BGS 308, Long basal rachis internode 1, lbi1

Curved peduncle = cr (1).
Long basal spike internode = bi (5).
Long basal spike internode = lb (7).
Rachisextensum = rac-a and rac-b (4, 8).

Monofactorial recessive (1, 5).
Located in chromosome 5HL (5); lbi1.a is about 16.0 cM distal from the raw1 (smooth awn 1) locus (5); the lbi1.a phenotype in Bowman backcross-derived line BW471 may be associated with retained SNP markers 1_0238 to 2_0550 (positions 55.85 to 130.68 cM) of 1H bins 06 to 11 or with 5HS bin 01 with SNP markers 2_0226 to 2_0553 (positions 3.14 to 26.06 cM) (2); the lbi1 phenotype is associated with the sdw8.ah (semidwarf 8) mutant and with SNP markers 2_0097 to 1_0477 (positions 154.37 to 173.49 cM) in 5H bins 09 to 10 of the Bowman backcross-derived line BW786 (NGB 20763, BGS 708) (2, 3); the lbi1 phenotype is associated with the ari-v.137 (breviaristatum-v) mutant and with SNP markers 2_1065 to 2_1244 (positions about 40.91 to 92.0 cM) in 5H bins 02 to 05 of Bowman backcrossed-derived line BW026 (2, 3).

The first or basal rachis internode is much longer than the other rachis internodes. Basal internode lengths range from less than 1 cm to more than 20 cm (5, 9). Genotype, environmental conditions, and tiller health alter basal rachis internode elongation in plants homozygous for the lbi1.a gene. Expression of the lbi1.a gene is commonly more pronounced in six-rowed cultivars than in two-rowed ones. In many environments, plants of the Bowman backcross-derived line BW471 were about 10% taller than Bowman and had longer peduncles. Rachis internodes were slightly longer and spikes often had one or two more fertile rachis nodes. Kernels of BW471 plants were often slightly longer and heavier than those of Bowman (3). The marker data for BW471 conflicts with the previously reported chromosomal location for lbi1.a, but the SNP marker pattern of the donor parent segments in BW471 suggests a six-rowed origin of the retained segments (2). This indicates more than one locus may be involved in expression of the long basal rachis internode trait.

Natural occurrence in Wisconsin Pedigree 38 (Barbless, CIho 5105, GSHO 580) (5), and in many other six-rowed cultivars of Manchurian origin (5, 8).

lbi1.a (GSHO 580) in Wisconsin Pedigree 38 (CIho 5105, ) (5); rac-a.2 (NGB 114845) and rac-b.1 (NGB 114844) in Bonus (NGB 14657, PI 189763) are not alleles of each other (6); but both rac-a.2 and rac-b.1 are reported to be alleles at the lbi1 locus (8).

lbi1.a (GSHO 580) in Wisconsin Pedigree 38; lbi1.a in Bowman (PI 483237)*5 (GSHO 2144); lbi1.a in Bowman*6 (BW471, NGB 20701).

1. Buckley, G.F.H. 1930. Inheritance in barley with special reference to the color of caryopsis and lemma. Sci. Agric. 10:460-492.
2. Druka, A., J. Franckowiak, U. Lundqvist, N. Bonar, J. Alexander, K. Houston, S. Radovic, F. Shahinnia, V. Vendramin, M. Morgante, N. Stein, and R. Waugh. 2011. Genetic dissection of barley morphology and development. Plant Physiol. 155:617-627.
3. Franckowiak, J.D. (Unpublished).
4. Gustafsson, Å., A. Hagberg, U. Lundqvist, and G. Persson. 1969. A proposed system of symbols for the collection of barley mutants at Svalöv. Hereditas 62:409-414.
5. Hehn, E.R. 1948. The inheritance of agronomic characters in barley. Iowa State Coll. Jour. Sci. 23:39-40. (Abstr.).
6. Lundqvist, U. (Unpublished).
7. Robertson, D.W., G.A. Wiebe, and R.G. Shands. 1955. A summary of linkage studies in cultivated barley, Hordeum species: Supplement II, 1947-1953. Agron. J. 47:418-425.
8. Tsuchiya, T. 1974. Further results of allelism testing in barley. Barley Genet. Newsl. 4:82-85.
9. Wiebe G.A., and D.A. Reid. 1961. Classification of barley varieties grown in the United States and Canada in 1958. U.S. Dep. Agric. Tech. Bull. 1224. 234 pp.

T.E. Haus and T. Tsuchiya. 1971. Barley Genet. Newsl. 1:167.

J.D. Franckowiak and U. Lundqvist. 1997. Barley Genet. Newsl. 26:258.
J.D. Franckowiak. 2010. Barley Genet. Newsl. 40:88-89.
J.D. Franckowiak. 2013. Barley Genet. Newsl. 43:125-126.