井冈霉素A对水稻纹枯病菌的毒力和作用机理研究

根据水稻纹枯病菌 Rhizoctonia solani AG- 1IA在含系列浓度井冈霉素 A马铃薯葡萄糖琼脂培养基 (PDA)上的菌丝生长速率 ,计算出药剂的毒力回归方程为:Y=3.2 30 9+0 .872 0 X,r=0 .9910 ,药剂的 EC50 =10 6 .9μg/ m L,EC75=6 34.5 μg/ m L。在含 5 0 0 μg/ m L井冈霉素 A的 PDA上水稻纹枯病菌的菌丝生长抑制率为 74 .1% ,而田间水稻植株上人工接菌的药效试验结果表明 ,5 0 μg/ m L药液喷洒后 7d和 14 d的防效即可分别达到 77.4 %和 76 .7% ,即药剂在 PDA平板上的理论抑制作用仅是田间活体植株上对病菌实际作用效果的 1/ 10。比较室内毒力和田间药效试验的结果可以看出 ,井冈霉素 A具有对病原菌和寄主植物双重作用的特性。研究首次发现 ,在室内培养基上不能有效抑制病菌生长的 1μg/ m L的井冈霉素 A可以在水稻植株未喷药部位产生防御水稻纹枯病的作用 ,且能够持续诱导植物防御反应相关酶——过氧化物酶 (PO)和苯丙氨酸解氨酶 (PAL)的活性增高,表明该药剂可以激发水稻抗性防卫反应的表达。

Studies on the Toxicity and Mechanism of Jinggangmycin A on Rhizoctonia solani AG-1 IA[ in vitro (on PDA) and in vivo (in rice plant)]

No significant difference was found on hyphal growth rate of Rhizoctonia solani IA on PDA plates containing 0, 0.5, and 1.0 μg/mL Jinggangmycin A(J A). The virulent regression equation of the antibiotic is Y =3.2309+0.8720 X , r =0.9910,and EC 50 =106.9 μg/mL,EC 75 =634.5 μg/mL. Antibiosis experiments in vitro showed 74.1% inhibitory effect on PDA plate containing 50 μg/mL J A; under the conditions in vivo , a similar control effect (77.4% and 76.7%) was obtained by using only 50 μg/mL J A after 7 d and 14 d with J A treatment. By comparing the virulence of J A to R . solani AG 1 IA on cultural medium ( in vitro ) and on field rice plant ( in vivo ), we found that virulence of J A was 10 times in vivo more than in vitro . In the rice upper leaves treated with 1 μg/mL J A, activities of peroxidase (PO) and phenylalanine ammonia lyase (PAL) in the low sheath, which were involved in the biosynthesis of antimicrobial secondary metabolites, were also stimulated and the high enzyme activities were kept for more than two weeks under the greenhouse conditions. These results suggested first that not only there is the direct toxicity of J A against the pathogen but also defense reactions were triggered in rice plant upon the J A treatment.