松梢枯病防治新技术及其机理研究

STUDIES ON NEW CONTROL MEASURES TO PINE DIEBACK AND THEIR MECHANISM

水杨酸和多效唑预处理可以减轻湿地松梢枯病的发生，水杨酸的效果尤佳。病原孢子萌发试验证明，多效唑具有抑菌或杀菌作用，而水杨酸对病原孢子萌发及菌丝生长均无抑制作用。因此认为水杨酸处理后是通过增强湿地松的抗性来抑制梢枯病的发生。经水杨酸和多效唑处理后，嫩梢中超氧化物歧化酶（ＳＯＤ）活性明显上升。ＳＯＤ在湿地松抗梢枯病上可能起积极作用。较高浓度的水杨酸及阿斯匹林引起嫩梢苯丙氨酸解氨酶（ＰＡＬ）活性下降。说明外源水杨酸对松树体内ＰＡＬ活性有反馈抑制作用。试验结果还表明，苗木比小树对水杨酸等化学药剂反应更加敏感。

Slash pine dieback caused by Sphaeropsis sapinea (Fr.) Dyko & Sutton was inhibited by pretreating the pine shoots with both salicylic acid (SA) and paclobutrazol solution. Salicylic acid manifested more effects than paclobutrazol in preventing the disease. The mechanism of action of the two chemicals was different. Paclobutrazol mode of action has shown similar to that of fungicide and it inhibited spore germination and mycelium growth of S. sapinea, whereas no inhibitory effects of SA on the spore germination and mycelium growth were detected in vitro. Therefore, the reduction in disease severity in SA Pretreated shoots was due to SA induced resistance of shoots of slash pine to dieback. Superoxide dismutase (SOD) activity in both salicylic acid and paclobutrazol treated shoots was significantly higher than that in control shoots. There is a positive correlation between SOD activity and resistance to dieback in slash pine. Phenylalanine ammonia lyase (PAL) activity in the shoots treated with higher concentration of SA and Aspirin decreased markedly, which implied that excessive exogenous SA and Aspirin induced feedback inhibition to PAL activity.