Deng X, Lou Z, Feng Z, Li H, Chen J, Civerolo E L
Laboratory of Citrus Huanglongbing Research, Department of Plant Pathology, South China Agricultural University, Guangzhou, Guangdong 510642, P. R. China.
Crop Diseases, Pests, and Genetics Research Unit, San Joaquin Valley Agricultural Sciences Center, United States Department of Agriculture-Agricultural Research Service, Parlier, CA 93648.
Plant Dis. 2008 Feb;92(2):314. doi: 10.1094/PDIS-92-2-0314C.
Atalantia buxifolia (Poir.) Oliv., synonym Severinia buxifolia (Poir.) Ten. as commonly found in literature, is a common landscape plant and a popular Chinese medicinal herb known as Jiubingle or Dongfengjie. It remains unclear if this rutaceous plant could host 'Candidatus Liberibacter asiaticus', the pathogen of citrus Huanglongbing (HLB) in Guangdong, P. R. China. This information is important for HLB control in citrus because infected A. buxifolia could serve as a source of inoculum. In August of 1994, three A. buxifolia plants adjacent to a citrus experimental orchard of the South China Agricultural University at Guangzhou were found showing leaf mottle/yellowing symptoms. Two buds from each plant were grafted onto three mandarin trees (Citrus reticulata cv. Pongan) in a psyllid-proof screenhouse for indexing. By October of 1995, typical leaf mottle symptoms were observed in all three grafted trees compared with a healthy control. In March of 1996, one of the A. buxifolia plants was transferred to a screenhouse and has been maintained there. The leaf mottle/yellowing symptoms persisted but did not significantly affect plant growth. DNA was extracted from leaf samples in October 2006 by using the CTAB (cetyltrimethylammoniumbromide) method and assayed by nested-PCR using the general bacterial 16S rDNA primer set fDl/rD1 as the first round of amplification and primer set OI1/OI2c as second round amplification (1,3). After agarose gel electrophoresis and staining with ethidium bromide, an approximate 1.1-kb DNA band was detected in symptomatic samples but not healthy leaf samples of A. buxifolia and C. reticulata. XbaI digestion of the amplicons yielded approximate 500- and 600-bp fragments, characteristic of 'Ca. L. asiaticus'. Similarly, a standard PCR with primer set A5/J2 (3) yielded an approximate 700-bp DNA band characteristic of 'Ca. L. asiaticus' from symptomatic samples only. To our knowledge, this is the first report of graft transmission and PCR detection of 'Ca. L. asiaticus' from A. buxifolia in Guangdong, P. R. China. This work also confirms the findings from Taiwan (2) that A. buxifolia could serve as a source of 'Ca. L. asiaticus'. References: (1) X. Deng et al. Online publication. doi:10.1094/PHP-2007-0419-01-BR. Plant Health Progress, 2007. (2) T.-H. Hung et al. Eur. J. Plant Pathol. 107:183, 2001. (3) S. Jagoueix et al. Mol. Cell. Probes 10:43, 1996.
酒饼簕（Atalantia buxifolia (Poir.) Oliv.，文献中常见的同义词为Severinia buxifolia (Poir.) Ten.）是一种常见的园林植物，也是一种广为人知的名为九比灵或东风桔的中国传统草药。目前尚不清楚这种芸香科植物是否能携带“亚洲韧皮杆菌”（‘Candidatus Liberibacter asiaticus’），即中国广东省柑橘黄龙病（HLB）的病原体。这一信息对于柑橘黄龙病的防治至关重要，因为受感染的酒饼簕可能成为接种源。1994年8月，在广州华南农业大学的一个柑橘试验果园附近发现了三株酒饼簕植株出现叶片斑驳/黄化症状。从每株植物上取两个芽嫁接到防虫网室内的三株柑橘（Citrus reticulata cv. Pongan）上进行检测。到1995年10月，与健康对照相比，所有三株嫁接树均出现了典型的叶片斑驳症状。1996年3月，其中一株酒饼簕植株被转移到防虫网室并一直保存在那里。叶片斑驳/黄化症状持续存在，但对植株生长没有显著影响。2006年10月，采用十六烷基三甲基溴化铵（CTAB）法从叶片样本中提取DNA，并使用通用细菌16S rDNA引物对fD1/rD1进行第一轮扩增，引物对OI1/OI2c进行第二轮扩增，通过巢式PCR进行检测（1,3）。经琼脂糖凝胶电泳和溴化乙锭染色后，在有症状的酒饼簕和柑橘叶片样本中检测到一条约1.1 kb的DNA条带，而健康叶片样本中未检测到。扩增产物经XbaI酶切产生约500和600 bp的片段，这是“亚洲韧皮杆菌”（‘Ca. L. asiaticus’）的特征。同样，仅使用引物对A5/J2进行标准PCR（3），仅从有症状的样本中产生了一条约700 bp的“亚洲韧皮杆菌”（‘Ca. L. asiaticus’）特征性DNA条带。据我们所知，这是中国广东省酒饼簕中“亚洲韧皮杆菌”（‘Ca. L. asiaticus’）嫁接传播及PCR检测的首次报道。这项工作也证实了台湾地区（2）的研究结果，即酒饼簕可能是“亚洲韧皮杆菌”（‘Ca. L. asiaticus’）的来源。参考文献：（1）X. Deng等人。在线发表。doi:10.1094/PHP - 2007 - 0419 - 01 - BR。《植物健康进展》，2007年。（2）T.-H. Hung等人。《欧洲植物病理学报》107:183，2001年。（3）S. Jagoueix等人。《分子细胞探针》10:43，1996年。
