BGS 178, Intermedium spike-c, int-c

Intensifer for Z = W (25).
Infertile intermedium = i (14, 23, 24)).
Allelic series Ih, I, i (14, 26).
Intermedium spike-c = int-c (8, 9, 19, 20).
Six-rowed spike 5 = v5 (vrs5) (27).
Hordeum vulgare TEOSINTE BRANCHED 1 = HvTB1 (22).

Monofactorial recessive (6, 7, 20, 24, 27).
Located in chromosome 4HS (5, 7, 20, 24, 27); int-c.a is about 13.1 cM proximal from the fch9 (chlorina seedling 9) locus (3, 5, 6, 7, 13); int-c.a is about 14.5 cM distal from the Kap1 (Hooded lemma 1) locus (3, 5, 6, 7, 13); int-c.a is about 3.5 cM from AFLP marker E4143-5 in subgroup 8 of the Proctor/Nudinka map (21); int-c.5 is associated with SNP markers 1_0113 to 2_1122 (positions 26.58 to 47.80 cM) in 4H bins 02 to 05 of the Bowman backcross-derived line BW421 (2); Int-c.a is associated with SNP markers 1_0312 to 2_1374 (positions 38.41 to 41.13 cM) in 4H bins 03 to 04 of the Bowman backcross-derived line BW911, with SNP markers 1_0409 to 2_1122 (positions 5.24 to 47.80 cM) in 4H bins 01 to 05 of the Bowman backcross-derived line BW889 and with SNP markers 1_0132 to 2_0109 (positions 38.41 to 39.48 cM) in 4H bins 03 to 04 of the Bowman backcross-derived line BW624 (2); near SNP marker 2_0302 (22), in 4H bin 04.

Alleles at the int-c (vrs5) locus alter the size of lateral spikelets (1, 6, 22). The lemma apex of lateral kernels is rounded or weakly pointed, awnless or short-awned (1, 11, 18). Lower lateral spikelets may develop poorly in some int-c mutants (6), while seed development may occur in all lateral spikelets of others (8, 17). Variability in lateral spikelet development exists among the int-c mutants, and environmental conditions can alter expressivity. The Int-c.a (formerly I) allele in six-rowed barley increases the size of lateral spikelets, while the int-c.b (formerly i) allele in two-rowed barley prevents anther development in lateral spikelets (11, 25). The int-c.5 mutant in Bonus produces fertile stamens in lateral spikelets (11). In the presence of the Int-c.h (formerly Ih) allele of Mortoni, lateral spikelets are male fertile and may occasionally set seed (10, 14). Spikes of vrs5.n plants appear similar to those of six-rowed barley, but lateral spikelets are smaller (less than half the size of the central spikelets) and broader (5, 6). The Int-c (HvTB1) gene is an ortholog of the maize domestication gene TEOSINTE BRANCHED 1 (TB1) (22). Seventeen barley mutations in the coding region for HvTB1 were correlated with lateral spikelet fertility phenotypes (22). Compared to Bowman the backcross-derived line for int-c.5, BW421, had slightly smaller leaf blades and smaller, lighter kernels, 4.2 vs.5.6 mg. In spite of more kernels per spike (lateral spikelet fertility), the grain yields of BW421 were slightly lower than those of Bowman. (4). Compared to Bowman, tillering was increased in BW421 (22) The increased size of sterile lateral spikelets in Bowman backcross-derived lines for Int-c.a, BW421 and BW889, seems to be associated with a slight increase in leaf blade size (4).

The dominant allele, Int-c.a, is present in six-rowed barley (22) and wild barley (28); the recessive allele, int-c.b, is present in many two-rowed cultivars (22, 28); an X-ray induced mutant in Gamma 4 (5, 7).

int-c.b (i) in two-rowed barleys (26); Int-c.h (Ih) in Mortoni (CIho 2210, GSHO 72) (10, 14); vrs5.n (v5) ((38X-197, OUM338, GSHO 776) in Gamma 4 (5, 7, 16); int-c.5 (NGB 115423, GSHO 1765) in Bonus (NGB 14657, PI 189763) (17, 20); int-c.7 (NGB 115425), -c.62 (NGB 116835), -c.63 (NGB 115481) in Bonus, -c.13 (NGB 115431), -c.15 (NGB 115433), -c.16 (NGB 115434), -c.18 (NGB 115436), -c.25 (NGB 115443), -c.29 (NGB 115447) in Foma (NGB 14659, CIho 11333), -c.33 (NGB 115451), -c.38 (NGB 115456), -c.45 (NGB 115463), -c.48 (NGB 115466), -c.49 (NGB 115467), -c.53 (NGB 115471), -c.56 (NGB 115474), -c.60 (NGB 115478) in Kristina (NGB 14661, NGB 1500) (15); int-c.70 (NGB 115488), -c.76 (NGB 115494), -c.78 (NGB 115496), -c.84 (NGB 115502) in Bonus, -c.95 (NGB 115513) in Hege (NGB 13692) (15).

vrs5.n (GSHO 776, OUM338) in Gamma 4; int-c.b in Hordeum distichon var. nigrinudum (GSHO 988); int-c.5 (NGB 115423, GSHO 1765) in Bonus; int-c.b from Compana (CIho 5438) in Bonneville (CIho 7248)*6 (CIho 16176) (10); vrs5.n from Manabe Island (OUL067, GSHO 766) in Bowman (PI 483237)*5 (GSHO 2102, BW904, NGB 20788); int-c.5 in Bowman*6 (GSHO 2003); int-c.5 in Bowman*7 (BW421, NGB 20654); Int-c.a from SEN “sib” from CIMMYT.in Bowman*4 (GSHO 2363); Int-c.a from SEN ‘sib” in Bowman*7 (BW889, NGB22322). Note that based on SNP markers the Bowman backcross-derived line from Manabe (GSHO 2002, BW904, NGB 20788); do not have the vrn5,n gene..

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