BGS 214, Early maturity 8, eam8

Early heading k = eak (31).
Early maturity-a = ea-a (12, 25).
Praematurum-a = mat-a (7, 12, 17, 18, 32).
Erectoides-o = ert-o (12, 22).
Hordeum vulgare Early flowering 3 = HvElf3 (2, 6, 32).

Monofactorial recessive (7, 11).
Located in chromosome 1HL (25); eam8.k is about 11.4 cM distal from the trd1 (third outer glume 1) locus and 20.9 cM distal from the Blp1 (Black lemma and pericarp 1) locus (25, 29); eam8.w is associated with SNP markers 2_0603 to 2_0138 (positions 199.04 to 202.26 cM) in 1H in bin 14 of the Bowman backcross-derived line BW290 (3); eam8.k is associated with SNP markers 1_0782 to 1_0443 (positions 193.83 to 206.12) in 1H bin 14 of the Bowman backcross-derived line BW289 (5); ert-o.16 is associated with SNP markers 1_0911 to 1_1509 (positions 177.51 to 199.04) in1H bins 13 to 14 of the Bowman backcross-derived line BW319 (5), in 1H bin 14.

Early heading early maturity 8 (eam8) is associated with decreased culm length, spike length, kernels per spike, and grain yield (20, 29, 31). Mutant plants are day-length neutral or photoperiod insensitive when grown in the fall at Kurashiki, Japan. They head about 20 days earlier than the standard mid-season cultivar, Akashinriki (31). Day-length neutrality was observed in early heading mutants isolated from spring barley in Sweden (4, 13). Under controlled environmental conditions, number of days to heading did not change as photoperiod is altered (4, 14). All mat-a induced mutants were characterized by yellowish-green seedlings at an early stage of development under controlled environmental conditions (3). Other eam8 mutants showed a similar response by becoming yellow green under specific growing conditions, 8 to 12 hours of illumination at low temperatures (below 10C) plus high temperature (20C or higher) during the dark period (9, 25, 29). The color change is caused by photothermal stress, which increases the zeaxanthin content at the expense of chlorophyll and other pigments (9, 23, 29). The mutant stock mat-a.8 was released as the cultivar Mari Mari (NGB 14656, NGB 1491, PI 428407) (13, 15). When grown under 12 h days, the levels of phytochrome B (phyB) decreased in light-grown BMDR-1 plants, containing a mutant allele at the eam8 locus, compared to normal plants (16). The instability in phyB content was reported to be responsible for photoperiod insensitivity of eam8 mutants (16). Under continuous light and with far-red light treatment for seven days, most differences in heading date between BMDR-1 and BMDR-8 (Shabet) are eliminated (23). The selection of independent eam8 mutations facilitated short growth-season adaptation and expansion of the geographic range of barley (6). When the eam8.k gene was placed in a winter barley genetic background [controlled by the sgh1.a (spring growth habit 1 or HvVrn2) gene], the vernalization requirement sgh1 (Vrn2) was expressed under all photoperiods and the early flowering phenotype was partially repressed in unvernalized plants (27).The Mat-a or Eam8 (HvELF3) locus has been cloned and is a homolog of the Arabidopsis thaliana circadian clock regulator Early Flowering 3 (ELF3) (6, 32). Among 87 mat-a alleles identified more than 20 different mat-a alleles had mutations leading to the defective putative ELF3 protein (32). The eam8 mutants have increased expression of the floral activator HvFT1 (Sgh3,, Vrn3). which is independent of allelic variation at Eam1 (Ppd-H1) locus (6). Early flowering of the mat-a (elf3) mutants lail to block excess gibberellin (GA) synthesis and expression of HvFT1 (2). Alvarez et al. reported that EARLY FLOWERING3 (ELF3) is a candidate gene for the earliness per se locus Eps-Am1 in Triticum monococcum (1).

An X-ray induced mutant in Maja Abed (NGB 8815, PI 184884) (10, 11, 14); natural occurrence in Kinai 5 (OUJ493) and Kagoshima Gold (OUJ219) (25, 30).

