Abstract
Vernalization, photoperiod and the relatively poorly defined earliness per se (eps) genes regulate flowering in plants. We report here the validation of a major eps quantitative trait locus (QTL) located on wheat 1DL using near isogenic lines (NILs). We used four independent pairs of NILs derived from a cross between Spark and Rialto winter wheat varieties, grown in both the field and controlled environments. NILs carrying the Spark allele, defined by QTL flanking markers Xgdm111 and Xbarc62, consistently flowered 3–5 days earlier when fully vernalized relative to those with the Rialto. The effect was independent of photoperiod under field conditions, short days (10-h light), long days (16-h light) and very long days (20-h light). These results validate our original QTL identified using doubled haploid (DH) populations. This QTL represents variation maintained in elite north-western European winter wheat germplasm. The two DH lines used to develop the NILs, SR9 and SR23 enabled us to define the location of the 1DL QTL downstream of marker Xgdm111. SR9 has the Spark 1DL arm while SR23 has a recombinant 1DL arm with the Spark allele from Xgdm111 to the distal end. Our work suggests that marker assisted selection of eps effects is feasible and useful even before the genes are cloned. This means eps genes can be defined and positionally cloned in the same way as the photoperiod and vernalization genes have been. This validation study is a first step towards fine mapping and eventually cloning the gene directly in hexaploid wheat.Electronic supplementary materialThe online version of this article (doi:10.1007/s11032-014-0094-3) contains supplementary material, which is available to authorized users.
Highlights
Genetic variation in emergence and maturation of wheat ears is the consequence of allelic variation at loci controlling the vegetative to floral transition, inflorescence development and stem extension
The results show that the 1DL heading quantitative trait locus (QTL) is an eps effect given that the near isogenic lines (NILs) with the Spark allele are early flowering
Our results show that the NILs have more than 90 % Rialto background (Fig. 2), and the average for the 18 NILs was 95 %
Summary
Genetic variation in emergence and maturation of wheat ears is the consequence of allelic variation at loci controlling the vegetative to floral transition, inflorescence development and stem extension. This variation has major implications for yield potential, abiotic and biotic stress tolerance/avoidance, interactions with agronomic interventions, and our ability for predictive breeding of germplasm adapted to specific environments. Three major sets of loci are responsible for the variation in flowering time observed in bread wheat varieties These loci, which interact with the environment in mediating the transition from vegetative to floral growth in wheat, are as follows: vernalization, photoperiod and the poorly understood earliness per se (Herndl et al 2008; van Beem et al 2005; Bullrich et al 2002). Spring (vernalization insensitive) cultivars have mutations in the promoter or a deletion within the first intron of the VRN-1 genes (Yan et al 2003)
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