The low molecular weight fraction of compounds released from immature wheat pistils supports barley pollen embryogenesis

Barley stripe mosaic virus-mediated somatic and heritable gene editing in barley (Hordeum vulgare L.)

Genome editing strategies in barley (Hordeum vulgare L.) typically rely on Agrobacterium-mediated genetic transformation for the delivery of required genetic reagents involving tissue culture techniques. These approaches are genotype-dependent, time-consuming, and labor-intensive, which hampers rapid genome editing in barley. More recently, plant RNA viruses have been engineered to transiently express short guide RNAs facilitating CRISPR/Cas9-based targeted genome editing in plants that constitutively express Cas9. Here, we explored virus-induced genome editing (VIGE) based on barley stripe mosaic virus (BSMV) in Cas9-transgenic barley. Somatic and heritable editing in the ALBOSTRIANS gene (CMF7) resulting in albino/variegated chloroplast-defective barley mutants is shown. In addition, somatic editing in meiosis-related candidate genes in barley encoding ASY1 (an axis-localized HORMA domain protein), MUS81 (a DNA structure-selective endonuclease), and ZYP1 (a transverse filament protein of the synaptonemal complex) was achieved. Hence, the presented VIGE approach using BSMV enables rapid somatic and also heritable targeted gene editing in barley.

A molecular framework for grain number determination in barley

Flowering plants with indeterminate inflorescences often produce more floral structures than they require. We found that floral primordia initiations in barley (Hordeum vulgare L.) are molecularly decoupled from their maturation into grains. While initiation is dominated by flowering-time genes, floral growth is specified by light signaling, chloroplast, and vascular developmental programs orchestrated by barley CCT MOTIF FAMILY 4 (HvCMF4), which is expressed in the inflorescence vasculature. Consequently, mutations in HvCMF4 increase primordia death and pollination failure, mainly through reducing rachis greening and limiting plastidial energy supply to developing heterotrophic floral tissues. We propose that HvCMF4 is a sensory factor for light that acts in connection with the vascular-localized circadian clock to coordinate floral initiation and survival. Notably, stacking beneficial alleles for both primordia number and survival provides positive implications on grain production. Our findings provide insights into the molecular underpinnings of grain number determination in cereal crops.

Applications of Impedance Flow Cytometry in Doubled Haploid Technology

Efficient doubled haploid (DH) plant production is of great interest in the plant breeding industry and research because homozygous lines are obtained within a single generation shortening the breeding cycle substantially. DH protocol development can be a time- and resource-consuming process due to numerous factors affecting its success and efficiency. Here we present concepts and examples about how critical success factors can be identified throughout a DH protocol and an early microspore response monitored by simple impedance flow cytometry (IFC) measurements, which will help to optimize each step of an androgenesis-based DH protocol.

Impact of Ascorbate-Glutathione Cycle Components on the Effectiveness of Embryogenesis Induction in Isolated Microspore Cultures of Barley and Triticale

Enhanced antioxidant defence plays an essential role in plant survival under stress conditions. However, excessive antioxidant activity sometimes suppresses the signal necessary for the initiation of the desired biological reactions. One such example is microspore embryogenesis (ME)-a process of embryo-like structure formation triggered by stress in immature male gametophytes. The study focused on the role of reactive oxygen species and antioxidant defence in triticale (×Triticosecale Wittm.) and barley (Hordeum vulgare L.) microspore reprogramming. ME was induced through various stress treatments of tillers and its effectiveness was analysed in terms of ascorbate and glutathione contents, total activity of low molecular weight antioxidants and activities of glutathione-ascorbate cycle enzymes. The most effective treatment for both species was a combination of low temperature and exogenous application of 0.3 M mannitol, with or without 0.3 mM reduced glutathione. The applied treatments induced genotype-specific defence responses. In triticale, both ascorbate and glutathione were associated with ME induction, though the role of glutathione did not seem to be related to its function as a reducing agent. In barley, effective ME was accompanied by an accumulation of ascorbate and high activity of enzymes regulating its redox status, without direct relation to glutathione content.

β-1,3-Glucanases and chitinases participate in the stress-related defence mechanisms that are possibly connected with modulation of arabinogalactan proteins (AGP) required for the androgenesis initiation in rye (Secale cereale L.)

This work presents the biochemical, cytochemical and molecular studies on two groups of PR proteins, β-1,3-glucanases and chitinases, and the arabinogalactan proteins (AGP) during the early stages of androgenesis induction in two breeding lines of rye (Secale cereale L.) with different androgenic potential. The process of androgenesis was initiated by tillers pre-treatments with low temperature, mannitol and/or reduced glutathione and resulted in microspores reprogramming and formation of androgenic structures what was associated with high activity of β-1,3-glucanases and chitinases. Some isoforms of β-1,3-glucanases, namely several acidic isoforms of about 26 kDa; appeared to be anther specific. Chitinases were well represented but were less variable. RT-qPCR revealed that the cold-responsive chitinase genes Chit1 and Chit2 were expressed at a lower level in the microspores and whole anthers while the cold-responsive Glu2 and Glu3 were not active. The stress pre-treatments modifications promoted the AGP accumulation. An apparent dominance of some AGP epitopes (LM2, JIM4 and JIM14) was detected in the androgenesis-responsive rye line. An abundant JIM13 epitopes in the vesicles and inner cell walls of the microspores and in the cell walls of the anther cell layers appeared to be the most specific for embryogenesis.

Species with Haploid or Doubled Haploid Protocols

In this chapter, we present a list of species (and few interspecific hybrids) where haploids and/or doubled haploids have been published, including the method by which they were obtained and the corresponding references. This list is an update of the compilation work of Maluszynski et al. published in 2003, including new species for which protocols were not available at that time, and also novel methodologies developed during these years. The list includes 383 different backgrounds. In this book, we present full protocols to produce DHs in 43 of the species included in this list. In addition, this book includes a chapter for one species not included in the list. This makes a total of 384 species where haploids and/or DHs have been reported up to date.

A High-Density, Sequence-Enriched Genetic Map of Hordeum bulbosum and Its Collinearity to H. vulgare

L., a wild grass and close relative of cultivated barley ( L.), gained importance in plant breeding as inducer of haploid plants in crosses with barley and also as a genetic resource for introgression of disease resistance/tolerance genes into cultivated barley. Genetic mapping of genes introgressed from is a prerequisite for their efficient utilization in barley breeding, but often hindered due to repressed recombination. The mechanism underlying the reduced frequency or lack of meiotic recombination between . and . chromatin in introgressed segments is not understood. It may be explained by lack of genome collinearity or other structural differences between both genomes. In the present study, two F mapping populations of were analyzed by genotyping-by-sequencing (GBS) and four dense genetic maps containing 1449, 996, 720, and 943 SNP markers, respectively, revealed overall a high degree of collinearity for all seven homeologous linkage groups of and . The patterns of distribution of recombination along chromosomes differed between barley and , indicating organizational differences between both genomes.