一株野生大豆内生真菌YD-25的筛选鉴定及其抗重金属活性研究

为了丰富野生大豆内生真菌资源,探究野生大豆内生真菌的生物学活性。从野生大豆植株内分离筛选出1株内生真菌YD-25,通过形态学和分子生物学相结合的方式鉴定菌株;采用控制单因素变量试验和正交试验确定菌株的最适生长条件;通过对比胞内、胞外产物和对照组培养大豆幼苗的株高测定菌株的促生效果;测定菌株抗重金属铜、铅、镉的能力和重金属胁迫下菌体的抗氧化酶活性变化。结果表明:YD-25菌落初期为白色,后期变为橘黄色,菌丝分支且产孢;经鉴定该菌株为黑附球菌(Epicoccum nigrum)。该菌株生长的最适pH为3.0,优化培养条件为可溶性淀粉4%、酵母浸粉0.5%、KH_2PO_4 0.15%、MgSO_4 0.05%,培养8 d。YD-25菌株的胞外产物对大豆幼苗有较好的促生长作用,第4天和第6天的促生率分别达到了15.4%和18.1%。同时具有良好的耐重金属镉、铅、铜的能力,除受Cd²⁺胁迫的YD-25菌株的SOD活性之外,受其它重金属胁迫的YD-25菌株各项酶活性均随着重金属浓度提高有不同程度的提高。

Screening and Identification of a Wild Soybean Endophytic Fungus YD-25 and Its Anti-heavy Metal Activity

In order to enrich the endophytic fungi resources of wild soybeans and explore the biological activities of endophytic fungi of wild soybeans. An endophytic fungus strain YD-25 was isolated from Glycine soja plants and identified by combining morphology with molecular biology. The optimum growth conditions of the strain were determined by controlling single factor variable experiment and orthogonal experiment. The growth promoting effect of the strain was determined by comparing the plant height of the soybean seedlings in the intracellular, extracellular, and control groups. The ability of the strain to resist heavy metals such as copper, lead and cadmium and the enzyme activity of the cells under heavy metal stress were determined. The results showed that the YD-25 colony was white at the beginning, and later turned into orange, the mycelium branched and sporulated. The strain was identified as Epicoccum nigrum. The optimal pH of the strain was 3.0, and the optimized culture conditions were soluble starch 4%, yeast dip powder 0.5%, KH2PO4 0.15%, MgSO4 0.05%, and cultured for 8 d. The extracellular product of YD-25 strain had a good growth promoting effect on soybean seedlings, and the growth promoting rates on 4 th and 6 th day reached 15.4% and 18.1%, respectively. At the same time, it had good resistance to heavy metal cadmium, lead and copper. Except for the SOD activity of Cd^2+ stressed YD-25 strain, the enzyme activities of YD-25 strains under other heavy metal stresses were increased in different degree with the increase of heavy metal concentration.