Nonhost resistance is a plant immune response to resist most pathogens. The molecular basis of nonhost resistance remains poorly understood but recognition of pathogen effectors by immune receptors, a response known as effector-triggered immunity, has been proposed as a component of nonhost resistance. We performed transient expression of 54 P. infestans RXLR effectors in pepper accessions using optimized heterologous expression methods and analyzed the inheritance of effector-induced cell death in an F2 population derived from a cross between two pepper accessions. Pepper showed a localized cell death response upon inoculation with P. infestans, suggesting that recognition of effectors may contribute to nonhost resistance in this system. Nonhost pepper accessions recognized from 2 to 36 effectors. Among the effectors, PexRD8 and Avrblb2 induced cell death on a broad range of pepper accessions. Segregation of effector-induced cell death in an F2 population derived from a cross between two pepper accessions fit a 15:1, 9:7 and 3:1 depending on the effector. Our genetic data suggests that single or two independent/complementary dominant genes are involved in the recognitions RXLR effectors. Our findings indicate that multiple loci recognizing a series of effectors underpin nonhost resistance of pepper to P. infestans and may confer resistance durability.

• Doil Choi(Department of Plant Science, College of Agriculture and Life Sciences, Seoul National University)