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Selective Medium for Isolating Penicillium digitatum. J. L. Smilanick, Graduate Research Assistant, Department of Plant Pathology, University of California, Riverside 92521. J. W. Eckert, Professor of Plant Pathology, Department of Plant Pathology, University of California, Riverside 92521. Plant Dis. 70:254-256. Accepted for publication 3 September 1985. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1986. DOI: 10.1094/PD-70-254.

Media varying in nutrients, pH, and inhibitory compounds were evaluated for selective development of colonies of Penicillium digitatum and suppression of fungal contaminants in plates exposed to the atmospheres of citrus groves and packinghouses. Thirteen species of common airborne fungi were replica-plated to the suppressive media and incubated at 20 C. o-Phenylanizole (OPA) and 2,3,4,6-tetrachloroanisole (TCA) were the most selective agents when added to potato-dextrose agar (PDA) enriched with 2 g each of neopeptone and yeast extract per liter, whereas PCNB and acidification to pH 3.5 were less effective. The enriched PDA medium adjusted to pH 5.5 and amended with OPA at 100 μg/ ml and PCNB at 500 μg/ml greatly inhibited the contaminant fungi and fungi encountered in citrus packinghouses. This selective medium did not affect the colony-forming potential of spores of P. digitatum but restricted the colony size, permitting more efficient enumeration of colonies forming from airborne spores of these pathogens.