烟草霜霉病检疫病理学特性的研究

PATHOLOGICAL CHARACTERISTICS OF TOBACCO BLUE MOLD FOR PLANT QUARANTINE

烟草霜霉病孢囊非凡的繁殖能力和独特的对世界不同地理气候区域的高度适应性，是病害广泛传播和迅速发展的关键因素。虽然关于烟草霜霉病的病原学、生物学和病理学方面已经作了广泛的研究，但涉及病原孢囊在检疫病理学方面的某些特性，则迄今工作甚少。本文在系列研究的基础上证明：（１）孢囊萌发活性与接种后的产孢日数密切相关。在可见产孢的第１～２ｄ内，１ｈ后孢囊即开始萌发，４ｈ后萌发率高达８３％以上，而在产孢第４～６ｄ后萌发率降为３６．１％及２９．６％。（２）孢囊的最低萌发温度为２℃，最适温度为１４～２１℃，最高温度为３５℃。（３）高温对孢囊活性的影响，因受热时间而异，短时间３０℃或３５℃高温后又转入适温对孢囊萌发有抑制作用，但仍有侵染活性。当３０℃超过１２ｈ或３５℃超过８ｈ，则孢囊侵染活性丧失。（４）当叶面饱和湿度期达４ｈ时，可以发生侵染，叶面饱和湿度期越长侵染率越高。（５）在适宜温湿条件下，每悬滴含５～６个孢囊，侵染率可达３０％以上，如含单个孢囊，侵染率可达１２％。运用以上数据将有利于提高烟草霜霉病风险分析的有效性。

The extreme propagation capability and high adaptability power to the world agro climatic regions of tobacco blue mold sporangia play an important role on the dispersal and development of the disease.Although many contributions on the pathogen taxonomy,biology,pathology have reported, so far only limited works on the pathological charctristics for plant quarantine.Based upon a series of experiments,the authors indicated that:(1)The germinability of the sporangia is closely related with the age of sporulation.For 1～2 days sporangia after visible sporulation,the germination percentage rise to 83% after 4 hr,incubation,while those of 4￣6 days after sporulation,its germination percentage down to 36.1% and 29.6%.(2)The lowest temperature for sporangia germination is 2℃.Optimum range for germination is 14￣21℃,and 35℃ is the highest.(3)The survivability of sporangia in high temperature depends on the length of exposure of sporangia under high temp. such as under 30℃ for 12 hr.or 35℃ for 8 hr.than transfer to 15￣20℃ for further incubation,the effect is mainly inhibition.If it is exposed under 30℃ over 12 hr.or 35℃ over 8 hrs.the sporangia loss its infectivity.(4)TBM infection could be achieved when the relative humidity on a leaf surface reaches sub saturated level for 4 hr.Infection increased positively with lengthening of the described relative humidity duration. (5)Under normal condition,each drop of a sporanguim containing 5￣6 spores can cause 33% infection,while containing only a single spore can still causes 12% infection.Evaluation of the above results,it will facilitate the pest risk analysis of Tobacco Blue Mold pathogen.