中文摘要：

链霉菌属是绝大多数已知抗生素和一些重要活性物质的产生菌,它对高等植物是否具有化感作用尚缺乏研究.从土壤中分离获得7个放线菌菌株,研究其对植物幼苗生长的抑制作用.结果表明：链霉菌6803菌株在固体和液体发酵培养时均强烈抑制油菜根和稗草根的生长,其液体发酵液的5倍稀释液对油菜和稗草苗生长的抑制分别达到60.7%和61.3%.常规形态与生理生化试验表明,该菌株属于链霉菌属金色类群;16SrRNA基因序列分析表明,该菌株为沙场链霉菌,基因序列相似性达到99.28%.此菌株经过80～100s紫外线照射筛选出的正突变菌株UV8024和UV100-2的10倍稀释发酵液对油菜幼苗生长的抑制作用比原始菌株分别提高了37.5%和38.1%,经过1%硫酸二乙酯诱变50min筛选出的正突变菌株D507的10倍稀释发酵液对油菜幼苗生长的抑制作用比原始菌株提高了29.8%.链霉菌6803菌株对高等植物具有化感作用,并可通过诱变育种提高其化感潜力.

英文摘要：

Streptomyces can produce an overwhelming majority of known antibiotics and several biologically active compounds,but whether Streptomyces can display allelopathic effects on higher plants is largely unknown.In this study,seven actinomyces strains isolated from soils showed inhibitory effect on plant seedlings growth,among which,Streptomyces sp.6803 had strong capability in inhibiting the seedlings growth of Brassica campestris and Echinochloa crusgalli in both solid and liquid cultures.The dilute solution （×5） of fermented broth inhibited the seedlings growth of B.campestris and E.crusgalli by 60.7% and 61.3%,respectively.Based on the morphological and physiological-biochemical characteristics and 16S rRNA sequencing,Streptomyces sp.6803 was identified as Streptomyces arenae,with the 16S rRNA sequence identity being 99.28%.Ultraviolet radiation and diethyl sulfate （DES） were used to produce mutants to enhance the allelopathic potential of this strain.After 80 and 100 seconds of ultraviolet radiation,the dilute solution （×10） of fermented broth of obtained mutants UV8024 and UV100-2 showed 37.5% and 38.1% higher inhibition effect on the root growth of B.campestris seedlings,respectively,compared with the control.The mutant D507 obtained through 1% DES treatment for 50 min showed 29.8% higher inhibition effect on the root growth of B.campestris seedlings.This study showed that Streptomyces sp.6803 had allelopathic effect on higher plants,and it was possible to enhance the allelopathic potential of the strain via mutation breeding.