Wheat Seed Colonized with Atoxigenic Aspergillus ̄ avus: Characterization and Production of a Biopesticide for A ̄ atoxin Control

B iocont rol of a ̄ atox in cont am inat ion using atox igenic Aspergillu s ̄ avu s to com pet it ively ex clude a ̄ atox in-produc ing strains has previously been report ed, and is current ly in the third year of commercial-scal e t est s ( treat ing 50 ± 200 ha per annum ) . W heat seed coloniz ed with atox igenic A. ̄ avu s has been used in the commercial trials. R equirem ent s for product ion of this coloniz ed wheat seed are described and the spore y ield of wheat is com pared to other subst rates. T he study suggest s that the m ost cost -eVect ive inoculum product ion would require coloniz at ion of wheat ( 10 6 conidia k g 2 1 of wheat seed) at 25% ( w /w) moist ure for 18 h at 31ÊC. To prevent fungal growt h and associat ed wheat aggregat ion in st orage, seed had to be dried below 15% ( w /w) m oist ure, although a moist ure cont ent of 35% ( w /w) did not reduce viabilit y in sealed cont ainers stored at 18 ± 25ÊC over an 8-mont h period. T he dry biopest icide had m ult i-year st abilit y without ref rigerat ion and withstood temperat ures of 70ÊC for 20 m in. S porulat ion of the product occurred within 3 day s at 31ÊC and 100% relat ive hum idit y with y ields averaging 4.9 3 10 9 conidia g 2 1 by day 7.