Poster Session: Biochemistry and Cell Biology of Host Resistance

599-P

QTL mapping of fruit rot resistance to the plant pathogen Phytophthora capsici L. in a recombinant inbred line Capsicum annuum L. population.
R. NAEGELE (1), H. A. Ashrafi (2), T. Hill (2), S. Reyes Chin-Wo (2), A. Van Deynze (2), M. Hausbeck (1)
(1) Michigan State University, East Lansing, MI, U.S.A.; (2) University of California, Davis, CA, U.S.A.

Phytophthora capsici is an important pepper (Capsicum annuum L.) pathogen causing fruit, crown, root rot, and foliar blight in both field and greenhouse production systems. Previously, an F6 recombinant inbred line population was evaluated for fruit rot susceptibility; partial and isolate-specific resistance was found among lines. In our study, fruit rot resistance was mapped in the same F6 population between Criollo del Morelos 334, a landrace from Mexico, and ‘Early Jalapeno’ using a high-density genetic map. Isolate-specific resistance was mapped independently in 66 of the lines evaluated. Heritability of the resistance for each isolate at 3 and 5 days post inoculation (dpi) was moderately high (h²=0.48 to 0.63 and h²=0.74 to 0.83, respectively). Significant additive and epistatic QTL were identified for resistance to isolates OP97 and 13709 (3 and 5 dpi) and 12889 (3 dpi only). QTL for fruit phenotypic traits showed potential linkage with disease resistance QTL. The partial fruit rot resistance from CM334 suggests that this may not be an ideal source for fruit rot resistance in pepper.