A Novel Bioplastic Formulation (Mater-Bi®) for Carrying Conidia of a Non-Aflatoxigenic Strain of Aspergillus Flavus.

Biocontrol strategies have been widely used for controlling a variety of soil-borne pathogenic fungi in horticultural crops and for controlling aflatoxin contamination of peanuts, cotton and corn. A several year study demonstrated that aflatoxin contamination of Mississippi corn is dramatically reduced by field application of wheat grains inoculated with the atoxigenic Aspergillus flavus strain K49 (NRRL 30797). To develop alternative delivery systems of this atoxigenic strain, a series of laboratory studies were conducted to assess the efficiency of a novel granular formulation of bioplastic termed Mater-Bi^® (Novamont S.p.A., Italy). Mater-Bi^® granules (5 mm long and 3 mm diameter) to serve as a carrier for delivering this A. flavus strain. Mater-Bi^® granulaes were inoculated with a K49 conidia suspension and dried to attain a final density of log 7 conidia granuale^-1. The formulation showed > 90 and 70% survival after 6 months of storage at temperatures from 5 and 25^oC, respectively.  The colonization of microbiologically active and sterilized soil was assessed. Incubation of 20-g soil samples receiving a single Mater-Bi^® granule for 60-days resulted in log 4.2 to 5.4 propagules of A. flavus g^-1 soil in microbiologically active and sterilized soil, respectively. Increasing number of granules had no effect on the size of the introduced A. flavus population, as evaluated by cultural methods and quantitative PCR. After 60-day incubation, a shift in the composition of the fungal community structure with the predominance of the A. flavus K49 profile was observed using DGGE. In addition to the maintenance of rapidly vegetative growth and colonization of soil samples, these studies indicate that Mater-Bi^® has excellent potential to serve as a carrier to deliver biocontrol applications of A. flavus K49. This formulation is being investigated for its utility as a carrier to deliver other biocontrol fungi.