Biocontrol of Aspergillus flavus on Peanut Kernels Using Streptomyces yanglinensis 3-10

Abstract

The bacterium, Streptomyces yanglinensis 3-10, shows promise in the control of many phytopathogenic fungi. In this study, S. yanglinensis and its antifungal substances, culture filtrate (CF3-10) and crude extracts (CE3-10), were evaluated for their activity in reducing growth and aflatoxin AFB1 production by Aspergillus flavus, both in vitro and in vivo on peanut kernels. The results showed that in dual culture conditions, S. yanglinensis reduced the mycelial growth of A. flavus about 41% as compared to control. The mycelial growth of A. flavus was completely inhibited on potato dextrose agar amended with CF3-10 at 3% (v/v) or CE3-10 at 2.5 μg/ml. In liquid culture experiments, growth inhibition ranged from 32.3 to 91.9% with reduction in AFB1 production ranging from 46.4 to 93.4% using different concentrations of CF3-10 or CE3-10. For in vivo assays, CF3-10 at 0.133 ml/g (v/w) or CE3-10 at 13.3 μg/g (w/w) reduced the postharvest decay of peanut kernels by inhibiting visible growth of A. flavus leading to an 89.4 or 88.1% reduction in AFB1 detected, respectively. Compared with the controls, CF3-10 and CE3-10 in A. flavus shake culture significantly reduced expression levels of two AFB1 biosynthesis genes, aflR and aflS. Furthermore, electron microscopy observation showed that CF3-10 (2%, v/v) caused hyphae growth to be abnormal and shriveled, cell organelles to degenerate and collapse, large vacuoles to appear. These results suggest that S. yanglinensis 3-10 has potential as an alternative to chemical fungicides in protecting peanut kernels and other agricultural commodities against postharvest decay from A. flavus.

High Efficacy of the Volatile Organic Compounds of Streptomyces yanglinensis 3-10 in Suppression of Aspergillus Contamination on Peanut Kernels

“…Streptomyces spp. are well known as producers of hydrolytic enzymes and antifungal metabolites with inhibitory effects against many plant pathogenic fungi including Aspergillus species (Mander et al, 2016;Shakeel et al, 2018). Use of the VOCs from Streptomyces for control of Aspergillus contamination in peanut kernels has not been reported so far.…”

“…are soil dwelling bacteria, they can grow and produce versatile secondary metabolites in soil. S. yanglinensis 3-10 was proved to produce antifungal metabolites which showed inhibitory effects on A. flavus growth and aflatoxin production and other plant pathogenic fungi (Lyu et al, 2017;Shakeel et al, 2018). It is an acidophilic species with high adaptation ability in acidic soils in southern China.…”

Control of Aflatoxigenic Molds by Antagonistic Microorganisms: Inhibitory Behaviors, Bioactive Compounds, Related Mechanisms, and Influencing Factors

“…Several other Streptomyces species (Table 1) have been evaluated as bioactive agents providing an antagonistic activity against aflatoxigenic isolates. Shakeel et al [28] demonstrated that culture filtrates and crude extracts of S. yanglinensis could completely inhibit mycelial growth of A. flavus. Studies demonstrated that S. anulatus [29], S. alboflavus [30], and S. roseolus [31] also exerted an effective antifungal activity toward aflatoxigenic strains and other common agricultural crops pathogens.…”

“…Streptomyces spp., known to produce over 7500 bioactive compounds including anticancer agents, vitamins, and antibiotic compounds, have a better tolerance to water stress [28]. They usually do not secrete toxic residues that may contaminate environments because of their natural origin.…”

Rhizopus oligosporus Activity in Crude Extract and Powder Form to Reduce Aspergillus flavus and Aflatoxin Contamination in Corn

“…Bacteria and non-toxigenic fungi were commonly used for Aspergillus flavus biocontrol and aflatoxin degradation. Streptomyces yanglinensis 3-10 ( Shakeel et al 2018) and Bacillus subtilis UTBSP1 (Farzaneh et al 2016) showed promising activity to control Aspergillus flavus in peanut kernel and pistachio nut. Non-toxigenic Aspergillus flavus (Ehrlich 2014) and Rhizopus stolonifer (Iqbal et al 2014) as mycelium or extract inhibited Aspergillus flavus growth.…”