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Cephalosporium leaf stripe - an emerging threat to wheat crops in short rotations

Project Report No. 542

Cephalosporium leaf stripe - an emerging threat to wheat crops in short rotations

by

Neil D Havis and Kalina Gorniak

Crop and Soil Systems Research Group, SRUC, West Mains Road, Edinburgh EH9 3JG

 

Abstract

Cephalosporium gramineum is a fungus which causes distinct yellow stripes on the upper foliage of cereal crops and can also lead to the production of stunted white ears in crops. The fungus is thought to be carried on the trash of preceding crops. It has been recognised on cereals crops and grass weeds. The aims of this project were to establish if all wheat varieties were equally at risk from the disease, the effect on yield of the disease, the ability of seed treatment chemicals to control the fungus and the effect of cultivation methods on disease levels. Field and laboratory experiments were used to look the effects of these different factors on disease levels. Field experiments with the winter wheat Recommended List varieties showed that there are differences in susceptibility to the fungus. Resistance ratings were calculated from the data generated in the project. The disease was shown to have a negative effect on yield in winter wheat in field trials although the strength of this interaction varied from year to year. Trial results indicated that leaf stripe symptoms are greater in winter wheat than barley or oats.

In order to detect the presence of the fungus in crop, seed and soil samples, a new molecular diagnostic was developed. The test showed the presence of the fungus in leaves and in seed but no fungus was detected in soil samples taken from the field trial site. The fungus was detected in seed from the trial site and from samples collected across the UK. Movement in seed may be a possible way in which the fungus can spread to new areas.

Pure colonies of the fungus were produced from barley and wheat leaves sampled in the first year of the field trial. Growth of the fungus was reduced by the fungicides used in seed treatments in a laboratory bioassay. This implies that seed treatments may be exerting some control of the pathogen. However initial glasshouse tests to measure this effect proved inconclusive. The effect of cultivation techniques on the disease development was studied in a series of field trials. The results were inconclusive as in one year the ploughed plots had more disease and the following year it was the plots which had minimum cultivation. Research from North America suggests that the disease favours minimum cultivation as this leaves more trash from previous crops on the soil surface. This trash acts as a source of inoculum to infect the following crop. The effect of soil quality on disease levels in the field trials in the second growing season was measured. Damaged roots have been suggested as another cause of increased disease levels. Poor soil structure could contribute to root damage. No clear correlation between observed disease and soil moisture or structure quality was observed. However, testing did show that minimum cultivation plots had poorer structure than the ploughed plots and this may have contributed to higher levels of disease in the 2010 season.

In conclusion, the disease has been shown to be higher in wheat but resistance is available through variety selection. The efficacy of seed treatment chemicals is yet to be established. Cultivation may also affect disease levels and monitoring of the disease spread via infected plants would be appropriate.

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