Lettuce germplasm resistance to western flower thrips vectors of Impatiens necrotic spot virus

Impatiens necrotic spot virus (INSV) is an orthrotopovirus, mainly transmitted by Frankliniella occidentalis (Western flower thrips, WFT). The virus has caused up to 100% yield losses in California and became a major challenge in lettuce production. Florida is the third-largest lettuce-producing state after California and Arizona. While cases of INSV have not been reported in Florida lettuce, it has been reported in ornamental crops before. The widespread of WFT poses a significant risk of INSV outbreak if it were to be introduced. Therefore, this study examined lettuce accessions to identify lettuce resistant to WFT as a proactive measure for thrips management and mitigate potential impact of INSV. Thirty-five accessions were screened in no-choice experiments for thrips resistance. Lettuce at 5-6 leaf stage were infested with 7 female thrips that were reared on a susceptible control cultivar Okeechobee. After 14 days, immatures (larvae and pupae) and adult thrips per plant were counted. A breeding line 50100, cultivars Cherokee, Eruption, La Brillante, and Hacienda, and a plant introduction (PI)251246 showed significantly lower immatures than Okeechobee, indicating resistance to WFT. Conversely, cultivar Western Red Leaf had significantly higher immatures, suggesting susceptibility. Subsequently, no-choice and choice bioassays were conducted and further validated thrips resistance in breeding line 50100 and cultivar Eruption, having significantly lowest number of thrips and percentage of damage compared to Okeechobee. These results highlight promising candidates for identifying genomic regions conferring resistance to WFT, supporting the development of resistant lettuce.