Investigation of fusarium infection and mycotoxin levels in harvested wheat grain (1998)

Abstract

The MAFF-funded winter wheat disease survey of 1998 indicated that the level of fusarium ear blight was the highest since national monitoring of ear diseases began in 1987. A rapid response enabled grain samples to be collected from 53 of the most severely affected crops. Trichothecene mycotoxin and polymerase chain reaction (PCR) analysis were undertaken on each grain sample to try and relate the presence of particular Fusarium species with mycotoxin contamination of grain. These data were also analysed against agronomic factors collected during the national disease survey.

The level of mycotoxin detected in the grain samples was generally low. The predominant species responsible for the outbreak was M. nivale, a non-mycotoxin producer. It is the predominance of this species that probably accounted for the low levels of mycotoxin detected. Even so, four per cent of samples contained 1 ppm DON, a level equivalent to the tolerance limit suggested for the EU. A strong correlation (0.68) was seen between the amount of F. culmorum and F. graminearum DNA detected in the sample by PCR and the production of DON and NIV. This suggests that had the outbreak been dominated by a mycotoxin producing species, such as F. culmorum or F. graminearum, much higher levels ofmycotoxin would have been present in grain samples. In 1998 the level of F. graminearum detected was unusually high (40% of samples infected). Increased incidence of F. graminearum has been indicated in countries where maize has been increased in closed rotation with wheat. However, there was no evidence from the survey to suggest that the increased incidence of F. graminearum in 1998 was linked with maize as a previous crop.

Regional differences in disease levels were shown with the most severely affected crops grown in the South West and Wales. PCR analysis indicated that the more aggressive species, F. culmorum and F. graminearum, were more abundant in regions with the highest disease severity. These regions are, in general, warmer than the rest of the UK. As F. culmorum and F. graminearum prefer warmer conditions (optimum growing temperature 20-25°C) this may account for their increased presence.

Although no cultivar is totally resistant to fusarium ear blight, the survey has shown differences in disease levels between cultivars. Indicating that the choice of cultivar needs to be considered if trying to reduce the risk from fusarium.

The rapid collection of grain following the 1998 harvest and the information gathered has provided valuable and unique data on the epidemiology of the species involved. The use of PCR analysis has provided accurate data on the relative contribution of the species involved to the disease levels recorded and tomycotoxin production.

Previous experimental work funded by the HGCA (project report No. 143) indicated that high humidity conditions during anthesis could lead to significant mycotoxin contamination of grain in the UK. This project has confirmed that this occurs in the field in wet seasons and has generated data, which will be useful in the development of disease forecasting schemes and assessing future risks of mycotoxin contamination of grain in the UK.