The Investigation And Study On Peach Yellow Disease In Longquanyi District Of Chengdu City

Peach, a native fruit tree of China, is popular for its beauty, good taste, fruit rich in nutrition and so on. In recent, peach yellow disease becomes more and more serious, and presents up-trend year by year. In the paper, the healthy peach, diseased peach were employed to study the symptom, the modality and detecting of the pathogen; And the distribution and annual variation of the pathogen in peach tissue were studied by staining with DAPI, and transmission electron microscope was used for research transmission insect vectors; In addition to, the pathophysiology including activity of POD and PPO, POD isozyme and esterase isozyme were researched by using spectrophotometer and polyaerylamicle electrophoretic methods. The results were showed as follow.The results of investigation of the peach yellow disease are: peach leaves become yellow little by little except for leaves vein at first; Then, leaves vein become yellow, too; Finally, the texture of leaves is friable and, and many little pore form in leaves. It is easy to fall off peach tree; The incident of peach yellow disease is to 26%～45%; yellow leaf's rate amounts to 85%; yellow disease index is 36.4. It is serious to impair tree vigor class, quality and yield.The paper detected pathogen of peach yellow disease by histochemistry technology, polymerase chain reaction and treatment by acheomycin. (1) The sky-blue phloem was observed by staining with denese under optical microscope; Fluorescence spots were found in the phloem of leaf midrib which was stained by DAPI. The pathogen was confirmed by analysis with polymerase chain reaction using a pair of universal primer, which was designed by Lee according to phytoplasma 16SrDNA. An amplified product of the 1.5kb particularity DNA fragment was acquired in samples from infected peach, but not in healthy peach. The result of treatment by acheomycin showed that the pathogen of peach yellow disease was susceptive to acheomycin, peach yellow leaves resumed green incoordinately. (2) The phytoplasmas of peach yellow disease are mainly globose, oval, and some is like dumbbell, protonema and erose shape, which showed the phytoplasma of peach yellow disease has a polymorphism. The phytoplasmas are 40～850nm or so. There are two kinds of phytoplasmas having high and low electron cloud density. Phytoplasmas having low electron cloud density are like vacuole with two unit membranes which...