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Influence of Aspergillus candidus on Production of Aflatoxin in Rice by Aspergillus parasiticus. R. A. Boller, Research Plant Pathologist, Market Quality Research Group, ARS, USDA, P. O. Drawer ED, College Station, Texas 77840; H. W. Schroeder, Research Leader, Market Quality Research Group, ARS, USDA, P. O. Drawer ED, College Station, Texas 77840. Phytopathology 64:121-123. Accepted for publication 3 July 1973. DOI: 10.1094/Phyto-64-121.

Infection by Aspergillus parasiticus, and the level of aflatoxin contamination, increased in rice stored at 35 C and 100% relative humidity (RH), following inoculation with mixtures of conidia of A. candidus and A. parasiticus, as the proportion of A. parasiticus increased. Infection by A. candidus remained high throughout storage regardless of the ratio of species in the inoculum. When the number of conidia of A. parasiticus in the inoculum was equal to or less than the number of conidia of A. candidus, A. candidus became the dominant species after 7 days in storage at 25-35 C and RH of 85, 90, and 100%. Only small amounts of aflatoxins, or none, were detected under these conditions. Aflatoxin B₁ in rice inoculated with the greatest ratio of A. parasiticus to A. candidus (7:1) ranged from 3-5% of that detected in rice inoculated only with A. parasiticus. Toxin production was reduced more rapidly than the percentage of infection by A. parasiticus as a result of competition by A. candidus in all treatments.