Analysis Of Volatile Components Of Beneficial Strains For Cymbidium Hybridum And Their Effect On Plant Growth

The commercial crop Cymbidium hybridum is a perennial herb belonging to the Orchidaceae genus Cymbidium.As one of the most important potted flowers and fresh cut flowers in the world,potted flowers are popular in domestic and foreign markets.Previous studies found that Cymbidium hybridum formed a symbiotic relationship with some fungi,which can increase the fresh weight and dry matter accumulation of the host seedlings.In this study,the components of volatile organic compounds(VOCs) of beneficial strains from Cymbidium spp.were compared.The main purpose of this study is related to exploring the influence of culture medium,detection method on VOCs composition and relative content of ML01;elucidating the effects of fungal VOCs(mVOCs) on the growth of Arabidopsis thaliana and the possible mechanism involved,and exploring the role of key aromatic substance,γ-Decalactone,released from ML01 in the regulation process.This study will lay a foundation for further explaining the mechanism of m VOCs affecting plants.The main research results of this paper are as follows:(1)A co-culture system of fungi and Arabidopsis was established to test the effect of m VOCs on the growth of Arabidopsis.The steps of the system included:1)Select the seedlings of Arabidopsis thaliana with similar condition,which have germinated in vertical plate for 5 d;2)Arabidopsis thaliana and fungi were co-cultured in a 13x13cm square petri dish;3)The fungi were cultured in a self-made 30 cm~2 aluminum foil container to ensure sufficient growth space for the fungi and physically isolation from Arabidopsis thaliana;4)Put nine Arabidopsis plants per dish to ensure the normal lateral root growth;5)The sealing material is clingfilm.The plates were placed vertically and the temperature is 25℃ to 26℃.In this co-culture system,the volatile components of the beneficial strains ML01,M1and C2Y1 of Cymbidium hybridum could be clearly observed to promote the elongation of the primary roots,the increase of the number of lateral roots and the accumulation of plant biomass of wild type Arabidopsis.(2)Being effected by ML01 VOCs for 4 days,the lateral root number of Arabidopsis mutants tir1-1,which lack auxin receptor gene remains the same,but three other ethylene signal path mutants’response similar to the wild type,thus speculate ML01 VOCs promote Arabidopsis lateral root growth without depending on ethylene signal path,but associated with auxin signal path.(3)The suitable detection method of beneficial strains VOCs for cymbidium hybridum was determined,and the species and relative content of volatile substances in different culture media and different growth periods were analyzed by gas chromatography-mass spectrometry.Through a series of comparisons,the volatile components of ML01,M1,Piriformospora indica(DSM11827) and C2Y1 were summarized.The important volatile components of ML01 include prodecyllactone,hexadecanoic acid,2,6,10,14-tetramethylpentadecane,decanal,phytane,methyl tetradecanoate and isobutyl phthalate.The most important volatile components of M1 are ethyl benzoate,2,6-ditert-butylbenzoquinone,Decane,3,6-dimethyl-,acetophenone and Oxalic acid,decyl propyl ester.The volatile components of piriform spores in India are ethyl benzoate,methyl benzoate,octanone and n-tridecane.The main volatile component of C2Y1 is propyl decanolide.(4)The effect of ML01 characteristic aroma componentγ-Decalactone on the growth of Arabidopsis thaliana was related to the concentration.The lateral root growth of Arabidopsis thaliana was significantly promoted by the treatment with 29.4μM prodecalacolide,but the root growth of Arabidopsis thaliana was inhibited by the concentration higher than 58.8μM.