The plant-associated Bacillus amyloliquefaciens strains MEP218 and ARP23 capable of producing the cyclic lipopeptides iturin or surfactin and fengycin are effective in biocontrol of sclerotinia stem rot disease

Abstract

Aims: This work was conducted to identify the antifungal compounds produced by two previously isolated Bacillus sp. strains: ARP23 and MEP218. Both strains were subjected to further analysis to determine their taxonomic position and to identify the compounds responsible for their antifungal activity as well as to evaluate the efficiency of these strains to control sclerotinia stem rot in soybean. Methods and Results: The antifungal compounds were isolated by acid precipitation of cell‐free supernatants, purified by RP‐HPLC and then tested for antagonistic activity against Sclerotinia sclerotiorum. Mass spectra from RP‐HPLC eluted fractions showed the presence of surfactin C15, fengycins A (C16–C17) and B (C16) isoforms in supernatants from strain ARP23 cultures, whereas the major lipopeptide produced by strain MEP218 was iturin A C15. Alterations in mycelial morphology and sclerotial germination were observed in the presence of lipopeptides‐containing supernatants from Bacillus strains cultures. Foliar application of Bacillus amyloliquefaciens strains on soybean plants prior to S. sclerotiorum infection resulted in significant protection against sclerotinia stem rot compared with noninoculated plants or plants inoculated with a nonlipopeptide‐producing B. subtilis strain. Conclusions: Both strains, renamed as B. amyloliquefaciens ARP23 and MEP218, were able to produce antifungal compounds belonging to the cyclic lipopeptide family. Our data suggest that the foliar application of lipopeptide‐producing B. amyloliquefaciens strains could be a promising strategy for the management of sclerotinia stem rot in soybean. Significance and Impact of the Study: Sclerotinia stem rot was ranked as one of the most severe soybean disease in Argentina and worldwide. The results of this study showed the potential of B. amyloliquefaciens strains ARP23 and MEP218 to control plant diseases caused by S. sclerotiorum.

Bio-suppression of Sclerotinia Stem Rot of Tomato and Biostimulation of Plant Growth Using Tomato-associated Rhizobacteria

“…In this way, decreased or delayed germination of sclerotia, achieved using this rhizobacteria collection, could be useful to reduce primary pathogen inoculum as noted with the lipopeptides producing B. amyloliquefaciens strains [13]. Similar effects have been reported by other authors on phytopathogenic fungi, suggesting that biosurfactant lipopeptides can traverse the fungal cell wall and induce serious alterations in plasma membrane permeability of active and resting structures [56,57].…”

“…These findings are in agreement with previous reports [31] showing that isolate DF35 is able to inhibit sclerotial germination by 100%, but limits the mycelial growth by 50% only while the other bacteria, isolated from canola and soybean plants, cause 100% inhibition of mycelial growth and germination of sclerotia. Alterations in sclerotial germination and mycelial morphology are observed in the presence of lipopeptidescontaining supernatants from Bacillus strains cultures [13]. Sclerotia treated by bacterial cells exhibit changes in color and less resistance with impaired consistency [21].…”

“…Their main mode of action is their fungicidal effect on sclerotia through preventing them from germinating even under favorable conditions [13]. In fact, S. sclerotiorum spends 90% of its life cycle in soil as a sclerotia, able to survive up to 5 years in soil, and during their myceliogenic germination, the hyphae grow towards host roots and hypocotyls causing shoot wilt [55].…”

“…Biocontrol is eco-friendly, safe and may provide long-term protection to the crop. Reduced Sclerotinia Stem Rot incidence and severity have been demonstrated in numerous studies and successful disease control was achieved using fungi [10][11][12][13][14], bacteria [7,12,[15][16][17] or biofungicides [18][19][20] in many cropping systems. The most efficient bacteria used for Sclerotinia Stem Rot management belonged mainly to the genera Bacillus [1,9,[12][13]21], Pseudomonas [7,22], Enterobacter [23,24], Serratia [22,[25][26][27], and at a lesser extent Streptomyces, Burkholderia, Pantoea, and Paenibacillus [22,25].…”

Improvement of Antagonistic Activity of Bacillus megaterium MHT6 against Fusarium moniliforme using He-Ne Laser Irradiation

“…B. substilis has been found to produce antibiotic compounds such as lipopeptides including fengycin, iturin and surfactin families (Alvarez et al, 2012). Especially the lipopeptides of fengycin have displayed strong antifungal activity against a wide range of plant pathogens fungus (Pérez-García et al, 2011;Yánez-Mendizábal et al, 2012;Falardeau et al, 2013).…”