Fusarium sporotrichioides sherb. Toxins evaluated in cereal grain with trichoderma harzianum

Abstract

Fusarium head blight is one of the most severe diseases of small grain cereals and is caused by several toxigenic Fusarium species. Yield losses and mycotoxin accumulation in grain are caused by the disease. F. sporotrichioides and F. poae produce type A trichothecenes. Saprophyte fungal antagonists, especially Trichoderma harzianum, are effective biocontrol agents against several fungal soil-borne plant pathogens. These fungal antagonists can reduce the production of Fusarium spp. mycotoxins in some crop plants. The aim of this study was to examine the influence of T. harzianum AN4 on the production of type A trichothecenes by F. sporotrichioides in cereals. The accumulation of six trichothecene mycotoxins (scirpentriol, i.e. STO, T-2 tetraol, T-2 triol, HT-2 toxin i.e., HT-2, T-2 toxin i.e., T-2, diacetoxyscirpenol, i.e., DAS) was reduced on average, by over 89% in bioassays of F. sporotrichioides and Trichoderma isolate AN4 on a liquid medium and on solid substrates (seeds of naked and husked oats and wheat). The reduction in our experiments depended on fungal isolate and substrate. From the three isolates of F. sporotrichioides used in the experiments, the highest accumulation of all the metabolites after 21 days by F. sporotrichioides in nearly all substrates, was recorded for strain ZFR 159. On the liquid medium inoculated with F. sporotrichioides ZFR 159, the amount of type A trichothecenes was the lowest (STO, T-2 tetraol, and T-2 triol not detected, HT-2 toxin 0.02 ppm, DAS 0.10 ppm, T-2 toxin 0.99 ppm). The highest total concentration of these toxins was produced by this isolate in husked oat cv. German (180.16 ppm), but in naked oat cv. Akt the toxin concentration was low (27.62 ppm). Trichothecene accumulation by T. harzianum AN4 was reduced the most in oat cv. Akt (98.48%) in the liquid medium (98.22%), while the lowest reduction was in oat cv. German (48.77%). The non-toxigenic T. harzianum AN4 isolate proved to be a useful biocontrol agent against the toxigenic F. sporotrichioides in cereals, significantly reducing the production of six type A trichothecenes. This is the first report on effective biocontrol of F. sporotrichioides in cereals by T. harzianum.