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ARS Home » Southeast Area » Fort Pierce, Florida » U.S. Horticultural Research Laboratory » Citrus and Other Subtropical Products Research » Research » Research Project #440129

Research Project: CAP: Combining cultural and genetic approaches for grove success to unravel and enhance resistance/tolerance to Huanglongbing

Location: Citrus and Other Subtropical Products Research

Project Number: 6034-21000-019-006-R
Project Type: Reimbursable Cooperative Agreement

Start Date: Oct 1, 2020
End Date: Aug 31, 2023

Objective:
The research objective of this proposal is to investigate the root collapse associated with Huanglongbing (HLB)-impacted trees and methods to mitigate it by promoting root health. Our previous work demonstrates that as HLB severity increases, the root microbiome becomes enriched in soil-borne pathogens.

Approach:
We will conduct experiments to empirically determine if these pathogens exacerbate the Huanglongbing (HLB)-associated root (and canopy) decline. We will integrate field studies that test HLB resistant/tolerant rootstocks and use of soil amendments that promote root health to determine if they suppress pathogenic shifts in the microbiome and prolong tree longevity/productivity under HLB pressure. These field studies will include newly established and mature groves. To support our field trials and decipher the genes/gene pathways that dictate resistance or susceptibility to HLB, we will determine how rootstocks and scions respond to Candidatus Liberibacter asiaticus using a large collection of citrus genotypes that cover a spectrum of highly HLB-susceptible to HLB-resistant using a combination of global transcriptomics and expression quantitative loci mapping underpinned by a Citrus/Poncirus pan-genome analysis. We will use this data as a source of HLB resistance genes to functionally test sectors of the citrus immune system and to create HLB-resistant rootstocks and scions using CRISPR/Cas9 gene-editing with a new plant transformation strategy that increases the efficiency of citrus regeneration. We will integrate this research with a robust extension and outreach program in combination with an economic cost-benefit analysis structured around adoption of treatments that enhance root health in commercial citriculture.