2.2.24
IDENTICAL CHARACTERISTICS OF JAPANESE PHYTOPLASMAS TRANSMITTED BY SCLERORACUS FLAVOPICTUS

M TANAKA1, T SHIOMI2, T UEHARA1 and I MATSUDA1

1National Agricultural Research Centre, Tsukuba 305-8666, Japan; 2National Institute of Agro-Enviromental Science, Tsukuba 305-8604, Japan

Background and objectives
In Japan, numerous occurrences of phytoplasmal disease transmitted by the leafhopper, Scleroracus flavopictus Ishihara, have been reported. Biological properties such as experimental host range have been investigated for only two or three isolates of these pathogenic phytoplasmas and little is known about of their genetic relatedness[1]. To clarify this, we compared 12 isolates of S. flavopictus-transmitted phytoplasmas (SF-phytoplasmas) for experimental host range, symptoms on test plants and nucleotide sequences of 16S rDNA.

Material and methods
Diseased plants of gentian, udo (Aralia cordata), tsuwabuki (Farfugium japonicum), azuki bean, Cosmos bipinnatus, chervil, red clover, Geranium thunbergii and Glaucidium palmatum, naturally infected with SF-phytoplasma, were collected from various places in Japan. Twelve phytoplasmas were isolated from these naturally infected plants, and maintained in greenhouse-grown garland chrysanthemum (Chrysanthmum coronarium) by serial inoculation through an insect vector, S. flavopictus. Experimental host ranges of SF-phytoplasmas were tested by allowing infective leafhopper vectors to feed on 33 species of plants belonging to 14 families. The 16S rDNAs of SF-phytoplasmas were amplified by PCR from infected plants. After purification by spin column, each 16S rDNA fragment (1368 bp) was sequenced in both strands using eight primers [2].

Results and conclusion
A total of 32 species of the test plants (but not Artemisia indica) were infected with SF-phytoplasmas by vector inoculation. No difference was found in 12 SF-phytoplasmas for experimental host range and symptoms on test plants. Analysis of 16S rDNA revealed that all 12 SF-phytoplasmas had identical nucleotide sequences and were phylogenetically closely related to the X-disease phytoplasma. These results indicate that the phytoplasmal diseases transmitted by S. flavopictus in Japan were caused by identical pathogenic phytoplasmas belonging to the X-disease phytoplasma group.

References
1. Okuda S, Prince JP, Davis RE, Dally ED, Mogen B, Kato S. 1997. Plant Disease 81, 301-305.
2. Namba S, Oyaizu H, Kato S, Iwanami S, Tsuchizaki T. 1993. International Journal of Systematic Bacteriology 43, 461-467.