BGS 315, Six-rowed spike 3, vrs3

Six-rowed spike 3 = v3 (5).
Intermedium spike-a = int-a (8, 9, 12, 17).
Intermedium spike-g = int-g (8, 9, 14).

Monofactorial recessive (5, 7, 8, 12, 14).
Located in chromosome 1HL 6,10, 18); int-a.1 is near the centromere and proximal from the ert-b (erectoides-b) locus (10, 18); int-a.1 is associated with SNP markers 2_0619 to 1_1361 (positions 50.96 to 82.35 cM) in 1H of the Bowman backcross-derived line BW419 (2), vrs3.f is associated with SNP markers 1_0575 to 1_0075 (positions 37.21 to 82.35 cM) in 1H of the Bowman backcross-derived line BW902 (2); int-a.1 is located between molecular markers 1_0520 and 2_1217 [82.35 to 81.26 cM based on the scale in (2)] in 1H bin 08 (1); only one gene, MLOC_69611.1 located at 47.52 cM, carried a unique mutation in both BW419 (int-a.1) and BW902 (vrs3.f) (1, 3).

The upper half of the spike appears six-rowed, but lateral spikelets in the lower half are reduced in size. The basal portion of the spike appears two-rowed. Awns on the lateral spikelets range from normal near the top, to awnletted or pointed in the middle, to awnless at the base of the spike. Seeds may develop in lateral spikelets of only the upper two-thirds of the spike. Lateral spikelets may be pedicellated in some stocks. Central spikelets often have double awns, one on the lemma and one on the palea. The rachilla may be deformed (5, 6, 7, 8, 14, 16). In Bowman backcross-derived lines for int-a.1 and vrs3.f, BW419 and BW902 respectively, plants were often slightly shorter, rachis internodes were slightly longer, and kernels were thinner than those of Bowman. Kernel weights for BW419 ranged from 70 to 85% of normal compared to only 60 to 75% for those of BW902. Grain yields of Bowman lines BW419 and BW902 were often lower than those of Bowman (4). Compared to Bowman, BW419 and BW902 had more kernels per spike, but tiller numbers and seed weights were reduced (11). The VRS3 gene encodes a putative histone Lys demethylase with a conserved zinc finger and Jumonji C and N domain (1, 3). Comparative transcriptome analysis of the row-type mutants at the Vrs3, Vrs4, and Int-c (Vrs5) loci confirmed that all three genes act as transcriptional activators of Vrs1 variants and produce quantitative variation in the expression levels of VRS1 and differences in the number of developed lateral spikelets (3). The naturally occurring variants Vrs3.w (Haplotype 45) and Vrs3.x (Haplotype 46) were identified as present predominantly in two-rowed spring barleys and six-rowed winter barleys, respectively (1), and could explain the row-type associations with winter and spring growth habit (1, 15, 19). Combining a vrs3 mutant allele (int-a.1 or vrs3.f) with natural six-rowed alleles of vrs1 and vrs5 (int-c) loci leads to increased lateral grain size and greater grain uniformity (1).

A gamma-ray induced mutant in Hakata 2 (OUJ807, PI 263407) (5, 7); an X-ray induced mutant in Bonus (NGB 14657, PI 189763) (12).

vrs3.f (Kmut 213, OUM292, GSHO 774) in Hakata 2 (OUJ807, PI 263407), vrs3.g (Xb 388.8, Piro-1), vrs3.h (Xd 160.46, Piro-3), vrs3.i (X15 1463, Piro-5), vrs3.j (X17 3555, Piro-8) in Piroline (PI 539132) (7); int-a.1 (NGB 115419) in Bonus (NGB 14657, PI 189763) (13); int-a.2 (NGB 115420) in Bonus (14, 17); int-a.8 (NGB 115426),-a.9 (NGB 115427), -a.10 (NGB 115328), -a.64 (NGB 115482) in Bonus, -a.14 (NGB 115432), -a.17 (NGB 115435), -a.21 (NGB 115439), -a.27 (NGB 115445), -a.30 (NGB 115448), -a.31 (NGB 115449), -a.32 (NGB 115450), -a.34 (NGB 115452), -a.35 (NGB 115453), -a.37 (NGB 115455) in Foma (NGB 14659, CIho 11333), -a.46 (NGB 115464), -a.51 (NGB 115469), -a.52 (NGB 115470), -a.54 (NGB 115472), -a.55 (NGB 15473), -a.59 (NGB 115477), -a.61 (NGB 115479) in Kristina (NGB 14661, NGB 1500) (14); int-a.71 (NGB 115489), -a.74 (NGB 115492), -a.77 (NGB 115495), -a.79 (NGB 115497), -a.86 (NGB 115504), -a.88 (NGB 115506) in Bonus, -a.102 (NGB 115520), -a.103 (NGB 115521) in Hege (NGB 13692) (13); wildtype alleles Vrs3.w [Haplotype 45 in Morex (CIho 15773)] and Vrs3.x [Haplotype 46 in Bowman (PI 483237)] were present predominantly in two-rowed spring barleys and six-rowed winter barleys, respectively (1).

vrs3.f (GSHO 774) in Hakata 2; int-a.1 (NGB 115419, GSHO 170) in Bonus; vrs3.f in Bowman (PI 483237)*7 (GSHO 2056, BW902, NGB 22334); int-a.1 in Bowman*5 (GSHO 2055); int-a.1 in Bowman*7 (BW419, NGB 20652).

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