Etiology Of Verticillium Wilt Of Cercis Chinensis

Cercis chinensis Bunge is a kind of deciduous shrub or small arbor belongs to Cercis.Lof Fabaceae, which originated in China and distributed in Shaanxi, Henan, Gansu, Hebei andHubei provinces. It’s widely used as a afforestation plant in parks and urban streets. Cercischinensis Bunge has great medical value because its wood, root and the bark can be used asmedical materials. Verticillium wilt-a new disease of Cercis chinensis was discovered on theChinese redbud in Shaanxi and Henan provinces which leads to the deaths in large acreage,thus causing great damage to the ornamental and economical values of the Cercis chinensis.We carried out the etiology of the Verticillium wilt of Cercis chinensis, main results are asfollows:1. The symptom of Verticillium wilt of Cercis chinensis is as follows: there are two formsof symptom of the diseased leaves. Type I is withered leaf with gray-green color, which ismainly manifested as dehydrating and wilting from the edge of the leaf at the beginning, thenthe diseased region extends to the center of the leaf, latterly the leaf becomes curled and thecolor turned to gray-green. Type II is the wilt leaf with yellow color, which is mainlymanifested as turning yellow and wilting from the edge of the leaf at the early stage, then thediseased parts extend to inner part of the leaf where existing a obvious division between thehealthy and diseased regions, latterly the leaf shriveled and the color turned to dark orange orbrown, whereas the diseased leaf doesn’t fall off. Brown lesions can be observed under thebark of the diseased branches and in the transverse section of the xylem, phloem and medulla.The symptom is more serious on one side of individual branches of the tree.2.6strains were isolated from the disease plants by tissue isolation method(CC001-CC006). CC001was proved to be the pathogen of the wilt disease according to theKoch’s Rule. The strain was identified as Verticillium dahliae based on ITS-rDNA sequenceusing ITS1/ITS4as primers and morphological characteristics.3.17species of cultivated plants and weeds which belongs to9families containingsolanaceae, leguminous, cruciferae and malvaceae were used for the host range test ofCC001, the result turns out that CC001can only infect cotton and potato besides Chineseredbud, which indicates that CC001has a host specificity to some extent. 4. The results of biological characteristics of CC001are as follows: the optimal mediumfor the growth of CC001is PSA medium, the optimal medium for the sporulation of CC001isPCA medium. CC001can growth under the pH value of4.5-11, the optimal pH value is7forthe growth of hyphae and5for sporulation. The best carbon sources are fructose and starchfor the growth of hyphae and sporulation respectively. Nitrogen source test indicates thatammonium nitrogen is more suitable for the growth of hyphae and sporulation than nitratenitrogen.There are no related reports on Verticillium wilt of Cercis chinensis so far all over theworld. Researches in this paper reveal the occurrence regularity of the disease and lay afoundation of further study of the prevention and control methods.