Chung B N, Choi G S
540-41, Top-Dong, Kwonsun-Gu, National Institute of Horticultural and Herbal Science, Rural Development Administration, Suwon 440-310, Republic of Korea.
Plant Dis. 2010 Jun;94(6):792. doi: 10.1094/PDIS-94-6-0792A.
In December 2009, commercially grown poinsettia (Euphorbia pulcherrima Willd cv. Ichibang) exhibited typical phytoplasma-like symptoms in 95% of an affected field in Yongin, Korea (Gyeonggi Province). Symptoms consisted of flat stems and fascicles and an abnormal number of apexes resulting in a cockscomb form of stem and flower bud proliferation. Leaf narrowing with curling of bracts was also associated with the disease. Symptomatic poinsettia plants were not marketable. Poinsettias, cv. Ichibang, without symptoms were obtained from a breeding collection in a glasshouse of the National Institute of Horticultural and Herbal Science in Suwon (Gyeonggi Province). The presence of phytoplasmas in symptomatic and healthy-looking flowers and stems of cv. Ichibang was demonstrated by PCR analysis with primer pair R16mF2/R16mR1 (1), which amplifies phytoplasma 16S rDNA regions. PCR products (~1,427 bp), were obtained from both symptomatic and healthy-looking plants, sequenced, and registered under the GenBank Accession Nos. of GU461275 and GU461277, respectively. Symptomatic poinsettia and healthy poinsettia sequences had 99.6 and 100% identity with U.S. PoiBI isolate FJ376625, indicating poinsettia stem flat disease is caused by PoiBI. A branch-inducing factor in poinsettia has been known for several decades, but only since 1997 was this graft transmissible factor identified as a PoiBI phytoplasma (1), belonging to the peach X-disease phytoplasma group (16S rRNA III) subgroup 16SrIII-H (2). Normally, phytoplasmas are associated with host quality loss, but abnormally, infection in poinsettia generates a desirable, free-branching growth habit. In this study we found that PoiBI could be detrimental to the quality of poinsettia depending on the cultivar and agronomic practice. Poinsettia stem flat disease presumably occurred because of increased levels of phytoplasma caused by successive stem cutting for commercial use. To our knowledge, this is the first report of PoiBI phytoplasma that affected marketability of poinsettia in Korea. References: (1) I. M. Lee et al. Nature Biotech. 15:178, 1997. (2) I. M. Lee et al. Int. J. Syst. Bacteriol. 48:1153, 1998.
2009年12月，韩国京畿道龙仁市一片受影响田地中95%的商业化种植的一品红（Euphorbia pulcherrima Willd cv. Ichibang）出现了典型的类植原体症状。症状包括茎扁平、丛生以及顶芽数量异常，导致茎和花芽呈鸡冠状增生。叶片变窄并伴有苞片卷曲也与该病有关。有症状的一品红植株无法进入市场销售。无症状的一品红品种Ichibang取自水原市（京畿道）国立园艺和草药科学研究所温室中的一个育种收集区。通过使用引物对R16mF2/R16mR1（1）进行PCR分析，证实了一品红品种Ichibang有症状和看似健康的花朵及茎中存在植原体，该引物对可扩增植原体16S rDNA区域。从有症状和看似健康的植株中均获得了PCR产物（约1427 bp），进行了测序，并分别在GenBank登录号GU461275和GU461277下注册。有症状的一品红和健康一品红序列与美国PoiBI分离株FJ376625的序列一致性分别为99.6%和100%，表明一品红茎扁平病是由PoiBI引起的。几十年来人们一直知道一品红中有一个促分枝因子，但直到1997年这个可通过嫁接传播的因子才被鉴定为一种PoiBI植原体（1），属于桃X病植原体组（16S rRNA III）亚组16SrIII - H（2）。通常，植原体与宿主品质下降有关，但异常的是，一品红感染后会产生一种理想的、自由分枝的生长习性。在本研究中我们发现，根据品种和农艺实践，PoiBI可能对一品红的品质有害。一品红茎扁平病可能是由于为商业用途连续进行茎切段导致植原体水平升高而发生的。据我们所知，这是关于影响韩国一品红市场适销性的PoiBI植原体的首次报道。参考文献：（1）I. M. Lee等人，《自然生物技术》，15:178，1997年。（2）I. M. Lee等人，《国际系统细菌学杂志》，48:1153，1998年。
