Infection and development of spot blotch and tan spot on timely and late seeded wheat

Abstract

Non-toxigenic strains of Aspergillus flavus offer the potential to control aflatoxin contamination by competitive displacement of indigenous populations of A. flavus colonizing corn. Two sets of experiments were conducted to assess the competitiveness of strain K49 when challenged against two toxigenic isolates (F3W4 or K54) using a pin-bar inoculation technique. In 2007, corn ears were inoculated with six ratios of strain K49 and F3W4 in two experimental sites. A second study assessed the ability of equal densities of K49 when challenged with toxigenic strains F3W4 and K54 in 2007 and 2008. In the Stoneville site, when K49 comprised 10% of the inoculum, aflatoxin concentrations were reduced to ~500 ppb compared to 3500 ppb when inoculated with 100% F3W4. At the Elizabeth site, a 30% and 90% reduction in aflatoxin was observed when 10% and 50% of the inoculum was non-toxigenic strain K49, respectively. Strain K49 was capable of reducing aflatoxin contamination by ~90% when challenged with the high producing strain K54 or the moderate producer F3W4. In challenges with either F3W4 or K54, greater than 85% of isolates recovered were nontoxigenic, while 100% of the isolates were toxigenic when inoculated with F3W4 or K54 alone. These studies indicate that competition is affected by location and environmental conditions associated with the study, however, strain K49 had a similar degree of efficacy in competition with two toxigenic strains of varying potential for aflatoxin production.