Studies On Identification Of Pathogeny Of Mulberry Mosaic Dwarf Disease By Electrophoresis

Mulberry mosaic dwarf disease was reported in 1957 and named in 1958. it is one ofthe main diseases on mulberry. Up to now, it was only discoveried in China. It was reportedthat this disease has being threated the extensive mulberry fields in many provinces andmunicipality, such as Jiangsu, Zhejiang, Anhui, Hunan, Hubei, Henan, Sichuan, Chongqing,Guangdong, Guangxi. The incidence of disease is about 20%-30% in common mulberryfields, or 60%-80% in severe ones, ever more than 90% in very few ones. This diseasebrings leaves crimpling, deforming, and size reducing. Symptoms are including dwarf, leafmosaic, and yellow spot emerging on the leaf surface. Infected mulberry grows slowly, thinand shorten as the auxiliary bud on the branch emerge early resulting in more lateral branch.This disease makes the mulberry trees growth abnormal, result in serious damage evendeath. Sequentially, the yield of mulberry trees is reduced and the quality of leaves is low.The aftermath restricts seriously the production and development of sericulture as lowquality cocoons.This disease had been approved to be infectious by tubular budding grafting test, eventhough the causing agent is still unknown. Viral-like particle was observed in diseasedsample by microscopy investigation previously, but it is not succeeded to purify virion fromleaves with symptoms, and also failed in back-inoculation using partially purified vironcomponent. It has been known that mulberry seedling was reproduced mainly by grafting.So, it is helpful to control the overspreading of this disease by prohibiting the export of cionshoot at the nidi and strengthen quarantine when the cion shoot is imported.Total nucleic acid RNAs were extracted from the mulberry leaves with or withoutsymptoms, and subjected to return-polyacrylamide gel electrophoresis (Return-PAGE) andtwo-dimensional polyacrylamide gel electrophoresis (2D-PAGE). Coleus blumei viroid (CbVd) and Apple dimple fruit Viroid (ADFVd) was used as a positive control. The resultshows that viroid-like circular RNA were detected from samples, It is suspected that thepossible relationship between viroid,like RNA and mulberry mosaic dwarf diseaseaccording to the symptom and the occurrence laws. To our knowledge, this is the firstreport of viroid-like RNA isolated from mulberry. This result will be confirmed by moreresearch.