Submitted to: Journal of Applied & Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 26, 1996
Publication Date: N/A
Interpretive Summary: Phytoplasmas are associated with diseases in several hundred plant species. The development of molecular-based tools, especially polymerase chain reaction PCR) assays using universal primers, has made it possible for us to detect and identify a wide array of phytoplasmas. Based on restriction fragment length polymorphism (RFLP) analysis of PCR-amplified d 16S RDNA sequences, we have proposed a comprehensive classification scheme for differentiation and identification of phytoplasmas. New phytoplasma strains have been identified all over the world, but the information of phytoplasmas associated with many important tree and shrub diseases in China is nonexistent. The absence of this regional information on phytoplasmal diseases has impeded the international exchange of the germplasms. In this study we have applied molecular methods (nested PCR assays and DNA finger printing of PCR amplified 16S rRNA and ribosomal protein gene sequences) for identification and characterization of phytoplasmas associated with cherry, jujube and other trees and shrubs infected with phytoplasmal. The results revealed that the two phytoplasmas associated with cherry lethal yellows and jujube witches' broom are new phytoplasma taxa that are only present in this region. The information and pathogen-identification technology will be of benefit to diagnosticians and to APHIS for implementation of a new quarantine regulations.
Nested PCR detected phytoplasmas from most symptomatic and some asymptomatic trees and shrubs associated with cherry lethal yellows (CLY, jujube witches'-broom (JWB), paulownia witches'-broom (PaWB), mulberry dwarf (MD) and others. Restriction fragment length polymorphism (RFLP) analyses of 29 phytoplasma 16S rDNA sequences (R16F2n/R16R2 nested PCR products) revealed that CYL and JWB phytoplasmas were closely related an belonged to 16S rDNA group V (elm yellows and related phytoplasmas) subgroup B, and that PaWB and MD phytoplasmas belonged to group I (aster yellows and related phytoplasmas) subgroup D and subgroup B, respectively. Based on RFLP analysis of ribosomal protein gene sequences, the CYL and JWB phytoplasmas were distinct from one another and belonged to two separate subgroups. The CYL and JWB are new phytoplasma taxa which have not been reported in other geographical regions.