Efficacy of volatile compounds from <i>Streptomyces philanthi</i> RL‐1‐178 as a biofumigant for controlling growth and aflatoxin production of the two aflatoxin‐producing fungi on stored soybean seeds
Sawai Boukaew, Poonsuk Prasertsan
Abstract
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 (B1, B2 and G2) (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 (B1, B2 and G2) 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.