A Novel Source of Resistance to Pepper yellow leaf curl Thailand virus (PepYLCThV) (Begomovirus) in Chile Pepper

Chile pepper (Capsicum annuum L.) is an increasingly important vegetable and spice crop. Among the most devastating chile pepper–infecting viruses, especially in tropical and subtropical regions, are members of the whitefly transmitted Begomovirus, which cause pepper yellow leaf curl (PYLC). An effective PYLC management strategy is the development of resistant cultivars. However, genetic recombination, acquisition of extra DNA components, and synergistic interactions among different begomoviruses have resulted in the rapid emergence of new viruses that can infect new hosts, cause new disease symptoms, and overcome host resistance. In this project, 98 Capsicum entries comprising breeding lines, open pollinated varieties, genebank accessions, and wild species were screened for resistance to strains of Pepper yellow leaf curl Thailand virus (PepYLCThV). We used a randomized complete block design with three replications and 10 plants per replication in field net-houses at two locations (Khon Kaen and Kamphaeng Saen, Thailand) using augmented inoculation by viruliferous whiteflies. Scoring was done at ≈60, 90, and 120 days after inoculation using a standardized 6-point scale (1 = no symptoms to 6 = very severe symptoms), and the average of the scores of 10 plants within each replication was used for analysis. Although no entry was immune to the disease, the breeding line 9852-123 was highly resistant. Several accessions and lines were moderately resistant at both locations, although a high level of variability within these entries was observed. Overall, the disease severity at the Khon Kaen location was greater compared with Kamphaeng Saen, highlighting the importance of multilocation testing for disease resistance. The resistant entry identified here can be used to study gene action and to move resistance genes into well-adapted germplasm.