| The Trichoderma spp. exists in soil and grows on the remains of plants and animals, most of them are antagonist for pathogen of many plant disease. Because of their biocontrol abbility to pathogen, Trichoderma spp. are attracting more and more interest. A strain of Trichoderma sp. was isolated by us and identified as Trichoderma pseudokoningii.In this paper, The antagonistic ability of Trichoderma pseudokoningii against several pathogen and its efficacy for control of grey mold were studied, the induced resistance of tomato and cucumber seedlings by its polysaccharides and extract were also studied.In the last we studied the liquid fermentative condition of Trichoderma pseudokoningii. Following conclusions can be made from the study above.Trichoderma pseudokoningii showed antagonistic ability against Botrytis cinerea, Fusarium oxysporum, Fulvia fulva, Alternaria solani, Phytophthora capsici and Colletotrichum capsici in dual culture. The suppressive rates of T.pseudokoningii to the pathogens were 73%, 62% , 86% , 77% , 68%, 91% respectively. In bioassay with stem segments and leaf pieces of tomato T. pseudokoningii reduced incidence and index of the disease grey mold caused by Botrytis cinerea .And in glasshouse experiments with tomatoes the same result was obtained. When the concentrations of T. pseudokoningii up to 10~8cfu/ml the biocontrol effecacy was as good as or even better than that of Thiophanate -methyl.Dry mycelium of Trichoderma pseudokoningii was extracted with water and the extract was used to apply to the roots to induce resistance against fusarium wilt. Results indicated that the extract of all concentrations tested could protect the seedlings against the wilt and the efficacy depends on the concentration. Extract of 4%(g/ml) provided 53.8% protection, but when the concentration up to 6, 8% no further protection was observed. PAL and POD activities and lignin deposition in hypocotyls increased rapidly 6, 30, 30h after treated with 4% extract, respectively.The inoculation tests before and after treatment showed that it took 4days for the seedlings after treatment to acquire resistance to the fusarium wilt. Otherwise, the treated seedlings also showed resistance against grey mould when conadia of Botrytis cinerea were inoculated at stem and leaves 4 days after treatment. As the extracts did not inhibit the growth of mycelia of Botrytis cinerea and Fusarium oxysporum in vitro, it was inferred that the controlling effects on disease of extracts were attributed to induced resistance of plant, and the resistance was systemic and unspecial. We assume that PAL and POD might result in lignification and thus be associated with the defense against the diseases.Two polysaccharides(TPS-l, TPS-2) were isolated from the culture filtrate by decoloration through 3520 adsorption column chromatography, deprotein with Saveag method, ehanol precipitation and SephadexG-75 colum chromatography.The polysaccharides of TPS-1, TPS-2 are 97% > 89% by phenol-sulphuric acid method assay,and the molecular weight are about 4811 Da> 2468Da.After the tomato seedlings were treated with TPS-1 in different concentrations (50-600mg/L) , the effect of TPS-1 on the activities of defense enzymes and the efficacy in controlling grey mold of tomato were researched. The results indicated that the activities of phenylalanine ammonialyase (PAL )> peroxidase (POD)> polyphenoloxidase (PPO ) increased and the disease rate of grey mold of tomato decreased after the treatment with TPS-1. The enzymes activities reached a peak on the 3rd or 4th after the treatment. The enzymes activities rose with the increasing of TPS concentration. When the concentration was 200 mg/L, the highest activities of PAL, POD , PPO increased by 123%,146%, 102% compared with CK. TPS could significantly protect tomato seedlings against grey mold. As the TPS did not inhibit the growth of mycelial of Botrytis cinerea in vitro, it was inferred that the disease controlling effects of TPS were attributed to induced resistance of plant.The liquid fermentative condition of Trichoderma pseudokoningii were studied through single factor and orthogonal design experiments. The optimized fermentation control parameters are as follows: culture medium formula is wheat bran 30g/L,maize powder 30g/L, glucose 7.5g/L,KH2PO4 lg/L. The optimum flask fermentation period is 6d. The fermentation temperature and the initial pH-value of culture medium is 30°C and 5.0-6.0 respectively. The results will provide scientific basis for fast, efficient, and practical industrialization production of Trichoderma pseudokoningii preparation. |
PDF Full Text Request