| Cucumber Fusarium wilt is a kind of soil borne fungal disease which is very easy to occur and often serious harm to the production of cucumber. In this study, different local soil samples were collected, isolated Trichoderma and green house pot experiment screening high efficiency strains both can inhibit Fusarium wilt and stimulate the growth of cucumber; The text has detected four aspects to explore the influencing factors of Trichoderma strains against Fusarium wilt, such as inoculation method, soil temperature, humidity, bacteria content; The action model of 4 Trichoderma strains against F. oxysporium have been compared,exploded their competition, biological activity of the metabolites, mycoparasitism and bate on the pathogenic factors of F. oxysporium; It was also studied the effect of different Trichoderma on soil microbial communities and soil enzyme activities. The main results were as follows:Collected 210 soil samples, isolated 68 Trichoderma strains, through confrontation culture with F. oxysporium screened 24 active Trichoderma strains, then screened 4 inhibition rate more than 80% ones to be expolded. Pot experiment showed that the control effects of 4 Trichoderma strains on Fusarium wilt were 66.57%,59.15%,54.24% and 45.80% respectively. They aslo had a certain role in promoting the growth of cucumber, increasing the fresh weight of above ground and under ground parts significantly.4 Trichoderma strains identified by morphologic observation were Trichoderma harzianum (abbreviated as TH), Trichoderma viride (abbreviated as TV), Trichoderma longibrachiatum (abbreviated asTL) and Trichoderma koningii (abbreviated as TK).Inoculation methods effected the control efficiencies of different Trichoderma strains against Fusarium wilt, mixing soil with Trichoderma was applicable to TL strain and TV strain, control efficiencies were ideal, rates reached 75.74% and 70.76% respectively, and promoted the growth of stem, leaf and root significantly, especially for root growth. Dipping root with Trichoderma was applicable to TH strain, the control rate was outstanding, reached 70.85%, spray method only applied to TV strain. The control efficiencies of Trichoderma strains against Fusarium wilt were inluenced by temperature, at 25℃, the control efficiencies of 4 strains were more than 50%, TL strain was the highest with value reached 67.13%, and 4 strains of Trichoderma strains on cucumber growth promoting were strongest; the effects of soil humidity on 4 Trichoderma strains against the Fusarium wilt were weak, with humidity changed had unobvious differences. The amount of Fusarium wilt was closely related to the control efficiencies of Trichoderma strains. When the content of Fusarium wilt increased from 2% to 8%, the control efficiencies of Trichoderma strains were reduced significantly.There were obvious competitive effects of different Trichoderma strains against F. oxysporium, Trichoderma strains could grown on and covered the F. oxysporium gradually. TH strains had the strongest competitive effect, inhibition rate was 67.70%; the non volatile metabolites of Trichoderma strains inhibited F. oxysporium growth of mycelia and the germination of spores, TH and TL were the best. The inhibitory effect of the volatile compounds produced by TH strain was stronger, inhibition rate was 55.46%. Trichoderma strains were able to mycoparasite on the F. oxysporium, causing hyphae of the pathogen broken, cell contents leaked. TL strains and TH strains were significant. The inhibitory effects of Trichoderma strains against the pectinase and cellulase activity of F. oxysporium were significantly, TH strain was the strongest, causing pectinase activity of F. oxysporium felled from 88.9 U/ml to 30.38 U/ml, cellulase activity fellde from 105.31U/mL to 38.22 U/mL.4 strains inhibited the biological activity of the toxin of F. oxysporium significantly, and TH was highest, decreasing the inhibition of toxin on root from 80.89% to 18.47%. The chitinase activity and beta-1,3-glucanase activity of two Trichoderma strains in different ferment time were obvious, chitinase activity of TH strain was higher,168h reached 0.161U/mL; beta-1,3-glucanase activity of TL strain was higher,96h reached 0.553U/mLAdded Trichoderma into soil can inhibit fungi coloning on root and soil of cucumber, comparing with CK the highest was reduced by 67.05%. Different Trichoderma strains could significantly inhibit the number of fungi in root, rhizosphere soil and bulk soil. Compared with the contrast, the number of fungi was reduced, highest one decreased 67.25%. The number of fungi in bulk soil was lower than contrast, TK strain with less effect decreased 23.31%. With Trichoderma added, the amount of fungi on root decreased continually, after adding TH and TL strains, the number of fungi decreased rapidly. As time going by, with Trichoderma strains applied, the number of bacteria in root, rhizosphere soil and bulk soil was rised continually. In the whole growth period of cucumber, the number of bacteria in the rhizosphere soil changed with time showed rising trend, but lower than contrast. The number of bacteria in bulk soil increased from 1.54×109CFU/g dry soil to 2.29×109CFU/g dry soil after TV strain was applied, lower than that of contrast by 9.94%-31.85%, the number of bacteria in root was lower than 33.33% at most. The fluctuation of actinomycetes in root, rhizosphere soil and bulk soil was not visible.Applied different Trichoderma strains, the activity of urease in rhizosphere soil of cucumber had differences. The activity of urease in rhizosphere soil of contrast increased 70.79% compared with 7 days before, then decreased gradually. The activity of urease in rhizosphere soil of 4 Trichoderma strains was lower than that of contrast, compared with initial transplanted. The activity of urease in rhizosphere soil of TV strain was highest, up to 54.21%. The activity of invertase in rhizosphere soil improved after 4 Trichoderma strains were applied, the highest was 20.43%. The activity of catalase in the rhizosphere soil increased evidently after 4 Trichoderma strains were applied, it was higher than that of the contrast by 47.83% at most. |
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