International Database for Barley Genes and Barley Genetic Stocks

BGS 25, Xantha seedling 1, Xnt1

BGN  48:65
Stock number: BGS 25
Locus name: Xantha seedling 1
Locus symbol: Xnt1

Previous nomenclature and gene symbolization:

Xantha a = Xa (7).
Xantha-h = xan-h (11, 12, 14).
Chlorina-125 = Clo-125 (11, 12)


Monofactorial incomplete or semi-dominant (7, 12); allelic to recessive xantha-h (xan-h) mutants (4).
Located in chromosome 7HL (7); Xnt1.a is over 35.9 cM distal from the lks2 (short awn 2) locus (7, 13). Xnt1.a is associated with SNP marker 2_0354 (position 171.87 cM) in 7H bin 10 of a presumed heterozygous plant of the Bowman backcross-derived line BW919 (2); Clo.125 was not associated with any 7H SNP markers in a presumed heterozygous plant of the Bowman backcross-derived line BW186 (2), in 7H bin 10.


Segregation is observed each generation for xantha, chlorina, and green seedlings, but only the last two classes survive to maturity. Chlorina plants have a slightly yellow-green in color until near maturity. Crosses to chlorina plants produce chlorina and green F1 plants in a 1:1 ratio. In the progeny of chlorina plants, xantha, chlorina, and green plants occur in a 1:2:1 ratio (7). Color differences between normal and heterozygous plants are observed in the Xnt1.a2 mutant only just prior to heading (10). Mutants at the Xnt1 locus must be maintained as heterozygous stocks (3, 7). The semi-dominant mutants at the Xnt1 locus are defective in the 42 kDa protein subunit (42-kDa XANTHA-H) involved in insertion of Mg2+ into protoporphyrin IX (4). The heterozygous chlorina seedlings have 25-50% of Mg-chelatase activity of green seedlings. The semi-dominant Xnt1 mutants are alleles at the xan-h locus, but the lethal recessive xantha-h mutants do not retain the defective protein in the 42-kDa subunit (4, 5, 6). The chlorophyll content of xan-h heterozygotes is reduced slightly (1).

Origin of mutant:

An ethyl methanesulfonate induced mutant in the cross Akashinriki (OUJ659, PI 467400) X linkage tester 191 (OUL094) (7); . a sodium azide induced mutant in Bonus (NGB 14657, PI 189763) (8).

Mutational events:

Xnt1.a in the hybrid Akashinriki X linkage tester 191 (OUM215) (7, 12); Xnt1.a2 in translocation stock T6-7d (10); Xnt1.a3 in MC 20 (PI 357319) (9); semi-dominant mutants Chlorina-125 (Xnt1.125) in Bonus (NGB 14657, PI 189763), Chlorina-157 (Xnt1.157), Chlorina-161 (Xnt1.161) in breeding line Ca710516 (Triumph/Goldspear) (4, 10, 11); xan-h.30, -h.38, -h.56, and -h.57 in Bonus (5, 8, 11, 12). All Xnt1 and xan-h mutant stocks are stored in the Biology Department, Lund University with Mats Hansson who is the coordinator for chlorophyll biosynthesis (5).,

Mutant used for description and seed stocks:

Xnt1.a (GSHO 1606) in the hybrid Akashinriki X linkage tester 191 Xnt1.a in Bowman (PI 483237, NGB22812)*7 (GSHO 1862, BW919, NGB 20790); Xnt.125 (Clo-125).


1. Braumann, I., N. Stein, and M. Hansson. 2014. Reduced chlorophyll biosynthesis in heterozygous barley magnesium chelatase mutants. Plant Physiol. Bioch. 78:10-14.
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. 2010. Genetic dissection of barley morphology and development. Plant Physiol. 155:617-627.
3. Franckowiak, J.D. (Unpublished).
4. Hansson, A., C.G. Kannangara, D. von Wettstein, and M. Hansson. 1999. Molecular basis for semidomiance of missense mutations in the XANTHA-H (42-kDa) subunit of magnesium chelatase. Proc. Natl. Acad. Sci. USA 96:1744-1749.
5. Henningsen, K.W., J.E. Boynton, and D. von Wettstein. 1993. Mutants at xantha and albina loci in relation to chloroplast biogenesis in barley. Biologiske Skrifter 42:8-349. (The Royal Danish Academy of Sciences and Letters)
6. Jensen, P.E., B.L. Petersen, B.M. Stummann, K.W. Henningsen. R.D. Willows, U.C. Vothknecht, C.G. Kannangara, and D. von Wettstein. 1996. Structural genes for Mg-chelatase subunits in barley: Xantha-f, -g and –h. Mol. Gen. Genet. 250:383-394.
7. Konishi, T. 1972. An incomplete dominant chlorophyll mutation on chromosome 1. Barley Genet. Newsl. 2:43-45.
8. Lundqvist, U. (Unpublished).
9. Prina, A.R., M. del C. Arias, and M.C. de la Fuente. 1996. A new mutant allele for Xa/xa gene and its use for location of newly induced mutants in the long arm of barley's chromosome 1. Barley Genet. Newsl. 25:31-33.
10. Prina, A.R., and E.A. Favret. 1988. Influence of marker genes on the expression of somatic mutations. J. Hered. 79:371-376.
11. Simpson, D.J., O. Machold, G. Høyer-Hansen, and D. von Wettstein. 1985. Chlorina mutants of barley (Hordeum vulgare L.). Carlsberg Res. Commun. 50:223-238.
12. Simpson, D.J., and D. von Wettstein. 1992. Coordinator’s report: Nuclear genes affecting the chloroplast. Stock list of mutants kept at Carlsberg Laboratory. Barley Genet. Newsl. 21:102-108.
13. Takahashi, R., J. Hayashi, T. Konishi, and I. Moriya. 1972. Inheritance and linkage studies in barley. V. Locating seven new mutant genes. Ber. Ohara Inst. landw. Biol., Okayama Univ. 15:147-168.
14. von Wettstein, D., S. Gough, and C.G. Kannangara. 1995. Chlorophyll biosynthesis. Plant Cell 7:1039-1057.


T. Konishi and J.D. Franckowiak. 1997. Barley Genet. Newsl. 26:71.


J.D. Franckowiak and U. Lundqvist. 2018. Barley Genet. Newsl. 48:65-66.