【摘要】 <正> 柑桔黄龙病是我国南方柑桔产区的一种毁灭性病害,其中尤以广东、福建受害最烈,使这些地区的柑桔生产受到严重威协,据调查,现此病已蔓延到湖南、江西、浙江、云南、贵州、广西、四川等9个省(区)。 1976年,林孔湘教授将国内柑桔叶片上表现斑驳症状的病害定名为斑黄病,以区别更多还原

【Abstract】 Both yellow shoot and blotchy yellows are the most destructive disease of citrus trees in South China.Citrus shoots infected with yellow shoot or blotchy yellows were collected from Guang dong, Guangxi and Fujian provinces and autonomous region, and grafted on the Ponkan seedlings in the green house in Guangzhou. When symptoms had appeared the leave vein was ultrathin sectioned and examined under the electromicroscope. The pathogen of blotchy yellows presented itself in various forms in seive cell, such as round, irregular or filamentous, Its size raned from 547-677nm with 17-24.1nm triple layer membrane. It was sensitive to penicillium and might be transmitted through the xylem.The pathogen ot yellow shoot disease was also pleornorphic, Its size ranging from250-520 nm in diameter. The cell membrane was 19-25.9nm thick, and both the electrondense outer zone and inner zone could be resolved into a triple-layered unit membrane. The pathogens of these two diseases belongs to Gracilicutes, they may be named"Gracilicutelike bacterium".更多还原