Association of the NAD(P)H-bispecific nitrate reductase structural gene with the Nar7 locus in barley

Abstract

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 cross was made between a wild-type cultivar, Morex (Nar7 Nar7), and Az70 (nar7w nar7w), a mutant from the cultivar Steptoe that is deficient in NAD(P)H-bispecific nitrate reductase activity. A probe specific to the NAD(P)H-bispecific nitrate reductase structural gene detected restriction fragment length polymorphism between the parents. This probe was used to classify selected F2 progeny for restriction fragment length genotype. All the NAD(P)H nitrate reductase deficient F2 progeny (24/101) possessed the Az70 restriction fragment genotype. The absence of recombination between the NAD(P)H-bispecific nitrate reductase deficient genotype and the NAD(P)H-bispecific nitrate reductase restriction fragment length genotype indicates that the two traits are closely associated in inheritance and that Nar7 is probably the NAD(P)H-bispecific nitrate reductase structural gene.Key words: Hordeum vulgare, nitrate reductase, restriction fragment length polymorphism.