Fungi that infect cottonseeds before harvest.

As a part of an investigation of aflatoxins and other mycotoxins in cottonseeds at harvest, samples of seeds collected from the 1971 crop at locations across the U.S. Cotton Belt were examined to determine the kinds of microorganisms causing internal or seed-coat infection in the field. Aspergillus flavus infection was absent from all seeds examined from most areas but was present in some samples from Arizona, California, and Texas. Fusarium spp., Alternaria sp., and A. niger caused internal infection at many locations; Colletotrichum gossypii and Rhizopus stolonifer were present in seeds from some areas but were generally much less common. Many of the infections with A. niger were in the seed coat. Bacterial infections were fairly frequent. In a series of commerical samples from Arizona. A. flavus infection was found in 61% of seeds, with fiber showing the bright, greenish-yellow (BGY) fluorescence that is diagnostic for A. flavus boll rot. Aflatoxin contamination was also concentration in the same seeds. The above findings agree with previous data showing that aflatoxin contamination of cottonseeds before harvest occurs rarely, if at all, in most parts of the U.S. Cotton Belt and that when such contamination does occur, it tends to be concentrated in seeds with the BGY fluorescence in their fiber and seed fuzz.