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Influence of Temperature on Production of Aflatoxin in Rice by Aspergillus parasiticus. R. A. Boller, Research Plant Pathologist, and H. W. Schroeder, Research Leader, Market Quality Research Group, ARS, USDA, P. O. Drawer ED, College Station, Texas, 77840. Phytopathology 64:283-286.

Aspergillus parasiticus rapidly invaded rough rice stored at 85% relative humidity (RH), the minimum RH which consistently supported production of aflatoxins.  After 14 days at 25, 30, or 35 C, almost 80% of the kernels were invaded.  After 7 days, more than 90% of the kernels of inoculated rice were infected by A. parasiticus at 15, 25, 30, and 35 C and at temperatures which alternated 20-40 C and 100% RH, the RH most favorable for maximum production of aflatoxins.  At 85% RH, small quantities of aflatoxin B1 (trace, to 5 μg/kg) were detected in rice stored at 30 and 35 C.  Aflatoxin production and/or accumulation in rice stored at 100% RH appeared to increase with temperature but not necesarily with prevalence of infection.  Rates of infection and colonizations of inoculated kernels by species of the natural mycoflora increased with temperature.  The relative dominance of species at different times during storage appeared to be temperature-related.  Decreases in quantities of aflatoxins detected during storage appeared to reflect, in part, the activity of competing species.

Additional key words: Aspergillus glaucus group, A. flavus group, A. candidus, Penicillium.