单 位：
中国科学院应用真菌学研究所河北省沙岭子农業試驗站
摘 要：
在河北省沙岭子农业試驗站和北京农業大学試驗农場1955和1956两年所进行的病薯栽培試驗,表示土中的重复侵染是中心病株形成过程的基本特征。当挖掘出土初期的病薯时,發現直接与种薯病斑相連的幼芽都在出土之前变黑死去,剛剛露土的幼芽中,靠近已死幼芽的莖基也开始部分变色,距离較远的则仍然健全。在已出土的衰弱幼苗上常常可以看到露在地面的莖基部分也显出暗褐色的病斑,但是沒有孢子囊,而該病斑的地下部分则披有一層孢子囊趺缜o斑并不全是达到莖基的終点,而达到莖基終点的,也不与种薯病斑相連接。1956年在两地播种的789穴病薯中發現了9株这种病苗,其中5株迅速萎蔫而枯死,1株發生莖斑痊愈現象。只有少数出現較晚而維持較长久的弱苗遇到适合气候时能够在地面上形成孢子囊傳染到本株或同穴中其他植株的叶片缙诓∶绲闹饕饔孟匀辉谟谛纬傻叵骆咦幽乙砸鹜ㄖ姓诔沙さ慕≈昵o基的感染。在成株莖部上病菌只能在皮层扩展引致条紋状的暗褐色病斑。这种病斑不严重影响植株的生长發育,但是在露出地面后随时可以形成孢子囊成为空中傳染的經常潜在来源。出土病苗的观察以及幼苗地上部接种試驗結果說明病害延迟流行的原因,一方面是受病的幼苗容易枯死,另一方面是在早期气候下不能得到形成孢子和再侵染所需要的温湿度的配合。建議在各地預测站选擇适当地点播种病薯,以便观察病害中心的發展情况,作为預測預报的根据。
译 名：
OVSERVATIONS ON THE FORMATION OF PRIMARY FOCI OF LATE BLIGHT IN A POTATO PLANTATION
作 者：
LIN CHWAN-KWANG,HWANG HO,WANG TAO-PENG,HWO SUO-HSIANG(Institute of Applied Mycology,Academia Sinica;Salingtze Agricultural Experiment Station,Hopeh Province)
摘 要：
Results of planting large amount of slightly but evidently diseased tubers undernatural field conditions obtained by inoculation during the harvesting time of theprevious year indicate that successive underground secondary infections from plantto plant of the same hill constitute the main feature of the process of formation ofprimary foci of subsequent aerial spread of the late blight in a potato plantation Inspection at the time of emergence revealed that all the sprouts found at theperiphery of and directly connected with the tuber lesions were blackened and diedunderground.Among the sprouts which were about to emerge,those standing closeto the dead sprouts were also discolored at their basal portion,while those furtherapart still entirely healthy.Dark brown extended lesions can sometimes be seen onthe stems of the weak potato seedlings,but sporangial covering was present onlyon their lower underground portions.The stem lesions did not always reach theextremity of the stem base.Even if they did,they might not be directly connectedwith the tuber lesions. Among a total of 789 hills planted with disesed tubers in Peking and Salintzein 1956,only 9 plants with stem lesions were found,of which 5 wilted and diedrapidly,1 with its lesion healed up.The remainder stayed long enough for thefungus to sporulate on their above-ground portion of the lesions and cause thefoliage infection of the same plant and adjacent plants at the onset of a favorable weather. It is believed that the significance of the weak diseased seedlings with basalstem lesions appeared early in the season consists chiefly in the capacity of givingrise to sporangia which may again infect the underground portion of the stem of ahither to healthy plant.On the stem of a larger plant,the fungous mycelium canonly exist in the cortical tissue spreading upward and downward from the infectioncourt to cause a dark brown stripe of irregular width.Stripe lesions of this typeapparently do nto impair the normal development of the plant,but their above-ground portions serve as a persistent potential source of aerial infection. Observations outlined above together with the results of an experiment ofseedling top inoculations under field conditions lead us to postutate that delayedaerial infection is due on the one hand to the fragility of the diseased seedlingsunder natural field conditions and on the other to the lack of a suitable combinationof moisture and temperature required for sporulation and infection as the springweather is characterized by very low night temperature. It is anticipated that local forcasting service may find it helpful to plant diseasedtubers in a proper field plot for the observation on the development.of the foci ofpotato late blight.
