Seedborne black Aspergillus species as maize seedling pathogens: role of fumonisin production and interaction with soilborne Pythium species

Abstract

Twenty-six strains of black Aspergillus (Aspergillus section Nigri) were studied as seedling pathogens of maize. There were two major research components. The first component was an evaluation of the pathogenicity of isolates from several black Aspergillus species and a comparison of the pathogenicity of isolates with and without fumonisin production. This was accomplished by testing inoculated seeds in warm germination and cold tests, and by evaluating growth of inoculated seeds in rolled paper towel assays. In the second component, four of these species were selected for evaluation of interactions between Aspergillus and Pythium as a seedling disease complex in maize. Seeds inoculated with Aspergillus were planted in soil infested with Pythium sylvaticum, Pythium torulosum, or a control in a cup assay, and scored on several criteria for seedling growth. Species of Aspergillus in section Nigri are commonly associated with maize kernels but there is little information about their effects on maize seed germination and seedling health. It has recently been discovered that some strains in this group have the capacity for producing the fumonisin mycotoxins, but it is not known what effect, if any, this has on pathogenicity in seedling disease. We compared 9 strains from Iowa, 4 from Illinois, and 13 from Italy in two seed-inoculation assays assessing their ability to affect germination and seedling growth. Some were fumonisin-producing strains and others were non-producing. Representatives of A. awamori, A. niger, A. phoenicis, A. tubingensis, and a single strain of A. carbonarius were included. Maize seeds of two different hybrids were inoculated with spores of each of these strains. They were evaluated for germination and seedling growth using a warm germination test, a cold test, and a rolled paper towel assay. Strains of each species reduced germination or