ASSOCIATION OF THE NAD(P)H-BISPECIFIC NITRATE REDUCTASE STRUCTURAL GENE WITH THE NAR7 LOCUS IN BARLEY

The NADH-specific and NAD(P)H-bispecific nitrate reductase genes from barley have been cloned and sequenced. To determine if the Nar7 locus encodes the NAD(P)H-bispecific nitrate reductase structural gene, a cr oss was made between a wild-type cultivar, Morex (Nar7 Nar7), and Az70 (nar7w nar7w), a mutant from the cultivar Steptoe that is deficient i n NAD(P)H-bispecific nitrate reductase activity. A probe specific to t he NAD(P)H-bispecific nitrate reductase structural gene detected restr iction fragment length polymorphism between the parents. This probe wa s used to classify selected F-2 progeny for restriction fragment lengt h genotype. All the NAD(P)H nitrate reductase deficient F-2 progeny (2 4/101) possessed the Az70 restriction fragment genotype. The absence o f recombination between the NAD(P)H-bispecific nitrate reductase defic ient genotype and the NAD(P)H-bispecific nitrate reductase restriction fragment length genotype indicates that the two traits are closely as sociated in inheritance and that Nar7 is probably the NAD(P)H-bispecif ic nitrate reductase structural gene.