Genetic analysis of several root hair mutants of barley

Introduction Root hairs are specialized epidermal cells that play an important role in uptake of water and nutrients from rhizosphere. Each hair is a long, tubular, non-dividing cell characterized by tip growth, i.e. by deposition of new membrane and cell wall precursors at a cell-growing tip. Several root hair mutants have been isolated and genetically characterized in Arabidopsis thaliana (Parker, 2000, Shiefelbein et al., 2000) however, besides a few reports in maize (Wen and Schnable, 1994), there is a lack of information about genetic basis of root hair development in monocotyledons. Recently, Engvild and Rasmussen (2004) described some barley mutants with changes in root hair phenotype, but for now without information on their genetic basis. Nevertheless, the growing resources of such barley germplasm can help to reveal the mechanisms underlying the process of root hair morphogenesis in monocotyledon species. and 'Delisa' was performed with the use of N-methylo-N-nitroso-urea (MNU) and sodium azide. To generate high frequency of gene mutations, the combined treatment with both mutagenes (Szarejko and Maluszynski, 1999) or double treatment of MNU was applied. The doses for treatment of Rudzik and Dema varieties were as follows: 1.5 mM NaN 3 /3h – inter-incubation germination/6h – 0.75 mM MNU/3h and for variety Krona: 1.75 mM NaN 3 /3h – inter-incubation germination/6h – 0.9 mM MNU/3h. For the varieties Diva, Karat and Delisa double treatment of MNU was used: 0.7 mM MNH/3h.-inter-incubation germination/6h-0.7 mM MNH/3h. The selection of root hair mutants was performed in the M 2 or M 3 generations. Subsequent generations (M 4-M 6) were used to perform homozygosity test and multiply seeds of homozygous lines with mutated root hair phenotype. The observations of root hair zone were done for plants growing in aeroponic conditions (Fig.1). The inheritance of the root hair phenotypes was analyzed in the F 1 and F 2 generations from the crosses between mutants and their parent varieties. Allelism test between mutants was performed. Results Seventeen mutants with changes in the root hair development and morphology have been identified after mutangenic treatments of barley varieties Rudzik, Dema, Krona, Diva, Karat, and Delisa. The mutations affected different stages of root hair development and were classified as belonging to one of four main root hair phenotypes (Table 1):-root hairless mutants, designated rhl,-mutants with development of root hairs blocked at the initial stage, forming only small root hair primordia, seen as 'bulges', designed rhp,-mutants with very short …