Effect Of Microelement On Genetic Stability And Biocontrol Efficency Of Trichoderma T23

Trichoderma is currently the most common application of biocontrol agents, but its biocontrol effect is not persistent and stable. The problems that to reduce influence of chemical pesticides, fertilizers must be resolved. In order to screen synergistic factor for Trichoderma biological pesticide production and its commercialization, the effect of microelements on the physiology and biochemistry, genetic variation and biocontrol effect of Trichoderma T23 were studied systemically.The utilization percents of Trichoderma T23 to Mg²⁺, Zn²⁺, Cu²⁺, Ca²⁺, Mn²⁺, Fe²⁺ and Mo⁶⁺were significantly different. Trichoderma T23 can largely absorpt Mg²⁺, Zn²⁺, Cu²⁺, Ca²⁺, Mn²⁺ and Fe²⁺, but can not use Mo⁶⁺ in PD and compound culture media.Effect of 7 microelements and their compounds on the growth and three enzymes (β-1,3-glucanase, chitinase and cellulose) of Trichoderma T23 were studied in detail. The results suggested that Mn²⁺, Ca²⁺, Mg²⁺, Cu²⁺, Zn²⁺ and Fe²⁺ could promote mycelium growth of Trichoderma T23. Ca²⁺, Mn²⁺, Zn²⁺, Fe²⁺, Cu²⁺; And Mg²⁺ could promote sporulation of Trichoderma T23, but Mo⁶⁺ inhibited it. Mn²⁺, Ca²⁺, Cu²⁺ and special concentration Zn²⁺,Fe²⁺ and Mo⁶⁺ could activate the activity ofβ-1,3-ghicanase of Trichoderma T23, but Mg²⁺ inhibited it. Low concentration Mg²⁺ and high concentration Cu²⁺ could activate the activity of cellulose. Zn²⁺ could activate the activity of chitinase, but Mn²⁺ and Ca²⁺ inhibited it. 7-microelementSeven microelements could obviously affect on physiological and biochemical indicators and genetic variation of Trichoderma T23 by subculturing. Mg²⁺, Zn²⁺ and high concentration Ca²⁺ and Cu²⁺ inhibited sporulation of Trichoderma T23; Mn²⁺ and Mo⁶⁺ could promote sporulation of Trichoderma T23. Low concentration Ca²⁺, Fe²⁺ and Mn ²⁺ could increase significantly wet weight of mycelium in long times, Mo⁶⁺ and Cu²⁺ inhibited it. The effect of Ca²⁺ onβ-1,3-glucanase was not obvious; Cu²⁺, Fe²⁺, Mg²⁺, Zn²⁺, Mn²⁺and Mo⁶⁺ could activate the activity ofβ-1,3-glucanase in varying degrees; Ca²⁺ and special concentration of Mn²⁺, Fe²⁺å’ŒP Mg²⁺ activated the activity ofcellulose.Among 70 random primers tested, 10 primers were able to generate distinct DNA fragments, in which, 75.9% of the 141 RAPD fragments were polymorphic. The sizes of the DNA fragments were between 500bp and 3000bp. 84.6% of primer S₆₅ of its fragments was polymorphic, It indicated that there were high genetic differentiation among tested strains; 57.1% of primer S₁₂₁₊S₁₂₄ of its fragments was polymorphic. It showed that all strains had genetic stability. Furthermore, based on NTSYSpc2.1 cluster analysis that was conducted using 32 strains.Under clustering results, 32 strains were divided into five groups in 0.77 of genetic distance. The times which different microelements induce Trichoderma T23 were different. The third-time stains induced by ZnSO₄, MgSO₄, CuSO₄, the fifth-time stains induced by MnSO₄, CaNO₃, and the seventh-time stains induced by (NH₄)₆Mo₇O₂₄ 22222 4H₂O, FeSO₄ were genetically diverse, the variation was produced when initialize stain was induced by for microelements for a long period time(seventh time).Microelements could significantly affect on biocontrol effect of Trichoderma T23. All strains were produced not inhibiting zones by dual test. The significant antagonistic action was found in antagonism of Ca(NO₃) disposal ,disposal 4 and disposal 8 against Fusarium oxysporum since former grew faster than latter. The biocontrol effect of disposal 4 to melon wilt was 86.05%. The activities of PAL, POD, PPO andβ-1,3-glucanase increased dramatically in the treatment of Trichoderma strainT23 induced by compound microelement,particularly after challenging inoculating with Fusarium, which thereby enhancing induced resistance of melon. Therefore the treatments with Trichoderma strain T23 induced by microelement compounds generally were more effective to induce resistance than any single microelement treatment in terms of the change of defense enzyme activities in their comparisons in biocontrol effect.The dynamic change of the population of Trichoderma T23 induced by microelement and their compounds in the colonized rhizosphere soil was found to be associated with the host growth period. MnSO₄, CuSO₄ and 7 microelement compounds promote colonization. The roles of FeSO₄, (NH₄)₆Mo₇O₂₄·4H₂O and Ca(NO₃)₂ are not obvious; ZnSO₄ and MgSO₄ inhibit colonization. Microelement compounds play promote roles in colonization, and the effects were better than single microelement.