United States of America, as Represented by the Secretary of Agriculture

The United States of America as Represented by the Secretary of

Robert Zablotowicz

Hamed K Abbas

Cesare Accinelli

Jeff Wilkinson

Maria L Sacca

Margaret E Lyn

A formulation containing conidia of non-toxigenic strains of fungi is a useful biocontrol agent for preventing toxin contamination in agricultural commodities, especially those for human and animal consumption such as peanuts, corn, cotton and tree nuts. The formulation of the invention is a water dispersible granule formulation suitable for spraying and includes non-toxigenic and/or non-aflatoxigenicstrains capable of inhibiting growth of fungi which produce aflatoxin and further capable of suppressing production of aflatoxin by the toxigenic fungi. A method of preparing the formulation is shown.

Water dispersible formulation for delivery of biocontrol fungi to reduce aflatoxin

Previous research demonstrated that aflatoxin contamination in corn is reduced by field application of wheat grains pre-inoculated with the non-aflatoxigenicstrain NRRL 30797. We evaluated the reliability and efficiency of replacing wheat grains with the novel bioplastic formulation Mater-Bi&#xae; to serve as a carrier matrix to formulate strain NRRL 30797. Mater-Bi&#xae; granules were inoculated with a conidial suspension of NRRL 30797 to achieve a final cell density of &#x2dc;log 7 conidia/granule. Incubation of 20-g soil samples receiving a single Mater-Bi&#xae; granule for 60-days resulted in log 4.2 to 5.3 propagules of/g soil for microbiologically active and sterilized soil, respectively. The bioplastic formulation was highly stable; Mater-Bi&#xae; is a suitable substitute for biocontrol applications ofNRRL 30797.

Granular bioplastic biocontrol composition

Previous research demonstrated that aflatoxin contamination in corn is reduced by field application of wheat grains pre-inoculated with the non-aflatoxigenicstrain NRRL 30797. To facilitate field applications of the biocontrol isolate, a series of laboratory studies were conducted on the reliability and efficiency of replacing wheat grains with the novel bioplastic formulation Mater-Bi&#xae; to serve as a carrier matrix to formulate this fungus. Mater-Bi&#xae; granules were inoculated with a conidial suspension of NRRL 30797 to achieve a final cell density of &#x2dc;log 7 conidia/granule. Incubation of 20-g soil samples receiving a single Mater-Bi&#xae; granule for 60-days resulted in log 4.2 to 5.3 propagules of/g soil for microbiologically active and sterilized soil, respectively. Increasing the number of granules had no effect on the degree of soil colonization by the biocontrol fungus. In addition to the maintenance of rapid vegetative growth and colonization of soil samples, the bioplastic formulation was highly stable, indicating that Mater-Bi&#xae; is a suitable substitute for biocontrol applications ofNRRL 30797.

The ability of twoLink isolates (CT3 and K49) to reduce aflatoxin contamination of corn was assessed in a four-year field study (2001 to 2004). Soil was treated with six wheat inoculant treatments: toxigenic isolate F3W4; the non-toxigenic isolate K49; the non-aflatoxigenic isolate CT3, two mixtures of CT3 or K49 with F3W4; and an autoclaved wheat control, applied at 20 kg/ha. In 2001, inoculation with the toxigenic isolate increased corn grain aflatoxin levels by 167% compared to the non-inoculated control, while CT3 and K49 inoculation reduced aflatoxin levels in corn grain by 86% & 60%, respectively. In 2002, inoculation of CT3 and K49 reduced aflatoxin levels by 61% and 76% compared to non-inoculated controls, respectively. In 2001 mixtures of toxigenic and non-toxigenic isolates had little effect on aflatoxin levels, but in 2002 inoculation with mixtures of K49 and CT3 reduced aflatoxin levels 68 and 37% compared to non-inoculated controls, respectively. In 2003 and 2004, a low level of natural aflatoxin contamination was observed (8 ng/g). However, inoculation with mixtures of K49+F3W4 and CT3+F3W4, reduced levels of aflatoxin 65 to 94% compared to the toxigenic strain alone. Compared to the non-sclerotia producing CT3, strain K49 produces large sclerotia, has more rapid in vitro radial growth, and a greater ability to colonize corn when artificially inoculated, perhaps indicating greater ecological competence. Results indicate that non-toxigenic, indigenousisolates, such as strain K49, have potential use for biocontrol of aflatoxin contamination in southern U.S. corn.

Growing community of inventors

Cleveland, MS, United States of America

Robert Zablotowicz