| Endophytic fungi are fungi that inhabited in the tissues of health plants and having no pathological stress or obvious infection to its hosts. There demonstrates positive symbiosis between the endophytic fungi and the hosts. The secondary metabolites of the endophytic fungi could facilitate the growth of the host plants directly or indirectly and improve the hosts’ resistance to biological or non-biological stresses. However, much renewed attention is now being paid to the endophytic fungi which are showing an ability of inhibiting to the pathogenic fungi and playing a part in the biological control. In this paper, we studied the endophytic fungi from Houttuynia cordataThunb, primarily investigated the distribution of the endophytic fungi in different organs in these plants and screened its antifungal activity. The target endophyte which have stronger antifungal activity has been identified by using morphology and molecular methods, and subjected its cultivate conditons. The main results are as follows:1. In total,127srains of endophytic fungi were isolated from the leaves, aerial stems and subterraneous stems of the experimental material WO1-100, WO1-94and WO1-86in spring (March,2010) and antumn (Octomber,2009) by using tissue isolation.2. From the distribution, the number of endophytic fungi were varied in different parts, but the distribution of trends were consistent:leaves> aerial stems> subterraneous stems. In these endophytic fungi,43strains were from the material W01-100, which occupied33.86%.50strains were from the material W01-86, with the precentage of39.37%.34strains were from the material W01-94, which occupied26.77%. The strains from the materials collected in spring occupied34.65%. The strains from the materials collected in autumn had the proportion of34.65%.3. Antifungal activity of127strains endophytic fungi was screened with5kinds of pathogenic fungi(Fusarium graminearum Sehw. Alternaria solani sorauer, Phytophthora capsici, Fusarium oxysporum f.sp.Niveum. Sclerotinia sclerotiorum(Lib.)de bary) as tested targets. All of these127strains endophytic fungi were have different inhibitions to those pathogenic fungi, and screened out26stains which could inhibit at least3kinds of pathogenic fungi with the inhibition ratio above40%. These26strains were cultivated in liquid medium respectively. The cultural liquid were extracted with acetic ether and concentrated, and then dissolved in acetone. The fungistasis of the extracts were determined by using those5kinds of pathogenic fungi as tested fungi. We finally chose out12,28and A5strains as our target strains according to results of activity screening results.4. Combined morphology with molecular identification of previous3target strains, it was identified that the strain12was Pestalotiopsis microspora belonged to Pestalotiopsis sp. The strain28was Chaetomium globosum of Chaetomium sp. The strain A5was Fusarium nematophilum in Fusarium sp.5. Using Fusarium oxysporum f.sp.Niveum as the test pathogenic fungi, we researched the fermentation conditions and the antifungal essence’s heat stability of the strain28. The results showed that antifungal essence of the strain28had a good stability when treated bellow the temperature of80℃. The strain28’s mycelium grew fast in the medium A and its antifungal ability was best when it was cultivated in the martin’s medium. To strain28, the initial pH of the liquid medium about6.9was favorable for mycelial growth and the initial pH about7.5was fit for accumulating the antifungal essence. The mycelial growth and antifungal ability was best when cultivated4days, but the antifungal ability fall off when cultivated to8days. The extracts of the strain28could inhibit other10kinds of pathogenic fungi, especially to the Exserohilum turcium (Pass.)Leonard et Suggs, Botrytis cinersa Persoon and Botrytis cinerea Pers.Ex Fr that the inhibition ratio was amount to100%. This result showed that the strain28had a broad spectrum in antifungal ability. We could study it intensively and develop its utilitized value. |
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