| Pepper phytophthora blight is a vital fungal disease during production, overuse of chemical pesticide is one of the main reasons for current agricultural environment deterioration in traditional agriculture. At present, the development and application of the biological pesticide comes to unprecedented historical opportunities and technical challenges with expansive development prospect. Several of endophytic fungi have been widely applied in biological control. In this scientific research, some endophytic fungi were isolated from Ixeris chinensis and were tested the antifungal activity. The results were as follow:1 The disinfection on the surface is essential in the isolation of the endophytic fungi, especially the choice of the disinfectant. Some factors of the disinfectant play an important role in the isolation of the endophytic fungi from the tissue of the plant, for example, the concentration, the sterilization ability and the time of the treatment about the disinfectant. Three common solutions: NaCIO, H2O2, HgCl were tested as disinfectant on the surface disinfection of Ixeris chinensis. The tests showed that the oxidation ability of H2O2 was weak while the sterilization ability of HgCl was too strong. Finally NaCIO (3.5%) was chosen as the best disinfectant of Ixeris chinensis, and sterilized for 4 min with roots while 3.5 min with leaves. The temperature of 26℃was chosen as the isolation and culture temperature, the most number of the endophytic fungi could be separated.2 24 strains endophytic fungi were isolated from Ixeris chinensis by tissue surface-sterilized, and including 15 strains from roots and 9 strains from leaves. The character of these endophytic fungi were observed. They were identified as Alternaria (8 strains), Penicillium (5 strains), Cercosporella (4 strains), Fusarium (1 strain), Verticillium (2 strains), Monilia (2 strains), Leptosphaeria (1 strain) and Gibberella (1 strain) by the analysis of their ITS sequences. At the same time, it is found that endophytic fungi which were isolated from vein were more than those from mesophyll during the isolation of endophytic fungi for leaves. Since transfusion tissue is abundant in nutrient substance and has a good property of air permeability, so most of the endophytic fungi will inhabit there. So the quantity of endophytic fungi isolated is:root>vein>mesophyll.3 16 kinds of target pathogenic fungi were subject to different degrees of inhibition when they cultured with 24 strains of antagonistic fungi isolated from Ixeris chinensis tested in the same plate. The results showed that LR3024 and LR3026 displayed the obvious effect of the antifungal activity. The pathogenic fungi (L1084) were inhibited strongly by the two strains antagonistic fungi at the same time and the average of the inhibiting rate were 52.5% and 50%. The active ingredients in the metabolites of the two strains of antagonistic fungi were unstable under UV irradiation and its inhibitory ability was lost. Therefore, it will only to be used as the biocontrol preparation.4 A series of growth studies of the two stains fungi had been took in the condition of different ecological factors. The results showed that PDA medium was the most suitable for the growth of two strains antagonistic fungi. The optimum growth temperature was 24～31℃and the most suitable temperature was 28℃. The two strains could grow better in pH5.0-8.0, and had no significant difference, finally tended to a stable pH value: LR3024 tended to pH6.6, LR3026 tended to pH6.1. The two strains had the maximum utilization of glucose in several different carbon sources.5 Combination of colony morphology, microscopic morphology, fermentation characteristics, ITS sequence analysis, two strains of endophytic fungi were identified ultimately. The results showed that: the LR3024 strain was Gibberella pulicaris and the LR3026 strain was Phoma radicina. |
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