|WU, WEI - Dalian University Of Technology|
|CAI, HONG - Yunnan Agricultural University|
|WEI, WEI - University Of Maryland|
|Lee, Ing Ming|
|CHEN, HAIRU - Yunnan Agricultural University|
Submitted to: Annals of Applied Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/23/2011
Publication Date: 1/1/2012
Citation: Wu, W., Cai, H., Wei, W., Davis, R.E., Lee, I., Chen, H., Zhao, Y. 2012. Identification of two new phylogenetically distant phytoplasmas from Senna surattensis plants exhibiting stem fasciation and shoot proliferation symptoms. Annals of Applied Biology. 160:25-34.
Interpretive Summary: Many ecologically and agriculturally important plant species are susceptible to diseases associated with infection by phytoplasmas, a group of small bacteria that lack a cell wall and are spread by insects. Due to global climate change and natural dissemination of insect vectors, occurrence of phytoplasmal diseases in the world has increased significantly in recent years. In the summer of 2008, a new disease of sunshine tree was observed in a naturally-forested area of southwest China. The disease was characterized by enlargement and flattening of stems, and excessive branching of shoots. Using DNA fingerprinting technology, we found that the diseased sunshine trees were infected by two mutually distinct phytoplasmas classified in two groups named 16SrV and 16SrXII, respectively. The 16SrV phytoplasma has a wide distribution in northern China but this is the first report that the phytoplasma has reached to one of the southernmost areas of the country. Phytoplasmas classified in group 16SrXII are considered serious quarantine pests in China, and no 16SrXII phytoplasma had been formally reported in China. In addition, this is the first report that sunshine tree is a natural host of the two phytoplasmas. The presence of the two phytoplasmas in sunshine trees growing in southwest China signals a significant expansion of both geographical distribution and host range of the two phytoplasmas. Further studies are warranted to assess potential impacts of the phytoplasmas on the region’s ecosystems. This report will be of interest to diagnostics laboratories, research scientists and extension personnel who are concerned with phytoplasma disease management. The information is also important to international quarantine agencies for implementation of new quarantine regulations.
Technical Abstract: Sunshine trees (Senna surattensis Burm.) exhibiting unusual stem fasciation symptoms were observed in Yunnan, China. Morphological abnormalities of the affected plants included enlargement and flattening of stems and excessive proliferation of shoots. An electron microscopic investigation revealed presence of single membrane bound mycoplasma-like bodies in sieve elements of symptomatic plants. With DNA templates extracted from diseased plants and phytoplasma universal primers P1/P7 and P1A/R16S-SR, nested polymerase chain reactions (PCR) produced amplicons of 1.5 kb. Subsequent restriction fragment polymorphism (RFLP) and nucleotide sequence analyses of the amplicons indicated that the diseased plants were infected by distinct phytoplasmas affiliated with two phylogenetically-distant taxa classified in two 16Sr groups (16SrXII and 16SrV). This is the first report that sunshine tree is a natural host of two evolutionarily divergent phytoplasmas and the first report that a ‘Ca. Phytoplasma australiense’-related strain is present in China. The findings signal a significant expansion of both geographical distribution and host range of 16SrXII and 16SrV phytoplasmas.