Study On Screening Of Trichoderma Harzianum And Associated Antagonisms To Rhizoctonia Solani Of Asparagus Rhizosphere

In this study, we isolated and identified asparagus Rhizoctonia solani, from the4Trichoderma harzianum strains, Screened the stronger Trichoderma harzianum TH strain has an antagonistic effect on asparagus Rhizoctonia solani and analyzed the prophylaxis and promoting effect on Trichoderma harzianum TH，biological characteristics and antagonistic mechanisms. Our study will provide a theoretical basis for biological control of Rhizoctonia solani of asparagus. The results were as follows:1. With field investigation, detection of pathogen, symptoms and pathogenic identification, and further amplification of rDNA-ITS segment, we determined the isolated asparagus damping off pathogen was Rhizoctonia solani based on rDNA-ITS sequence analysis. Through plate confrontation method, a stronger antagonistic strains of TH was screened among TD, TH, TM, TX Trichoderma harzianum strains for Rhizoctonia solani.2. The antagonistic mechanisms of Trichoderma harzianum TH mechanisms were investigated. The antagonistic effects were associated with antibiotic effect, parasitism and metabolites. In addition, we analyzed the enzyme producing abilities of Trichoderma harzianum TH. It showed that no protease producing, but it can secrete chitinase and cellulase.3. The biological characteristics antibacterial of Trichoderma harzianum TH broth on asparagus Rhizoctonia solani were investigated. The influence of different fermentation temperatures broth of Trichoderma harzianum TH exhibited high thermal stability. The fungal bacteriostatic rate remained at more than50%after the treatment at60℃. In the range of pH3.0~9.0, Trichoderma harzianum TH fermentation liquid can maintain its activity. NaCl and H2O2had a certain effect on the antibacterial activity of Trichoderma harzianum TH.0~6g/L Vc treatment had little effect on the inhibitory effect of Trichoderma harzianum TH broth.4. Compared with the control effect of50%carbendazim, the control effect of Trichoderma harzianum TH solution108cfu/mL, diluted2times,5times and10times reached36.05%~63.96%. The treatment of5times dilution behaved the best control efficiency, the control effect was63.96%. Trichoderma harzianum TH induced resistance effects on the seedling roots by inspiring the resistant enzymes such as SOD, POD, CAT, MDA, β-1,3-glucanase and chitinase activity.5. The seedling height, fresh and dry, fresh and dry weight ratio of root shoot ratio, root activity of different dilution of Trichoderma harzianum TH treatments were all increased significantly compared with the control. Different dilutions of Trichoderma harzianum TH treatments were also promoted the absorption of P, K, which will boost the growth of asparagus seedlings.Based on the morphology and molecular methods to identify the cause of Rhizoctonia solani fungi of asparagus, the present study identified and screened the stronger antagonistic effect Trichoderma harzianum TH strains on asparagus Rhizoctonia solani. Meanwhile, we investigated the antagonistic mechanism of Trichoderma harzianum TH, biological characteristics and seedling growth-promoting and control effect, which will have important significance to further reveal the asparagus fungal biological control.