ert-o.16 (NGB 112618, GSHO 489) in Maja Abed (NGB 8815, PI 184884) (10); eam8.k in Kagoshima Gold (OUJ 219), Kinai 5 (OUJ493, GSHO 765, CIho 11560), and Kindoku (OUU332) (26, 26, 30); mat-a.8 (NGB 110008, NGB 14656, NGB 1491, NGB 4694), -a.11 (NGB 110011), -a.12 (NGB 110012) in Bonus (NGB 14657, PI 189763) (11, 18); mat-a.27 (NGB 110027), -a.45 (NGB 110045), -a.46 (NGB 110046), -a.48 (NGB 110048), -a.62 (NGB 110062) in Bonus, -a.110 (NGB 110110), -a.130 (NGB 110130), -a.153 (NGB 110153), -a.221 (NGB 110221), -a.238 (NGB 110238), -a.255 (NGB 110255), -a.272 (NGB 110272), -a.274 (NGB 110274), -a.287 (NGB 110287), -a.289(NGB 110289), -a.294 (NGB 110294), -a.325 (NGB 110325), -a.338 (NGB 110338), -a.370 (NGB 110370), -a.384 (NGB 110384), -a.390 (NGB 110390),-a.404 (NGB 110404), -a.406 (NGB 110406), -a.407 (NGB 110407) in Foma (NGB 14659, CIho 11333), -a.509 (NGB 110509), -a.641 (NGB 110641), -a.703 (NGB 110703), -a.733 (NGB 110733),in Kristina (NGB 1500, NGB 14661), -a.753 (NGB 110753), -a.796 (NGB 110796), -a.797 (NGB 110797), -a.813 (NGB 110813), -a.832 (NGB 110832), -a.903 (NGB 116858), -a.909 (NGB 117440), -a.921 (NGB 117452) in Bonus, -a.961 (NGB 117492), -a.970 (NGB 117501), -a.976 (NGB 117507), -a.984 (NGB 117515), -a.1011 (NGB 117542), in Sv 79353, -a.1032 (NGB 117563), -a.1033 (NGB 117564), -a.1034 (NGB 117565), -a.1035 (NGB 117566), -a.1036 (NGB 117567), -a.1037 (NGB 117568), -a.1039 (NGB 117570), -a.1040 (NGB 117571), -a.1041 (NGB 117572), -a.1042 (NGB 117573), -a.1043 (NGB 117574), -a.1044 (NGB 117575), -a.1045 (NGB 117576), -a.1046 (NGB 117577), -a.1047 (NGB 117578), -a.1048 (NGB 117579), -a.1049 (NGB 117580) in Sv Vg74233 (14); mat-a.1050 (NGB 117581), -a.1051 (NGB 117582), -a.1052 (NGB 117583), -a.1053 (NGB 117584), -a.1054 (NGB 117585), -a.1055 (NGB 117586), -a.1056 (NGB 117587), -a.1057 (NGB 117588), -a.1058 (NGB 117589), -a.1059 (NGB 117590), -a.1060 (NGB 117591), -a.1061 (NGB 117592), -a.1062 (NGB 117593), -a.1063 (NGB 117594), -a.1064 (NGB 117595), -a.1065 (NGB 117596), -a.1067 (NGB 117598), -a.1069 (NGB 117600), -a.1070 (NGB 117601), -a.1071 (NGB 117602), -a.1072 (NGB 117603), -a.1073 (NGB 117604), -a.1074 (NGB 117605) in Sv Vg74233 (19); eam8.q (Ea8), eam8.r (Ea9), eam8.s (Ea10), eam8.t (Ea16) in Chikurin Ibaraki 1 (OUJ069, CIho 7370, GSHO 783) (28); eam8.u (Mut 2571) in Donaria (PI 161974) (9, 21); eam8.v in Munsing (CIho 6009, GSHO 636) (8, 23, 24); eam8.w in Early Russian (CIho 13839) (8), BMDR-1 (eam8.y) from the original mutant in a dwarf line backcrossed to Shabet (CIho 13827) (23).

eam8.k in Kinai 5 (OUJ493, GSHO 765, CIho 11560); ert-o.16 (NGB 112618, GSHO 489) in Maja Abed; eam8.k from Kinai 5 in Bonus*5 (30); mat-a.8 from Bonus in Tochigi Golden*5 (28); eam8.v from Munsing in Titan (CIho 16526)*7 (23); eam8.k in Bowman (PI 483237)*7 (GSHO 2063, BW289, NGB 20573); eam8.w from Early Russian in Bowman*7 (BW290, NGB 20574); ert-o.16 from Maja Abed in Bowman*7 (GSHO 2064); ert-o.16 in Bowman*8 (BW319, NGB 22114).

Mutants in eam8 are deficient etc

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2. Boden, S.A., D. Weiss, J.J. Ross, N.W. Davies, B. Trevaskis, P.M. Chandler, and S.M. Swan. 2014. EARLY FLOWERING3 regulates flowering in spring barley by mediating gibberellin production and FLOWERING LOCUS T expression. Plant Cell 26:1557-1569.
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