Physiological race characterization of phytophthora capsici isolates from several host plant species in Brazil using New Mexico recombinant inbred lines of capsicum annuum at two inoculum levels

Abstract

Phytophthora blight, caused by Phytophthora capsici, is one of the most destructive diseases worldwide that affects Capsicum pepper. Attempts to provide universally resistant cultivars has been unsuccessful, which may be the result of the use of different resistance sources, pathotypes, or races of P. capsici isolates and screening techniques. The screening method used at Embrapa Vegetables in Brazil to detect resistance to P. capsici in Capsicum was compared with the screening method used at New Mexico State University. Both screening methods produced similar and consistent results when a range of P. capsici isolates were used. It was concluded that either method can successfully differentiate resistant and susceptible individuals. In addition, 20 P. capsici isolates from Brazil were characterized for virulence using a subset of 26 New Mexico recombinant inbred lines of pepper (Capsicum annuum). Within the P. capsici populations from Brazil, eight new physiological races for the root rot disease syndrome were identified. A total of nine isolates were pathogenic only on the susceptible control, 'Camelot'. The ability to identify physiological races of P. capsici occurring in Brazil allows for a better understanding about race-specific resistance leading to improved approaches in breeding for durable resistant cultivars.