Volatile organic compounds produced by Bacillus velezensis L1 as a potential biocontrol agent against postharvest diseases of wolfberry

Abstract

Volatile organic compounds (VOCs) produced by antagonistic microorganisms have good biocontrol prospects against postharvest diseases. Infection caused by <i>Alternaria iridiaustralis</i> and 10 other significant fungal diseases can be successfully inhibited by VOCs produced by an identified and screened endophytic strain L1 (<i>Bacillus velezensis</i>). This study revealed the <i>in vivo</i> and <i>in vitro</i> biocontrol effects of VOCs released by <i>B. velezensis</i> L1 on <i>A. iridiaustralis</i>, a pathogenic fungus responsible for rot of wolfberry fruit. The inhibition rates of VOCs of <i>B. velezensis</i> L1 on the mycelial growth of <i>A. iridiaustrali</i>s <i>in vitro</i> were 92.86 and 90.30%, respectively, when the initial inoculum concentration on the plate was 1 × 10⁹ colony forming unit (CFU)/ml. Spore germination and sporulation were 66.89 and 87.96%, respectively. VOCs considerably decreased the wolfberry's disease index and decay incidence <i>in vivo</i>. Scanning electron microscopy revealed that the morphological and structural characteristics of <i>A. iridiaustralis</i> could be altered by VOCs. Ten VOCs were identified through headspace-gas chromatography-ion mobility spectrometry. Pure chemical tests revealed that 2.3-butanedione had the strongest antifungal effects, totally inhibiting <i>A. iridiaustralis</i> in wolfberry fruit at a 60 μl/L concentration. The theory underpinning the potential application of VOCs from <i>B. velezensis</i> is provided herein. This is also the first study to document the antifungal capabilities of the <i>B. velezensis</i> strain on postharvest wolfberry fruit. GRAPHICAL ABSTRACT.