Fusarium toxins in oats are a real threat for human and animal consumption, writes Dr Julio Isidro Sánchez, lecturer/assistant professor of crop science, University College Dublin.
Mycotoxins are poisonous substances produced by various filamentous fungi (also commonly referred to as moulds) that can be acutely toxic (eg. causing vomiting, nausea or even death) or chronically toxic (eg. cytotoxic, nephrotoxic, carcinogenic or mutagenic). The Food and Agriculture Organization of the United Nations (FAO) estimates that 25 per cent of the global food and feed is contaminated by mycotoxins and that the annual losses due to fungal disease and mycotoxin contamination is as high as $1bn in the United States alone (CAST 2003).
Fusarium Head Blight (FHB)
FHB, or scab, is one of the most serious diseases affecting wheat and barley worldwide. It is caused predominantly by Fusarium graminearum along with F. culmorum and F. avenaceum, which lead to the accumulation of mainly deoxynivalenol (DON) in grains that are toxic for humans and animals. Symptoms often are accompanied by evidence of the fungus, which may include purple-black perithecia and/or pink sporodochia on heads, especially on glumes. Seed from FHB-affected fields often is shrunken, or shriveled with a characteristically bleached appearance. Oat has long been regarded as more resistant to FHB than wheat or barley, simply because of the lack of visual symptoms on infected panicles, and the presence of long pedicels between spikelets that usually prevent the spread of fungal mycelia throughout the panicle. Nevertheless, oat grains can accumulate considerable mycotoxin amounts.
Main fungi affecting oats
Fusarium langthesiae and F. Poe are the main fungi affecting oats. These fungi accumulate trichothecenes type A (T-2, HT-2), which are 10 times more toxic than DON. In fact, the European Commission recommendation 2013/165/EU and the European Food Safety Authority (EFSA, 2017) also established a tolerable daily intake for T-2/HT-2 of 0.02 μg kg−1 body weight. The use of resistant oat varieties would be the most sustainable way to overcome such contaminations, but the selection of Fusarium-resistant oat varieties has been delayed due to a lack of knowledge about F. langthesiae and their impact on oat tissues.
UCD Lyons Research Farm
University College Dublin (Dr Fiona Doohan, Dr Julio Isidro Sánchez, Dr Amal Kahal and Mr Kane Kusack), in collaboration with Cranfield University (Dr Naresh Magan, Dr Angel Medina and Dr Carol Verheecke), supported through the Biotechnology and Biological Sciences Research Council and Science Foundation Ireland, started a project in 2017 focused on the oat: Fusarium pathosystem. This project aims to better understand the genetic diversity in UK and Irish heritage oat cultivars and unveil the genetic traits related to resistance to F. langesthiae infection and T-2/HT-2 toxin contamination, both under existing and future climate change (CC) scenarios. One of the aims of this project is to find genes associated with resistance to Fusarium to highlight chromosome locations of oats that would be used as hotspots for further studies. Currently, a diversity panel of 200 varieties, including Irish heritage genotypes, are currently being studied at the UCD Lyons Research Farm. At the same time, transcriptome analyses for F. langsethiae under existing and future climate change scenarios will facilitate a better understanding of the impact of climate change on oat cultivation and the routes for better resilience by integration of molecular, ecophysiological and phenotypic studies.