Efficacy of volatile compounds from Streptomyces philanthi RL-1-178 as a biofumigant for controlling growth and aflatoxin production of the two aflatoxin-producing fungi on stored soybean seeds.

Aims: This study aimed to apply the volatile organic compounds from Streptomyces philanthi RL-1-178 (VOCs RL-1-178) as a fumigant to protect soybean seeds against the two aflatoxin-producing fungi in stored soybean seeds.
Methods and Results: The antifungal bioassay tests on potato dextrose agar (PDA) dishes showed that 30 g l ^-1 wheat seed inoculum of S. philanthi RL-1-178 exhibited total (100%) inhibition on Aspergillus parasiticus TISTR 3276 and Aspergillus flavus PSRDC-4. Identification of the VOCs RL-1-178 using GC-MS revealed 39 compounds with the most abundant substances being geosmin (13·75%) followed by l-linalool (13·55%), 2-mercaptoethanol (9·71%) and heneicosane (5·96%). Comparison on the efficacy of the VOCs RL-1-178 (at 30 g l ^-1 wheat seed culture) and their four major components (100 µl l ^-1 each) on the suppression of the two aflatoxin-producing fungi on PDA plates revealed that the VOCs RL-1-178 as well as geosmin, l-linalool and 2-mercaptoethanol completely inhibited (100%) mycelial growth while heneicosane showed only 70·7% inhibition. Use of the VOCs RL-1-178 (30 g l ^-1 ) as a biofumigant on stored soybean seeds resulted in complete protection (100%) against the infection as well as complete inhibition on production of aflatoxin (B ₁ , B ₂ and G ₂ ) (analysed by HPLC) by the two aflatoxin-producing fungi.
Conclusions: The VOCs RL-1-178 displayed strong inhibitory effects on A. parasiticus TISTR 3276 and A. flavus PSRDC-4 as well as inhibited aflatoxin (B ₁ , B ₂ and G ₂ ) production.
Significance and Impact of the Study: These findings suggest that the VOCs RL-1-178 can be applied as a biofumigant to control the two aflatoxin-producing fungi on stored seeds products.
(© 2020 The Society for Applied Microbiology.)