Improved resistance to septoria in superior varieties

Abstract

Septoria tritici blotch has been the major disease of wheat in the UK for over two decades. It is the principal target for fungicides on wheat and the major target for resistance breeding. This project aimed to apply knowledge of the genetics of septoria to improve methods of selecting for resistance. This will help breeders to produce high-yielding, high-quality wheat varieties with good resistance to septoria. In turn, growing such varieties will promote cost-effective disease control in the UK’s major arable crop.

A study of diversity in a large number of wheat varieties, using the technique of association genetics, found that many genes in UK cultivars make moderate contributions to septoria resistance. The introduction of some of these genes can be traced back to breeding programmes between 30 and 55 years ago which aimed to increase yield and improve resistance to other diseases. Research in this project and elsewhere has shown that all 21 chromosomes in wheat carry genes which increase resistance to septoria. This type of resistance is likely to be durable and its effect in controlling disease is unlikely to be eroded through evolution of the fungus that causes septoria. The results of the project imply that breeders can improve septoria resistance by using parental lines which have diverse pedigrees and therefore probably have different resistance genes, then selecting progeny which combine genes from both parents.

In the past, many breeders found it difficult to produce new wheat varieties which combined septoria resistance with high yield. This project showed that there is a yield penalty of septoria resistance. While it is unlikely that the negative relationship between yield and septoria resistance can be broken completely, breeders should be able to select varieties which have a balance of these and other traits appropriate to current market conditions. This is reflected in the fact that many high-yielding varieties on the current Recommended List now have moderately good resistance to septoria.

To continue the current trend towards improved septoria resistance in high-yielding varieties, breeders will need to make use of genetically diverse parental varieties, well-adapted to UK conditions. As agricultural practices develop and the climate changes, the profile of diseases on wheat and other crops is likely to vary. As with septoria, the use of association genetics to study a wide range of varieties, followed by genetic analysis to investigate the relationship of disease resistance to other traits, can be applied to new diseases. This will support the efforts of breeders to release high-yielding varieties in which diseases can be controlled effectively and economically.