烟草野火病重要流行环节的初步定量研究Ⅰ病斑内细菌数量的自然消长及经雨露浸出的动态变化

Preliminary Quantitative Studies on the Key Epidemic Stages of Tobacco Wildfire Disease Ⅰ. Number Variation of Bacteria in the Lesion and Soaked Out to the Plant Surface by Rain and Dew

对烟草野火病流行过程中重要环节———野火病菌在烟草病斑中数量消长及野火病菌经雨、结露浸出到烟草植株体表的数量动态进行了初步定量研究。结果表明 :野火病日龄与病斑内菌体数量的关系为一单峰曲线 ,在病斑显现后的 3～ 4d里病斑内的细菌数量增长很快 ,约在第 5d达到高峰 ,以后逐渐平稳下降 ,在病斑日龄达到 15d时其细菌数量仍在一个较高水平上 ;病斑内的细菌可经降雨浸出到烟草体表 ,降雨时间与烟草体表流淌的雨水中的野火病菌数量关系也为一单峰曲线 ,开始时雨水中的细菌数量迅速上升 ,约经 2～ 3h达到高峰 ,继而又迅速下降 ,约在 4～ 8h以后雨水中的细菌数量达到一较低水平 ,但此水平可一直维持到48h ;病斑内的细菌亦可经露水浸出到烟草体表 ,露水中的细菌数量与露时的关系大体为一倒“J”型曲线 ,即在结露时间达 7～ 10h以后露水中的细菌数量不再有明显变动 ,可能是浸出的细菌与病斑内细菌数量之间达到了相对的动态平衡。

The present paper is based on the key stages in epidemic process of tobacco wildfire disease caused by the bacteria Pseudomonas syringae pv tabaci these bacteria proliferate in the tobacco plants and have been soaked out to the plant surface by rain and dew were first quantitatively studied. Results showed that: the relationship between the day age of the lesion and the number of bacteria in the lesion is an unimodal curve with the regression equation The number of bacteria increased quickly after the lesion appearing 3～4 days with the peak of bacteria appearing in 5 days, then it gods down steady with the number of bacteria maintaining on the high level in 5 day Bacteria in lesion are soaked out to the plant surface by rain, the number of bacteria goes up quickly according to the rainfall duration extending. The peak of bacteria appears kin 2～3 hours then it descends fast and number of bacteria stands on the low level in 4～10 hours However the low level unfluctuate for 48 hours Bacteria in lesion are also soaked out to the plant surface by dew The relationship between the dew age and the soaking number of bacteria in dew is a back “J" shape equation which the number of bacteria is steady before dewing 7～ 10 hours It is possible that the dewed bacteria has a variable balance with the number of bacteria in lesion