农抗120对苹果树腐烂病菌的作用研究

EFFECT OF AGRICULTURAL ANTIBIOTIC 120 AGAINST APPLE TREE CANKER, VALSA MALI

试验表明:农抗120单用,和农抗120加助剂B,对苹果树腐烂病菌菌丝的生长,均有明显的抑制作用。最小抑菌浓度为250μg/ml和125μg/ml;最小杀菌浓度为2000μg/ml和1000μg/ml。其杀菌作用机理是使病菌体的原生质凝集,小分子物质外流,形成大量空泡,菌体重量剧减。病菌在该浓度中浸泡12小时后便失去致病力。涂药试验:先刮除病斑,再用农抗120 1000μg/ml或农抗120加助剂B500μg/ml涂抹处理,16天后复发率仍为零,不刮除病斑,只用刀划刻病枝再涂药液,4天后病斑又继续扩展。

Results of the laboratory experiments conducted in Beijing showed that the growth of the apple tree canker pathogen, Valsa mali, could be effectively inhibited by Agricultural Antibiotic 120 (AA 120), a product of Streptomyces hygrospinosus var. beijingensis, or AA 120 plus a fluxing agent B (AA 120+B). The minimum inhibiting concentration against V. mali was 250 μg e.i./ml and 125 μg e.i./ml, respectively, the minimum bactericidal concentration was 2,000 μg e.i./ml and 1,000 μg e.i./ml, respectively. The mechanism of inhibiting and killing the pathogen was found to be inducing condensation of the cytoplasm, discharging of the endoplasm material and formation of hollow vesicles in the cells, and consequently causing dramatic weight reduction of the hyphae. Submerging the hyphae of V. mali in AA 120 (2,000 μg e.i./ml) or AA 120+B (1,000 μg e.i./ml) for 12 hr resulted in loss of pathogenicity of the pathogen. In the outdoor experiment on apple trees, the canker spots were scraped off and treated with AA 120 at 1,000 μg e.i./ml or AA 120+B at 500 μg e.i./ml. The resurgence rate of the canker was 0 after 16 days. Treating the canker spots with the same concentration of AA 120 or AA 120+B without scrapping off the canker spots but scarring them resulted in resurgence of the pathogen 4 days after the treatment.