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<p>In vitro mutagenesis via isolated microspore culture provides an efficient way to produce numerous double haploid (DH) lines with mutation introduction and homozygosity stabilization, which can be used for screening directly. In this study, 356 DH lines were produced from the malt barley (Hordeum vulgare L.) cultivar Hua-30 via microspore mutagenic treatment with ethyl methane sulfonate or pingyangmycin during in vitro culture. The lines were subjected to field screening under high nitrogen (HN) and low nitrogen (LN) conditions, and the number of productive tillers was used as the main screening index. Five mutant lines (A1-28, A1-84, A1-226, A16-11, and A9-29) with high numbers of productive tillers were obtained over three consecutive years of screening. In the fifth year, components related to N-use efficiency (NUE), including N accumulation, utilization, and translocation, were characterized for these lines based on N uptake efficiency (NUpE), N utilization efficiency (NUtE), and N translocation efficiency (NTE). The results show that the NUpE of four mutant lines (A1-84, A1-226, A9-29, and A16-11) improved significantly under HN, whereas that of two lines (A1-84 and A9-29) improved under LN. As a result, their NUE improved greatly. No improvement in NUtE was observed in any of the five mutant lines. A1-84 and A9-29 were selected as an enhanced genotype in N uptake, and A1-28 showed improved NTE at the grain-filling stage. Our results imply that high-NUpE mutants can be produced through microspore mutagenesis and field screening, and that improvement of NUE in barley depends on enhancement of N uptake.</p

Expression analysis of three SERK-like genes in barley under abiotic and biotic stresses

<p>Somatic embryogenesis receptor-like kinases (SERKs), a subfamily of receptor-like kinases, showed important roles in plant response to abiotic and biotic stresses in addition to embryogenesis and organogenesis in numerous plant species. In the present study, three orthologs of <i>SERK</i> genes (<i>HvSERK1/2/3</i>) were isolated from barley, and their expression patterns during <i>in vitro</i> culture of microspores as well as their responses to different stresses including salinity and powdery mildew were characterized. Sequence analysis suggested that three <i>HvSERK</i> genes were highly conserved in the grass family. Subcellular localization showed the HvSERK1 protein located on the plasma membrane. The <i>HvSERK1</i> transcript was up-regulated during the microspore culture period, suggesting its roles in microspore embryogenesis. <i>HvSERK1</i> and <i>HvSERK3</i> showed the highest expression level in the leaves; however no difference was detected for <i>HvSERK2</i> expression in different plants’ tissues. Under salt stress, all three <i>HvSERK</i> genes were quickly induced in microspore-derived embryogenic calli, whereas only <i>HvSERK1</i> was up-regulated in the roots of barley seedlings. Moreover, only <i>HvSERK2</i> was induced in the barley leaves upon powdery mildew inoculation. These results suggest that barley <i>SERK</i> genes may participate in barley microspores’ development and plant response toward salt and fungal stress, and the function of them has some evolutionary changes.</p