Genome editing of the disease susceptibility gene CsLOB1 in citrus confers resistance to citrus canker

• Published in: Plant biotechnology journal Vol. 15; no. 7; pp. 817 - 823
• Main Authors: Jia, Hongge, Zhang, Yunzeng, Orbović, Vladimir, Xu, Jin, White, Frank F., Jones, Jeffrey B., Wang, Nian
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01.07.2017; John Wiley and Sons Inc
• Subjects: adverse effects; Bacteria; bacterial canker; breeding; Candidatus Liberibacter asiaticus; Canker; Cas9; Citrus - genetics; Citrus - microbiology; Citrus canker; Citrus fruits; Citrus greening; Citrus paradisi; CRISPR; crop production; Disease control; Disease resistance; Disease Resistance - genetics; Disease susceptibility; Disease Susceptibility - metabolism; Editing; Fruits; Gene Editing; Gene Expression Regulation, Plant - genetics; genes; Genetic aspects; Genetic research; Genome editing; Genomes; Genomics; Grapefruit; grapefruits; greening disease; Health aspects; high-throughput nucleotide sequencing; juvenility; Mutation; Pathogens; Plant bacterial diseases; Plant breeding; Plant diseases; Plant Diseases - genetics; Plant Diseases - microbiology; Plants (botany); Plants, Genetically Modified - genetics; Plants, Genetically Modified - microbiology; polyembryony; Polyploidy; RNA, Plant - genetics; sgRNA; Side effects; Target detection; Tree crops; trees; Xanthomonas citri; Xanthomonas citri; Cas9; sgRNA; Citrus paradisi
• ISSN: 1467-7644; 1467-7652; 1467-7652
• DOI: 10.1111/pbi.12677

Citrus is a highly valued tree crop worldwide, while, at the same time, citrus production faces many biotic challenges, including bacterial canker and Huanglongbing (HLB). Breeding for disease‐resistant varieties is the most efficient and sustainable approach to control plant diseases. Traditional breeding of citrus varieties is challenging due to multiple limitations, including polyploidy, polyembryony, extended juvenility and long crossing cycles. Targeted genome editing technology has the potential to shorten varietal development for some traits, including disease resistance. Here, we used CRISPR/Cas9/sgRNA technology to modify the canker susceptibility gene CsLOB1 in Duncan grapefruit. Six independent lines, DLOB2, DLOB3, DLOB9, DLOB10, DLOB11 and DLOB12, were generated. Targeted next‐generation sequencing of the six lines showed the mutation rate was 31.58%, 23.80%, 89.36%, 88.79%, 46.91% and 51.12% for DLOB2, DLOB3, DLOB9, DLOB10, DLOB11 and DLOB12, respectively, of the cells in each line. DLOB2 and DLOB3 showed canker symptoms similar to wild‐type grapefruit, when inoculated with the pathogen Xanthomonas citri subsp. citri (Xcc). No canker symptoms were observed on DLOB9, DLOB10, DLOB11 and DLOB12 at 4 days postinoculation (DPI) with Xcc. Pustules caused by Xcc were observed on DLOB9, DLOB10, DLOB11 and DLOB12 in later stages, which were much reduced compared to that on wild‐type grapefruit. The pustules on DLOB9 and DLOB10 did not develop into typical canker symptoms. No side effects and off‐target mutations were detected in the mutated plants. This study indicates that genome editing using CRISPR technology will provide a promising pathway to generate disease‐resistant citrus varieties.