Isolation, Evaluation And Application Of Bio-control Of Tirchoderma Asperellum

Trichoderma is one of the most important biocontrol fungi that can control plantdiseases. It has a great development potential function. One biocontrol Trichodermastrain was isolated and screened from Changbai mountain natural reserve in this study.The main issue was about researching the biological characters, exploring the betterfermentation conditions of liquid and solid two-phase fermentation, and developingmaize seed coatings of the Trichoderma strains.The main research results were summarized as follows.Thirty-six Trichoderma strains were isolated and gained by Pour Plate method fromforty-two soil samples collected from Changbai mountain natural reserve in Jilin. Sixantagonistic Trichoderma strains against Sclerotinia sclerotiorum, Colletotrichumglocosporioides, Thanatephorus cucumeris, Cercospora eae, Fusarium oxysporum,Exserohilum turcicum, Fusarium graminearum Schw and Pythium graminicola werescreened by using confrontation culture, cultivating face to face, and cultivating incellophane film methods. One of these strains, T31possessed prominent bioactivityand used in this study. The inhibition rate of T31was ranged from44.5%to77.9%.The higher inhibition on the mycelial growth of Exserohilum turcicum was77.91%.The microscopic observation showed that T31had the significant parasitic effectagainst Magnaporthe grisea.T31was identified by culture characteristics, morphology and molecular biologymethods. T31was identified as Trichoderma asperellum.Several basic bio-characteristics of T31were tested by determining myceliumgrowth and sporulation. PDA was the most favorable medium for the myceliumgrowth and spores production. The optimum temperature was ranged from25℃to30℃. The optimum pH was6.0. Interestingly, continuous light could promote spores production. Zn²⁺and Ca²⁺could promote mycelium growth, but high consistency ofFe2+and Cu2+could inhibite mycelium growth. Mn2+and Mg2+could promote sporesproduction slightly.Trichoderma fermentation was used liquid and solid two-phase methods in thepaper. Using single factor test and orthogonal test for liquid fermentation, theoptimum fermentation medium and condition were optimized. The optimal culturemedium was richead medium. The liquid fermentation condition of T31was thatinitial pH was7.0, liquid volume was20mL in100mL, inoculation volume was0.5%,and C:N was5:1. Solid fermentation was optimized by using Plakett-Burman andRSM methods. The optimal cultivation conditions were: nitrogen source was added0.5%; trace elements was added10%; matrix humidity was95%; inoculation amountwas40%; matrix pH was6.0; fermentation time was for12d, and surfactant wasadded1.5%. The maximum conidium production was1.3×1010/g.Seed coatings assistants were screened by using single factor test. The compoundfilm former was prepared by mixing4.0%PVA solution and4.0%CS solution at theratio of7:3. The optimal assistants concentrations were dispersant0.3%, tackifier2.0%, nutritional agent0.5%, antifreeze agent3.0%, preservative0.3%, defoarmers0.5%. According to assistant concentration to prepare maize seed coatings, theindicators were good. The bio-control effect of maize root rot was44.3%.Maize seed coatings could induce maize to produce system resistance toExserohilum turcicum. Results of RT-PCR showed that PR5and PR10genesexpression increased in maize leaves after Exserohilum turcicum infection. Itindicated that Trichoderma could induce transduce system resistance signal.Trichoderma could inspire resistance to plant disease on the ground.