Evaluation of the Antifungal Activity of Bacillus amyloliquefaciens and B. velezensis and Characterization of the Bioactive Secondary Metabolites Produced against Plant Pathogenic Fungi

Abstract

Endophytic bacteria are plant-beneficial bacteria with a broad host range. They provide numerous benefits to their hosts, helping them tolerate several biotic and abiotic stresses. An interest has recently been developed in endophytic bacteria which are producing bioactive compounds that contribute to the biological control of various phytopathogens. This research paper aimed to investigate the potentiality of new local strains of endophytic bacteria such as Bacillus amyloliquefaciens and B. velezensis and the production of several antimicrobial metabolites associated with the biocontrol of Alternaria sp., which cause serious diseases and affect important vegetable crops in Egypt. Twenty-five endophytic bacteria isolates were obtained from different plants cultivated in El-Sharkia Governorate, Egypt. Dual culture technique was used to evaluate the bacterial isolates’ antagonistic potentiality against Alternaria sp. and Helminthosporium sp. The most active bacterial isolates obtained were selected for further screening. The antifungal activity of the most active endophytic bacterial isolate was assessed in vivo on pepper seedlings as a biocontrol agent against Alternaria sp. A significant antifungal activity was recorded with isolates C1 and T5 against Alternaria sp. and Helminthosporium sp. The bacterial endophyte discs of C1 and T5 showed the highest inhibitory effect against Alternaria sp. at 4.7 and 3.1 cm, respectively, and Helminthosporium sp. at 3.9 and 4.0 cm, respectively. The most active endophytic isolates C1 and T5 were identified and the 16S rRNA sequence was submitted to the NCBI GenBank database with accession numbers: MZ945930 and MZ945929 for Bacillus amyloliquefaciens and Bacillus velezensis, respectively. The deformity of pathogenic fungal mycelia of Alternaria sp. and Helminthosporium sp. was studied under the biotic stress of bacteria. The culture filtrates of B. amyloliquefaciens and B. velezensis were extracted with different solvents, and the results indicated that hexane was the most efficient. Gas Chromatography-Mass Spectrometry revealed that Bis (2-ethylhexyl) phthalate, Bis (2-ethylhexyl) ester, and N,N-Dimethyldodecylamine were major constituents of the endophytic crude extracts obtained from B. amyloliquefaciens and B. velezensis. The in vivo results showed that Alternaria sp. infection caused the highest disease incidence, leading to a high reduction in plant height and in the fresh and dry weights of pepper plants. With B. amyloliquefaciens application, DI significantly diminished compared to Alternaria sp. infected pepper plants, resulting in an increase in their morphological parameters. Our findings allow for a reduction of chemical pesticide use and the control of some important plant diseases.

In vivo and In vitro evaluation of the antifungal activity of the PGPR Bacillus amyloliquefaciens RaSh1 (MZ945930) against Alternaria alternata with growth promotion influences on Capsicum annuum L. plants

“…Furthermore, as reported by Agarwal et al [55] and Xu et al [56], these outcomes suggest that antibiosis tends to be the biocontrol mechanism, employed by certain species of Bacillus against F. oxysporum, A. alternata, and Helminthosporium sp. Moreover, in this study, the antibiosis activity has been linked to the production of antifungal volatile compounds by B. amyloliquefaciens RaSh1 that are detected in its extract by GC-MS profiling, such as Bis (2-ethylhexyl) phthalate, Bis (2-ethylhexyl) ester, N,N-Dimethyldodecylamine, and Dibutyl phthalate [32]. These compounds are reported to have antimicrobial and antifungal activities against unicellular and filamentous fungi [57][58][59].…”

“…B. amyloliquefaciens RaSh1 (MZ945930) was previously isolated from B. oleracea leaves, identified, and reported for its ability to produce a variety of bioactive compounds with antifungal properties [32]. B. amyloliquefaciens RaSh1 was cultivated in 1000 mL Erlenmeyer flasks with 250 mL of nutrient medium and incubated for 48 h at 37 °C on an incubator shaker at 100 rpm.…”

“…The obtained results indicated that B. amyloliquefaciens RaSh1 exhibited a strong antagonistic activity against A. alternata that proved its potent activity. Due to the release of antifungal metabolites, B. amyloliquefaciens RaSh1 has been examined for its fungitoxic action against a variety of soil-borne fungi [16,32]. Among these metabolites that are produced by B. amyloliquefaciens are lipopeptides (e.g.…”

Unravelling the effect of control agents on Gnomoniopsis smithogilvyi on a chestnut‐based medium by proteomics

“…28 Since G. smithogilvyi and the biocontrol agents were not in direct contact, the different responses could be due to the production of a dissimilar volatile profile or to the diffusion of different extracellular compounds in the medium, as previously described for other B. amyloliquefaciens strains. 29,30 When facing HOR, G. smithogilvyi produced a particular morphological phenotype. Macroscopically, G. smithogilvyi produced a whitish and regular mycelium, similar to the control (Figs.…”

Alleviation of the adverse effects of NaCl stress on tomato seedlings (Solanum lycopersicum L.) by Trichoderma viride through the antioxidative defense system

“…Due to their sessile nature, plants are frequently exposed to various biotic and abiotic stresses that can negatively impact agriculture productivity by up to 50%. These stresses are interrelated and can cause biochemical, morphological, and physiological changes that can lead to plant death (Evelin et al 2019 ; Gupta et al 2020 ; Soliman et al 2022 ). After potatoes, tomatoes ( Solanum lycopersicum L.) are the second-most important solanaceous crop produced and consumed globally (Al-Aysh et al 2012 ; Metwally et al 2022a ), with a global production of 186.8 million tons in 2020 (FAO 2020 ).…”