Rutgers breeders Jim Simon and Rong Di attend to sweet basil bred at Rutgers Hort Farm III.
Sweet basil (Ocimum basilicum L.) downy mildew disease (DM), caused by Peronospora belbahrii, continues to be a worldwide threat to the basil industry despite the recent release of Rutgers DM resistant varieties as the pathogen also continues to evolve. Using a proprietary transient gene editing vector, the Rutgers team successfully applied CRISPR/Cas9 technology to modify the sweet basil DM-susceptible gene, homoserine kinase (ObHSK) and generate DM-resistant mutant plants.
Rutgers’ CRISPR-edited ObHSK mutant sweet basil plants displayed significantly improved resistance to DM, when challenged with P. belbahrii inoculation under greenhouse conditions. The team obtained the first-ever national USDA-APHIS (Animal and Plant Health Inspection Services) permit to field test ObHSK mutant sweet basil plants outdoors at Rutgers Horticulture Farm III. Two years in a row, these ObHSK mutant sweet basil plants showed delayed DM disease onset and less severe symptoms, compared to non-edited plants, when exposed to severe disease conditions in the field.
Gene-edited, transgene-free, DM resistant sweet basil plants are now being bred into the series of Rutgers DMR sweet basils in order to reduce the plants’ natural susceptible genes to disease while conserving the disease resistant genes already bred into the sweet basils. This approach provides additional protection and will directly benefit farmers, consumers, and the environment by reducing the need for fungicide applications and its associated costs. This approach used does not involve GMO, allowing Rutgers new varieties to meet conventional and organic-grower and market needs. This research has been supported by USDA-NIFA and has resulted in the following publication and patent:
2021. Zhang, Y., C. Low, M. A. Lawton, J. E. Simon and R. Di. 2021. CRISPR-editing of sweet basil (Ocimum basilicum L.) homoserine kinase gene for improved downy mildew disease resistance. Frontiers in Genome Editing-Genome Editing in Plants 3:629769. DOI:10.3389/fgeed.2021.629769.
Rong Di, Michael A. Lawton and J. E. Simon. Gene-edited basil plants resistant to downy mildew, Patent No. US 12,356,912 B2. Issued July 15, 2025.
