International Database for Barley Genes and Barley Genetic Stocks

BGS 116, Non-brittle rachis 2, btr2

BGN  43:80
Stock number: BGS 116
Locus name: Non-brittle rachis 2
Locus symbol: btr2

Previous nomenclature and gene symbolization:

Non-brittle rachis = r (14).
Non-brittle rachis = b (8).
Non-brittle rachis 2 = bt2 (3).


Monofactorial recessive in crosses to Hordeum vulgare subsp. spontaneum (8, 10, 14).
Located in chromosome 3HS (12, 13); btr2.b is very close or semi-allelic to the btr1 (non-brittle rachis 1) locus (12, 13); the Btr1/Btr2 complex is about 15.4 cM distal from the alm1 (albino lemma 1) locus (13); btr2.b is in a 4.3 cM interval between markers KFP216-RisP114 (4); btr1.a was placed within 0.8 cM of AFLP markers e09m25-08 and e45m11-11 (1, 5, 6, 9); the e09m25-08STS-ext sequence is tightly linked with btr1/btr2 locus (1); Btr is associated with SNP markers 2_0742 to 1_0081 (positions 29.05 to 61.77 cM) in 3H bins 030 to 05 of the Bowman backcross-derived line BW102 (2); likely in 3H bin 04.


Joints at the rachis nodes are tough or non-brittle, which prevents segmentation or disarticulation of the rachis prior to maturity. Plants homozygous for the btr2.b allele do not shatter prior to harvest in contrast to wild barley (Hordeum vulgare subsp. spontaneum) (12). All cultivars with the btr2.b allele have a dominant allele at the Btr1 locus. When crossed to cultivars with the btr1.a allele at the Btr2 locus (genotype btr1btr1Btr2Btr2), F1 plants have a brittle rachis. The segregation ratio in the F2 generation is 1 brittle: 1 tough rachis (12). The majority of the cultivars distributed in Oriental region of the Old World have the btr2.b allele (11, 13). Failure to identify recombinants between the btr1 and btr2 loci is attributed to close linkage (5, 9). The abscission layer in barley is probably similar to that described in Oryza sativa (7).

The e09m25-08STS-ext sequence is tightly linked with btr1/btr2 locus and exhibits a high amount of sequence diversity in wild barley, but is less polymorphic within either the East- or the West-type groups (1).

Origin of mutant:

A spontaneous mutant in Hordeum vulgare subsp. spontaneum (1, 3, 8, 14).

Mutational events:

btr2.b in an unknown race of Hordeum vulgare subsp. spontaneum (10, 13).

Mutant used for description and seed stocks:

btr2.b in Sakigoke (OUJ349, GSHO 842); btr2.b in Bowman (PI 483237); Btr1Btr2 from R.I. Wolfe's Multiple Dominant Marker Stock (GSHO 1565) in Bowman*10 (GSHO 1937, BW102, NGB 20508).


1. Azhaguvel, P., and T. Komatsuda. 2007. A phylogenetic analysis based on nucleotide sequence of a marker linked to the brittle rachis locus indicates a diphyletic origin of barley. Ann. Bot. 2007 100:1009-1015.
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. Johnson, I.J., and E. Åberg. 1943. Inheritance of brittle rachis in barley. J. Am. Soc. Agron. 35:100-106.
4. Kandemir, N., A. Yildirim, D.A. Kudrna, P.M. Hayes, and A. Kleinhofs. 2004: Marker assisted genetic analysis of non-brittle rachis trait in barley. Hereditas 141:272-277.
5. Komatsuda, T., and Y. Mano, 2002. Molecular mapping of the intermedium spike (int-c) and non-brittle rachis1 (btr1) loci in barley (Hordeum vulgare L.). Theor. Appl. Genet. 105:85-90.
6. Komatsuda, T., P. Maxim, N. Senthil, and Y. Mano, 2004. High-density AFLP map of nonbrittle rachis 1 (btr1) and 2 (btr2) genes in barley (Hordeum vulgare L.). Theor. Appl. Genet. 109:986-995.
7. Li, C., A. Zhou, and T. Sand. 2006. Rice domestication by reduced shattering. Science 311:1936-1939.
8. Schieman, E. 1921. Genetische Studien an Gerste. I. Zur Frage der Brüchigkeit an Gerste. Z. Indukt. Abstammungs. Vererbungsl. 26:109-143.
9. Senthil, N., and T. Komatsuda. 2005. Inter-subspecific maps of non-brittle rachis genes btr1/btr2 using occidental, oriental and wild barley lines. Euphytica 145:215-220.
10. Takahashi, R. 1955. The origin and evolution of cultivated barley. p. 227-266. In M. Demerec (ed.) Advances in Genetics, Vol. 7. Academic Press, New York.
11. Takahashi, R. 1964. Further studies on the phylogenetic differentiation of cultivated barley. p. 19-26. In S. Broekhuizen, G. Dantuma, H. Lamberts, and W. Lange (eds.) Barley Genetics I. Proc. First Int. Barley Genet. Symp., Wageningen, 1963. Centre for Agricultural Publications and Documentation, Wageningen.
12. Takahashi, R., and J. Hayashi. 1959. Linkage study of the complementary genes for brittle rachis in barley. Preliminary note. Nogaku Kenkyu 46:113-119. [In Japanese with English summary.]
13. Takahashi, R., and J. Hayashi. 1964. Linkage study of two complementary genes for brittle rachis in barley. Ber. Ohara Inst. landw. Biol., Okayama Univ. 12:99-105.
14. Ubisch, G. von. 1915. Analyse eines Falles von Bastardatavismus und Faktorenkoppelung bei Gerste. Z. Indukt. Abstammungs. Vererbungsl. 14:226-237.


R. Takahashi. 1972. Barley Genet. Newsl. 2:182.


J.D. Franckowiak and T. Konishi. 1996. Barley Genet. Newsl. 26:150.
J.D. Franckowiak. 2013. Barley Genet. Newsl. 43:80-81.