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Isolation, Storage, and Inoculum Production Methods for Alternaria dauci. J. O. Strandberg, Professor and plant pathologist, University of Florida, Institute of Food and Agricultural Sciences, Central Florida Research and Education Center, Sanford 32771; Phytopathology 77:1008-1012. Accepted for publication 10 December 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-1008.

Alternaria dauci was isolated from diseased carrot leaves, seedlings, or infested seeds by simple isolation methods. Pathogenicity or viability of the isolates was not related to sources of the fungus. Isolates stored for 6 mo on carrot leaf agar showed little change in pathogenicity, sporulation, or colony type. Conidia produced on cellulose disks impregnated with carrot leaf extract and then dried and stored at low relative humidity maintained viability and pathogenicity for at least 18 mo. On agar media, a pH from 6.0 to 6.5 was optimum for mycelial production; a pH near 7 was optimum for conidial production. Growth rate was proportional to temperature from 12 C to 28 C; significant growth was observed as low as 12 C. Minimum daylength of 4 hr was required for abundant production of conidia. A medium made from dried carrot leaves allowed reliable culture, storage, and production of conidia of A. dauci. Conidia to inoculate plants were efficiently recovered by washing them from agar plates with water containing a surfactant.