BGS 98, Early maturity 6, Eam6

The Eam6.h variant was demonstrated to be an allele at the Praematurum-c (mat-c) locus (2). However, continued use of the Eam6 nomenclature as locus and allele symbols is recommended because the large phenotypic differences occur between the mat-c mutants (see BGS 579) and the Eam6.h allele.

Early heading = Ea (16).
Early maturity 6 = Ea6 (13).
Earliness per se 2S = eps2S (8).
Early 16 = ea-c16 (6).
Praematurum-c = mat-c (2, 14).
Hordeum vulgare CENTRORADIALIS = HvCEN (2).

Monofactorial dominant (16).
Located in chromosome 2HS (16); Eam6.h is about 13.5 cM proximal from the vrs1 (six-rowed spike 1) locus (4, 5); Eam6.h is near the gsh5 (glossy sheath 5) locus based on linkage drag (1, 2); Eam6.h is near molecular marker ABC167b in 2H bin 08 (11, 15); a maturity QTL mapped near SNP marker bPb-3677 at 57.5 cM in the progeny of a Nure/Tramois cross (2); the praematurum-c (mat-c) mutants were determined to be allelic and the structural gene HvCEN (Hordeum vulgare CENTRORADIALIS) and mapped at 57.5 cM (2); the mat-c.19 deletion is in a 0.27 cM segment of 2H near SNP markers 2_887, 2_0537, and 2_0390 (10), in 2H bin 07.

Alleles at the Eam6 locus alter the timing of floral initiation when barley is grown under long-day conditions. In temperate climates, the Eam6.h gene induces spring barley to head two to five days earlier than plants with the recessive allele (4, 11). A much stronger response to long photoperiods is associated with the the Early maturity 1 (Eam1, Ppd-H1) gene. Tohno-oka et al. (15) reported that Eam6 gene from Morex (CIho 15773) is effective when the photoperiod is 13 hours or longer and that the Eam1 gene from Steptoe (CIho 15229) induces early heading when the photoperiod is 14 hours or longer. In North Dakota, plants with both the Eam1 and Eam6 genes head one to two days earlier than those with only the Eam1 gene (4). The maturity factors, Eam1 and Eam6 genes, for early heading were studied by Yasuda and named “A” and “B”, respectively (17). A QTL for response to long photoperiods in North America, two- and six-rowed barleys were reported in the Eam6 region of 2H (7, 12). Eam6 may interact with other maturity genes because a QTL for early heading was detected in 2HS under both short- and long-day environments in the Harrington/Morex mapping population (8). In the dihaploid progeny from Nure (winter) barley crossed to Tramois (spring) barley, the earliness allele from Nure was associated with fewer days to head and higher kernel weights and yields over 13 Mediterranean sites (2). These are short-day environments in which the Eam1 gene is not expressed. A QTL for earliness was present at the Eam6 position in a genome-wide association study (GWAS) in collections of Mediterranean spring and winter barleys (3) and a worldwide core collection of spring barleys (1). The mat-c.19 deletion and several other mat-c mutants affect the barley ortholog of Antirrhinum majus CENTRORADIALIS (AmCEN) gene (2) and Arabidopsis thaliana TERMINAL FLOWER 1 (AtTFL1) gene (10).

Natural occurrence in many spring, six-rowed barley, represented by the cultivar Morex (CIho 15773) (15). The early variant (haplotype II) at the (Hordeum vulgare CENTRORADIALIS ( HvCEN) locus occurs in both wild and cultivated barleys (2).

Eam6.h in an unknown cultivar (15), possibly introduced into Midwest six-rowed spring barleys via Trebi (CIho 936) (4); Eam6.h in Morex (CIho 15773) (8, 11, 15). The early variant (haplotype II) at the Eam6 locus is present in many winter barley cultivars (2).

Eam6.h in Morex (CIho 15773, GSHO 2492); Eam6.h (haplotype I) from Nordic (CIho 15216) is present in Bowman (PI 483237) (2, 4).

