BGS 65, Early maturity 1, Eam1

Early maturity = Ea (8).
Early maturity 1 = Ea1 (7).
Photoperiod response gene H1 = Ppd-H1 (11).

Monofactorial dominant (9, 13).
Located in chromosome 2HS (1, 8, 13); weakly linked to the vrs1 (six-rowed spike 1) locus (1, 15, 19); the Ppd-H1 (Eam1) locus is in the 6 cM interval between the RFLP loci XMWG858 and XpsrB9, 1 cM proximal to XM WG858 (11, 12); specific sequence tagged site (STS) markers were developed for the Eam1 gene of Igri (3); in bin 2H-04 near RFLP marker MWG858 (13); in Azumamugi 6 cM proximal from marker ABG602 (15), Eam1.c is associated with SNP markers 1_0216 to 2_1338 (positions 47.48 to 66.78 cM) in 2H bins 04 to 06 of the Bowman backcross-derived line BW280 (4); Eam1.d is associated with SNP markers 12_1386 to 2_1261 (position 50.56 cM) in 2H bin 05 of the Bowman backcross-derived line BW281 (4); Eam1.f is associated with SNP markers 1_0216 to 2_1015 (positions 47.48 to 48.68 cM) in 2H bin 04 of the Bowman backcross-derived line BW282 (4), likely in 2H bin 05.

This gene controls the strong response of some cultivars to long photoperiods. The Eam1 gene is described as a simply inherited dominant and the main factor for early maturity (1, 7, 8, 14). Under long-day condition, a near-isogenic line with Eam1 is reported to be 7 to 8 days earlier than the eam1 line 'ea1' (16). The early maturity gene is weakly linked to the vrs1 (six-rowed spike 1) locus (1, 13, 19). In North Dakota, USA, progenies from crosses of Bowman to Hordeum vulgare subsp. spontaneum, California Coast and North African accessions, facultative winter barleys, far northern spring barleys (from Finland and Alaska), and winter barleys, extremely early segregates were found (6). The Eam1 locus in barley is homoeologous to the Ppd1, Ppd2, and Ppd3 loci in wheat, which control strong photoperiod response (11, 12). The reduced photoperiod responsiveness of the ppd-H1 (eam1.a) mutant is explained by altered circadian expression of the photoperiod pathway gene CONSTANS (CO) (10, 19) and reduced expression of its downstream target, FLOWERING LOCUS T (HvFT1), a key regulator of flowering (2, 18). The CCT (CO, CO-like, and TOC1) domain mutation was a G-to-T change and produced a Gly-to-Trp change in the CCT domain of the barley pseudo-response regulator (PRR) gene (18). The DNA code sequence of the dominant alleles was variable among accessions while the recessive allele was not (18). Alleles at the Eam1 locus interact with flowering time control mutants at the eam7 (17) and eam10 (2), but not eam8 (5), loci to induce earlier heading under both short and long days.

The strong photoperiod response to short nights occurs naturally in many barley cultivars and its wild relative, Hordeum vulgare subsp. spontaneum.

A single dominant gene controls early maturity based on a cross to Lion (Eam1.b) (PI 32767, GSHO 27) (8); Eam1.e (GSHO 1569) was isolated from the Australian cultivar Prior (PI 221325) (9, 16); eam1.a is the normal allele in Manchurian six-rowed cultivars (7, 16); eam1.a is the allele present likely in many two-rowed cultivars from Europe origin (16).

Eam1.c in Estate (PI 57700, GSHO 1316); Eam1.c from Estate in Bowman (PI 483237)*7 (GSHO 1871); Eam1.c from Estate in Bowman*8 (BW280, NGB 20564); Eam1.d from KT1031 (a winter barley from Bulgaria, GSHO 1568) in Bowman*9 (GSHO 1872, BW281, NGB 20565); Eam1.e from Prior in Betzes*7 (Erbet, CIho 13826) (4); Eam1.f from Hordeum vulgare subsp. spontaneum in Bowman*8 (GSHO 1873, BW282, NGB 20566).

