International Database for Barley Genes and Barley Genetic Stocks

BGS 638, NADH nitrate reductase-deficient 2 (molybdenum cofactor), nar2

BGN  35:195
Stock number: BGS 638
Locus name: NADH nitrate reductase-deficient 2 (molybdenum cofactor)
Locus symbol: nar2

Previous nomenclature and gene symbolization:



Monofactorial recessive (4).
Location in chromosome 5HL (2); nar2.a2 is near molecular marker ABC324 in 5H bin 06 (2); morphological marker data placed nar2 about 8.4 cM proximal from the nld1 (narrow leafed dwarf 1) locus (5); about 23 cM distal from the mtt2 (mottled leaf 2) locus (5).


The nar2 mutants are characterized by a pleiotropic loss of nitrate reductase and xanthine dehydrogenase activity due to defective molybdenum cofactor synthesis or insertion (4). Some alleles are viable (nar2.a2), but they have a definite light green color and loss of vigor (3). The and homozygotes are not viable and they must be maintained as heterozygotes (1).
No images

Origin of mutant:

A sodium azide induced mutant in Steptoe (CIho 15229) (4).

Mutational events:

nar2.a2 (Az34, GSHO 2415) in Steptoe (CIho 15229) (4); (R9401), (R9201) in Maris Mink (PI 467824) (1).

Mutant used for description and seed stocks:

nar2.a2 (GSHO 2415) in Steptoe.


1. Bright, S.W.J. P.B. Norbury, J. Franklin, D.W. Kirk, and J.L. Wray. 1983. A conditional lethal cnx-type nitrate reductase-deficient barley mutant. Mol. Gen. Genet. 189:240-244.

2. Kleinhofs, A. 1997. Integrated barley RFLP and classical marker maps. Barley Genet. Newsl. 27:105-112.

3. Kleinhofs, A. (Unpublished).

4. Kleinhofs, A., T. Kuo, and R.L. Warner. 1980. Characterization of nitrate reductase-deficient barley mutants. Molec. Gen. Genet. 177:421-425.

5. Melzer, J.M., A. Kleinhofs, D.A. Kudrna, R.L. Warner, and T.K. Blake. 1988. Genetic mapping of barley nitrate reductase-deficient nar1 and nar2 loci. Theor. Appl. Genet. 75:767-771.


A. Kleinhofs. 2005. Barley Genet. Newsl. 35:196.