Isolation and identification of a tomato endophyte FQ-G3 and its disease-resistant and growth-promoting properties

Abstract:

Gray mold caused by Botrytis cinerea is one of the major diseases affecting tomato production. The currently used fungicides are gradually restricted due to residues, pathogen resistance, and food safety. Therefore, screening out antagonistic microorganisms has gradually become an effective approach for the biocontrol of gray mold. [Objective] We screened out endophytic strains capable of endowing plants with disease resistance and promoting plant growth from tomato plants and evaluated their biocontrol potential, aiming to provide a theoretical basis for developing a new approach for the biocontrol of tomato gray mold. [Methods] The endophytic bacteria and fungi were isolated from different parts of tomato plants by the tissue culture method, and the candidate strains were preliminarily identified by 16S rRNA and ITS sequence analysis. The endophytes with antagonistic activity against B. cinerea were screened by confrontation culture and fruit inoculation in vitro. Furthermore, we examined the abilities of the strain to secrete indole-3 acetic acid (IAA), protease, and siderophores and the promoting effects on the growth of Arabidopsis thaliana and tomato seedlings.[Results] A total of 72 endophytic bacterial strains and 31 endophytic fungal strains were isolated from different parts of tomato plants. An endophytic bacterium FQ-G3 with strong inhibitory activities against several pathogens was screened out and was identified as Bacillus velezensis. FQ-G3 showed the inhibition rate of 80.93% against B. cinerea in vitro and inhibited the mycelial expansion on tomato fruits in vivo. The strain could secrete IAA, protease, and siderophores, and promote the growth of A. thaliana and tomato seedlings. [Conclusion] The endophytic strain FQ-G3 isolated from tomato plants endows plants with disease resistance and promotes plant growth, and thus can serve as a candidate for the prevention and control of gray mold. The findings enrich the tomato endophyte resources and provide support for the control of gray mold and the growth promotion of tomato.