山楂丛枝病类菌原体(MLO)的电镜观察

Observation by Electron Microscope for Mycoplasma-like Organism in Large Chinese Hawthorn with Witches' Broom

山楂(Crataegus pinnatifida var.major N.E.Br.)为我国特产果树,全国已有十多个省市栽培山楂,种植面积不断扩大,仅北京市就达10万亩,约400万株,成为山区农民致富的一种重要途径。近年来,由于山楂丛枝病的发生,造成山楂苗木和大树枝条枯死,影响果实产量。据在北京市各区县调查,在山楂种植地区内,病害严重发生的约达20％左右。该病1988年在北京市农林科学院林果所资源圃内发现,危害山楂品种较多,以小楂或以小楂为砧术的品种发病严重。病害有不断发展的趋势,成为当前山楂生产中的一大障碍。

Large Chinese hawthorn (Crataegus pinnatifida var. major N. E. Br.) witches' broom was found in Beijing in China. Plant-diseased sprouted later, and there was not a distinct internodes on branches. Little leaves were bunchy and yellow. Branches infected withered slowly from the top downwards. Flowers were faded and degenerated, small and deformed. Flower buds can't produce normal fruit-twigs and fruits. White flowers turn pink or purplish red.Transmission electron microscope revealed numerous-spherical and elliptical MLO, in the sieve element of the top or the vein or the pedicel from MLO-infected plants. They were measured, the spherical is 433 nm and elliptical is 480nm×609nm. MLO, havn't been found in healthy plant samples.