Suppression of tomato gray mold by a new strain of autolytic Lysobacter enzymogenes (LE16) in greenhouse

Abstract:

[Objective] Facility agriculture has experienced a surge in populairty in China which features a large population and little arable land.Greenhouse cultivation guarantees tomato security in China.However,greenhouse tomato are prone to gray mold (induced by Botrytis cinerea),leading to huge yield loss.Biocontrol is safe for human being and animal and environmentally friendly.It is urgent to seek more biocontrol microorganisms to improve the control effect.[Methods] In the current series of experiments,the biocontrol potentitial of a self-isolated new strain (LE16) of autolytic Lysobacter enzymogenes was explored.To be specific,pure culture was carried out to test the antagonism of LE16 fermentation broth against B.cinerea.Biochemical analysis,liquid chromatography-mass spectrometry,and transcriptome techniques were used to clarify the synthesis and secretion of extracellular hydrolases and antifungal compounds of LE16,and differentially expressed genes in B.cinerea,with a view to elucidating the antifungal mechanism.The inhibitory effect of LE16 fermentation broth on tomato gray mold was evaluated with the pot experiment in a greenhouse.[Results] LE16 synthesized and released siderophore,a variety of extracellular enzymes related to disease resistance (including phosphatase,protease,cellulase,β-1,3-glucanase and lysozyme),9 antifungal compounds (ustiloxin D,N-undecylbenzenesulfonic acid,rifabutin,nanaomycin,tigecycline,minocycline,m-cresol,cinnamic acid and cyclopentanone),and P-salicylic acid that is able to stimulate systemic acquired resistance in plants.The crude extract of LE16 fermentation broth significantly inhibited the growth and reproduction of B.cinerea,and the inhibition rate was 34.99%-100%,much higher than those of L.lysobacterium HYP18 and Ceriporia lacerata HG2011 on solid culture.Additionally,LE16 fermentation broth significantly induced the differential expression of genes in B.cinerea.The differentially expressed genes were involved in biological processes,cellular components,molecular functions (e.g.,protein synthesis,DNA replication and repair,and signal transduction),and metabolic pathways related to proteins,glycine,serine and threonine.In the greenhouse experiment,LE16 fermentation broth significantly enhanced the activity of antioxidant enzymes,including superoxide dismutase and peroxidase,in tomato leaves,and alleviated the damage to cell membranes caused by the pathogen.The inhibitory effect against gray mold varied from 72.54% to 74.42%,slightly lower than that of the chemical pesticide pyrimethanil.[Conclusion] LE16 suppresses the incidence of tomato gray mold in the greenhouse by multiple mechanisms,such as the synthesis and release of extracellular hydrolases,siderophore and antifungal compounds,and the induction of resistance to disease in the plants.Thus,LE16 shows a promising potential in controlling tomato gray mold in the greenhouse.