罗汉果青枯病菌生物学特性初步研究

对罗汉果青枯病菌的生长温度、pH、碳氮营养等生物学特性进行了测定。试验结果表明，罗汉果青枯病菌Lu L3菌株能在pH5.0～8.5和12～40 ℃的范围内生长，最适生长的pH范围为6.0～7.5，最适生长的温度范围为28～35 ℃。测试的6株病原菌株，其生长均能利用蔗糖、葡萄糖、乳糖、山梨醇、麦芽糖、甜醇和甘露醇作为碳源，利用蛋白胨、牛肉浸膏、酵母浸膏、硝酸铵、硝酸钾和脲作为氮源。气温、土壤种类和罗汉果的生育期对病原菌入侵寄主有影响。在20～35 ℃范围内，气温升高利于病原菌的入侵，病害发生严重；病原菌在黏土中入侵寄主容易，在壤土中入侵寄主困难；罗汉果植株越小越利于病原菌的入侵，花蕾期后，未观察到植株被病原菌侵染。接种病原菌Lu L3菌株后，12 h时植株的根表分离到接种的病原菌株；24 h时根内分离到接种的病原菌株；36 h时茎内分离到接种的病原菌株。

A preliminary study on the biological characteristics of the pathogen of the bacterial wilt of Siraitia grosvenorii

The temperature, pH, carbon and nitrogen source for the growth of the strains isolated from the bacterial wilt of Siraitia grosvenorii were tested. The results showed that the strain Lu L3 could grow at 12-40 ℃ and pH 5.0-8.5, but the optimal temperature and pH ranges were 28-35 ℃and 6.0-7.5, respectively. Six strains could use glucose hydrate, lactose sorbitose, D fructose, maltose, dulcitol and mannitol as carbon source and pancreas peptone, beef extract, yeast extract, potassium chloride, ureae and potassium nitrate as nitrogen source for their growth. Temperature, soil type and different growth period of S. grosvenorii could affect the invasion of the strain Lu L3. Under 20-35 ℃, the higher the temperature, the more serious the bacterial wilt of S. grosvenorii caused by the strain Lu L3. In sabulous soil, the strain Lu L3 invaded the host successfully and caused serious bacterial wilt. But the pathogens could not invade the host easily in sabulous loam soils. The pathogens invaded the host easily at seedling stage of S. grosvenorii. Infected plants by the pathogens were not seen during the period of blossoms. Strain Lu L3 could colonize on the root surface, inside the roots and stems of S. grosvenorii at 12, 24 hours and 36 hours after inoculation with the strain.