松球壳孢菌的致病性研究

实验证明 ,国内供试松球壳孢菌 (Sphaeropsissapinea)的致病力明显高于美国的B型菌株 ,与A型相似 ,致病性较强。B型也能无伤侵入 ,只是发病率明显低于A型。伤口并不是病菌侵入的唯一途径 ,自新梢伸长至针叶发育完全期间 ,病菌可直接侵入树木当年嫩梢并使之枯萎 ;此后 ,随着梢部组织的不断成熟与老化 ,伤口对病菌侵入与危害的作用才得以显现出来 ,无伤接种时不发病或只产生部分枯叶。气孔也是病菌侵入的途径之一。病菌不但可侵入当年新稍 ,而且还可于枝梢的 2a和 3a生处有伤侵入 ,使之染病甚至死亡。油松(Pinustabulaeformis)、赤松 (P .densiflora)、彰武松 (P .densifloravar .zhangwuensis)较樟子松 (Pinussylvestrisvar.mongolica)抗病 ,且彰武松主要表现为“耐病”。幼龄的樟子松较大龄的抗病。树势削弱的枝梢抗病性能降低 ,发病快而重。潜育期和繁殖期的长短与寄主、树势、组织的成熟程度和气温等有关

STUDIES ON THE PATHOGENICITY OF SPHAEROPSIS SAPINEA

Inoculations revealed that the Chinese isolates of Sphaeropsis sapinea were similar to American A isolates in pathogenicity which was much nore aggressive than B isolates.Type B isolates could also penetrate host without wounding,but with lower incidence than type A.During the periods of shoot elongation and needle development the fungus could directly enter the current year shoots and eventually kill them,then with shoot maturation,the role of wounding was gradually shown up,and inoculations of nonwounded shoots resulted in no symptoms or only some necrotic needles.The fungus could also enter needles through stomata.It could infect and kill twigs through wounds on the 2 nd or the 3 rd year node.%Pinus tabulaeformis,P.densiflora% and %P.densiflora %var.%zhangwuensis% were more disease resistant than %Pinus sylvestris% var.%mongolica,%and %P.densiflora %var.%Zhangwuensis %showing a sort of disease tolerance.Young trees of %Pinus sylvestris% var.%mongolica% were more disease resistant than old ones.After inoculation shoots weakened by girdling showed symptoms more rapidly and severely than non weakened ones.The durations of incubation and reproduction were related to host species,tree vigor,maturity of host tissue, and air temperature,etc.