MOLECULAR MAPPING, CHROMOSOMAL ASSIGNMENT, AND GENETIC DIVERSITY ANALYSIS OF PHYTOCHROME LOCI IN BARLEY (HORDEUM-VULGARE)

Phytochromes belong to a family of photoreceptors that perceive, inter pret, and translate light signals that effect plant growth and develop ment. The objectives of this study were to use a heterologous phytochr ome cDNA probe from oat to (1) identify phytochrome loci in barley, (2 ) determine the chromosomal and genomic location of phytochrome gene(s ) in barley, and (3) assess the extent of genetic variation at phytoch rome loci in cultivated barley (Hordeum vulgare). Restriction fragment length polymorphism (RFLP) analysis detected four distinct phytochrom e loci in barley, arbitrarily designated phy1, phy2, phy3, and phy4. W heat-barley addition line analysis indicated that phy1, phy2, and phy3 are located on barley chromosomes 7, 4, and 5, respectively, while ph y4 represents duplicate loci located on barley chromosomes 2 and 7. Li nkage mapping confirmed our results using wheat-barley addition line a nalysis and located the phy1 and phy3 loci to the short arm of barley chromosome 7 and to the centromeric region of barley chromosome 5, res pectively. Two to three alleles were detected at each of the five phyt ochrome loci examined. Genetic diversity values for the phytochrome lo ci were near previous estimates for RFLPs. Division of the barley samp les based on spike morphology indicated that the revel of diversity in two- and six-rowed barley is about equal, although significant differ ences in allelic frequencies were detected between the subgroups.