BGS 348, Early maturity 5, Eam5

Early maturity = Ea (11, 17).
Early maturity 3 = Ea3 (4, 5).
Early maturity 5 = Ea5 (7).
Early maturity 8 = Ea8 (12).
Hordeum vulgare phytochrome C early = HvPhyC-e (8, 9).

Monofactorial dominant (16, 18); semi-dominant (9).
Located in chromosome 5HL (4, 8, 9), Eam5.x is very close to the raw1 (smooth awn 1) locus (16, 17, 18); a QTL for earliness associated with the Sgh2 ((spring growth of habit 2) locus among spring type segregates from the winter parent (1, 10, 13, 14, 16); Eam5.x is associated with SNP markers 1_0094 to 1_0589 (positions 187.39 to 234.98 cM) in 5H bins 10 to 14 of Bowman backcross-derived line BW286 (2), Eam5.x is associated with SNP markers 1_0094 to 1_0589 (positions 187.39 to 247.08 cM) in 5H bins 10 to 13 of Bowman backcross-derived line BW285 (2); Eam5.x is associated with SNP markers 1_1507 to1_0870 (positions 192.80 to 274.24 cM) in 5H bins 10 to 14 of Bowman backcross-derived line BW291 (2). BW285, BW286 and BW291 have identical SNP markers from 1-1090 to1_0095 (positions 203-.85 to 210.59 in 5H bin 11 (2); the Eam5 locus is linked to Sgh2 (Vrn-H1) (spring growth habit 2) locus at a distance of 1.5 cM and to HvCK2α (Casein Kinase II alpha) by 3.1 cM (8), in 5H bin 11.

An earliness factor closely linked to the rough awn gene was identified in spring barley (17).Plants with the Eam5 gene head 3 to 10 days earlier than normal sibs under short-day conditions (3, 11). Early heading is commonly associated a shorter stature compared to normal sibs. The slight reduction in height is also observed under long-day conditions. Peduncles and rachis internodes are slightly shortened (3). The Eam5.x gene appears to be the common early maturity gene present in winter sown spring barley cultivars used in China and Japan; and it is present in the ICARDA/CIMMYT barley lines developed in Mexico. Complex interactions with other genes conditioning photoperiod response have been observed ( 3, 18). Takahashi and Yasuda (16) classified plants that were about 10 days earlier than normal spring barley under short days as having the Sgh2.I (spring growth of habit 2, grade 1) gene. The earliness gene from Indian Barley showed a dominant inheritance pattern (16). Early heading caused by a QTL in 5HL was associated with decreased sensitivity to frost injury (1, 10). The Sgh2 (Vrn-H1) locus is closely linked to the candidate gene for photoperiod sensitivity, the red/far-red light photoreceptor Phytochrome C (HvPhyC) (5, 15), which was later demonstrated to cosegregate with early flowering (8, 9). BW285 with the Eam5.x gene has the linked recessive allele, sgh2.b, for winter growth habit at the Sgh2 (Vrn-H1) locus while Bowman has the recessive allele at the Eam5 locus and the dominant spring growth habit allele Sgh2.I (9). Eam5.x (HvPhyC) interacts with long-day response gene Eam1 (Ppd-H1) to accelerate flowering under short-day conditions (9, 18). This is the response reported by Takahashi and Yasuda (16). BW285 and several Japanese cultivars have specific mutation named haplotype 7 in the first exon of HvPhyC (9). The difference in responses associated with the Eam5.x gene reported by Nishida et al. (8) and Pankin et al. (9) may be caused by the presence of the Eam6.h (early maturity 6) or eps-2S (earliness per se 2S) allele in the Bowman backcross-derived lines (3).

Natural occurrence in Indian cultivars (4, 6); present in Japanese winter barleys (8, 10, 13, 16), isolated from ICARDA/CIMMYT selection CMB85-533-H-1Y-1B-0Y-5B (Higuerilla*2/Gobernadora) (3).

Eam5.x in CMB85-533 (3), Eam5.x in fall planted Chinese and Japanese cultivars (13, 14, 16).

Eam5.x in CMB85-533; Eam5.x from CMB85-533 in Bowman (PI 483237)*6 (GSHO 3424); Eam5.x from CMB85-533 in Bowman*7 (BW 285 and BW 286, NGB 20569 and NGB 20570); Eam5.x from Japanese breeding line (DH6) in Bowman*5 (BW 291, NGB 20575).

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J.D. Franckowiak. 2002. Barley Genet. Newsl. 32:109.

J.D. Franckowiak and G. Yu. 2007. Barley Genet. Newsl. 37:260-261.
J.D. Franckowiak and G. Yu. 2015. Barley Genet. Newsl. 45:123-125.