International Database for Barley Genes and Barley Genetic Stocks
BGS 268, Laxatum-b, lax-b
Stock number: BGS 268
Locus name: Laxatum-b
Locus symbol: lax-b
Previous nomenclature and gene symbolization:
Laxatum-1 = lax-1 (3, 4).
Monofactorial recessive (4).
Located in chromosome 6HL (5); lax-b.1 is about 27.3 cM distal from the rob1 (orange lemma 1) locus (5); lax-b.1 is about 18.8 cM proximal from the xnt5 (xantha seedling 5) locus (5); lax-b.1 is associated with SNP markers 1_0061 to 1_0040 (positions 70.15 to 107.26 cM) in 6H bins 05 to 07 of the Bowman backcross-derived line BW459 (1), SNP markers retained from the donor parent in BW459 suggest that the lax-b locus is close to the centromere (2).
Plants are weak and short (3/4 normal), spikes are lax and spikelet number per spike is reduced. Seeds are small and thin and have a shrunken endosperm (xenia), which is detectable in the heterozygous condition (4). Treatment of leaves after tillering with GA3 increases rachis internode length (7). Seed set is reduced in the Bowman backcross-derived line (2). Plants of the Bowman backcross-derived line for lax-b.1, BW459, were slightly shorter and weaker than Bowman plants. Rachis internodes of BW459 were 10 to 20% longer, but fertile spikelets per spike were 10 to 50% fewer. Compared to Bowman, kernels of BW459 were thin (3.5 vs. 3.8 mm) and long 11.0 vs, 9.4 mm) and weighed less (42 vs. 59 mg). Grain yields of BW459 were about 10% those of Bowman (2).
Origin of mutant:
A neutron induced mutant in Bonus (NGB 14657, PI 189763) (6).
lax-b.1 (NGB 116335, GSHO 1776) in Bonus (NGB 14657, PI 189763) (4).
Mutant used for description and seed stocks:
lax-b.1 (NGB 116335, GSHO 1776) in Bonus; lax-b.1 in Bowman (PI 483237)*7 (GSHO 2083, BW459, NGB 20690).
1. 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.
2. Franckowiak, J.D. (Unpublished).
3. 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.
4. Larsson, H.E.B. 1985. Morphological analysis of laxatum barley mutants. Hereditas 103:239-253.
5. Larsson, H.E.B. 1985. Linkage studies with genetic markers and some laxatum barley mutants. Hereditas 103:269-279.
6. Lundqvist, U. (Unpublished).
7. Stoy, V., and A. Hagberg. 1967. Effects of growth regulators on ear density mutants in barley. Hereditas 58:359-384.
U. Lundqvist and J.D. Franckowiak. 1997. Barley Genet. Newsl. 26:248.
U. Lundqvist and J.D. Franckowiak. 2014. Barley Genet. Newsl. 44:113.