Yokomi Raymond K, Selvaraj Vijayanandraj, Maheshwari Yogita, Saponari Maria, Giampetruzzi Annalisa, Chiumenti Michela, Hajeri Subhas
First, second, and third authors: U.S. Department of Agriculture-Agricultural Research Service, San Joaquin Valley Agricultural Sciences Center, 9611 South Riverbend Avenue, Parlier, CA 93648-9757; fourth and sixth authors: Institute for Sustainable Plant Protection, National Research Council, Sezione di Bari, Via Amendola 165/A, 70126 Bari, Italy; fifth author: Department of Soil Plant and Food Science, University of Bari, Via Amendola 165/A, 70126 Bari, Italy; and seventh author: Citrus Pest Detection Program, Central California Tristeza Eradication Agency, 22847 Road 140, Tulare, CA 93274-9367.
Phytopathology. 2017 Jul;107(7):901-908. doi: 10.1094/PHYTO-01-17-0007-R. Epub 2017 Apr 28.
Most Citrus tristeza virus (CTV) isolates in California are biologically mild and symptomless in commercial cultivars on CTV tolerant rootstocks. However, to better define California CTV isolates showing divergent serological and genetic profiles, selected isolates were subjected to deep sequencing of small RNAs. Full-length sequences were assembled, annotated and trifoliate orange resistance-breaking (RB) isolates of CTV were identified. Phylogenetic relationships based on their full genomes placed three isolates in the RB clade: CA-RB-115, CA-RB-AT25, and CA-RB-AT35. The latter two isolates were obtained by aphid transmission from Murcott and Dekopon trees, respectively, containing CTV mixtures. The California RB isolates were further distinguished into two subclades. Group I included CA-RB-115 and CA-RB-AT25 with 99% nucleotide sequence identity with RB type strain NZRB-G90; and group II included CA-RB-AT35 with 99 and 96% sequence identity with Taiwan Pumelo/SP/T1 and HA18-9, respectively. The RB phenotype was confirmed by detecting CTV replication in graft-inoculated Poncirus trifoliata and transmission from P. trifoliata to sweet orange. The California RB isolates induced mild symptoms compared with severe isolates in greenhouse indexing tests. Further examination of 570 CTV accessions, acquired from approximately 1960 and maintained in planta at the Central California Tristeza Eradication Agency, revealed 16 RB positive isolates based on partial p65 sequences. Six isolates collected from 1992 to 2011 from Tulare and Kern counties were CA-RB-115-like; and 10 isolates collected from 1968 to 2010 from Riverside, Fresno, and Kern counties were CA-RB-AT35-like. The presence of the RB genotype is relevant because P. trifoliata and its hybrids are the most popular rootstocks in California.
加利福尼亚的大多数柑橘衰退病毒（CTV）分离株在耐CTV的砧木上的商业栽培品种中生物学特性温和且无症状。然而，为了更好地界定表现出不同血清学和遗传特征的加利福尼亚CTV分离株，对选定的分离株进行了小RNA深度测序。组装了全长序列，进行了注释，并鉴定出了CTV的枳橙抗性破坏（RB）分离株。基于其全基因组的系统发育关系将三个分离株置于RB进化枝中：CA-RB-115、CA-RB-AT25和CA-RB-AT35。后两个分离株分别通过蚜虫传播从含有CTV混合物的默科特树和德科朋树中获得。加利福尼亚RB分离株进一步分为两个亚进化枝。第一组包括CA-RB-115和CA-RB-AT25，与RB型菌株NZRB-G90的核苷酸序列同一性为99%；第二组包括CA-RB-AT35，与台湾文旦/SP/T1和HA18-9的序列同一性分别为99%和96%。通过检测嫁接接种的枳橙中的CTV复制以及从枳橙传播到甜橙，证实了RB表型。在温室索引试验中，与严重分离株相比，加利福尼亚RB分离株引起的症状较轻。对从大约1960年获得并保存在加利福尼亚中部衰退病根除机构植物中的570份CTV材料进行进一步检测，基于部分p65序列发现了16个RB阳性分离株。1992年至2011年从图莱里县和克恩县收集的6个分离株与CA-RB-115相似；1968年至2010年从里弗赛德县、弗雷斯诺县和克恩县收集的10个分离株与CA-RB-AT35相似。RB基因型的存在具有相关性，因为枳橙及其杂种是加利福尼亚最受欢迎的砧木。
