三唑酮、三唑醇种子处理对小麦根围丝核菌群体数量的影响

The Effect of Seed Treatment with Triadimefon and triadimenol on Rhizoctonia spp. in Wheat Rhizosphere

根围土壤稀释培养的结果表明,以R/S为指标,0.03ai.％三唑酮、三唑醇种子处理后,根围引起小麦纹枯病的丝核菌群体明显下降。未进行种子处理的小麦根围丝核菌群体(R/S)出现二次升降,形成越冬期峰区和拔节期峰区。三唑酮、三唑醇拌种后,根围土壤中丝核菌群体明显被控制。尤其是在越冬期,根围丝核苗群体不能形成峰区;在拔节期,报围丝核菌群体也能控制40—60％。可以认为,三唑类杀菌剂种子处理对根围小麦纹枯病病原丝核菌群体的控制是其主要控病机制之一。

In order to clear up the mechanism of seed treatment with triazoles in controlling wheat sharp eyespot,the population of Rhizoctonia spp. (the pathogen) in the rhizosphere was studied by the soil-dilution and plating method with the modified Li's selective medium. The colony forming unit (cfu) per gram rhizosphere soil (R) and the ratio of population in rhizosphere to population in soil (R/S) were used to evaluate the effect of treatment. The result demonstrated that R/S reflected the effect of fungicides on the dynamics of Rhizoclonia spp. in the rhizosphere,because R/S can eliminate the influence of the original difference in Rhizoctonia population between sampling sites or sampling times (Table 1). During the growth period of the untreated wheat, Rhizoctonia spp. population in the rhizosphere rose and fell twice, forming 2 peaks, the winter peak and the elongation stage peak (Fig. l),in accordance with the incidence of wheat sharp eyespot observed by the authors in 1989. Triazole seed treatment inhibited the growth of the pathogen in the rhizosphere and controlled the population,especially in winter. The winter peak of the pathogen population was suppressed by 63. 3-67. 2%;the elongation peroid peak was reduced by 40. 87- 60. 61%. The suppression of Rhizoctonia spp. population in the rhizosphere is one of the mechanisms of controlling wheat sharp eyespot by seed treatment with triazoles.