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Influence of Diurnal Temperature Cycles on Infection of Cotton Bolls by Aspergillus flavus. R. G. Gilbert, Research Microbiologist, U.S. Water Conservation Laboratory and Western Cotton Research Laboratory, Phoeniz, AZ 85040; J. L. McMeans(2), and R. L. McDonald(3). (2)(3)Plant Physiologist, and Biological Science Technician, respectively, U.S. Water Conservation Laboratory and Western Cotton Research Laboratory, Phoeniz, AZ 85040. Phytopathology 65:1043-1044. DOI: 10.1094/Phyto-65-1043.

Excised cotton bolls were inoculated with an aflatoxin-producing strain of Aspergillus flavus (ATCC #26994), and were placed in growth chambers for 7 or 3 days with short (2-hour) or long (10-hour) diurnal maximum temperature cycles. The maximum and minimum temperatures were 30-32 C and 16-18 C, respectively. The percent bright greenish-yellow (BGY) fluorescence of locks and seeds, as well as seed infection of BGY-fluorescent seeds, increased as the duration of the daily maximum temperature of 30 C increased, and/or as the number of diurnal maximum temperature cycles of 30 C increased. Aflatoxin did not accumulate in A. flavus-infected seed, regardless of treatment.

Additional keywords: Gossypium hirsutum L., mycotoxins.