Abstract
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.
Highlights
Nitrogen (N) is an essential macronutrient for crop growth and development, which is usually required to achieve maximum yields in modern agriculture (Wu et al, 2011)
Our results reveal that microspore mutagenesis combined with field screening is an efficient approach to generate homozygous mutant lines for genetic improvement of N-use efficiency (NUE)
Hua-30, isolated microspores of Hua-30 were treated with the two types of chemical mutagens (EMS and PYM) at low concentrations
Summary
Nitrogen (N) is an essential macronutrient for crop growth and development, which is usually required to achieve maximum yields in modern agriculture (Wu et al, 2011). Improved crop varieties with high N-use efficiency (NUE) are considered the best economic strategy for agricultural sustainability (Quan et al, 2016). An early successful case reported in oilseed rape Canola produced five DH mutant lines with tolerance to the herbicide imidazolinone by microspore mutagenesis using ethyl nitrosourea (Swanson et al, 1989). In another successful reported case, in Brassica carinata, nine mutant lines with changes in erucic acid concentration were obtained from nearly 400 DH lines produced by microspore mutagenesis using sodium azide (Barro et al, 2001). A study in Chinese cabbage produced six stable inheriting mutants from 1304 regenerated plants by microspore mutagenesis using EMS (Huang et al, 2016). In addition to chemical mutagenesis, microspore mutagenesis using radiation has been successful in B. napus (Beaith et al, 2005) and Chinese cabbage (Huang et al, 2014)
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