Oral Technical Session: Fungal Diversity and Management

189-O

Phytophthora fruit rot resistance, population structure, and genetic diversity in a diverse pepper (Capsicum spp.) collection.
R. P. NAEGELE (1), A. Tomlinson (1), M. K. Hausbeck (1)
(1) Michigan State University, East Lansing, MI, U.S.A.

Pepper is extensively grown throughout Europe, Asia, North and South America. Phytophthora capsici Leonian, a major disease of pepper, is distributed worldwide and can cause fruit, crown, and root rot in addition to foliar blight. The mechanisms of control between diseases have minimal overlap and current resistant cultivars only provide root and crown rot control. Immature, green fruit of 120 pepper (Capsicum spp.) germplasm lines representing 5 continents and 45 countries were evaluated for fruit rot resistance. Fruit were inoculated with two virulent isolates of P. capsici. For each isolate, fifteen fruit were evaluated; lesion diameter and density of pathogen growth were evaluated 3 and 5 days post inoculation (dpi). Significant isolate-specific interactions and line differences were detected at 3 and 5 dpi. Most lines in this study exhibited a high degree of susceptibility (>70% incidence at 5 dpi) to fruit rot. No line was completely resistant to both isolates tested. However, partial resistance was detected in the population. Population structure and genetic diversity were estimated using 27 polymorphic simple sequence repeat markers on the pepper genotypes. Population structure associations with country of origin, disease resistance and continent of origin were evaluated. The partially resistant material identified in this study offer useful sources for incorporating fruit rot resistance into commercial varieties.