樟疫霉在自然发病土壤中的季节变化

SEASONAL POPULATION FLUCTUATION OF Phytophthora cinnamomi IN NATURALLY INFESTED SOILS

应用诱饵分离技术对上海地区两个自然发病土壤中樟疫霉（Phytophthoracinnamomi）的密度进行了为期25个月的测定．结果表明．樟疫霉在两个不同寄主土壤中呈季节性规律变化，夏、秋季最高，其带菌土样率和回收菌株数分别高达44％和83株；冬季最低，在土壤中检测不到．春季开始回升．该菌密度与某些生态因子的回归分析结果表明．它主要与土壤温度呈显著相关（P＜0.05）．最适土温25℃左右．小于10℃时检测不到。该菌密度在土壤中的季节变化与寄生植物病害的发生存在着内在联系．该菌密度越高，寄主病害越重。此外．本文还就以诱饵法作为检测分析土壤中土传病原菌生态变化的一种有效途径作了探讨。

The seasonal population fluctuation of Phytophthora cinnamomi in naturally infected soils of Shanghai area was determined by bait trapping technique during 25 months.The results showed that the pathogen population in two different soils fluctuated regularly,it reached the maximum in summer and autumn when the rate of soil samples with detected P.cinnamomi and number of isolates recovered from soils were 44 % and 83, respectivcly, and reached the minimum in winter when no pathogen was detected. In spring, the populations started to grow up. The regression analysis demonstrated that there was a significant relationship (P＜0.05 )between pathogen population and soil temperature ; the optimum soil temperature was about 25℃,and when the temperature declined to below 10℃no pathogen was detected. Also, it was found that seasonal pupulation fluctuation of this pathogen was connected internally with the disease incidence of host plants- The more abundant pathogen population was counted, the higher trapping disease incidence of host plants was found.Additionally,the fact that the bait trapping method could be used as a good way for detecting the population fluctuation of some soil-borne pathogens in soils was also discussed in this paper.