Water and temperature relations of Fusarium langsethiae strains and modelling of growth and T-2 and HT-2 mycotoxin production on oat-based matrices

In the UK and Northern Europe, ripening oats can become contaminated with T-2 and HT-2 mycotoxins, produced mainly by Fusarium langsethiae. There are indicative levels related to the maximum limits for oat grain for these toxins. The objectives of this study were to examine the effect of interacting conditions of temperature (10-30 °C) and water activity (a_w, 0.995-0.90) on (a) lag times prior to growth, (b) growth and (c) T-2 and HT-2 toxins by two strains of F. langsethiae isolated from oats in the UK and compare this with the type strain (Fl201059) which has been genomically sequenced, and (d) develop (and validated with published data) a probabilistic models for impacts of temperature × a_w on growth and toxin production. All three strains had an optimum a_w range and temperature of 0.995-0.98 and 25 °C for growth. For T-2 + HT-2 production these were 0.995 a_w and 20 °C. Overall, the type strain produced higher amounts of T-2 + HT-2 with a HT-2/T-2 ratio of up to 76. Using this study data sets and those from the literature, probabilistic models were developed and validated for growth and T-2 + HT-2 toxin production in relation to temperature × a_w conditions. These models, when applied in stored oats, will be beneficial in determining the conditions on the relative level of risk of contamination with these two toxins in the context of the EU indicative maximum levels.

Fusarium Toxins in Cereals: Occurrence, Legislation, Factors Promoting the Appearance and Their Management

Fusarium diseases of small grain cereals and maize cause significant yield losses worldwide. Fusarium infections result in reduced grain yield and contamination with mycotoxins, some of which have a notable impact on human and animal health. Regulations on maximum limits have been established in various countries to protect consumers from the harmful effects of these mycotoxins. Several factors are involved in Fusarium disease and mycotoxin occurrence and among them environmental factors and the agronomic practices have been shown to deeply affect mycotoxin contamination in the field. In the present review particular emphasis will be placed on how environmental conditions and stress factors for the crops can affect Fusarium infection and mycotoxin production, with the aim to provide useful knowledge to develop strategies to prevent mycotoxin accumulation in cereals.

A non-linear model for temperature-dependent sporulation and T-2 and HT-2 production of Fusarium langsethiae and Fusarium sporotrichioides

This research has produced new quantitative data on the sporulation and T-2+HT-2 toxin production that could be further integrated to develop a comprehensive disease or toxin prediction model for Fusarium langsethiae and Fusarium sporotrichioides. Experiments were conducted to determine the effect of temperature or incubation time on sporulation and the effect of temperature on T-2+HT-2 toxin production of strains of the two species. F. sporotrichioides demonstrated a preference for higher temperatures than F. langsethiae during sporulation; the optimum temperature was 24.5 ± 0.7 °C for F. langsethiae and 32.3 ± 2.1 °C for F. sporotrichioides, according to the Beta equation fitted to the data. The dynamics of sporulation over different incubation times were fitted by a Gompertz function. The maximum spore production was estimated to be after 18 and 8 d incubation at optimum temperatures for F. langsethiae and F. sporotrichioides, respectively. F. sporotrichioides produced more T-2+HT-2 than F. langsethiae. The best fit of the effect of temperature on T-2+HT-2 production in wheat grains was obtained with a Beta equation showing an optimum temperature of 14.7 ± 0.8 °C for F. langsethiae and 12.1 ± 0.2 °C for F. sporotrichioides. The optimum temperature for mycotoxin production was lower than for sporulation.