Multifaceted intervention of Bacillus spp. against salinity stress and Fusarium wilt in tomato

Abstract

Aim: This study aimed to screen halotolerant Bacillus strains able to promote growth and protect tomato plants against salt stress and Fusarium wilt (Fusarium oxysporum f. sp. lycopersici). Methods and Results: We evaluated some halotolerant strains of Bacillus spp. (Bacillus velezensis (AP-3) and Bacillus spp. (AP-6, AP-85 and AP-100)) to promote growth of tomato plants grown under salinity stress conditions and to protect them against Fusarium wilt disease. Such strains had been previously selected among 154 bacterial strains through biochemical tests (siderophores and indoleacetic acid productions, cellulase and catalase activity, nitrogen fixation and phosphate solubilization) in the presence of 100-mmol l À1 NaCl. Besides the above-mentioned strains, B. subtilis QST-713 (Serenade TM ) was also evaluated. Compared to control plants, aboveground dry weight increased in plants inoculated with AP-6, AP-85, AP-3, AP-100 and QST-713 strains developed in the absence of salt stress. The same tendency occurred for root dry weight; however, AP-3 strain was more effective, promoting an increase of 163%, when compared to control. Chlorophyll index and height increased >40 and 53%, respectively, for all Bacillus strains. Saline stress reduced plant growth regardless of the presence of Bacillus. Height, stem diameter, and aboveground and root dry weights increased in plants treated with Bacillus strains grown under saline conditions when compared to control. Bacillus velezensis AP-3 reduced the severity of Fusarium wilt in tomato by 50% when compared to control. Conclusion: Halotolerant Bacillus strains controlled tomato Fusarium wilt, increased growth as well as tolerance to salt stress. Significance and Impact of the Study: We demonstrated the efficacy of halotolerant Bacillus strains to control Fusarium wilt and improve tomato growth. We also demonstrated that these Bacillus strains protect tomato plants against salt stress. Bacillus can be used in an eco-friendly way because they are considered Generally Recognized As Safe.

Bacillus cereus EC9 protects tomato against Fusarium wilt through JA/ET-activated immunity

“…The ability of members of the B. subtilis -like group to biosynthesize specialized compounds with antimicrobial activity have made this species attractive for use as biocontrol agents ( Caulier et al., 2019 ; Penha et al., 2020 ). Thus, treatment of tomato seeds with antifungal B. velezensis AP3 ( Medeiros and Bettiol, 2021 ), B. subtilis MMS9 ( Patel and Saraf, 2017 ), and B. amyloliquefaciens FZB24 ( Elanchezhiyan et al., 2018 ) suppressed Fusarium wilt of the plant. In our study, the antifungal DD6, which contains biosynthetic gene clusters (BGC) associated with well-known antimicrobial secondary compounds, was unable to significantly decrease the development of symptoms of Fusarium wilt disease in tomato ( Figure 1 ).…”

“…In recent years, biological control of Fusarium wilt of tomato has attracted considerable attention ( La Torre et al., 2016 ; Sallam et al., 2019 ; de Lamo and Takken, 2020 ; Doan et al., 2020 ; Vinchira-Villarraga et al., 2021 ). Several species of the bacterial genus Bacillus have proved to be promising biocontrol agents, since they protect through several modes of action, such as competition, parasitism, antibiosis, and induced resistance ( Akram et al., 2016 ; Elanchezhiyan et al., 2018 ; Bhattacharya et al., 2019 ; Medeiros and Bettiol, 2021 ; Zhang et al., 2021 ). For the latter mechanism, some Bacillus species can activate immediate defense responses, predisposing the plant to react faster and stronger to subsequent pathogen attack, a mechanism known as defense priming ( Tonelli and Fabra, 2014 ; Wang et al., 2014 ; Mauch-Mani et al., 2017 ).…”

Management of take-all disease caused by Gaeumannomyces graminis var. tritici in wheat through Bacillus subtilis strains

“…For example, Bacillus strain QST-713 (Serenade TM ) promotes the growth of tomato plants and protects them from salt stress and Fusarium oxysporum f. sp. lycopersici attack (Medeiros and Bettiol, 2021 ). In greenhouse and field experiments, the application of the commercial biocontrol treatment Stargus (with the active ingredient B. amyloliquefaciens F727) was effective in controlling the severity of crown and root rot induced by Phytopythium vexans infesting ginkgo and red maple plants (Panth et al, 2021 ).…”

Biocontrol activity and action mechanism of Bacillus velezensis strain SDTB038 against Fusarium crown and root rot of tomato

“…The study of PGPR, mainly including Mesorhizobium and Allorhizobium, intracellular PGPR, and Bacillus, Pseudomonas and Azotobacter extracellular PGPR (Li et al, 2020), has attracted the attention of scholars at home and abroad. To screen salt-tolerant Bacillus strains and growth-promoting microorganisms, Medeiros and Bettiol (2021) evaluated: the production of iron carriers and indoleacetic acid (IAA) and solubilization of phosphate. A study found that SDTB038 could produce indole acetic acid.…”