摘要
雨水在黑胫病的重复侵染上起重要作用。烟茎上的孢子囊被雨水冲刷到地面上,释放出大量的游动孢子,随地面活水进行侵染。孢子囊只产生在较幼嫩的组织上,主要着生在烟茎顶端,其次在茎中部,茎基部分则极少发现。山东夏烟产生孢子囊的主要时期为移栽(6月底至7月初)以后到7月下旬。连续大雨有利于产生孢子囊。人工接种后4～5天是产生孢子囊的高峰。
1.Rainfall,which plays an important role in the subsequent secon-dary infections of black shank,is the most important factor for epi-phytotics.Heavy rainfall always washes down the sporangia from dise-ased plants and sinks them into the soil.Whereby the rain water willspread and run over the field surface together with the inoculum.2.Sporangia are always formed abundantly on the delicate tips oftobacco plants,followed by the middle parts and the bassl parts of stem.The amount of breed follows the above order in a decreasing sequence.In Shantung,the most important period for sporangial formation is from the time of transplanting tobacco to the latter part of the month of Ju-ly.Continuous heavy rainfall can raise the humidity of the atmosphere,and benefits the production of sporangia.The sporangial formation ini-tiats after 3-4 days.Maximum breed of sporangia is observed after 4～5days on the leisions.The sporangial existence can last 6～9 days.3.The minimum,optimum,and maximum temperature for sporang-ial production are 13℃,25～30℃,and 37℃ respectively.4.Under controlled conditions,at 25～30℃,sudden drops of tempera-ture of 5-15℃caused the rapid and voluminous liberation of zoosporeswithin a short pereod of time.This experiment simulated the field condi-tion in summer,when sudden rainfall causes the temperature to drop 3～5℃ from 25.3～29.0℃,and where almost identical effects to this experi-ment has been observed.The emptied sporangia percentage of 33.7～59.2%was reached within half an hour,after the droping in temperature.Thegradual temperature drop in the night also causes 10% of the total spo-rangia to liberate all its zoospors.5.The liberated zoospores will flow among the surface water,andit was revealed by bioassay that the inoculum potential of the soil tendsto increase prominently where large numbers of sporangial plants havebeen in existence acompany with contionuous rainfall.The inoculum ofthe surface soil(0～5cm)is the highest,with the 15～20 cm depth levalcoming in next,while the l
出处
《植物病理学报》
CAS
1984年第1期39-45,共7页
Acta Phytopathologica Sinica
