Citrus Pathology Lab

All elite commercial citrus cultivars are susceptible to HLB. However, wild and relatives of citrus (such as Australian lime) tolerate HLB. One mechanism of HLB tolerance is reducing callose and reactive oxygen species (ROS) accumulation when infected with CLas. Therefore, if we understand how citrus relatives regulate callose and ROS upon infection, we can reprogram commercial citrus to respond in a similar manner, enabling tolerance in elite commercial citrus scions. In this project, we will identify citrus accessions with elevated basal callose levels, test their HLB tolerance, and identify genetic markers that will help us identify genetic defects (i.e., elevated callose and ROS accumulation) within commercial citrus, and use this knowledge for breeding purposes. One approach to rapidly introducing HLB resistance in our cultivars is using transgenic or transient expression approaches. We will use citrus tristeza viral vector (CTV) or transgenic approaches to overexpress or downregulate citrus defense genes, or combine them to make Valencia or Hamlin tolerant/resistant like wild citrus and some relatives. The outcome of this project will allow us to: 1) understand better the molecular mechanisms underlying HLB susceptibility and tolerance, 2) obtain new citrus germplasms with reduced CLas-induced callose and ROS accumulation, 3) acquire potential biomarkers for conventional breeding, 4) identify citrus genes involved in defense mechanism and manipulate them with gene editing or balanced expression approaches for HLB resistance, and 5) better understand citrus immune system leading to HLB susceptibility and tolerance.