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Factors Affecting Production of the Mycotoxin F-2 by Fusarium roseum. Caesaria P. Eugenio, Former Research Assistant, Department of Plant Pathology, University of Minnesota, St. Paul 55101; C. M. Christensen(2), and C. J. Mirocha(3). (2)(3)Professor, and Associate Professor, respectively, Department of Plant Pathology, University of Minnesota, St. Paul 55101. Phytopathology 60:1055-1057. Accepted for publication 15 February 1970. DOI: 10.1094/Phyto-60-1055.

All 43 isolates of Fusarium roseum that were tested, chiefly from corn stored on the cob in cribs on farms in Minnesota, produced some F-2, and seven were rated as high producers. No isolate of any of the other eight species of Fusarium tested produced detectable amounts of F-2 [6-(10-hydroxy-6-oxo-trans-1-undecenyl)- β-resorcylic acid lactone]. After preliminary incubation for 2 weeks at 22-25 C, more F-2 was produced with continued incubation at 15 C than at other temp tested. In polished rice as a substrate, more F-2 was produced at a moisture content of 60-65%, and in corn at a moisture content of 45%, w/w basis, before autoclaving, than at other moisture contents tested. A larger amount of F-2 was produced on polished rice than on any other substrate tested, followed by corn, then wheat; very small amounts of F-2 were produced on oats or barley, and none on soybeans or peas. No more than trace amounts of F-2 were produced on any of the liquid media tested. When F. roseum and each of a number of other microflora were inoculated onto autoclaved moist grain at the same time, little or no F-2 was produced, and when the competing organisms were inoculated after F. roseum had grown for 1 week, F-2 production was lower than in the controls, but still moderately high. Single-ascospore lines of the two mass isolates that were highest in F-2 production differed greatly in the amount of F-2 they produced.