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Maximising the potential of Aegilops ventricosa introgression for Pch1 eyespot resistance and increased grain protein in wheat

Project Report No. 614

Maximising the potential of Aegilops ventricosa    introgression for Pch1 eyespot resistance and increased grain protein in wheat

Paul Nicholson1 and Marianna Pasquariello1

1John Innes Centre, Norwich Research Park, Norwich NR4 7UH

Abstract

Eyespot is a damaging disease that affects the stem base of cereals, particularly in second-wheat situations. The most potent source of resistance to eyespot was introduced into wheat from the relative Aegilops ventricosa. This resistance is believed to be due to a single gene (but this is unproven) on chromosome 7D. Other factors were also believed to have been transferred to wheat along with the eyespot resistance. These include the positive trait of increased grain protein content and the negative trait of reduced yield under some conditions. The relationship between the three traits is unknown.

This project aimed to produce plant materials, knowledge on the location of the three traits (Pch1, protein content and yield) and DNA markers to track the three traits in breeding programmes. This will allow breeders to select the desirable traits conferred by this segment while removing the deleterious ones from their varieties. The project achieved its three objectives:

1.    To establish whether Pch1 eyespot resistance gene on chromosome 7D is in an identical position to a second weaker eyespot resistance (Pch2) are located on chromosome 7A.

It was determined that the two resistances are not in equivalent positions on their respective chromosomes. DNA markers were produced to both resistances.

2.    To establish the location of the positive grain protein and the negative yield penalty traits and to produce diagnostic DNA markers for these to allow selection for the former and against the latter.

It was demonstrated that both traits were distant from Pch1 and from each other. Selected lines carrying a very short segment of 7DV containing Pch1 and/or the grain protein trait were provided to plant breeders for incorporation into new varieties.

3.    To sequence the region of chromosome containing Pch1 and attempt to identify the Pch1 gene. The region about Pch1 on the Ae. ventricosa chromosome was sequenced and several candidate genes identified. 

It was shown that the introgressed segment contains several resistance genes not found in wheat. It was demonstrated that a gene previously suggested by several other researchers as a candidate for Pch1 is not, in fact, involved in resistance to eyespot. The remaining candidates for Pch1 await further work to establish whether any of them can confer increased resistance to eyespot.

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