From Meg McGrath, Long Island Horticultural Research & Extension Center, mtm3@cornell.edu:
Plants of downy mildew resistant sweet basil variety Prospera severely affected by downy mildew were observed in a commercial greenhouse planting in Suffolk County, NY, in fall 2022. Seed of Prospera and DiGenova were sown in our laboratory at LIHREC. Seedlings of both varieties inoculated with spores from the commercial plants became severely affected, thereby documenting presence of the new pathogen race (race 1). This appears to have been an isolated occurrence in 2022 since there were no reports from other U.S. growers of affected Prospera (unreported cases are possible), and Prospera exhibited excellent resistance in the variety trial at LIHREC. There was a report from a Croatian grower.
For more information and photographs see Occurrence on Long Island of Basil Downy Mildew Pathogen Race 1 that Overcomes some Resistant Varieties.