Roy Avijit, Choudhary Nandlal, Hartung John S, Brlansky R H
University of Florida, Plant Pathology Department, Citrus Research and Education Center, Lake Alfred 33850.
USDA-ARS, MPPL, Beltsville Agricultural Research Center, Beltsville, MD 20705.
Plant Dis. 2013 Sep;97(9):1227-1234. doi: 10.1094/PDIS-01-12-0012-RE.
Citrus tristeza virus (CTV) isolates have been grouped into six genotypes: T3, T30, T36, VT, B165, and resistance breaking (RB) based on symptoms, host range, and genomic sequence data. The RB genotype has recently been identified with the novel property of replicating in trifoliate orange trees, a resistant host for the other five genotypes. Puerto Rican CTV isolate B301 caused mild vein clearing symptoms in Mexican lime but did not induce seedling yellows or stem pitting reactions in appropriate indicator Citrus spp., which are typical host reactions of the isolate T30. The isolate B301 was not detected by the genotype specific primer (GSP), which identifies the CTV-T3, -T30, -T36, -VT, and B165 genotypes. A primer pair for reverse transcription polymerase chain reaction (RT-PCR) amplification of the CTV-RB genotype was designed from the heat shock protein (p65) region based on the complete genomic sequences of trifoliate RB isolates from New Zealand available in the GenBank databases. The amplicon sequence from isolate B301 was 98% identical to that of the other trifoliate RB isolates. In addition, B301 was successfully inoculated into 'Carrizo citrange' (a trifoliate hybrid) but did not induce any symptoms. Furthermore, the complete genome sequence of B301 followed by the phylogenetic analysis revealed that the isolate is part of the RB clade with other CTV-RB isolates from New Zealand and Hawaii. Additional CTV isolates obtained from Puerto Rico were tested with the RB-GSP and confirmed the presence of trifoliate RB isolates in mixed infection with known CTV genotypes. Although this is the first report of a CTV trifoliate RB genotype from Puerto Rico, this genotype was present there prior to 1992.
柑橘衰退病毒（CTV）分离株已根据症状、寄主范围和基因组序列数据分为六种基因型：T3、T30、T36、VT、B165和抗性突破型（RB）。最近发现RB基因型具有在枳橙树上复制的新特性，枳橙树是其他五种基因型的抗性寄主。波多黎各CTV分离株B301在墨西哥酸橙上引起轻度脉明症状，但在合适的指示柑橘品种中未诱发幼苗黄化或茎陷点反应，而这些是T30分离株的典型寄主反应。基因型特异性引物（GSP）无法检测到分离株B301，该引物可鉴定CTV-T3、-T30、-T36、-VT和B165基因型。基于GenBank数据库中可获得的来自新西兰的枳橙RB分离株的完整基因组序列，从热休克蛋白（p65）区域设计了一对用于逆转录聚合酶链反应（RT-PCR）扩增CTV-RB基因型的引物。分离株B301的扩增子序列与其他枳橙RB分离株的序列有98%的同一性。此外，B301成功接种到“卡里佐枳橙”（一种枳橙杂交品种）中，但未诱发任何症状。此外，B301的完整基因组序列经系统发育分析表明，该分离株与来自新西兰和夏威夷的其他CTV-RB分离株同属RB进化枝。用RB-GSP对从波多黎各获得的其他CTV分离株进行了检测，证实了枳橙RB分离株与已知CTV基因型混合感染的存在。尽管这是关于来自波多黎各的CTV枳橙RB基因型的首次报道，但该基因型在1992年之前就已存在于那里。
