Effect of fenpropimorph, prochloraz and tebuconazole on growth and production ofT-2 and HT-2 toxins by Fusarium langsethiae in oat-based medium.

摘要

Fusarium langsethiae has been isolated from infected cereals in central andnorthern Europe where it has been identified in the last decade as the mainspecies involved in the occurrence of high levels of T-2 and HT-2 toxins, mainlyin oats. The efficacy of three fungicides (prochloraz, tebuconazole,fenpropimorph) for controlling growth of two strains of F. langsethiae isolatedfrom oats was examined at 0.96 and 0.98 a(w) at 15, 20 and 25 °C on oat-basedmedia. The concentrations necessary for 50 and 90% growth inhibition (ED₅₀ andED₉₀ values) were determined. The effect on the trichothecene type A mycotoxinsT-2 and HT-2 was also determined. Without fungicides both strains grew faster at0.98 than at 0.96 a(w) and the influence of temperature on growth rates was25>20>15 °C. Prochloraz and tebuconazole were more effective than fenpropimorphagainst F. langsethiae. Strain, temperature and type of fungicide significantlyinfluenced the ED₅₀ and ED₉₀ values for growth. The concentration ranges underdifferent environmental conditions were: prochloraz (0.03-0.1 and 0.3-1.5),tebuconazole (0.06-0.9 and 1.3-8.2), and fenpropimorph (22-59 and 125-215 mgl⁻¹). Production of T-2 and HT-2 toxins was influenced by temperature, a(w),type of fungicide and dose. Levels of T-2 were usually higher than those of HT-2 under the same conditions. The biosynthesis of T-2 toxin increased after 10day incubation, but was reduced with decreasing temperature and increasingfungicide dose. At 0.98 a(w) T-2 levels increased in cultures containingfenpropimorph while at 0.96 a(w) the toxin concentrations increased in responseto the other two fungicides. Low doses of prochloraz or tebuconazole enhancedtoxin production when compared with untreated cultures for strain 2004-59 at0.96 a(w) and 20-25 °C. HT-2 was hardly detectable in the treatments withprochloraz or tebuconazole at 0.98 a(w). This is the first study on the effectof these anti-fungal compounds on control of growth of F. langsethiae and onproduction of T-2 and HT-2 toxi