Brassica napus phyllosphere bacterial composition changes with growth stage

Aims: Phyllosphere bacteria play critical roles in plant growth promotion, disease suppression and global nutrient cycling but remain understudied. Methods: In this project, we examined the bacterial community on the phyllosphere of eight diverse lines of Brassica napus for ten weeks in Saskatoon, Saskatchewan Canada. Results: The bacterial community was shaped largely by plant growth stage with distinct communities present before and after flowering. Bacterial diversity before flowering had 111 core members with high functional potential, with the peak of diversity being reached during flowering. After flowering, bacterial diversity dropped quickly and sharply to 16 members of the core community, suggesting that the plant did not support the same functional potential anymore. B. napus line had little effect on the larger community, but appeared to have more of an effect on the rare bacteria. Conclusions: Our work suggests that the dominant bacterial community is driven by plant growth stage, whereas differences in plant line seemed to affect rare bacteria. The role of these rare bacteria in plant health remains unresolved.