1. Barbacki, S. 1930. [Studies in barley. II. Variability and inheritance of some physiological characters. The importance of breeding characters]. Men. Inst. Nat. Polon. Ec. Rur. Puawy 11:579-610. [In Polish with English summary.]
2. Campoli, C., A. Pankin, B. Drosse, C.M. Casao, S.J. Davis, and M. von Korff. 2013. HvLUX1 is a candidate gene underlying the early maturity 10 locus in barley: phylogeny, diversity, and interactions with the circadian clock and photoperiodic pathways. New Phytologist 199:1045-1059.
3. Decousset, L., S. Griffiths, R.P. Dunford, N. Pratchett, and D.A. Laurie. 2000. Development of STS markers closely linked to the Ppd-H1 photoperiod response gene of barley (Hordeum vulgare L.). Theor. Appl. Genet. 101:1202-1206.
4. Druka, A., J. Franckowiak, U. Lundqvist, N. Bonar, J. Alexander, K. Houston, S. Radovic, F. Shahinnia, V. Vendramin, M. Morgante, N. Stein, and R. Waugh. 2011. Genetic dissection of barley morphology and development. Plant Physiol. 155:617-627.
5. Faure, S., A.S. Turner, D. Gruszka, V. Christodoulou, S.J. Davis, M. von Korff, and D.A. Laurie. 2012. Mutation at the circadian clock gene EARLY MATURITY 8 adapts domesticated barley (Hordeum vulgare) to short growing seasons. Proc. Natl. Acad. Sci., USA 109: 8328-8333.
6. Franckowiak, J.D. (Unpublished).
7. Franckowiak, J.D. 1992. Mapping a gene for photoperiod sensitivity in barley. Agron. Abstr. 1992:96.
8. Griffee, F. 1925. Correlated inheritance of botanical characters in barley, and the manner of reaction to Helminthosporium sativum. J. Agric. Res. 30:915-935.
9. Hockett, E.A., and R.F. Eslick. 1972. Registration of Erbet barley (reg. no. 127). Crop Sci. 12:712-713.
10. Laurie, D.A. 1997. Comparative genetics of flowering time. Plant Mol. Biol. 35:167-177.
11. Laurie, D.A., N. Pratchett, J.H. Bezant, and J.W. Snape. 1994. Genetic analysis of a photoperiod response gene on the short arm of chromosome 2 (2H) of Hordeum vulgare (barley). Heredity 72:619-627.
12. Laurie, D.A., N. Pratchett, J.H. Bezant, and J.W. Snape. 1995. RFLP mapping of five major genes and eight quantitative trait loci controlling flowering time in a winter X spring barley (Hordeum vulgare L.) cross. Genome 38:575-585.
13. Mackie, W.W. 1926. Inheritance of resistance to Helminthosporium californium in a cross between Chevalier barley, a resistant variety, and Abyssinian, a susceptible variety. Phytopathology 16:764. [Abstr.].
14. Neatby, K.W. 1929. An analysis of the inheritance of quantitative characters and linkage in barley. Sci. Agric. 9:701-718.
15. Sameri, M., K. Takeda, and T. Komatsuda. 2006. Quantitative trait loci controlling agronomic traits in recombinant inbred lines from a cross of oriental- and occidental-type barley cultivars. Breed. Science 56:243-252.
16. Smail, V.W., R.F. Eslick, and E.A. Hockett. 1986. Effect of genetically and environmentally induced heading date differences on yield and adaptation of an isogenic barley pair. Crop Sci. 26:889-893.
17. Stracke, S., and A. Börner. 1998. Molecular mapping of the photoperiod response gene ea7 in barley. Theor. Appl. Genet. 97:797-800.
18. Turner, A., J. Beales, S. Faure, R.P. Dunford, and D.A. Laurie. 2005. The pseudo-response regulator Ppd-H1 provides adaptation to photoperiod in barley. Science 310:1031-1034.
19. Wexelsen, H. 1934. Quantitative inheritance and linkage in barley. Hereditas 17:307-348.

J.D. Franckowiak and L.W. Gallagher. 1997. Barley Genet. Newsl. 26:101-102.

J.D. Franckowiak. 2014. Barley Genet. Newsl. 44:64-66.
J.D. Franckowiak. 2017. Barley Genet. Newsl. 47:54-56.