Bio-Priming with Bacillus Isolates Suppresses Seed Infection and Improves the Germination of Garden Peas in the Presence of Fusarium Strains

Abstract

Seed infection caused by <i>Fusarium</i> spp. is one of the major threats to the seed quality and yield of agricultural crops, including garden peas. The use of <i>Bacillus</i> spp. with multiple antagonistic and plant growth-promoting (PGP) abilities represents a potential disease control strategy. This study was performed to evaluate the biocontrol potential of new <i>Bacillus</i> spp. rhizosphere isolates against two <i>Fusarium</i> strains affecting garden peas. Six <i>Bacillus</i> isolates identified by 16S rDNA sequencing as <i>B. velezensis</i> (B42), <i>B. subtilis</i> (B43), <i>B. mojavensis</i> (B44, B46), <i>B. amyloliquefaciens</i> (B50), and <i>B. halotolerans</i> (B66) showed the highest in vitro inhibition of <i>F. proliferatum</i> PS1 and <i>F. equiseti</i> PS18 growth (over 40%). The selected <i>Bacillus</i> isolates possessed biosynthetic genes for endoglucanase (B42, B43, B50), surfactin (B43, B44, B46), fengycin (B44, B46), bacillomycin D (B42, B50), and iturin (B42), and were able to produce indole-3-acetic acid (IAA), siderophores, and cellulase. Two isolates, <i>B. subtilis</i> B43 and <i>B. amyloliquefaciens</i> B50, had the highest effect on final germination, shoot length, root length, shoot dry weight, root dry weight, and seedling vigor index of garden peas as compared to the control. Their individual or combined application reduced seed infection and increased seed germination in the presence of <i>F. proliferatum</i> PS1 and <i>F. equiseti</i> PS18, both after seed inoculation and seed bio-priming. The most promising results were obtained in the cases of the bacterial consortium, seed bio-priming, and the more pathogenic strain PS18. The novel <i>Bacillus</i> isolates may be potential biocontrol agents intended for the management of <i>Fusarium</i> seed-borne diseases.