*marko.maricevic@bc-institut.hr

Pre-harvest sprouting (PHS) can reduce the grain yield and bread-making quality of wheat. The main component of wheat resistance to PHS is the level of seed dormancy, which can result from two mechanisms, seed coat imposed dormancy and embryo dormancy. The biochemical mechanisms of seed dormancy include embryo sensitivity to abscisic acid (ABA).

In the present study, a genome-wide association study (GWAS) was conducted by evaluating a panel of 200 European wheat cultivars for seed dormancy (SD), embryo dormancy (ED), and embryo response to ABA (E-ABA).

The panel was genotyped using the 25K Single Nucleotide Polymorphism (SNP) array. The field trials were conducted in four environments in Croatia and SD, ED and E-ABA were evaluated by germination tests with whole grains in water, half grains in water and half grains in 20 M ABA, respectively. Based on the LOD threshold (–log10(p) > 3.5) GWAS identified a total of 35 quantitative trait nucleotides (QTNs) significantly associated with SD, which were located on chromosomes 1D, 3A, 3D, 4A, 4B, 5B and 7D and explained 6.4−14.1% of the phenotypic variance.

Among them only QTNs from chromosomes 4A (1) and 5B (4) were stable, occurring in two or more environments. For ED, a total of 33 significant QTNs were found on chromosomes 3A, 3B, 3D, 4A, 4B, 5B, 6A, 6B, 7B and 7D, which explained 6.4−8.9% of the phenotypic variance. Stable QTNs for ED were located on chromosomes 3A (3), 3B (1), 3D (6), 4A (1) and 7D (1).

For E-ABA, a total of 33 significant QTNs were identified on chromosomes 1B, 1D, 3A, 3D, 4A, 4D, 5A, 5D, 7B and 7D explaining 7.9−12.6% of the phenotypic variance, of which stable QTNs were located on chromosomes 1D (1), 4A (6) and 5D (1). Nine significant QTNs (all from chromosome 4A) were common to SD and E-ABA, 12 significant QTNs were common to ED and E-ABA (of which 9 from the homoeologous group 3 chromosomes), and 4 QTNs (all from chromosome 4A) were common to all three traits in single environments.

Of the stable QTNs only one, located on chromosome 4A, was common to SD and E-ABA, and another, also from chromosome 4A, was shared by ED and E-ABA.