SEED TREATMENT USING PRE-INFILTRATION AND BIOCONTROL AGENTS TO REDUCEDAMPING-OFF OF CORN CAUSED BY SPECIES OF PYTHIUM AND FUSARIUM

Bioassays were conducted in a greenhouse at 18 degrees C to determine the effectiveness of a seed treatment used in combination with biocont rol agents for the reduction of corn damping-off caused by species of Pythium and Fusarium. Corn seeds were. infiltrated with tap water, dra ined, air-dried, and then coated with biomass of an antagonistic fungu s, Gliocladium virens isolate Gl-3, or an antagonistic bacterium, Burk holderia capacia isotates Bc-B or Bc-1, or a combination of Gl-3 with each of the bacterial isolates. A nonsterile field son was infested wi th a combination of pathogens: Pythium ultimum, P. arrhenomanes, and F usarium graminearum at 2 inoculum rates (1x and 4x). Pre-infiltration enhanced (P less than or equal to 0.05) disease control with most trea tments at both inoculum rates, Treatments with biocontrol agents alone err in combination, as well as the fungicide captan, effectively redu ced the disease at a pathogen inoculum rate of 1x, resulting in greate r (P less than or equal to 0.05) seedling stands, plant height, and fr esh weight, and lower (P less than or equal to 0.05) Foot rot severity compared with untreated seeds in infested soil At a pathogen inoculum rate of 4x, stands were lower (P less than or equal to 0.01) and root -rot severity was higher (P < 0.01) compared to those at 1x for all tr eatments. Nevertheless, coating seeds with all biocontrol agents (alon e or in combination), except with Bc-1 alone, reduced disease (P less than or equal to 0.05) compared to untreated seeds in infested soil. A t both inoculum rates of 1x and 4x, coating seeds with Gl-3 + Bc-B was more effective (P less than or equal to 0.05) in disease control than any other treatment, resulting in stands, growth rate (plant height a nd fresh weight), and root rot severity similar to plants from untreat ed seeds in noninfested soil. In addition, when the exudate from a 2-h infiltration of corn seed was added to the seeds during seed coating, seedling stand was often lower and root rot severity was often higher than those from infiltrated seeds (P less than or equal to 0.05). The se results indicated that the infiltration process removed certain exu dates, including nutrients and/or stimulants (not detected in this stu dy) that might be utilized by pathogens to initiate seed infection. A thin-layer chromatography (TLC) profile of the, exudates showed the pr esence of eight amino acids and three major carbohydrates.