Eyespot is a disease of the stem base of wheat that poses a frequent threat to the UK wheat crop, as yield losses of up to 40% can occur in eyespot epidemics.
Only three sources of resistance to eyespot are known to be present in modern commercial wheat cultivars.
The most potent of these is the dominant gene Pch1, that derives from chromosome 7DV of the wheat relative Aegilops ventricosa and was introduced into hexaploid wheat by introgression of a large segment of 7DV into chromosome 7D of wheat. Wheat varieties carrying this segment are highly resistant to eyespot but, unfortunately varieties carrying this 7DV segment suffer from ‘linkage-drag’ due to deleterious genes carried on the 7DV segment and can suffer a significant yield deficit in the absence of the disease.
As with many introgressions from wheat relatives, the rate of recombination between the introgressed segment and the native wheat chromosome is significantly reduced. In contrast to the negative effect on yield, there is evidence that the Ae. ventricosa introgression carries other beneficial traits along with eyespot resistance.
The Pch1 7DV segment also confers a 2-3% higher grain protein content and 100-150 greater dough strength units resulting in enhanced bread making potential.
Marianna’s project aims to isolate Pch1 and also to precisely locate the region conferring increased grain protein content and to sever the linkage between the positive traits conferred by the 7DV segment and the negative effect on yield.
Ultimately the aim is to produce plant materials, knowledge on the location of the three traits (Pch1, grain protein and yield) and DNA markers to enable plant breeders to track them in their breeding programmes.
Pasquariello M., Ham J., Burt C., Jahier J., Paillard S., Uauy C., Nicholson P. (2016)The eyespot resistance genes Pch1 and Pch2 of wheat are not homoeoloci.Theoretical and applied genetics (online)Publisher's version: 0040-5752