Ascophyllum nodosum based plant biostimulant shapes the bacterial community in the rhizosphere of corn.

BACKGROUND

Plant biostimulants are an emerging class of agricultural inputs known to enhance plant growth and improve their tolerance to abiotic stress. While biostimulants are widely used, their mechanisms of action remain poorly understood. This study investigates the effects of an Ascophyllum nodosum-based biostimulant (ANE) on the rhizosphere bacterial communities of corn (Zea mays).

RESULTS

Root exudates from ANE root-treated plants promoted the swarming motility of Pseudomonas protegens (CHA0), a plant growth-promoting rhizobacterium. Gene expression analysis showed that root exudates from 0.01% ANE-treated plants up-regulated P. protegens CHA0 genes associated with chemotaxis (cheW, cheV), pyoverdine (pvdS), pyrrolnitrin (prnD), and hydrogen cyanide (hcnA) biosynthesis compared to controls. ANE also significantly altered rhizosphere microbiome composition, increasing the abundance of genera such as Chryseolinea, Pseudoxanthomonas, Novosphingobium, Quadrisphaera, Turneriella, and Kitasatospora. Liquid chromatography-high resolution mass spectrometry (LC-HRMS) and partial least squares-discriminant analysis (PLS-DA) revealed distinct chemical profiles in the root extracts of ANE-treated plants. Specifically, ANE increased the concentrations of benzoxazinoids, including 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) and 6-methoxybenzoxazolinone (MBOA) in maize roots by approximately 1.4-fold and 1.76-fold, respectively.

CONCLUSION

Overall, these findings suggest that ANE modifies the rhizosphere microbiome by influencing the chemical composition of both root tissue and root exudates.