Potential use of Streptomyces mycarofaciens SS-2-243 as a biofumigant to protect maize seeds against two aflatoxin producing fungi
Streptomyces mycarofaciens SS-2-243 has been found to produce non-volatile compounds possessing antifungal activity against the growth of plant pathogens, but the effect of its volatile compounds remain unknown. Therefore, the efficacy of volatile compounds from S. mycarofaciens SS-2-243 (volatiles SS-2-243) grown on wheat seeds for 12 days was evaluated against four pathogenic fungi. In vitro studies using an antifungal bioassay tests on PDA dishes indicated that the volatiles SS-2-243 could totally suppress the growth of all four strains with most pronounced activity (100% inhibition) against Aspergillus parasiticus TISTR 3276 and A. flavus TISTR 3041. Identification of the volatiles SS-2-243 using gas chromatography–mass spectrometry (GC–MS) revealed 33 compounds, with the most abundant being 2-methylisoborneol. Effect of the inoculum size and spore concentration of S. mycarofaciens SS-2-243 prepared as a wheat seed inoculum on the suppression of the two aflatoxin producing fungi was studied. Complete growth inhibition (100%) was achieved at the optimum wheat seed inoculum size of at least 30 g L−1 and 107 spore mL−1. Use of 30 g L−1 wheat seed culture of S. mycarofaciens SS-2-243 could completely kill the conidia of A. parasiticus TISTR 3276 and A. flavus TISTR 3041 with 1 h and 3 h exposures, respectively. Based on the promising antifungal activity of the volatiles SS-2-243, fumigation with 30 g L−1 wheat seed culture of S. mycarofaciens SS-2-243 for 24 h completely controlled the growth of the two aflatoxin producing fungi infecting maize seeds, without adverse effects on maize seed germination. The main effect of the volatiles SS-2-243 was damage and complete inhibition of conidia germination as evident by scanning electron microscope (SEM) images. Therefore, this biofumigant has good potential to control the two aflatoxin producing fungi.
KeywordsAflatoxin producing fungi Biofumigation Maize seeds Streptomyces mycarofaciens Volatile compounds
This research study was financially supported by the Agricultural Research Development Agency (Public Organization) grant number PRP5905021490 and the Thailand Research Fund (grant no. RTA6080010). The copyediting service of RDO/PSU and proof-reading by Dr. Seppo Karrila are gratefully acknowledged.
Compliance with ethical standards
Conflict of interest
The authors declare having no conflict of interest.
Human and animal studies
This research did not involve human and/or animal participants.
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