Phytoplasma associated with Chinese tallow tree yellowing disease in China represents a new 16SrIII subgroup

Summary Recently, samples of the Chinese tallow tree (Sapium sebiferum) displaying yellowing symptoms were collected from a grove in Tai'an, Shandong Province, China. The association of phytoplasma with yellowing disease was ascertained using nested polymerase chain reaction (PCR) of the 16S rRNA gene by using the phytoplasma-specific universal primer pair P1/P7, followed by R16F2n/R16R2 as nested primers, and rp genes primed using rpL2F3/rp(I)R1A followed by rp(III)-FN/rp(I)R1A. The sequence and phylogenetic analyses of the 16S rRNA gene and rp genes revealed that the phytoplasma associated with the Chinese tallow tree belonged to the 16SrIII group (the X-disease group). Computer-simulated and gel-based restriction fragment length polymorphism (RFLP) analyses revealed that the RFLP patterns were different from the reference patterns of all previously established 16SrIII subgroups, with the maximum similarity coefficient exceeding the threshold for delineation of a new subgroup RFLP pattern type within the 16SrIII group. Thus, the phytoplasma associated with the Chinese tallow tree yellowing disease, designated as ‘CTTY’, represents a new subgroup (16SrIII-Y). This study shows the Chinese tallow tree as a new host of phytoplasma belonging to the 16SrIII group in China and worldwide.