BGS 118, Low number of tillers 1, lnt1

Reduced number of tillers = rnt (7).
Intermedium spike-l = int-l (6).

Monofactorial recessive (7).
Located in chromosome 3HL (7); lnt1.a is about 30.5 cM distal from the uzu1 (uzu 1) locus (7, 8); lnt1.a mapped about 7.8 cM from SSR marker GBM1043 in 3HL (4); lnt1.a was not associated with any SNP markers in the Bowman backcross-derived line BW494 (2); int-l.81 is associated with SNP markers 2_1517 to 2_1405 (positions 158.21 to 187.28 cM) in 3H bins 11 to12 of the Bowman backcross-derived line BW428 (2), in 3H bin11 (1).

The tiller number is reduced to 2 to 4 per plant. These tillers are formed soon after seedling emergence; hence, no late-emerging tillers are observed. Culms are thick, and stiff and leaves are dark green (7). Plant mutants at the lnt1 locus fail to produce secondary tillers (1). Occasional spike malformations occur in most environments. The spike may have irregular rachis internode lengths and is relatively short. The lower portion of the spike appears more compact than the upper portion (1, 6). Lateral spikelets in two-rowed cultivars are enlarged and have a pointed apex. Plants homozygous for a recessive allele at the lnt1 locus headed slightly earlier than normal sibs (6). Compared to Bowman, the grain yields of the backcross-derived lines for lnt1.a (BW494) and int-l.81 (BW428) were about 10% of those of Bowman. Kernels were longer and wider and weighed up to 20% more (3). Double mutant plants with the lnt1.a and int-b.3 (intermedium spike-b) genes produced uniculm plants (1). The lnt1.a gene showed an epistatic interaction with high tillering mutants gra-a.1 (granum-a) int-m.85 (intermedium spike-m), mnd1.a (many noded dwarf 1) and mnd6.6 (many noded dwarf 6), producing double mutant plants with 2 to3 tillers (1). Reduced transcript levels for Contig12274, Bell-like homeodomain protein (JuBel2) in lnt1.a plants and co-segregation with JuBel2 were observed (1).

A spontaneous mutant in the hybrid Chikurin Ibaragi 2/Miho Hadaka (7).

lnt1.a (GSHO 833) in Mitake (OUJ408) (7); int-l.81 (NGB 115499, GSHO 1771) in Bonus (NGB 14657, PI 189763) (3, 6); lnt1.b (FN468, GSHO 3678) in Steptoe (CIho 15229) may be an allele based on phenotypic similarity (5).

lnt1.a (GSHO 833) in Mitake; int-l.81 (NGB 115499, GSHO 1771) in Bonus; lnt1.a in Bowman (PI 483237)*8 (GSHO 1984, BW494, NGB 22157); int-l.81 in Bowman*6 (GSHO 1961, BW428, NGB 22152).

1. Dabbert, T., R.J. Okagaki, S. Cho, S. Heinen, J. Boddu, and G.J. Muehlbauer. 2010. The genetics of barley low-tillering mutants: low number of tillers-1 (lnt1). Theor. Appl. Genet. 121:705-715.
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. (Unpublished).
4. Liu, Y.X., X.-H. Sun, B.-L. Xu, and G.-Y. Chen. 2012. Genetic analysis and molecular mapping of low-tillering mutants (cul2.b and lnt1.a) in barley (Hordeum vulgare L.). J. Plant Sci. 7:105-112.
5. Kleinhofs, A. (Unpublished).
6. Lundqvist, U., and A. Lundqvist. 1988. Induced intermedium mutants in barley: origin, morphology and inheritance. Hereditas 108:13-26.
7. Nonaka, S. 1973. A new type of cultivar, Mitake, with very few in number, but thick and stiff culms. Barley Genet. Newsl. 3:45-47.
8. Nonaka, S. 1974. Further information of the rnt locus on chromosome 3. Barley Genet. Newsl. 4:56-58.

1. NGB 115499 (https://www.nordic-baltic-genebanks.org/gringlobal/accessiondetail?accid=NGB 115499)

S. Nonaka. 1973. Barley Genet. Newsl. 3:120.

T. Tsuchiya. 1980. Barley Genet. Newsl. 10:113.
J.D. Franckowiak and U. Lundqvist. 1997. Barley Genet. Newsl. 26:153.
J.D. Franckowiak. 2013. Barley Genet. Newsl. 43:82-83.
J.D. Franckowiak and U. Lundqvist. 2017. Barley Genet. Newsl. 47:74-75.