Identification of two new phylogenetically distant phytoplasmas from Senna surattensis plants exhibiting stem fasciation and shoot proliferation symptoms



Y. Zhao, Molecular Plant Pathology Laboratory,

USDA-Agricultural Research Service, Room

213, Building 004, BARC-West, 10300

Baltimore Avenue, Beltsville, MD 20705, USA.



Sunshine trees (Senna surattensis) 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 produced amplicons of 1.5 kb. Subsequent restriction fragment polymorphism 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 ‘Candidatus 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.