Growth inhibition and induction of systemic resistance against Pythium aphanidermatum by Bacillus simplex strain HS-2

ABSTRACT

Biological control of plant disease with plant growth-promoting rhizobacteria (PGPR) has increasingly become noteworthy as they provide an alternative and supplement to synthetic chemicals without environmental contamination. Numerous Bacillus species have been used for seed treatment, induction of systemic resistance and suppression of both root and foliar disease-causing organisms. As a Bacillus species, Bacillus simplex also features antifungal and plant growth-promoting activities, but its ability to induce systemic resistance remains obscure. In this study, a Bacillus simplex strain HS-2 was isolated with both in vitro and in vivo activities against Pythium aphanidermatum in tobacco. The early plant defence responses were investigated to further illuminate the mechanisms by which the strain confers plant protection. Results showed that HS-2 primed tobacco for pathogen challenge through enhancing reactive oxygen species production and callose deposition in roots, that is, establishing a systemic resistance potential state. Bacillus simplex strain HS-2 is involved in both jasmonic acid/ethylene- and salicylic acid-dependent defence signals, as proven by the synergistic elicitation of gene expression for both pathways. However, sequential priming for different signal pathways may exist. Thus, the discovery and characterisation of Bacillus simplex strain HS-2 provide a novel biocontrol agent for plant diseases.

KEYWORDS:

• Bacillus simplex
• Pythium aphanidermatum
• antibiosis
• induced systemic resistance
• priming

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Guo-peng Miao http://orcid.org/0000-0001-6774-3122

Additional information

Funding

This study was supported by Educational Commission of Anhui Province of China [grant number KJ2016A668] and Natural Science Foundation of Anhui Province [grant number 1708085QC52].