Delivery of Ppd1 tools & novel allelic effects useful to UK/EU wheat improvement

Abstract

Agro-environmental adaptation is critical to many aspects of crop performance and yield. A key component of adaptation to specific environments is developmental rate and flowering time, controlled in part by photoperiod response (Ppd) and earliness per se (Eps) genes. Another important factor in successful crop improvement is the availability of sufficient genetic variation from which to select plant types with optimal performance for target environments. The objectives of this study were threefold: (1) development of near iso-genic lines (NILs) carrying individual Ppd and Eps genes, (2) characterisation of Ppdand Eps NILs for flowering time and yield and (3) introduction of novel genetic variation from synthetic hexaploid wheat lines (SHW) developed at CIMMYT.

Eps QTL in the current study were identified using data from previous studies carried out by project partners at the John Innes Centre (JIC) in Norwich. Although the accepted definition suggests that Eps loci reduce the time to flowering regardless of prevailing conditions, it is clear from previous studies at the JIC that environment had a significant influence on the expression of Epsgenes over experimental years. In contrast to these previous results, Eps effects on flowering time in the current study were found to be relatively reproducible over experiments and years with a consensus emerging as follows (derivative population Spark x Rialto (SR) and Charger x Badger (CB), followed by chromosomal location of the gene): SR-1D>SR-3A>SR-7A>SR-3B>SR-6B>[CB-3A, CB-3B, CB-6A, CB-6B & CB-7A].

The current project represents the first systematic introduction of novel genetic variation into UK wheat germplasm from the D-genome ancestor of wheat (Aegilops tauschii) via synthetic hexaploids since early studies at the Plant Breeding Institute in the 1940s and 50s. The SHWs used here were developed at CIMMYT by crossing elite tetraploid durum wheat with A. tauschii. Markers were used to identify a representative subset of CIMMYT SHWs which were backcrossed into two UK wheat varieties, Paragon and Xi-19, generating over 5600 recombinant lines in total. Field selection took a pre-breeding approach, with a focus on yield components including increased biomass, and the first yield trials indicated several lines which out-performed Xi-19. The best germplasm is being integrated into commercial breeding programmes.