Submitted to: Mycopathologia
Publication Type: Abstract Only
Publication Acceptance Date: 10/24/2001
Publication Date: 1/10/2002
Interpretive Summary: Application of nontoxigenic strains of Aspergillus flavus and A. parasiticus to soil around peanut plants effectively reduces pre- and post-harvest aflatoxin contamination. Further development of this technology has focused on the evaluation of different biocontrol formulations and the effect of biocontrol treatments on peanut seed germination and plant survivability. Evaluation of Biocontrol Formulations: A simple, economical technique for producing an aflatoxin biocontrol formulation was reported at the 2000 Aflatoxin Elimination Workshop. Briefly, the technique involves the coating and entrapment of spores of nontoxigenic strains on the surface of a small grain, which serves as both carrier and substrate. A three-year study was conducted to determine the effectiveness of this formulation technique compared with the more traditional formulation produced by solid-state fermentation. Formulations tested included solid-state fermented rice, spore-coated rice, and spore-coated barley. There were no significant differences among formulations in : (1) establishing biocontrol fungi in soil; (2) displacing toxigenic strains in the peanut crop; (3) reducing aflatoxin contamination. Because of the new formulation technique eliminates the need for sterilizing and drying the substrate, which is a requirement of solid-state fermentation, and is amenable to rapid, large scale production, it offers distinct advantages over solid-state fermentation for production of biocontrol formulations. Effect of Treatment on Peanut Seed Germination and Plant Survivability: Peanuts from fields that were either treated or not treated with the nontoxigenic, biocontrol strains were planted the following year to determine if infection by nontoxigenic strains affected seed germination or plant survivability. During crop year 1999, peanuts were subjected to severe late-season drought stress and were stored under temperature and relative humidity conditions conducive for fungal proliferation. After storage, both treated and untreated peanuts were highly colonized by Aspergillus species. However, the incidence of nontoxigenic strains in treated peanuts was 96.4% compared with only 3.9% in untreated peanuts. Aflatoxin contamination was reduced by 96.7% in treated peanuts. In crop year 2000, treated and untreated seeds were each planted in 10 replicate plots with 100 seeds per plot. Percent germination, as evidenced by cracking of the soil surface, averaged 77.8% for untreated peanuts and 77.9% for treated peanuts. The emergence of plants averaged 76.0% for both groups, and 99% of those plants survived for at least 21 days in both groups. Results showed that the nontoxigenic strains used for biocontrol were no more pathogenic to peanuts than were toxigenic strains found naturally in peanuts.
Technical Abstract: not required