Abstract
Main conclusionBoth mutant ert-c.1 and ert-d.7 carry T2-T3 translocations in the Ert-c gene. Principal coordinate analyses revealed the translocation types and translocation breakpoints. Mutant ert-d.7 is an Ert-cErt-d double mutant.Mutations in the Ert-c and Ert-d loci are among the most common barley mutations affecting plant architecture. The mutants have various degrees of erect and compact spikes, often accompanied with short and stiff culms. In the current study, complementation tests, linkage mapping, principal coordinate analyses and fine mapping were conducted. We conclude that the original ert-d.7 mutant does not only carry an ert-d mutation but also an ert-c mutation. Combined, mutations in Ert-c and Ert-d cause a pyramid-dense spike phenotype, whereas mutations in only Ert-c or Ert-d give a pyramid and dense phenotype, respectively. Associations between the Ert-c gene and T2-T3 translocations were detected in both mutant ert-c.1 and ert-d.7. Different genetic association patterns indicate different translocation breakpoints in these two mutants. Principal coordinate analysis based on genetic distance and screening of recombinants from all four ends of polymorphic regions was an efficient way to narrow down the region of interest in translocation-involved populations. The Ert-c gene was mapped to the marker interval of 2_0801to1_0224 on 3HL near the centromere. The results illuminate a complex connection between two single genes having additive effects on barley spike architecture and will facilitate the identification of the Ert-c and Ert-d genes.
Highlights
Plant architecture has fundamental impact on crop performance
Successful crosses were confirmed by testing F1 lines with polymorphic single-nucleotide polymorphism (SNP) markers
Χ2 (3:1) 0.022 (9:3:3:1) 4.67 (9:3:3:1) 5.38 (9:3:3:1) 1.49 (9:3:3:1) 1.97 (9:3:3:1) 5.80 (9:3:3:1) 3.47 (3:1) 0.00 (9:3:3:1) 0.00 (9:3:3:1) 3.56 (9:3:3:1) 1.36. Their spikes have a compact appearance caused by a reduction in rachis internode length. They have historically been mapped to chromosomes 3HL and 7HS, respectively, but a later study using near-isogenic lines BW305 and BW306 suggested that both mutations are located on chromosomes 3H or 2H (Druka et al 2011), which can be interpreted as they would be allelic
Summary
Plant architecture has fundamental impact on crop performance. For example, the pronounced increase in crop yield due to application of fertilizers required the simultaneous introduction of short-culm alleles in cereal elite cultivars during the “green revolution”; the Rht-D1b and Rht-B1b DELLA alleles in wheat and sd alleles in rice (Hedden 2003). Before selection of the sdw1/denso “green revolution” alleles, the plant architecture of wheat and barley had already been shaped by millennia-long selection during the process of domestication and adaptation in the Neolithic revolution Page 2 of 15. The mutation in the Q gene was suggested first to occur in tetraploid wheat during domestication (Sormacheva et al 2015) It encodes an APETALA2 (AP2) transcription factor which regulates many domestication-related traits. HvAP2 alleles, Zeo and Zeo, were found in 2-row spring UK barley as natural occurrences (Houston et al 2013) Both alleles cause pleiotropic effects including cleistogamy (Nair et al 2010; Houston et al 2013), denser spike, and a haplotypedependent change in plant height (www.nordgen.org/bgs; Franckowiak and Lundqvist 2012)
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