Detection and Eradication of Alternaria radicina on Carrot Seed. B. M. PRYOR, Graduate Research Assistant; Department of Plant Pathology and the Plant Protection and Pest Management Graduate Group, University of California, Davis 95616. R. M. DAVIS, Cooperative Extension Specialist, and R. L. GILBERTSON, Assistant Professor, Department of Plant Pathology and the Plant Protection and Pest Management Graduate Group, University of California, Davis 95616. Plant Dis. 78:452-456. Accepted for publication 8 January 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0452.

Alternaria radicina was recovered from carrot seed following a 10-day incubation on a semiselective agar medium, Alternaria radicina Selective Agar (ARSA). A significantly higher proportion of A. radicina-intested seed was detected in individual seed lots assayed on ARSA than was detected by the standard freezer-blotter seed assay. The identity of A. radicina recovered on ARSA was confirmed by inoculation of carrot root tissue. Based on seed assays using ARSA, 24% (seven of 29) of randomly selected commercial carrot seed lots planted in the Cuyama Valley, California, in 1992, contained low levels of A. radicina (≤0.1%). Seed treatments for eradicating the pathogen from infested seed were evaluated. Hot water (50°C for 30 min) or hot sodium hypochlorite (0.1% or 1.0% at 50°C for 30 min) eradicated A. radicina from infested carrot seed with a minimal reduction in seed germination.

Keyword(s): carrot black rot, Daucus carota, seedborne pathogen, seed testing