DON content in oat grains in Norway related to weather conditions at different growth stages

Abstract

High concentrations of the mycotoxin deoxynivalenol (DON), produced by Fusarium graminearum have occurred frequently in Norwegian oats recently. Early prediction of DON levels is important for farmers, authorities and the Cereal Industry. In this study, the main weather factors influencing mycotoxin accumulation were identified and two models to predict the risk of DON in oat grains in Norway were developed: (1) as a warning system for farmers to decide if and when to treat with fungicide, and (2) for authorities and industry to use at harvest to identify potential food safety problems. Oat grain samples from farmers' fields were collected together with weather data (2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013).A mathematical model was developed and used to estimate phenology windows of growth stages in oats (tillering, flowering etc.). Weather summarisations were then calculated within these windows, and the Spearman rank correlation factor calculated between DONcontamination in oats at harvest and the weather summarisations for each phenological window. DON contamination was most clearly associated with the weather conditions around flowering and close to harvest. Warm, rainy and humid weather during and around flowering increased the risk of DON accumulation in oats, as did dry periods during germination/seedling growth and tillering. Prior to harvest, warm and humid weather conditions followed by cool and dry conditions were associated with a decreased risk of DON accumulation. A prediction model, including only pre-flowering weather conditions, adequately forecasted risk of DON contamination in oat, and can aid in decisions about fungicide treatments.

HT-2 and T-2 toxins in Norwegian oat grains related to weather conditions at different growth stages

“…Nine percent of the samples contained HT2 + T2 levels above the indicative limit set for unprocessed oats (1000 μg kg −1 ), and 25% of the samples contained HT2 + T2 values higher than our more rigorous level of 500 μg kg −1 used in this study. The same samples were also tested for DON contamination (Hjelkrem et al 2017) and no significant (p < 0.05) relationship was observed between the concentrations of the two mycotoxins (μg kg −1 oat grain) in an ordinal regression analysis (using the natural logarithm). A total of 148 weather variables, based on air temperature, rainfall and relative humidity were summarised within each of the ten estimated phenology windows for all 188 oat fields included in this study.…”

“…Our approach is based on the window-pane methodology (Coakley et al 1982;Kriss et al 2010) that is used to quantify the importance of environmental variables within temporal windows. A similar mathematical model, designed to predict growth stages of oats based on sowing time and weather conditions, was recently developed to quantify the relationship between weather conditions and DON accumulation in Norwegian oats (Hjelkrem et al 2017). In the present study, we identified possible associations between the occurrence of HT2 + T2 toxins in harvested oat grains and weather conditions between sowing and harvest.…”

“…Predicted growth stages, as opposed to the number of days from sowing, were chosen because the relationship between number of days from sowing and phenological development in oats had been shown to be quite poor (Hjelkrem et al 2017). Furthermore, the use of phenological growth stages has previously been proposed as an improvement when modelling the accumulation of HT2 + T2 in oats (Xu et al 2014).…”

“…Likewise, models developed in the UK to predict concentrations of HT2 + T2 in oat grains included mainly pre-flowering variables (Xu et al 2014). In contrast, a model developed to predict the risk of DON contamination in harvested oat grains in Norway included only three out of the eight weather variables examined in the period prior to flowering (Hjelkrem et al 2017). Fusarium langsethiae is regarded as the main HT2 + T2 producer in oats in both Norway and UK (Hofgaard et al 2016a;Edwards et al 2012), whereas F. graminearum is the most important DON producer in Norwegian oats (Hofgaard et al 2016a).…”

“…The BBCH scale was used to define plant growth stages (GS) (Lancashire et al 1991), and dates for all growth stages from sowing to harvest were estimated for each grain sample by using the Oat Phenology Model (Hjelkrem et al 2017). For the further analysis, the dataset for each grain sample was separated into ten intervals reflecting the different plant developmental stages (phenology windows).…”