| EFFECT OF HUMIDITY ON MYCOTOXIN PRODUCTION |
| |
Mycotoxins are secondary metabolites
produced by some of the FHB pathogens in the UK. It is thought that in some
cases the role of the toxin may be to aid infection of the plant by the pathogen.
Mycotoxins are of concern due to their potentially harmful effect to both humans
and animals.
|
Mycotoxins produced by FHB pathogens
in the UK include:
|
| Fusarium species |
Main mycotoxins produced |
| F. culmorum |
Deoxynivalenol, nivalenol, zearalenone |
| F. graminearum |
Deoxynivalenol, nivalenol, zearalenone |
| F. avenaceum |
Enniatins |
| F. poae |
HT-2 and T-2 toxins, diacetoxyscirpenol, nivalenol |
| M. nivale |
None confirmed |
|
| |
The European Commission is currently
evaluating the risk posed by a number of trichothecenes toxins produced by Fusarium
species. These include deoxynivalenol (DON), nivalenol (NIV), T-2 toxin,
HT-2 toxin and zearalenone. Maximum limits in foodstuffs will be introduced
shortly.
|
The work presented here forms part
of a three-year project funded by the HGCA on the 'Epidemiology and control
of fusarium ear blight' (Project Report No. 143).
|
The incidence of wet weather (high humidity) is the most important factor in the development of FHB.
|
The effect of humidity on FHB and mycotoxin production was assessed in trials carried out between1994 and 1996.
Symptom development, ear infection, mycotoxin production and yield loss were assessed under three humidity
regimes ambient, medium (>70%) and high (>80%). Control of humidity was achieved using mist irrigation.
|
In 1994, individual plots were inoculated with one of the four FHB pathogens; Fusarium avenaceum,
Fusarium culmorum, Fusarium poae or Microdochium nivale. In subsequent years inoculation
with Fusarium graminearum was also included. Plots were inoculated at early anthesis (GS60).
|
GC/MS analysis was used to detect the trichothecene mycotoxins produced by individual FHB pathogens under
varying conditions of humidity in 1995 and 1996. Results from 1995 (ambient and high humidity treatments only)
are shown below.
|
| |
| Humidity |
Treatment |
Trichothecene (ppb) |
| |
|
DON |
3-acetyl
DON |
15-acetyl
DON |
Nivalenol |
MAS |
| Ambient |
Control |
20 |
|
|
12 |
5 |
| F. avenaceum |
|
|
|
7 |
|
| F. culmorum |
385 |
15 |
|
286 |
|
| F. graminearum |
419 |
|
|
|
|
| F. poae |
|
|
|
8 |
|
| M. nivale |
|
|
|
8 |
|
| |
| High |
Control |
21 |
|
|
14 |
|
| F. avenaceum |
|
|
|
12 |
|
| F. culmorum |
776 |
22 |
|
588 |
|
| F. graminearum |
786 |
|
14 |
22 |
|
| F. poae |
|
|
|
12 |
|
| M. nivale |
|
|
|
25 |
|
|
|
DON = deoxynivalenol, MAS = monoacetoxyscirpenol. |
| |
- As humidity increased so did the amount of toxin produced, with F. culmorum
and F. graminearum producing the highest levels of toxin in grain.
|
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