Identification of Aster Yellows Phytoplasma in Dendranthema grandiflorum

Phytoplasmas were identified from two chrysanthemum (Dendranthema grandiflorum) plants showing different symptoms ; one with stusting, rosette, and excessive branching (Ph-ch1), and the other with stunting and chlorosis (Ph-ch2). Electron microscopy of midrib of the plants with the symptoms revealed that numerous phytoplasmas were localized in the phloem cells. The disease was transmitted from infected plants to healthy ones by grafting. Phytoplasma-specific DNA was detected in polymerase chain reaction (PCR) analysis with template DNA extracted from the leaves of Ph-ch1 and Ph-ch2, both of which yielded a same DNA band corresponding to 1.5 kb. Using a specific primer pair (R16F1/R1) synthesized based on aster yellows (AY) phytoplasma, a DNA fragment of 1.1 kb was amplified by PCR. Endonuclease restriction patterns of the 1.1 kb PCR products from Ph-ch1 and Ph-ch2, which were dgeste with each of the restriction endonucleases Sau3A, Hha, Alu and Rsa, were same as those of AY phytoplasma from periwinkle. This suggests that the chrysanthemum plants (Ph-ch1 and Ph-ch2) be infected with a phytoplasma belonging to AY phytoplasma.