丙硫菌唑对水稻纹枯病菌的生物活性研究

丙硫菌唑是目前广泛应用的三唑类广谱杀菌剂。为了明确其对水稻纹枯病菌的生物活性，采用生物测定的方法研究了丙硫菌唑对水稻纹枯病菌的抑菌活性，应用生理生化和分子生物学方法研究了丙硫菌唑对水稻纹枯病菌的可溶性蛋白合成、麦角甾醇合成、 DNA 合成、菌丝脂质过氧化程度、菌丝细胞膜通透性以及水稻防御酶活性的影响。通过田间药效试验研究了其防治纹枯病效果及对水稻的安全性。结果表明，丙硫菌唑对94株水稻纹枯病菌有较高的抑菌活性，平均EC₅₀值为（1.062 9 ± 0.795 9）mg·L^-1。没有出现敏感性下降的抗药性群体，可以釆用菌株的平均EC₅₀值作为水稻纹枯病菌对丙硫菌唑的敏感性基线。丙硫菌唑导致病菌麦角甾醇含量降低，菌丝细胞渗透压、菌丝脂质过氧化程度升高，DNA含量和可溶性蛋白含量随降低。丙硫菌唑使POD、CAT、SOD和PAL 4个植物基础防御酶活性升高，具有一定诱导抗病性。田间试验结果显示4.8×10⁵ mg·L^-1丙硫菌唑悬浮剂，每亩施用剂量为25、30和35 mL时，对水稻纹枯病的防治效果分别达90.40%、96.29%和98.17%，与对照试剂噻呋酰胺的防效相当，且对水稻生长安全。

Study on the bioactivity of prothionazole to Rhizoctonia solani caused by rice sheath blight

Prothioneazole is a broad-spectrum triazole fungicide at present. In order to clear out the bioactivity of prothionazole to Rhizotonia solani caused by rice sheath blight, the mechanism of action of prothioneazole was preliminarily confirmed by determining the contents of DNA, MDA, ergosterol and protein in the hyphae of R. solani, and the changes of defense enzyme activities in rice, the osmotic pressure of mycelial cells and mycelial lipid peroxidation were studied with the method of physiology, biochemistry and molecular biology. The control effects of prothionazole on rice sheath blight were studied by a field experiment and bioassay in vitro. The results showed that prothionazole had high antifungi activity against 94 strains of rice sheath blight, and the average EC₅₀ value (1.062 9 ± 0.795 9) mg·L^-1 of these strains could be used as the baseline of the sensitivity of rice sheath blight fungi to prothioxazole in this area. The changes in DNA, soluble protein and ergosterol contents in the hyphae of R. solani treated with different concentrations of prothioconazole showed that prothioconazole would lead to the reduction of sterols content, the increase of the osmotic pressure of mycelial cells and degree of the mycelial lipid peroxidation, and the decrease of DNA and soluble protein contents. The activities of POD, CAT, SOD and PAL showed an increasing trend under the action of a series of insecticides, and they had certain inductive disease resistance. The results of field efficacy experiment showed that prothionazole suspension at the dosage of 25, 30 and 35 mL per mu in the concentration of 4.8×10⁵ mg·L^-1 had good control effect on rice sheath blight, reaching 90.40%, 96.29% and 98.17%, respectively, and the control effects were similar to those of the control agent, thiofuramide. The safety evaluation of prothionazole on rice showed that different concentrations of prothionazole had no significant effect on the normal rice growth.