Volatile Organic Compounds from Rice Rhizosphere Bacteria Inhibit Growth of the Pathogen Rhizoctonia solani

Abstract

Rice sheath blight, a fungal disease caused by Rhizoctonia solani, seriously threatens rice production. Some of the volatile organic compounds (VOCs) produced by microbes are inhibitory to the growth of the plant pathogen, and hence may have the potential as environmentally friendly antifungal substances. However, information on the inhibitory effect of VOCs released by rice rhizosphere bacteria on R. solani is scarce. In this study, bacteria from the rice rhizosphere capable of inhibiting the growth of R. solani via releasing VOCs were screened using a double Petri dish assay. Headspace solid phase microextraction and gas chromatography mass spectrometry (GC/MS) were used to identify and quantify the VOCs. The contributions of VOCs to the inhibition of the growth of R. solani were estimated by constructing a random forest model, and were verified using pure compounds. Nine strains (i.e., Pseudomonas sp. No. 3, Enterobacter sp. No. 26, Enterobacter sp. No. 34, Pseudomonas sp. No. 35, Ralstonia sp. No. 50, Bacillus sp. No. 62, Arthrobacter sp. No. 146, Brevibacillus sp. No. 2–18, and Paenisporosarcina sp. No. 2–60) showed various inhibition on R. solani growth via VOCs. The inhibitory effect ranged from 7.84% to 100%, with Ralstonia sp. No. 50 completely inhibiting the growth of R. solani. Five VOCs (i.e., benzoic acid ethyl ester, 3-methyl-butanoic acid, 2-ethyl-1-hexanol, 3-methyl-1-butanol, and 6-methyl-5-hepten-2-one) identified by random forest model were confirmed to be toxic to R. solani when applied as a pure chemical compound. In particular, benzoic acid ethyl ester, 3-methyl-butanoic acid, and 2-ethyl-1-hexanol were lethal to R. solani. In summary, the rice rhizosphere bacteria (Ralstonia sp. No. 50) and VOCs (benzoic acid ethyl ester, 3-methyl-butanoic acid, and 2-ethyl-1-hexanol) showed potential to be used as new resources for biological control of rice sheath blight.

Microbial volatile organic compounds: Antifungal mechanisms, applications, and challenges

“…In particular, Ralstonia sp. completely inhibits the growth of R. solani as a result of VOC production, among which ethyl benzoate, 3-methylbutanoic acid, 2-ethylhexan-1-ol, 3-methylbutan-1-ol, and 6-methylhept-5-en-2-one are confirmed to be toxic to R. solani (Wang et al, 2021a). Additionally, R. solani is also inhibited by VOCs derived from several Streptomyces spp.…”

Volatiles of the Apicomplexan Alga Chromera velia and Associated Bacteria

“…11‐Methyltridecan‐2‐one ( 67 ) was the most abundant volatile in “ C. coralii ” A01A‐333. All these ketones have been reported from different bacterial strains [46,52,69,70–72] . Because of their widespread occurrence, such methyl ketones have been classified as common bacterial volatiles [9] .…”

Antifungal Potential of Bacillus velezensis CE 100 for the Control of Different Colletotrichum Species through Isolation of Active Dipeptide, Cyclo-(D-phenylalanyl-D-prolyl)

“…Bacterial volatiles are distinctive metabolites synthesized during bacterial growth and have been recognized as potent antimicrobial compounds against phytopathogens. These compounds can easily evaporate and diffuse in heterogeneous environments in solids, liquids, and gases [ 39 ]. The genus Bacillus is a major producer of antifungal VOCs [ 40 ].…”