1. Alqudah, A.M., R. Sharma, R.K. Pasam, A. Graner, B. Kilian, and T. Schnurbusch. 2014. Genetic dissection of photoperiod response based on GWAS of pre-anthesis phase duration in spring barley. PLoS ONE 9(11): e113120.
2. Comadran, J., B. Kilian, J. Russell, L. Ramsay, N. Stein, M. Ganal, P. Shaw, M. Bayer, W. Thomas, D. Marshall, P. Hedley, A. Tondelli, N. Pecchioni, E. Francia, V. Korzun, A. Walther, and R. Waugh. 2012. Natural variation in a homolog of Antirrhinum CENTRORADIALIS contributed to spring growth habit and environmental adaptation in cultivated barley. Nature Genet. 44:1388-1392.
3. Comadran, J., J.R. Russell, A. Booth, A. Pswarayi, S. Ceccarelli, S. Grando, A.M. Stanca, N. Pecchioni, T. Akar, A. Al-Yassin, A. Benbelkacem, H. Ouabbou, J. Bort, F.A. van Eeuwijk, W.T.B. Thomas, and I. Romagosa. 2011. Mixed model association scans of multi-environmental trial data reveal major loci controlling yield and yield related traits in Hordeum vulgare in Mediterranean environments. Theor. Appl. Genet. 122:1363-1373.
4. Franckowiak, J.D., and G. Yu (Unpublished).
5. Franckowiak, J.D., and U. Lundqvist. 1997. BGS 355, glossy sheath 5, gsh5. Barley Genet. Newsl. 26:300-301.
6. Gustafsson, Å., A. Hagberg, and U. Lundqvist. 1960. The induction of early mutants in Bonus barley. Hereditas 46:675-699.
7. Horsley, R.D., D. Schmierer, C. Maier, D. Kudrna, C.A. Urrea, B.J. Steffenson, P.B. Schwarz, J.D. Franckowiak, M.J. Green, B. Zhang, and A. Kleinhofs. 2006. Identification of QTLs associated with Fusarium head blight resistance in barley accession CIho 4196. Crop Sci. 46:145-156.
8. Krasheninnik, N. 2005. Genetic association of Fusarium head blight resistance and morphological traits in barley. Ph.D. Thesis. North Dakota State Univ., Fargo, ND.
9. 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 × spring barley (Hordeum vulgare L.) cross. Genome 38:575-585.

10. Matyszczak, I. 2014. Characterization of early maturity barley mutants praematurum-a, -b and –c. PhD. Thesis Aarhus University, Department of Molecular Biology and Genetics, Faculty of Science and Technology, Denmark.
11. Marquez-Cedillo, L.A., P.M. Hayes, A. Kleinhofs, W.G. Legge, B.G. Rossnagel, K. Sato, S.E. Ullrich, and D. M. Wesenberg. 2001. QTL analysis of agronomic traits in barley based on the doubled haploid progeny of two elite North American varieties representing different germplasm groups. Theor. Appl. Genet. 103:625-637.
12. Moralejo, M., J.S. Swanston, P. Muñoz, D. Prada, M. Elía, J.R. Russell, L. Ramsay, L. Cistué, P. Codesal, A.M. Casa, I. Romagosa, W. Powell, and J.L. Molina-Cano. 2004. Use of new EST markers to elucidate the genetic differences in grain protein content between European and North American two-rowed malting barleys. Theor. Appl. Genet. 110:116-125.
13. Robertson, D.W., G.A. Wiebe, R.G. Shands, and A. Hagberg. 1965. A summary of linkage studies in cultivated barley, Hordeum species: Supplement III, 1954-1963. Crop Sci. 5:33-43.
14. Søgaard, B., and P. von Wettstein-Knowles. 1987. Barley: genes and chromosomes. Carlsberg Res. Commun. 52:123-196.
15. Tohno-oka, T., M. Ishit, R. Kanatani, H. Takahashi, and K. Takeda. 2000. Genetic analysis of photoperiodic response of barley in different daylength conditions. p. 239-241. In S. Logue (ed.) Barley Genetics VIII. Volume III. Proc. Eighth Int. Barley Genet. Symp., Adelaide. Dept. Plant Science, Waite Campus, Adelaide University, Glen Osmond, South Australia.
16 Woodward, R.W. 1957. Linkages in barley. Agron. J. 49:28-32.
17. Yasuda, S. 1958. (Genetic analysis of the response to short photoperiod in a barley cross by means of the partitioning method.) Nogaku Kenkyu 46:54-62 [In Japanese].

J.D. Franckowiak and T. Konishi. 2002. Barley Genet. Newsl. 32:86-87.

J.D. Franckowiak. 2007. Barley Genet. Newsl. 37:216-217.
J.D. Franckowiak and U. Lundqvist. 2016. Barley Genet. Newsl. 46:57-59.