Objective 4 - Simon Griffiths (JIC)

Paragon gamma and EMS mutant lines

An EMS mutant population developed in WGIN 1 in the elite UK spring wheat Paragon has already been described. The resulting 6,500 fixed mutated lines, with extensive phenotypic descriptions of each available on the WGIN website are now widely used by the worldwide wheat community and form an important element of a number of funded UK projects. In WGIN the utility of this resource will be raised to a new level by the establishment of a mutant gene mapping pipeline for this and similar material such as the WGIN 1 Cadenza EMS population developed at RRes. Up to twenty individual lines exhibiting mutant phenotypes relevant to key traits will be crossed with lines selected from a collection of UK wheat varieties extensively genotyped in the DEFRA LINK Breeding for Improved Resistance to Septoria Triticeae (BIRST). The availability of the BIRST data set (kindly provided by James Brown and Lia Arraiano) allows the selection of lines with the maximum level of polymorphism with Paragon and the minimum likelihood of confounding the trait of interest. For example an investigation into an alternative dwarfing gene would not use a line from the BIRST set which carried Rht-D1b. So far lines with mutations with relevance to activities 8 and 9 have been chosen. These are grain shape, heading date, stature, and senescence. The strategy is to produce bulks of 30 F2 individuals from each phenotypic and subject each bulk to genotyping using Diversity Array Technology (DArT) markers. This strategy has been successfully applied in projects outside of WGIN including the Wheat Orange Blossom Midge DEFRA LINK project. This will allow routine mapping of mutations to genetic maps and show whether mutations are alleles of known genes eg Rht-D1 or Rht-B1 or effects not yet described e.g. alternative dwarfing alleles. Thus, sets of mutant lines chosen for their relevance to key traits for UK wheat improvement will be selected and genetically characterised to a depth not previously possible on this scale.

gamma mutant lines

The wide uptake of the Paragon gamma deletion lines developed in WGIN 1 as a simple reverse genetics tool is likely to continue. However the preliminary DArT analysis carried out already shows that a large set of nested and overlapping deletions could be identified for any locus in the existing deletion populations. This presents an opportunity for an important extension of this resource. Many QTL are not amenable to dissection by the classical approach of identifying recombinants, because they occur in regions of low recombination. These genes could be physically mapped using deletions. So, in the next phase of WGIN we propose increasing the number of Paragon deletion lines subjected to DArT analysis to 480, generating a complete set of overlapping deletions covering the wheat genome. Deletions will be related to genetic and emerging physical maps of the wheat genome. We also propose to increase the size of the gamma Paragon population treated with 250 Gy of gamma irradiation from 430 to 5,000 lines. This material would allow fine scale dissection of any specific locus.