| Root rot is one of the most serious disease of blueberry cultivation,which seriously restricts the development of blueberry industry.There are many disadvantages of chemical control of plant diseases,such as resistance of pathogen,serious environmental pollution,and destruction of ecological balance.Therefore,it is of great significance to explore new control method which is more effective and environmentally friendly.Biological control of plant diseases has the advantages of killing pathogen accurately without harming natural enemies and beneficial microorganisms,protecting the ecological balance,long-lasting control effect and no resistance of pathogens.Nowadays,biological control of diseases has become an important part of the sustainable development of forestry.In this study,in order to identify the blueberry root rot pathogen of Guizhou province,screen the effective biocontrol fungi against blueberry root rot,the pathogen of root rot was isolated and identified,the endophytic fungi were isolated from tissue of healthy blueberry,rhizosphere soil fungi were isolated from healthy blueberry rhizosphere soil,and biocontrol mechanism of advantagable antagonism strain was studied,control effect was explored by pot tests.The results are as follows.Meanwhile,the results could provide a theoretical basis for the control of blueberry root rot in Guizhou p rovince.（1）In this study,after collecting the rotten root samples of blueberry,the pathogenic isolation was studied by using the method of normal tissue sepration,the pathogenicity of pathogen was verified according to Koch’s Postulates,the pathogenic identification was studied based on morphological characteristics and the sequencing results of ITS,EF-1αandβ-tubline genes,the experimental results showed that the blueberry root rot pathogens of Guizhou province were Fusarium oxysporum and F.commune,which had high pathogenicity to blueberry seedlings,among them,strain LMGF6（F.commune）and LMGF7（F.oxysporum）had the strongest pathogenicity.（2）Using the plate confrontation test,11 biocontrol strains were screened out from 152endophytic fungi or rhizosphere soil fungi strains.The inhibition rate of 11 biocontrol strains against LMGF6 was as follows:TM11（68.01%）>M1（64.94%）>m3（64.91%）>M2（63.66%）>MG6（59.35%）>MG5（57.58%）>G14（57.53%）>G18（56.93%）>G11（55.68%）>G6（54.42%）>MY51（51.97%）;The inhibition rate of 11 biocontrol strains against LMGF7 was as follows:M1（66.90%）>TM11（65.65%）>M3（64.45%）>MG6（62.65%）>G6（62.03%）>G11（60.82%）>G18（60.24%）>G14（59.04%）>M2（56.02%）>MY51（52.40%）>MG5（50.56%）.According to morphological characteristics and molecular biological classification methods,strains G6 and G18 were identified as Schizophyllum commune,G11 and G14 as Bjerkandera adusta,MG5 and MG6 as Ascodesmis sphaerospora,M1 and M2 as Trichoderma longibrachiatum,MY51,M3 and TM11 as Phlebia acerina,Trichoderma koningiopsis and Trichoderma asperellum,respectively.Biological characteristics test showed that the optimal carbon sources of biocontrol strains were fructose and glucose,the optimal nitrogen sources were yeast extract and peptone,the optimal C/N was 20/1,the optimal growth temperature was 25℃-30℃,metal ions were toxic to biocontrol strains,and Cu2+was the most toxic.（3）The results showed that biocontrol fungi entangled and attached to the hyphae of pathogens,caused the hyphae to deform,shrink,dissolve and even break,which may be related to the cellulase,β-1,3-glucanase,protease and chitinase.The results showed that the volatile metabolites of four antagonistic strains had obvious inhibitory effect on root rot（P<0.05）,the highest inhibition rate was up to 42.26%.The non-volatile metabolites of three antagonistic strains had significant inhibitory effect on root rot（P<0.05）,the highest inhibition rate was up to 42.86%.The results showed that there are thirteen reported antimicrobial metabolites of non-volatile metabolites were detected,including Alkaloids,Ketones,Esters,Phenols and Organic acids.The results of plate culture experiments showed that biocontrol fungi had obvious inhibitory effect on six common plant pathogens,such as Neofusicoccum parvum,Fusarium graminearum and Colletotrichum sublineola,and some biocontrol fungi could produce IAA,had the characteristic of dissolving phosphorus and potassium.In general,antagonistic strains TM11、G18、MG6 and M1 had significant control effect on root rot pathogens through different ways.（4）The results showed that pathogen LMGF6 and LMGF7 had different pathogenicity to different blueberry varieties.The sensitivity of different blueberry varieties to pathogen was as follows:‘Lai gexi’>‘Ao nier’>‘Can Lan’.The results of greenhouse pot experiment showed that biocontrol strain had obvious control effects on blueberry root rot,the control effect of treatment 1（The seedlings were inoculated with biocontrol fungi for 48 hours and then inoculated with pathogens）was better than the control effect of treatment 2（The seedlings were inoculated with pathogens for 48 hours and then inoculated with biocontrol fungi）,and strain TM11 had the most significant control effect on pathogens,strain G18 and MG6 was followed.The control effect of different strain combination treatments was studied,results showed that the G18+MG6+TM11 treatment had the most significant control effect on pathogens,the control effects on LMGF6 and LMGF7 were 88.87%and 84.64%,respectively.The results showed that,compared with the treatment with water,the content of chlorophyll and the content of POD,SOD and CAT of were significantly improved.Compared with the fresh water seedlings,CAT content in root of seedlings inoculated with MG6+LMGF7 increased 1.08 times,CAT content in leaf of seedlings increased 86.70%;The SOD content in root was the highest of G18+MG6+LMGF6 treatment（539.37 U/g）,and that in leaf was the highest in TM11+G18+LMGF6 treatment（351.70 U/g）;POD content of seedlings inoculated with TM11 alone was the highest,Compared with the fresh water seedlings,POD content in root and leaf of seedlings increased 1.41 and 1.49 times,respectively.These results indicate that strain TM11,G18 and MG6 could induce the defense system of blueberry seedlings. |
