|Lee, Ing Ming|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/1997
Publication Date: N/A
Interpretive Summary: Chokecherry is an important native woody species that occurs in natural and planted stands in the northern Great Plains region of North America and provides important habitat and food for wildlife. It is also grown as field and farmstead windbreaks. A disease of chokecherry, long assumed to be X-disease, is considered to be the most limiting problem of chokecherry grown in the northern Great Plains. The present study was to determine if phytoplasmas were associated with diseased chokecherry in North Dakota. By electron microscopic observation, immunofluorescence microscopy, and by restriction fragment length polymorphism analysis of polymerase chain reaction (PCR)-products (16S rDNA sequences) amplified from diseased chokecherries, we confirmed that diseased chokecherries were associated with X-disease phytoplasma. Chokecherry X-disease was found to be widespread in North Dakota. The information and pathogen-detecting technology will be of benefit to diagnosticians for conducting further survey of distribution of the disease in other regions.
Technical Abstract: A phytoplasma was observed in diseased chokecherry plants in North Dakota by electron microscopy and identified with a phytoplasma-specific polyclonal antibody and with restriction fragment length polymorphism (RFLP) analysis of 16S ribosomal DNA (16S rDNA) sequence amplified with the nested polymerase chain reaction (PCR). The phytoplasma was partially purified directly from infected chokecherry plants for use in raising a polyclonal antibody in mice. Immunofluorescence staining demonstrated the chokecherry phytoplasma in North Dakota to be serologically related to phytoplasma associated with eastern X, western X, milkweed yellows, and pigeon pea witches'-broom disease. The antibody did not react with phytoplasmas associated with ash yellows, aster yellows, elm yellows, goldenrod yellows, spirea stunt, and palm lethal yellowing. The identity as X-disease phytoplasma was supported by RFLP analysis of the amplified products obtained form the nested-PCR by using two phytoplasma-universal primer pairs. The RFLP patterns from MseI and HpaII digestion indicated that the X-disease phytoplasma in chokecherry belongs to subgroup A in the 16S rRNA group III. The presence of X-disease symptoms, electron microscopic observation of phytoplasmas in symptomatic plants, detection with the polyclonal antibody, and detection and identification by PCR-RFLP analysis provided the first confirmation that chokecherry X-disease was found to be widespread in North Dakota based on positive serological detection of X-dis Dakota. X-disease in chokecherry was also confirmed in South Dakota and in Saskatchewan, Canada.