P-352 - GENE EDITING OF SWEET ORANGE IMMUNE RELATED GENES TO EXPLORE THEIR ROLES IN HUANGLONGBING DISEASE DEVELOPMENT

Citrus Huanglongbing (HLB), is the most severe threat to citrus production worldwide, caused by the phloem-colonizing bacterium Candidatus Liberibacter asiaticus (Las). Previous study suggests that HLB is an immune-mediated plant disease and Las causes systemic and chronic immune response in phloem tissues including reactive oxygen species (ROS) production and callose deposition, resulting in phloem cell death and HLB symptoms. Currently, the genetic mechanism underneath HLB immune-mediated disease development remains unknown. This study aims to investigate roles of citrus immune related genes in HLB disease development using CRISPR/Cas9 gene-editing technology. We hypothesize that the pattern-triggered immunity (PTI) pathway, is involved in Las-triggered immune response in citrus resulting in systemic oxidative stress and disease symptoms. By knocking out PTI-related genes involved in pathogen recognition, ROS production, and callose deposition, we aim to reduce HLB symptom severity and gain insight into the molecular mechanisms of disease development. We generated edited citrus lines targeting PTI related genes (FLS2, RLP-like protein, SOBIR1, BAK1, and PBL19). We will test the homozygous/biallelic mutants in ROS production, phloem cell death, callose deposition, Las titers and HLB disease development compared to wild type controls. Identification of genetic determinants responsible for HLB development is critical to develop HLB resistant/tolerant citrus varieties.