Impact of metabolites derived from Bacillus velezensis on the germination of tigernut seeds and the underlying molecular regulatory mechanism

This study investigated the effect of either Bacillus velezensis fermentation broth (referred to as sample BL) or the fermentation supernatant (with cells removed, labelled as sample FS) on tigernut germination. After 5 days of germination, compared with those in the water treatment (sample WW), the germination rate and shoot length of sample FS increased by 4.02% and 15.40%, respectively, while those of sample BL decreased by 5.73% and 24.31%, respectively, suggesting that key metabolites in the fermentation supernatant significantly regulated the germination characteristics of the seeds. However, the use of fermentation broth (containing the live strains) had the opposite effect. In addition, the utilization rate of stored substances in the FS group increased, and the levels of secondary metabolites such as flavonoids increased, which is consistent with the results of transcriptomics and metabolomics analyses. This study describes a new attempt to determine whether the secretion of this strain promotes the germination of tigernut seeds and alters the distribution of secondary metabolites in the tubers.