International Database for Barley Genes and Barley Genetic Stocks
BGS 71, Compositum 2, com2
Stock number: BGS 71
Locus name: Compositum 2
Locus symbol: com2
Previous nomenclature and gene symbolization:
Branching inflorescent, rachilla 2 = bir2 (4, 5).
Branched-5 = brc-5 (1, 2, 9, 10).
Monofactorial recessive (4, 12).
Located in chromosome 2HS (2, 4, 5); com2.g is linked to Eam1 (Early maturity 1) (4); brc1.5 maps in 2H subgroup 17 at about 55cM, near markers MWG2067 and CDO665 (2); BLASTn association of brh1.5 with rice gene FUZZY PANICLE (FZP) (10); com2.g is associated with SNP markers 1_0525 to 1_0325 (positions 65.03 to 90.54 cM) in 2H bins 04 to 06 of the Bowman backcross-derived line BW192 (3); com2.k is associated with markers 1_0943 to 1_1015 (positions 34.31 to 91.62 cM) in 2H bins 04 to 07 of the Bowman backcross-derived line BW187 (3); the Bowman backcross-derived line for com2.f, BW191, did not contain any donor parent SNP markers (3), likely in 2H bin 06.
The spike is malformed because spike branches fail to abort and spike branches form from rachis nodes in the basal half of the spike (1). Spike branches form at more rachis nodes under favorable conditions for vigor growth (6, 7). Plants of the Bowman backcross-derived line for com2.f and com2.g, BW191 and BW192, were slightly shorter than Bowman and often had slightly shorter awns. Kernel sizes were variable for BW191 and BW192 and averages weights were lower than those of Bowman. Kernels were on average shorter and thinner, but BW191 plants had smaller grains than those of BW192. Grain yields of BW191 and BW192 were commonly lower than those of Bowman (6). The degree of spike branching is in part dependent on environment (9). The com2 mutant disrupts production of COM2 containing an AP2/ERF (an ethylene-responsive element DNA binding factor) domain that represses inflorescence branch formation (9).
Origin of mutant:
An X-ray induced mutant in Donaria (PI 161974) (12).
com2.f (Mut 2201, GSHO 1700) in Donaria (PI 161974) (12); com2.g (GSHO 1703) from the ICARDA-CIMMYT collection of barley freaks (5); com2.k in Davis 1153 (GSHO 79) (3), brc1.5 (G22, SG-H3/5/8 from Köln) in BGRC 13145 of Braunschweig seed collection (2, 119, com2.25 (L228H, Irregular spike 25, (NGB 113475) in Foma (NGB 14659, CIho 11333) (8, 9); com2.m (TILLmore48), com2.n (TILLmore5865) in Barke (HOR 13170) in Gatersleben (IPK) Gene Bank (9). The variants com2.g, com2.k, and brh1.5 may have arisen from the same mutational event (S221R) (3. 9).
Mutant used for description and seed stocks:
com2.f (GSHO 1700) in Donaria; com2.f in Bowman (PI 483237)*7 (GSHO 2233, BW191, NGB 22023); com2.g in a freak stock from CIMMYT (GSHO 1703); com2.g in Bowman (PI 483237)*8 (GSHO 1878, BW192, NGB 22024); com2.k in Davis 1153 (GSHO 79); com2.k in Bowman*3 (BW187, NGB 22019). Based on marker retained in BW187 and BW192, the original donor parents might be identical.
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