The U.S. Citrus industry is facing unprecedented challenges from the spread of huanglongbing disease (HLB) in citrus-growing states like florida, texas and california

While traditional breeding approaches using wild relatives are one way of introducing disease tolerance into commercial citrus cultivars, these approaches often result in the loss of the carefully selected attributes of those commercial varieties. Thus, alternative approaches to rapidly generate new cultivars that are resistant to HLB and yet maintain their qualities would be extremely valuable. The proposed project will develop a population of crispr/CAS9 gene-edited plants, in which ~1200 HLB susceptibility genes will be targeted for mutation. We will then test these lines for resistance to XCC (the causative bacteria for citrus canker) and clas (the causative bacteria for HLB) since broad-spectrum resistance to bacterial diseases can be induced by mutating susceptibility genes. By targeting disease susceptibility genes in this way, we hope to be able to uncover those genetic variants that confer resistance to HLB. Part of this project also aims to develop the genetic resources necessary to carry out this project, including generating a high-quality reference genome for carrizo citrange, and developing low cost approaches to genotype plants using sequencing. This project will provide a sustainable resource for the citrus community that can be screened for resistance to other diseases and othervalue-added traits in the future, and thus accelerate discoveries that would benefit the U.S. Citrus industry for many years. This collection of citrus mutants will also help to identify intervention gene targets most worthy of advanced testing and commercialization. We will also study the societal impact of using crispr/CAS9 technologies, with a focus on increasing consumer acceptance of gene-edited citrus.