Antifungal Volatile Organic Compounds(VOCs)based Mutant Strain Screening And Mechanism Of Trichoderma Afroharzianum

Trichoderma spp.can produce anti-fungal and growth-promoting volatile organic compounds(VOCs),which are of great value in the fields of biological control and medicine.In the present study,strain ACCC 33109 of T.afroharzianum with high antifungal fungal activity was selected,the anti-fungal activity was improved by protoplast ultrviolet mutagenesis,the colonization efficiency of cucumber blight disease(Fusarium oxysporum sp.cucumberium)was monitored in a pot experiment by using the q PCR,the carbon metabolism was analyzed with Omnilog,and SPME/GC-MS and PGAP were used to compare the differential VOCs and related genes of wild type and mutant strains.The main findings are:1.A total of 828 mutant strains were obtained by 2-min ultraviolet mutagenesis.Of them,30mutants showed higher antifungal fungal activities than the wild type.MU153 showed the highest anti-fungal activity(53.9%),which was 16.7%higher than that of the wild type.The colony and conidiophagous morphology of mutant strains.Compared with ACCC 33109,the mycelia of MU153grew rapidly and densely,became flocculent,and produced pigment,the mycelia of MU239 grew rapidly and densely,became flocculent,while MU792 mycelia grew slowly and loosely,and the colony color changed from green to white in the late stage;the sizes of conidia and pedicels of MU153 and MU792 increased,and the base width and the length/width ratio of the conidia decreased,while the MU239 show opposite changes.2.Both ACCC 33109 and MU153 colonized well in soil,reatining 3.25?8.51×10~5 spores/g soil over 6 weeks in the pot experiment.MU153 showed higher biocontrol efficiency(84.9%)on F.oxysporum sp.cucumberium,which was 11.1%higher than that of ACCC 33109.Both strains showed growth-promoting effects.3.Omnilog phenotype analysis indicated that different strains varied in the capability of utilizing96 substances on FF plate.In comparison with ACCC 33109,MU153 had stronger metabolic ability to utilize 46 substances,with D-mannitol as the optimal carbon source;while MU239 and MU239 more efficiently utilized 36 and 27 substances respectively,and preferred sucrose as the best substrate.When using?-D-glucose as the carbon source,the highest VOCs inhibitory effects of ACCC 33109,MU153,MU239 and MU792 were achieved,which were 48.1%,56.2%,53.3%and 40.9%,respectively.4.GC-MS analysis indicated that the VOCs of different strains varied a lot.In comparison with ACCC 33109,MU153 had 15 specific VOCs,including 7 esters,4 alkanes and benzenes,2 aldehydes and 1 alkenes;and MU239 had 13 specific VOCs,including 7 alkenes,4 benzenes,and 1 of each alcohol and aldehyde.The VOCs related to anti-fungal activities were identified to be terpenes,aldehydes and alkenes.5.Pan-genome analysis revealed that ACCC 33109,MU153,MU239 and MU792 had 157 genes coding for 46 secondary metabolism-related proteins in common.In comparison with ACCC 33109,MU153,MU239 and MU792 had 10 and 14 more and 12 less genes coding for terpene synthase,polyketonase,non-ribosome polypeptidase.This study successfully obtained a mutant strain of T.afroharzianum with high yield of antifungal fungal VOCs,and undermined the biocontrol efficiency,carbon metabolism,VOCs components,and differential genes.It enriches the bioncontrol agent resources,and is of great importance in basic research and application.