Skip to main content
ARS Home » Pacific West Area » Riverside, California » National Clonal Germplasm Repository for Citrus » Research » Research Project #433437

Research Project: Selection, Molecular and Genetic Analysis of HLB Tolerant/resistant Variant Citrus Plants

Location: National Clonal Germplasm Repository for Citrus

Project Number: 2036-21000-011-05-R
Project Type: Reimbursable Cooperative Agreement

Start Date: Jan 15, 2017
End Date: Jan 14, 2020

Objective:
1. Select variant citrus plants or bud sports with HLB tolerance/resistance. 2. Identify citrus HLB-tolerant/resistant related genes for potential citrus genome editing targets through transcriptome profiling. 3. Identify genetic variants that are associated to HLB-tolerance/resistance in variant citrus plants. 4. Engineer HLB tolerance/resistance using genome editing technology.

Approach:
1. Select volunteer seedlings from years of natural fruit drop and bud sports from sweet oranges, grapefruit, and mandarin hybirds with natural HLB resistance/tolerance from commercial groves in Florida. Sustained tolerance to HLB will be demonstrated in greenhouse studies and field trials in Florida, where HLB is endemic. The quantity and quality of the fruit produced during the field trials will also be evaluated. 2. Profile the dual transcriptomes of 30 resistant/tolerant citrus plants and their 30 susceptible siblings before and after HLB infection using RNA-seq. Bioinformatics and functional genomic analysis will be used to predict a list of HLB tolerance/resistance-related genes. Expressions of selected genes will be verified by reverse transcription quantitative PCR (RT-QPCR)on HLB challenged citrus varities. 3. Re-sequence two tolerant/resistant and two susceptible sibling plants and their parents of a Duncan grapefrut line and a sour orange line. Bioinformatics and comparative genomics analysis will be used to identify HLB tolerance/resistance-related segment deletions, copy number variations (CNVs), structural variations (SVs), SNPs, and Indels in each citrus line. The identified variants will be further verified experimentally using RT-PCR.