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Abstract

Fungal species can infect cereals pre- or post-harvest resulting in the contamination of harvested grains with toxic chemicals known as mycotoxins. Fusarium species can infect cereal crops resulting in a disease, fusarium head blight, and the contamination of cereal grains with fusarium mycotoxins. Fusarium mycotoxins, HT2+T2 have been identified at high levels in UK oat grains at harvest. The European Commission is currently considering legislative limits for HT2 and T2 in cereals and cereal products for human consumption. Preliminary analysis of UK oat varieties at harvest has identified differences in the susceptibility of oats to Fusarium infection. Observed differences are: • Higher mycotoxin levels on winter compared to spring oats • Lower mycotoxin levels on naked compared to covered oats (although naked oat levels are higher than covered oats after de-hulling) • Higher mycotoxin levels on dwarf compared to conventional oats Field experiments will be conducted at several sites within the UK to identify if differences observed are under genetic control. Harvest samples will be analysed for Fusarium pathogens by quantitative PCR and for mycotoxins by ELISA.

Description

This PhD is part of a large Defra LINK-funded project “Harnessing new technologies for sustainable oat production and utilisation” (QUOATS - ).  The PhD is funded by contributions from the UK cereal levy board (HGCA-AHDB) and Ãå±±½ûµØ College.

Project background

Fungal species can infect cereals pre- or post-harvest resulting in the contamination of harvested grains with toxic chemicals known as mycotoxins.  Fusarium species can infect cereal crops resulting in a disease, fusarium head blight, and the contamination of cereal grains with fusarium mycotoxins.  Fusarium species can produce numerous mycotoxins including several trichothecenes.  The type A trichothecenes include the closely related mycotoxins, HT2 and T2.  These mycotoxins have been quantified at high levels in UK oat grains at harvest (Edwards, 2009).  These toxins are produced primarily by Fusarium langsethiae in UK oats (Imathiu, 2008).

The European Commission is currently considering legislative limits for HT2 and T2 in cereals and cereal products for human consumption.  Mycotoxin legislation requires growers to use “Good Agricultural Practice” to minimise mycotoxins within farm produce and for food processors to use “Good Processing Practice” to minimise mycotoxins in finished products (Edwards et al., 2009; Scudamore et al., 2007).  Previous studies have identified that there is little growers can do to minimise fusarium mycotoxins in cereals.  For oats, varietal choice was one factor growers could use to reduce fusarium mycotoxins.  Preliminary analysis of UK oat varieties at harvest from HGCA Recommended List variety trials has identified differences in the susceptibility of oats to Fusarium infection.   Spring oats have consistently low HT2 and T2, with no differences between varieties while winter oats have a higher concentration of HT2 and T2, and significant differences between varieties.  It is not known if this difference is due to genetics or differences in the agronomy of winter and spring drilled varieties.

Conventional oat varieties are husked and the husk is removed during processing for human consumption.  The de-husked oat is called a groat and is further processed to produce a range of oat products eg oat flakes.  Studies have shown that the majority of the mycotoxins are present in the husk.  Naked oat varieties have a loose husk, which is removed during harvesting.  Naked varieties have significantly lower HT2 and T2 at harvest, but this is highly likely to be due to the absence of the husks after harvest.  It is not known how the mycotoxin level of naked varieties compares to conventional husked varieties before harvest.

Dwarf varieties of oats are short-strawed compared to conventional varieties.  The mycotoxin concentration of dwarf varieties tends to be higher than conventional varieties although the relationship between plant height and mycotoxin levels is not consistent.  Differences maybe due directly to the morphological trait of crop height, or associated traits such as panicle length or maybe due to genetic linkage.

References

• Edwards SG (2007). Investigation of fusarium mycotoxins in UK barley and oat production. HGCA Project Report No. 415. London: HGCA.
• EDWARDS SG, BARRIER-GUILLOT B, CLASEN P-E, HIETANIEMI V AND PETTERSSON H (2009) Emerging issues of HT-2 and T-2 toxins in European cereal production. World Mycotoxin Journal 2: 173-179
• EDWARDS SG (2009) Fusarium mycotoxin content of UK organic and conventional oats.  Food Additives and Contaminants 26:1063-1069
• Imathiu SM (2008) Fusarium langsethiae infection and mycotoxin production in oats. Ãå±±½ûµØ College, UK. PhD Thesis.
• SCUDAMORE KA, BAILLIE H, PATEL S and EDWARDS SG (2007) The occurrence and fate of Fusarium mycotoxins during the industrial processing of oats in the UK.  Food Additives and Contaminants 24: 1374–1385

Aim

To understand the variation in the resistance of UK oat varieties to type A trichothecene-producing Fusarium species

Hypotheses

1. Winter oats are genetically more susceptible to Fusarium than spring oats
2. Naked oats are genetically more susceptible to Fusarium than conventional oats
3. Dwarf oats are genetically more susceptible to Fusarium than conventional oats

Proposed work program

1. To source suitable experimental material from on-going studies as part of QUOATS project and other studies conducted by QUOATS partners e.g.
   • QUOATS partners have trials in progress of winter and spring varieties drilled at different drilling dates in fully randomised replicated field experiments.
   • QUOATS partners have a mapping population of a short and tall winter varieties
2. To conduct field experiments with selected oats varieties (winter and spring) drilled in autumn and winter to see if identified difference in varieties is due to genetics or agronomy (ie drilling date).
3. To conduct field experiments with selected oats varieties (naked and covered) with panicle samples collected pre-harvest and oats post-harvest to identify difference in varieties HT2 and T2 content of panicles, oats, husks and groats.
4. To conduct field experiments with selected oats varieties (various heights) to identify relationship between height and HT2 and T2 levels.   
5. Based on results from 1-4 above, to conduct in depth studies to improve our understanding of Fusarium resistance.  For example, using selected lines from the QUOATS mapping populations of a short and tall variety cross, or the use of plant growth regulators to manipulate crop heights.

Experimental material will be analysed for Fusarium species by real-time quantitative PCR and for the mycotoxins, HT2 and T2 by ELISA.