Agroactive volatile organic compounds from microbes:Chemical diversities and potentials of application in crop protection

Synthetic chemicals have been widely used in modern agriculture as fertilizer,plant growth regulators and pesticides.Although the chemical inputs improved the crop production,it is well known about their negative effects,such as environmental residues in water,soil and animals,pest resistance and resurgence and the residues in agricultural produces.The demands for safer food and more friendly environment are now more preferred by humankind in the world.Microbes have already become an alternate for chemical inputs in some aspects in agriculture.The microbes can produce very diverse volatile organic compounds(mVOCs)which play important roles in the interactions between plant and microbes,or among intraspecies or interspecies of microbes.Many mVOCs showed diverse agroactivities,such as insecticidal,bactericidal,fungicidal,herbicidal,plant growth promotion and abiotic stress-tolerance inducing activities.The agroactive mVOCs have diverse structure-types,such as alkane,alkenes,alcohols,aldehydes,ketones,carboxylic acid,esters and lactones,ethers,aromatic ring,terpenes,heterocycles,sulphur-containing VOCs.The promising agroactive properties make it possible to apply mVOCs and their producing microorganisms or synthetic mimics or agroactive mVOCs in crop protection,and so this review focuses on the chemical diversity,agroactivities,and potential application of mVOCs.

Volatile organic compound emissions from straw-amended agricultural soils and their relations to bacterial communities:A laboratory study

A laboratory study was conducted to investigate volatile organic compound（VOC） emissions from agricultural soil amended with wheat straw and their associations with bacterial communities for a period of 66 days under non-flooded and flooded conditions. The results indicated that ethene, propene, ethanol, i-propanol, 2-butanol, acetaldehyde, acetone,2-butanone, 2-pentanone and acetophenone were the 10 most abundant VOCs, making up over 90% of the total VOCs released under the two water conditions. The mean emission of total VOCs from the amended soils under the non-flooded condition（5924 ng C/（kg·hr）） was significantly higher than that under the flooded condition（2211 ng C/（kg·hr））. One ＂peak emission window＂ appeared at days 0–44 or 4–44, and over 95% of the VOC emissions occurred during the first month under the two water conditions. Bacterial community analysis using denaturing gradient gel electrophoresis（DGGE） showed that a relative increase of Actinobacteria, Bacteroidetes, Firmicutes and γ-Proteobacteria but a relative decrease of Acidobacteria with time were observed after straw amendments under the two water conditions. Cluster analysis revealed that the soil bacterial communities changed greatly with incubation time, which was in line with the variation of the VOC emissions over the experimental period. Most of the above top 10 VOCs correlated positively with the predominant bacterial species of Bacteroidetes, Firmicutes and Verrucomicrobia but correlated negatively with the dominant bacterial species of Actinobacteria under the two water conditions. These results suggested that bacterial communities might play an important role in VOC emissions from straw-amended agricultural soils.