松幼苗和幼树离体枝对松材线虫侵染的反应

研究松树幼苗和幼树离体枝对松材线虫侵染的反应,表明组织褐变、失水萎蔫为病害外部症状表现标志;2月龄苗对线虫侵染的反应快速敏感,组织细胞褐变坏死反应明显。而茎已完全木质化的1 年生松幼苗和4~5年生幼树离体枝感染松材线虫后,外部症状表现为发病叶褪绿、变红褐色或褐色且萎蔫,症状首先出现在叶基部,很快向叶尖扩展,至整个针叶枯萎死亡。叶部症状的出现标志病害进入发展晚期,寄主已接近完全死亡,茎内失水和细胞褐变坏死已广泛发生。组织细胞褐变坏死反应则直接与线虫的迁移扩散、分布和数量有关。肉眼可见的皮层和髓的褐变通常发生在线虫出现之后,其褐变程度与线虫的数量呈正相关。

Reactions of Pine Seedling and in vitro Seedling Twig to the Infection of Bursaphelenchus xylophilus

The reaction of pine seedlings to infection of pine wood nematode(Bursaphelenchus xylophilus) was similar to that of in vitro seedling twigs.Both showed the sign of wilting and tissue brown spot,the reaction of 2 or 4-month seedlings to PWN appeared clearer and faster than that of 1-year-old pine seedlings and in vitro seedling twigs.After being infected by PWN,the needle of 1-year-old pine seedlings with the lignified stem began to change to be bronzing or brown and wilted,which appeared at the phyllopodium and expanded to leaf apex,then the needles withered and died.The sign showed that the disease had reached an advanced stage,where the host was almost dead and water loss in the stem and cell necrosis had widely occurred.The experiment showed the same results in in vitro seedlings.The necrosis was a common phenomenon caused by PWN and directly related to its moving,spreading,distribution and amount. The visible brown spot at cortex and marrow appeared after nematode occurrence,and the degree of internal pathological changes was linear to nematode amount.