BGS 752, Quantitative seed dormancy 1, Qsd1

Seed dormancy 1 = SD1 (4).
Quantitative seed dormancy 1 = Qsd1 (13).

Monofactorial recessive for a long seed dormancy period in wild barley (13); previously identified as a QTL in cultivated barley for seed dormancy (1, 3, 4, 5, 7, 11, 13, 17).
Located in chromosome 5HL (4, 17); Qsd1.b is in the centromeric region of 5HL (4); Qsd1.b is between RFLP markers Ale and ABC302 (4); Qsd1.b is near marker ABC302 (5); qsd1.a is located between 56.9 and 61.9 cM (10); the qsd1 locus is located in a 9,467 bp region between markers EST5 and EST4F (14).

Seed dormancy in barley is described as the inability of a viable embryo to germinate under environmental conditions favorable to germination (4). Dormant grain may require a storage period prior to re-planting or malting while non-dormant grain can result in pre-harvest sprouting in the field which can reduce malting and feed quality (4, 17). Seed dormancy levels are high among wild barley accessions and show geographical differentiation among barley cultivars (15). The first of two quantitative seed dormancy loci (Qsd1) involved in maintenance of post-harvest grain dormancy was identified as a QTL contributed by Steptoe (CIho 15229) in the doubled haploid progeny of a Steptoe by Morex (CIho 15773) cross (4, 17). The Qsd1.b allele in Steptoe for dormancy has a partly epistatic interaction with alleles at Qsd2 locus (4). The presence of the Steptoe allele at the Qsd1 locus kept precocious germination to a minimum until the end of the seed development process (12). QTL in the Qsd1 region were associated with different degrees of dormancy (7). The recessive qsd1.a allele from wild barley H602 (Hordeum vulgare subsp. spontaneum) encodes an alanine aminotransferase (AlaAT), which likely controls the metabolic flux associated with germination. Nineteen days after anthesis transcripts of the qsd1 RNA were present in the embryo, but not the endosperm (14). Variations in dormancy levels associated with the qsd1 locus exist among cultivated barley accessions and likely arose after domestication (14). Sequence variations in the AlaAT gene are inherited as dominants and reduce the level of dormancy observed in domesticated barley (14). In North American malting barley cultivars [Harrington (two-rowed) and Morex (six-rowed)], alleles at the Qsd1 locus are associated with little or no dormancy (1, 2, 3, 4, 6, 11, 17). The unexpected pattern of dormancy release observed in Triumph (PI 290195) by Prada et al. (11) might be closer to wild type than that of other cultivars. Higher lipoxygenase (LOX) content, which affects foam stability and beer flavor, was associated with more dormant alleles at the Qsd1 locus (8). Low values for other malting quality was associated with the presence of a Qsd1.b allele for dormancy in Baronesse (PI 568246) (2).

A wild type, qsd1.a, occurs as a recessive allele in wild barley (Hordeum vulgare subsp. spontaneum) accession H602 (8, 14); Qsd1 variants have accumulated in cultivated barley to reduce dormancy levels (14).

The allele, qsd1.a, is present in H602 and represents wild type (14); many Qsd1 variants are present in cultivated barley (7, 13, 14); partially dormant alleles (mutants) in the Qsd1.b series are present in Steptoe (CIho 15229) (4, 16, 17), in Triumph (PI 290195) (9), in Stirling (PI 466919) (1, 3), in Flagship (6); Haruna Nijo has a non-dormant allele (4, 13, 14); Harrington, Morex (CIho 15773), Chevron (CIho 1111), and Stander (PI 564743) may have the same non-dormant allele at the Qsd1 locus

qsd1.a in the wild barley accession H602; Qsd1.b variants in cultivars, both two- and six-rowed spring barley cultivars

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2. Castro, A., A. Benitez, P. Hayes, L. Viege, and L. Wright. 2010. Coincident QTL effects for dormancy, water sensitivity and malting quality traits in the BCD47 x Baronesse barley mapping population. Crop Pasture Sci. 61:691-699.
3. Gong, X., C. Li, M. Zhou, Y. Bonnardeaux, and G. Yan. 2014. Seed dormancy in barley is dictated by genetics, environments and their interactions. Euphytica 197:355-368.
4. Han, F., S.E. Ullrich, J.A. Clancy, V. Jitkov, A. Kilian, and I. Romagosa. 1996. Verification of barley seed dormancy loci via linked molecular markers. Theor. Appl. Genet. 92:87-91.
5. Han, F., S.E. Ullrich, J.A. Clancy and I. Romagosa. 1999. Inheritance and fine mapping of a major barley seed dormancy QTL. Plant Sci. 143:113-118.
6. Hickey, L T., W. Lawson, V.N. Arief, G. Fox, J. Franckowiak, and M.J. Dieters. 2012. Grain dormancy QTL identified in a doubled haploid barley population derived from two non-dormant parents. Euphytica 188:113-122.
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8. Jin, X.L., S. Harasymow, Y. Bonnardeaux, A. Tarr, R. Appels, R. Lance, G.P. Zhang, and C.D. Li. 2011. QTL for malting flavour component associated with pre-harvest sprouting susceptibility in barley (Hordeum vulgare L.). J. Cereal Sci. 53:149-153.
9. Lin, R., R.D. Horsley, N.L.V. Lapitan, Z. Ma, and P.B. Schwarz. 2009. QTL mapping of dormancy in barley using the Harrington/Morex and Chevron/Stander mapping populations. Crop Sci. 49:841-849.
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12. Romagosa, I., F. Han, J.A. Clancy, and S.E. Ullrich. 1999. Individual locus effects on dormancy during seed development and after ripening in barley. Crop Sci. 39:74-79.
13. Sato, K., T. Matsumoto, N. Ooe, and K. Takeda. 2009. Genetic analysis of seed dormancy QTL in barley. Breed. Sci. 59:645-650.
14. Sato, K., M. Yamane, N. Yamaji, H. Kanamori, A. Tagiri, J.G. Schwerdt, G.B. Fincher, T. Matsumoto, K. Takeda, and T. Komatsuda. 2016. Alanine aminotransferase controls seed dormancy in barley. Nat. Commun. 7:11625.
15. Takeda, K., and K. Hori. 2007. Geographical differentiation and diallel analysis of seed dormancy in barley. Euphytica 153:249-256.
16. Ullrich, S.E., J.A. Clancy, I.A. del Blanco, H. Lee, V.A. Jitkov, F. Han, A. Kleinhofs, and K. Matsui. 2008. Genetic analysis of preharvest sprouting in a six-row barley cross. Mol. Breed. 21:249-259.
17. Ullrich, S.E., P.M. Hayes, W.E. Dyer, T.K. Blake, and J.A. Clancy. 1993. Quantitative trait locus analysis of seed dormancy in "Steptoe" barley. Pp. 136-145. In: Walker-Simmons, M.K., and J.L. Ried. (eds.) Pre-harvest sprouting in cereals 1992. Am. Assoc. Cereal Chem., St. Paul, MN, USA.

J.D. Franckowiak. 2018. Barley Genet. Newsl. 48:181-183.