The chlorophyll-deficient mutant assay in barley ( Hordeum vulgare) a report of the U.S. environmental protection agency Gene-Tox program

Abstract

Barley, a self-fertilized, diploid plant with 2 n = 2 x = 14 relatively large chromosomes, is used extensively in genetic studies. The chlorophyll-deficient mutant assay is based on the appearance of discrete phenotypes (i.e., albina, xantha, viridis, striata and tigrina) in the M 2 generation following mutagenic treatments. These mutant phenotypes result from events affecting numerous loci distributed throughout the genome; therefore, the assay is relatively efficient. Although dorman and/or germinating seeds are generally treated, plants can be exposed to mutagens either at specific ontogenetic stages or throughout their life cycle. Experimental protocols are described in the literature. The review of literature pertaining to chemical mutagens identified 20 chemicals that have been tested in the barley chlorophyll-deficient mutant assay. Either a positive or a positive-dose-rleated response was reported for 95% of these; only N-methyl-bis-( β-chloroethul)amine hydrochloride was reported as negative. It appears that those compounds that are mutagenic in other organisms are also mutagenic in barley. Although most of the reports reviewed involved mutagenesis experiments under laboratory conditions, this assay might be useful for detecting mutagens in the ‘real world’ environment.