"Potato dextrose agar (PDA) is a nutrient medium that is recommended by APHA, FDA, USP, BP, EP, and JP for the growth of fungi. It is commonly used for plate counts of yeasts and molds in the examination of foods and dairy products. PDA can also be used to stimulate sporulation, maintain stock cultures of certain dermatophytes, and differentiate typical varieties of dermatophytes on the basis of pigment production.
PDA is made with potato extract and dextrose, which provide nutrients for fungal growth. The pH of the medium is adjusted to 3.5 with tartaric acid, which inhibits bacterial growth. It is important to avoid heating the medium after acidification, as this can hydrolyze the agar and prevent it from solidifying."