental plant; differing microbiomes were seen between different seed production farms. By comparison to a collection of bacterial isolates, we demonstrated that many of the members of the core microbiome were culturable. This allows for the possibility of exploiting these microbes in the future.