BGS 10, Short awn 2, lks2

Short awn = a (28, 30).
Short awn = lk (26).
Short awn 2 = lk1 (12).
Short awn 2 = lk2 (19).Short awn 4 = lk4 (3, 9).
Unbranched style 4 = u4 (25).
Breviaristatum-15 = ari-15 (8).
Breviaristatum-d = ari-d (5, 6, 8, 13).
Short awn 8 = lk8 (29).

Monofactorial recessive (11, 12, 13, 22, 25).
Located in chromosome 7HL (8, 19); position estimates for the lks2 locus ranged from 7.9 to 10.5 cM distal from the nud1 (naked caryopsis 1) locus (4, 22, 24); lks2 is about 2.8 cM distal from molecular marker WG541 in 7H bin 05 (15); lks2.b is 3.6 cM from AFLP marker E4138-3 in subgroup 6 of the Proctor/Nudinka map (16); lks2.b is about 8.6 cM proximal from RFLP marker WG380B in 7H bin 08 (1); lks2.b is located in the long arm of 7H and flanked by EST-based marker k04151 and k06123 (co-segregated with Bmac64) (27, 31); lks2.b is associated with SNP markers 2_0790 to 2_0060 (positions 73.96 to 97.66 cM) in 7H bins 06 and 07 of the Bowman backcross-derived line BW492 (2); ubs4.d is about 8.0 cM distal from the nud1 (naked caryopsis 1) locxus (25); ubs4.d is associated with SNP markers 2_0103 to 1_0563 (positions 139.96 to 154.35 cM) in 7H bins 08 to 09 of the Bowman backcrossed-derived line BW884 (2); ari-d.15 is associated with SNP marker 1_0169 (position 142.66 cM) in 7H bin 08 of the Bowman backcrossed-derived line BW041 (1); ari-d.44 is associated with SNP markers 1_0056 to 2_0092 (positions 51.93 to 153.29 cM) in 7H bins 04 to 09 of the Bowman backcross-derived line BW035 (2), likely in 7H bin 07. The Lks2 gene has been cloned (31).

Awns of both central and lateral spikelets of lks2.b spikes are reduced to about 3/5 that of the long awned type. Texture of the short awn is finer and more flexible than that of the long awn, especially in non-uzu genotypes (24, 26, 31). Kernel weights of lks2 plants were slightly reduced and kernels per spike were slightly increased, but other traits remained unchanged (23). The Atlas near-isogenic lines for lks2 (half awn) were found to respond better to environmental and genetic stress than the normal lines (20, 21). The awn length of heterozygotes in some crosses was shorter that of the normal parent. Awns, as measured from the tip of the last fertile spikelet on the spike to the tip of the awn, of BW492 were about 1/2 as long as Bowman awns, 5 to 6 vs. 11 to 12 cm (5). The number of longitudinal parenchyma cells in the Bowman backcross-derived line BW492 awns was about half that of Bowman awns (31). Kernels of BW492 plants were slightly lighter than those of Bowman and kernels widths averaged slightly less (5). Other agronomic traits were similar to those of Bowman (5). Allelism tests demonstrated that lks2.b gene in BW492 is allelic and dominant to ubs4.d gene in BW884 and to the ari-d.15 gene in BW041 (31). All 25 accessions identified as mutants at the lks2 locus had lesions in the Lks2 candidate gene (31). Among accessions with the lks2 phenotype, three variants were found: lks2.b1 and lks2.b2 in accessions fromChina, Japan, and Korea and lks2.b3 in accessions from Tibet (31). Stigmas ofari-d and ubs4 mutants have only a few very short branches, which prevents normal pollen reception and reduces seed set to 13 to 30% in uzu type plants. Both the uzu1.a and srh1.a (short rachilla hair 1) genes interact with ubs4.d to further reduce in seed set (25). The stigmas have very few stigma hairs (31). Pollen fertility is normal (25). Awn length is about 1/4 normal (4, 31). Seed set for plants of the Bowman backcross-derived lines for ari-d.15 and ubs4.d, BW041 and BW884, respectively, varied from about 10% for plants grown in greenhouses to nearly 50% for plants grown at Aberdeen, Idaho, USA (5). Grain yields of BW041 and BW884 ranged from 1/4 to 1/2 those of Bowman.Compared to Bowman, kernel weights of BW041 and BW884 varied from slightly lessto slightly more. Other morphological traits of BW041, BW492, and BW884 were similar to those of Bowman (5).

Spontaneous occurrence in some cultivars and distributed in China, Japan, Korea, and Nepal (9, 18, 22, 26, 31). A spontaneous mutant in Ao Hadaka (OUJ159) (25).

lks2.b1 and lks2.b2 in cultivars of Oriental origin, often associated with the dsp1.a (dense spike 1) gene (11, 22, 26, 31); lks2.b3 in accessions from the  Himalayas (including India, Nepal, and Tibet) (31); lks2.s (KM7) isolated from Kanto Nijo 29 by N. Kawada (31); ubs4.d (Ao Hadaka-hen, GSHO 567) in Ao Hadaka (OUJ159) (25); ari-d.15 (NGB 115861, GSHO 1652), -d.35 (NGB 115884), -d.51 (NGB 115904) in Bonus (NGB 14657, PI 189763) (8); ari-d.44 (NGB 115896), -d.57 (NGB 115911) in Bonus (10); ari-d.105 (NGB 115917), -d.107 (NGB 115919), -d.116 (NGB 115928), -d.129 (NGB 115940), -d.130 (NGB 115941), -d.150 (NGB 115961), -d.160 (NGB 115970), -d.186 (NGB 115996), -d.187 (NGB 115997), -d.192 (NGB 116002), -d.193 (NGB 116003), -d.232 (NGB 116042), -d.239 (NGB 116048), -d.240 (NGB 116049), -d.241 (NGB 116050), -d.242 (NGB 116051), -d.243 (NGB 116052), -d.247 (NGB 116058) in Foma (NGB 14659, CIho 11333), -d.288 (NGB 116105) in Kristina (NGB 1500, NGB 14661) (8, 10); a possible lks2 mutant in Morex (CIho 15773) (17, 18).

lks2.b (GSHO 566) in Honen 6 (OUJ469, PI 307495,) (20); lks2.b from Sermo (CIho 7776) in Betzes (PI 129430)*7 (CIho 16558, GP 36), lks2.b from Sermo in Compana (CIho 5438)*7 (CIho 16188, GP 40), lks2.b from Sermo in Decap (CIho 3351)*7 (CIho 16562, GP 44) (6); lks2.b from R.I. Wolfe's Multiple Recessive Stock (GSHO 3451) in Bowman (PI 483237)*9 (GSHO 1850, BW492, NGB 20720).

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J.D. Franckowiak 2007. Barley Genet. Newsl. 37:197-198. 

J.D. Franckowiak 2011. Barley Genet. Newsl. 41:66-68.

U. Lundqvist and J.D. Franckowiak 2015. Barley Genet. Newsl. 45:80-83.