BGS 730, Labile 1, lab1

Hordeum irregulare (2, 7).
Hordeum vulgare L. convar. labile (Schiem.) Mansf.) (10, 11).

Monofactorial recessive (6), but the vrs1.a (six-rowed spike 1) allele is required for expression (5, 10).
Located in chromosome 5HL (10); lab1.a is at approximately 80 cM of 5HL in an interval of 5.7 cM between closely linked markers BAR and ge00066s01 (10), likely in 5H bins 08 or 09.

The lab1.a variant causes variable spikelet development at rachis nodes and is characterized by missing kernels or a variable number of fertile spikelets at each rachis node in six-rowed spikes (2, 7). The lateral spikelets are missing more often than the central spikelets (4, 8, 9). All lab1.a (labile) accessions tested have the vrs1.a allele at the six-rowed spike 1 locus (8). The genetic background for labile phenotype is based on a six-rowed genotype with the six-rowed spike 1 with a recessive allele, vrs1.a1 or vrs1.a3, at the six-rowed spike 1 locus and dominant Int-c.a allele present at the intermedium spike-c loci (11). Suppression of lateral spikelet development starts in late stamen primordium (10).

Natural occurrence in barley accessions from Ethiopia (1, 2, 3, 6, 7).

lab1.a in PI 95306 and PI 25672 from Ethiopia (2).

lab1.a in HOR2573 and HOR5465 from Ethiopia (10).

1. Abay, F., and A. Bjørnstad. 2009. Specific adaptation of barley varieties in different locations in Ethiopia. Euphytica 167:181-195.

2. Åberg, E., and G.A. Wiebe. 1945. Irregular barley, Hordeum irregulare, sp. nov. J. Wash. Acad. Sci. 35:161-164.

3. Bjørnstad, A., and F. Abay. 2010. Multivariate patterns of diversity in Ethiopian barleys. Crop Sci. 50:1579-1586.

4. Djalali, M. 1970. Investigations on expressivity and penetrance of labile character of barley (Hordeum vulgare L.). Z Pflanzenzücht. 63:274-322.

5. Djalali, M., W. Hoffman, and W. Plarre. 1971. Genetics and varaibility of the labile-gene in barley under different environmental conditions. p. 201-207. In R.A. Nilan (ed.) Barley Genetics II. Proc. Second Int. Barley Genet. Symp., Pullman, WA, 1969. Washington State Univ. Press, Pullman.

6. Hadado, T.T., D. Rau, E. Bitocchi, and R. Papa. 2009. Genetic diversity of barley (Hordeum vulgare L.) landraces from the central highlands of Ethiopia: comparison between the Belg and Meher growing seasons using morphological traits. Genet. Resour. Crop Evol. 56:1131-1148.

7. Harlan, H.V. 1914. Some distinctions in cultivated barleys with reference to their use in plant breeding. Vol 137 Gov. Print. Off., U.S. Dept. Agr. Bull., illus. p. 38. Washington.

8. Saisho, D., M. Pourkheirandish, H. Kanamori, T. Matsumoto, and T. Komatsuda. 2009. Allelic variation of row type gene Vrs1 in barley and implication of the functional divergence. Breed. Sci. 59:621-628.

9. Takeda, K., and W. Saito. 1988. Inheritance of the percentage of missing lateral florets in ‘irregurale’ barley. Japan J. Breed. 38:72-80. (in Japanese with English summary p. 80).

10. Youssef, H.M., R. Koppolu, T. Rutten, V. Korzun, P. Schweizer, and T. Schnurbusch. 2014. Genetic mapping of the labile (lab) gene: a recessive locus causing irregular spikelet fertility in labile-barley (Hordeum vulgare convar. labile). Theor. Appl. Genet. 127:1123-1131.

11. Youssef, H.M., R. Koppolu, and T. Schnurbusch. 2012. Re-sequencing of vrs1 and int-c loci shows that labile-barleys (Hordeum vulgare convar. labile) have a six-rowed genetic background. Genet. Resour. Crop Evol. 59:1319-1328.

J.D. Franckowiak. 2015. Barley Genet. Newsl. 45:242.

J.D. Franckowiak. 2016. Barley Genet. Newsl. 46:137-138.