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Conidial Germination and Population of Aspergillus flavus in the Geocarposphere of Peanut. G. J. Griffin, Department of Plant Pathology and Physiology, Virginia Polytechnic Institute and State University, Blacksburg 24061; Phytopathology 62:1387-1391. Accepted for publication 12 June 1972. DOI: 10.1094/Phyto-62-1387.

Under greenhouse conditions, pegs of Virginia Bunch 46-2 peanut plants were introduced into small pots containing a nonsterile loamy fine sand artificially infested with washed conidia of a clone of Aspergillus flavus isolated from peanut fruit. Dilution plate analysis indicated the inner 0.5-mm layer of geocarposphere soil of pegs and mature fruits had A. flavus populations little different from nongeocarposphere soils. In contrast, the population of total fungi was greater, and the populations of bacteria and actinomycetes were much greater, in geocarposphere soils. Microscopic observation of the inner 0.5-mm soil layers indicated that no germination of conidia of A. flavus occurred in peg geocarposphere soil, and trace germination occurred in fruit geocarposphere soil for plants maintained in a growth chamber at 30 C. A. flavus conidia germinated readily in soil adjacent to pods after 16 hr at 30 C and 35 C when a 4- to 6-mm2 area of pod surface was superficially injured and inoculated with infested soil. Dry conidia applied to aerial portions of pegs in the greenhouse germinated at a low percentage. These findings are discussed in relation to the exogenous carbon and nitrogen requirements for spore germination.

Additional keywords: fungistatic substances, rhizosphere.