Molecular detection of Jujube witches' broom phytoplasmas inmicropropagated Jujube shoots

摘要

Jujube (Zizyphus jujuba Mill.) witches' broom (JWB) is the most important disease in the areas of jujube cultivation in China, where it occurs every year, Micropropagated shoots of the three most important cultivars ('Lizao', 'Junzao', and 'Muzao') in the National Jujube Gene Pool, collected at the Pomology Institute of Shanxi province, were tested for the presence of phytoplasmas. Phytoplasma ribosomal (16Sr) general and specific primer pairs were used in direct or nested polymerase chain reaction (PCR), Positive results were obtained only from symptomatic micropropagated samples of 'Lizao' and from phytoplasma controls. Restriction fragment length polymorphism (RFLP) analyses of PCR products with several restriction enzymes revealed that the phytoplasmas infecting the symptomatic plants belong to the 16SrRNA group V subgroup B. The positive correlation between symptoms and the presence of phytoplasmas was verified in tissue culture. Samples from apparently healthy shoots of 'Junzao','Muzao', and 'Lizao' were free of phytoplasmas.