Ninety-six mold isolates were obtained from naturally rotten citrus fruits. Among them, forty were identified as Penicillium italicum and twenty-four as P. digitatum. Twenty-four isolates of the former and twenty of the latter were tested for toxigenesis. They were first grown on Yeast Extract Sucrose (YES) broth for ten d at 22°C. Then, after mycelium removal, the cultures were sterilized by Millipore filtration and the toxicity of the sterile filtrates tested by four different bioassays; i.e. a bacterial test with Bacillus megaterium, a plant test with Lepidium sativum, a test with the brine shrimp Anemia salina and the chick (Gallus domesticus) embryo test. In P. digitatum, 95% of the filtrates were toxic to B. megaterium, 100% caused strong inhibition of seed germination in L. sativum, 75% showed acute toxicity to the brine shrimp and 65% were toxic to the chick embryo, while the figures for P. italicum filtrates were about 96%, 71%, 87%, and 42%, respectively. The results observed with the four different tests didn't always correlate.

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