中文摘要：

真菌拮抗功能是自然健康土壤对病原真菌所具有的免疫能力，这种能力与土壤中许多可分泌拮抗物质的细菌有关，而假单胞菌和芽胞杆菌是目前研究最多的具拈抗功能的种群。乙草胺是北方使用量最大的除草剂．目前它的施用对土壤真菌拮抗能力的影响还未见报道。本文通过室内模拟培养，考察不同浓度乙草胺（0、50、150、250mg·kg^-1土）对土壤真菌拮抗能力的影响，并运用PCR—DGGE（变性梯度凝胶电泳）方法研究真菌拮抗功能逐渐下降的土壤样品中假单胞菌和芽胞杆菌群落结构变化情况。结果表明，在实验室微宇宙条件下，乙草胺的施用会降低土壤真菌拮抗能力。在处理第12d时可以得到土壤真菌拮抗功能差异显著的土壤样品。土壤芽胞杆菌多样性随乙草胺浓度的升高而下降，而假单胞菌多样性变化不大。乙草胺胁迫下芽胞杆菌和假单胞菌群落结构都发生明显改变，尤其是芽胞杆菌（处理土壤样品与对照的群落结构相似性为0．60），且施加浓度越高，群落结构组成偏离自然土壤越远。真菌拮抗能力的降低与假单胞菌和芽胞杆菌多样性和结构的改变相关。

英文摘要：

Fungistasis is one of soil important functions which have shown to be closely correlated with soil bacterial community especially with Bacillus and Pseudomonas genus. Any factors which have effects on soil bacterial community can influence the fungistasis including a- grochemicals such as acetochlor which was widely applied in north China. The effects of different concentrations ofacetochlor （0, 50, 150 and 250 mg.kg^-1） on soil fungistasis was investigated in laboratory microcosm soil, and the characteristics of Pseudomonas and Bacillus genus community structure in treated soil was studied by Bacillus and Pseudomonas specific PCR-DGGE （polymerase chain reaction coupled with denatured gradient gel electrophoresis）. The results showed that the soil fungistasis declined with the application concentration increasing of acetochlor at the 12th day. At the same time, the diversity of Bacillus and Pseudomonas in soil treated with acetochlor was lower than that in the control. The diversity index of Bacillus decreased from 3.05 to 1.98 with acetochlor concentration increasing （0 to 150 mg.kg^-1）, but it was 2.53 at 250 mg.kg^-1 ofacetochlor. The community structure of BaciUus and Pseudomonas, especially Bacillus, were significantly different from that in the control soil, and the higher concentration of acetochlor applied, the more degenerated of soil fungistasis was as well as the further bacterial community structure deviated from the control soil.