description
- Eyespot is the most important disease of the stem base of cereals in the UK causing £12-20 million per annum in lost yield, in addition to significant expenditure on fungicides. Only three sources of resistance to eyespot are known to be present in modern wheat cultivars. The most potent of these is the gene Pch1, which originates from a wild grass. This resistance was introduced into wheat by conventional crossing, replacing a large segment of one of the wheat chromosomes with the equivalent portion from the wild grass (so-called 7DV segment). The two other eyespot resistances (Pch2 and QTL5A) both come from the variety Cappelle Desprez but they both have only moderate effects on eyespot resistance. Wheat varieties carrying the 7DV segment are highly resistant to eyespot and it has also been observed that varieties containing the 7DV segment have a higher grain protein content. Unfortunately varieties carrying this 7DV segment suffer a yield penalty and it is only relatively recently that Pch1 carrying varieties have been developed that also possess high yield potential. We have shown that most of these varieties carry the full size original segment and so it appears that the negative yield effect of the 7DV segment is compensated by other factors in these new varieties. Efforts to separate the desirable eyespot resistance and protein content traits from the deleterious yield effect have been seriously hindered by two factors: an apparent reduction in recombination between the native wheat chromosome and the 7DV segment and a lack of suitable DNA markers. However, recent advances in marker technology have made it possible to characterise the 7DV segment and identify lines carrying much smaller segments. In this project we aim to isolate the Pch1 gene and also identify the part of the7DV segment that confers the increased grain protein content. This will enable plant breeders to develop wheat varieties that carry the desirable parts of the 7DV segment (Pch1 eyespot resistance and the part responsible for increased grain protein content) without the undesirable (yield penalty) parts. Pch1 lies in a region of 7DV that is similar to that of the moderately effective eyespot resistance gene Pch2 from Cappelle Desprez. These two resistances are potentially due to 'sister' genes and we will determine whether this is the case or whether they are in similar but not identical positions.