Generating Disease Resistant Citrus Varieties using Cas9/sgRNA

Citrus industry faces multiple disease challenges in Florida, including citrus Huanglongbing (HLB) caused by Candidatus Liberibacter asiaticus (Las) and citrus canker caused by Xanthomonas citri subspecies citri (Xcc). Generating disease resistant citrus varieties will provide an efficient and sustainable term solution to either HLB or caner disease. However, the traditional approach of breeding for resistant plants for citrus is difficult and has not provided a timely solution to control HLB or canker due to the long juvenility, large tree size, and prevalence of polyembryonic seeds in commercial varieties. Here we will present our progress in generating disease resistant citrus varieties via CRISPR technology. Firstly, we will report our latest progress in generating canker resistant citrus by modifying the CsLOB1 gene and the effector binding elements (EBEs) of PthA4 in the CsLOB1 Promoter (EBEPthA4-CsLOBP) of the CsLOB1 gene via Cas9/sgRNA technology. CsLOB1 is a susceptibility gene for citrus canker and is induced by the pathogenicity factor PthA4, which binds to the EBEPthA4-CsLOBP to induce CsLOB1 gene expression. Secondly, we will present our progress in identifying the critical virulence factors, e.g., Sec-dependent effectors (SDEs) of Las and their putative targets in citrus. We aim to generate HLB resistant or tolerant plants by disrupting the interaction between SDEs and their targets in citrus.