Bacterial seed endophytes promote barley growth and inhibits Fusarium graminearum in vitro.

Objectives: Seeds host microbes that function in plant growth and phytopathogen resistance. The aim of the work was to investigate total bacterial community in malting barley seeds and whether their bacterial seed endophytes have dual functional roles in plant growth-promotion and inhibition of Fusarium graminearum, the causative agent of Fusarium head blight (FHB) in barley. We used culture dependent and culture independent methods.

Results: Phylogenetic classification of seed endophytic bacteria based on sequencing data identified B. subtilis, B. licheniformis and B. pumilis as predominant subgroups. Location driven divergence in bacterial endophytic communities was evident based on a clear separation of the samples from Crookston and other location samples. The bio-primed seeds using one hundred and seventy bacterial isolates showed that 3.5% (6/170) of the bacterial isolates conferred greater than 10% increase in both root length (RL) and shoot length (SL), while 19.4% (33/170) and 26.5% (45/170) showed RL and SL specific growth effects, respectively, relative to controls. Among the six bacterial isolates that increased RL and SL, five (#29, #63, #109, #124 and #126) also significantly inhibit the growth of F. graminearum based on in vitro assays. This study identified novel seed bacterial endophytes that could be further exploited for promoting growth during seedling establishment and as biocontrol for combating the devastating scab disease.