Detection And Molecular Characterization Of Citrus Viroids In Hunan Province

Investigations and studies about citrus viroids were persisting since 1970s, many kinds of citrus viroids were identified and some citrus viroids which cause no symptom but conducing dwarfing were used in commercial high density citrus producing. However, China, as the citrus origin area in the world and one of the biggest citrus cultivating countries, has a long history and a abroad areas of citrus cultivating and is in riched in citrus resources. But almost none studies has reported the resources of citrus viroids in China, except the reports about investigating and detecting citrus exocortis viroid (CEVd). Therefore, as one of the citrus origin areas, Hunan is one of the biggest and oldest citrus producing provinces, citrus cultivating is popular all over the province. The object of this study is to investigate and collect samples from citrus producing area in Hunan Province, further advanced by detecting and amplying primarily citrus viroids. The main results of this study were shown as follow:1. An effective RT-PCR technique was established for detecting citrus viroid types, and four types were recognized, i.e. CEVd, CVd-I, CVd-II and CVd-III, the later two were identified for the first time in China. sPAGE was used to identify all of citrus viroids in once a time.2. Inoculating the detected samples which contain CVd-II or CVd-III, or CVd-II and CVd-III on Etrog citron, and keeping them in glassroom.3. Cloning the full sequences of the citrus viroids detected by RT-PCR and sequencing. Analysising the sequences with the reported sequences in Genbank with DNAMAN software and Blast and the characters and subtypes of the citrus viroids. The sequencing results indicated that the CVd-II seemed to be a new subtype; most of CVd-III detected in the present study are CVd-IIIb which could be further developed as a dwarfing agent.4. Trying to purify useful citrus viroids (CVd-IIa, CVd-IIIb etc. )from the mixed citrus viroids and citrus viroids having different characters of sequence as special resources in Hunan Province. Meanwhile, dwarfing trial was done in parts of samples and the results of dwarfing is marked in four samples, Y1,Y2,Y3 and Y4, from Changsha, compared with Etrog citron which is free of virus and viroid.