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ARS Home » Pacific West Area » Parlier, California » San Joaquin Valley Agricultural Sciences Center » Crop Diseases, Pests and Genetics Research » Research » Publications at this Location » Publication #320333

Title: Fighting HLB with Citrus tristeza virus (CTV): Heterogeneity in the genome ends of CTV is an important consideration

item NG, JAMES - University Of California
item CHEN, ANGEL - University Of California
item Yokomi, Raymond - Ray

Submitted to: Citrograph
Publication Type: Trade Journal
Publication Acceptance Date: 11/15/2015
Publication Date: 1/5/2016
Citation: Ng, J., Chen, A., Yokomi, R.K. 2016. Fighting HLB with Citrus tristeza virus (CTV): Heterogeneity in the genome ends of CTV is an important consideration. Citrograph. 7:76-81.

Interpretive Summary: DNA technology has enabled RNA genomes of many viruses to be converted to DNA which, in turn, can be manipulated to serve different purposes. A Florida strain of Citrus tristeza virus (CTV) has been engineered to express genes that induce RNA interference (i)-mediated silencing of the Asian citrus psyllid (ACP), vector of the pathogen that causes Huanglongbing (HLB) (also known as greening disease) of citrus. It also was capable of expressing therapeutics against the HLB pathogen. The ACP has become firmly established in urban areas in the Los Angeles Basin and other southern counties and is spreading into central California where the majority of the State's citrus is grown. HLB disease has been detected in several dooryards in the Los Angeles area. Therefore, HLB is likely to affect commercial citrus groves in the foreseeable future. HLB is the most devastating disease of citrus worldwide. Infection can result in rapid loss of tree vigor and production, and trees may die within three years. The only effective control of HLB disease has been vector control by insecticides. This strategy is not sustainable long-term and is harmful to biological control agents and the environment. This report documents the initial objective of determining nucleotide diversity of several mild California CTV isolates. These data are essential for development of infectious complementary(c) DNA clones of CTV because nucleotide sequences determine essential functions for CTV RNA translation, replication, and assembly. Now that the consensus sequences of the RNA ends are known, construction of full-length infectious cDNA clones of several California CTV strains can begin. When completed, this CTV gene vector will be a new tool to combat citrus pests through transient expression of RNAi against the ACP or antimicrobial peptides against the HLB bacterial pathogen.

Technical Abstract: As California prepares for a potential showdown with Huanglongbing (HLB), contemporary disease control strategies that use low inputs, yet produce high value control, are needed to manage the disease. With biotechnology, Citrus tristeza virus (CTV) may be developed into a tool for protection or treatment of citrus trees. Specifically, the goal is to engineer an infectious complementary (c)DNA clone of a mild strain of California CTV that can be modified for the control of HLB (and also of other biotic agents-induced damages of citrus). The initial step was to analyze nucleotide variability at the genome ends of California CTV strains with T30- and T36-genotypes. This was critical because construction of an infectious cDNA clone for each of these CTV strains requires the correct nucleotide (molecules of nucleic acid) sequence in these locations for essential functions such as CTV RNA translation, replication, and assembly. A biologically active CTV full-length cDNA will provide a template for manipulation of the CTV viral genome to facilitate development and testing of therapeutic proteins and RNA silencing/interference against HLB and other citrus pests and pathogens.