001. Geromy G. Moore, Brian M. Mack, Shannon B. Beltz. Southern Regional Research Center, Agricultural Research Service, United States Department of Agriculture, New Orleans, USA. Testing the Efficacy of eGFP-Transformed Aspergillus flavus as Biocontrol Strains. Food and Nutrition Sciences, 4 (4), 2013, Pages: 469-479.

Current biological control methods to prevent pre-harvest aflatoxin contamination of corn, cottonseed, and ground and tree nuts involve field inoculation of non-aflatoxigenic Aspergillus flavus. To date, the efficacy of this approach requires annual reapplication of the biocontrol agent. The reason for this requirement is uncertain. To track the dispersal and test the longevity of these strains, we prepared fluorescent biocontrol strains by incorporating into them the gene expressing the enhanced green fluorescent protein (eGFP). We first investigated the effects of eGFP transformation on the ability of the fluorescent fungus to compete with its non-fluorescent homolog, and then with other heterologous non-aflatoxigenic strains as well as with aflatoxigenic isolates. Our findings indicate that, in these studies, detection of fluorescence was variable, with some fluorescent strains exhibiting enhanced growth and sporulation post-transformation. In our tests, not all transformed strains proved to be good candidates for tracking because their fluorescence was reduced over the course of our study. Most of the transformed strains retained fluorescence and showed robust colony growth in an artificial competitor environment; therefore, they should be suited for further trial under more natural settings. Our ultimate objective is to determine if out-crossing between biocontrol strains and native field populations is occurring in a natural setting.

Keywords: Aspergillus; Biocontrol; Green Fluorescent Protein (GFP); Aflatoxin; Fungal Competition; Afla-Guard®; AF36.

002. Peter A.H.M. Bakker, Rogier F. Doornbos, Christos Zamioudis, Roeland L. , Berendsen, Corné M.J. Pieterse. Plant-Microbe Interactions, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrech, Netherlands. Induced Systemic Resistance and the Rhizosphere Microbiome. Journal of Plant Pathology, 29 (2), 2013, Page: 136-143.

Microbial communities that are associated with plant roots are highly diverse and harbor tens of thousands of species. This so-called microbiome controls plant health through several mechanisms including the suppression of infectious diseases, which is especially prominent in disease suppressive soils. The mechanisms implicated in disease suppression include competition for nutrients, antibiosis, and induced systemic resistance (ISR). For many biological control agents ISR has been recognized as the mechanism that at least partly explains disease suppression. Implications of ISR on recruitment and functioning of the rhizosphere microbiome are discussed.

Keywords: disease suppressive soils, plant pathogens, Pseudomonas spp.