普通农业植物病理学双语课件.pptx

Melons/CucumberDiseases;1.DownyMildew瓜类霜霉病;1.2Symptoms;Whenleavesareinfectedbyaheavysporeshower,smallindividualnecrotic(坏死)andchloroticflecks(褪绿斑)appearontheuppersurfaceInamoistenvironment,sporulation(产孢)occursonthelowerleafsurface.Thechloroticflecksappearaslightbrownareaswhenhelduptothelight.Areaswithactivesporulationgivetheundersurfaceapurplishordarkbrownsootyappearance.;1.3Pathogens（病原物）;1.3.2Shape（形态）

Themycelium(菌丝体)nosepta(隔膜),colorless,spreadinthehostintercellularspace,orentersthehostcelltoabsorptnutrientbytheovalorbranchingfingerhaustorium(吸器).

无性繁殖产生孢囊梗(sporangiophore)和孢子囊(sporangium)。孢囊梗由寄主叶片的气孔伸出，单生或2~5根丛生，无色，主干上有3~5次锐角分枝，分枝顶端产生孢子囊。孢子囊淡褐色，椭圆形或卵圆形，顶端具乳突。孢子囊在水中萌发产生6~8个游动孢子。;Thefungalgrowthconsistsoflargelemon-shapedsporescalledsporangiathatareborneonbranchedstructurescalledconidiophores.

游动孢子无色，圆形或卵形，有2根鞭毛，在水中游动30~60min后形成休止孢，再萌发产生芽管，从寄主气孔侵入。孢子囊在较高温度和湿度不充足的条件下，也可直接萌发产生芽管侵入寄主。

Thisfungusmayproducetheoospore,butisextremelyrare.;1.3.3Pathogen(病原)biology

Pathogenissuitabletogrowandreproduceunderthehumidity,itssporangium(孢子囊)production,sprouting,zoospore(游动孢子)sproutingandinvasionrequesttheveryhighhumidityandthemoisturecontent.whentheleafbladehasthewaterfilm,under15℃sporangiumcansproutafter1.5h,after2hthezoosporeinvadehostimmediately.Ifnowaterfilmontheleafblade,difficulttocomeon.

病菌适宜于高湿下生长繁殖，其孢子囊的产生、萌发，游动孢子的萌发、侵入均要求很高的湿度和水分。叶片上有水膜时，15℃下孢子囊经1.5h即可萌发，2h后游动孢子随即萌发并侵入寄主。若叶片上无水膜，即使接种病菌也很难发病。;病菌喜欢偏低温度，孢子囊(sporangium)在5-32℃范围内都可萌发，萌发适温为15-22℃，温度升高孢子囊可直接萌发产生芽管。病菌在10-28℃范围内均可侵入寄主，侵入适温为16-22℃，产生孢子囊的最适温度为15-20℃。

Resistanceofzoosporeisbad,thelifeisshort,onlysurvivesgenerally1~5d.;1.3.4DifferentiationofPathogenicity(致病性)ofPlantPathogensandhost

PathogenmainlyinfectsCucumber,melon,muskmelon,pumpkin,andtowelgourd.

国外报道，病菌存在不同的专化型或生理小种。但我国有的学者提出我国的黄瓜霜霉病菌不存在生理分化现象