|CHENG, MINGYUAN - University Of Alaska|
|DONG, JIAHONG - Yunnan Academy Of Agriculture Sciences|
|Lee, Ing Ming|
|LASKI, PAUL - University Of Alaska|
|ZHANG, ZHONGKAI - Yunnan Academy Of Agriculture Sciences|
|MCBEATH, JENIFER - University Of Alaska|
Submitted to: European Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2015
Publication Date: 6/1/2015
Citation: Cheng, M., Dong, J., Lee, I., Bottner-Parker, K.D., Zhao, Y., Davis, R.E., Laski, P.J., Zhang, Z., Mcbeath, J.H. 2015. 16SrXII group phytoplasma strains, including 16SrXII-E (‘Candidatus Phytoplasma fragariae’) and a new 16SrXII subgroup, 16SrXII-H, are associated with diseased potatoes … in the Yunan and Inner Mongolia regions of China. European Journal of Plant Pathology. 142:305-318.
Interpretive Summary: Potato is one of the most important crops in China following rice, wheat and corn. China has become the world’s leading potato producer since 1993, accounting for about 22% of worldwide potato production. One of the major constraints to production is potato phytoplasma. In recent years, phytoplasma diseases affecting potato have become wide spread throughout the potato growing regions in China. Only a few studies on potato phytoplasmal diseases have been reported from potato growing regions. The phytoplasmas (cell wall-less plant bacterial pathogens) that cause potato diseases are largely unknown in China. In the present study, we performed an extensive disease survey in 2006 and 2007 using molecular means in two potato growing regions, Yunan and Inner Mongolia. We identify diverse phytoplasma strains belonging to both existing (subgroup E) and new members in the phytoplasma group XII. This is the first report that these strains caused diseases in potato China and other parts of the world. This information will aid extension workers in China for disease control and diagnosticians and will aid implementation of quarantine regulation in the US.
Technical Abstract: Potato is an important crop widely cultivated in China. Recently, potato diseases with characteristic symptoms of phytoplasmal infections were found in potato fields. In 2006 and 2007, samples exhibiting symptoms including rosette and upright growth, upward rolling, yellowing and purpling of leaves, shortened and thickened internodes and formation of aerial tubers were collected from Yunnan and Inner Mongolia and analyzed for the presence of phytoplasmas. DNA was extracted from tissues of 63 symptomatic and 10 asymptomatic plants. Phytoplasma 16S rDNA was amplified by PCR with primer pair P1/P7, followed by nested PCR with P1A/P7A, P1A/16S-SR or R16F2n/R16R2n. Twenty nine symptomatic plants, but no asymptomatic plants, tested positive for phytoplasmas. Nested PCR products were cloned and sequenced. Sequence analysis indicated that the phytoplasmas from diseased potatoes shared 98.1-99.8% similarity with 'Candidatus Phytoplasma fragariae' (16SrXII-E) and other 16SrXII subgroups. RFLP and phylogenetic analyses indicated that phytoplasmas of 16SrXII group were associated with diseased potatoes in China; these strains are most closely related to subgroup 16SrXII-E. Our results showed that four strains belonged to 16SrXII-E, ten strains were designated as a new 16SrXII subgroup, 16SrXII-H, and subgroup affiliations of all others were not determined. The genetic diversity of these strains was corroborated by sequence analyses of ribosomal protein gene, the elongation factor Tu gene (tuf) and preprotein translocase membrane subunit gene (secY). These results illustrated the complexity and diversity of phytoplasmas associated with potatoes in China.