Impact of the 7-bp deletion in HvGA20ox2 gene on agronomic important traits in barley (Hordeum vulgare L.)

Abstract

Background: Alike to Reduced height-1 (Rht-1) genes in wheat and the semi dwarfing (sd-1) gene in rice, the sdw1/denso locus involved in the metabolism of the GA, was designated as the 'Green Revolution' gene in barley. The recent molecular characterization of the candidate gene HvGA20ox2 for sdw1/denso locus allows to estimate the impact of the functional polymorphism of this gene on the variation of agronomically important traits in barley.

Results: We investigated the effect of the 7-bp deletion in exon 1 of HvGA20ox2 gene (sdw1.d mutation) on the variation of yield-related and malting quality traits in the population of DHLs derived from cross of medium tall barley Morex and semi-dwarf barley Barke. Segregation of plant height, flowering time, thousand grain weight, grain protein content and grain starch was evaluated in two diverse environments separated from one another by 15° of latitude. The 7-bp deletion in HvGA20ox2 gene reduced plant height by approximately 13 cm and delayed flowering time by 3-5 days in the barley segregating DHLs population independently on environmental cue. On other hand, the sdw1.d mutation did not affect significantly either grain quality traits (protein and starch content) or thousand grain weight.

Conclusions: The beneficial effect of the sdw1.d allele could be associated in barley with lodging resistance and extended period of vegetative growth allowing to accumulate additional biomass that supports higher yield in certain environments. However, no direct effect of the sdw1.d mutation on thousand grain weight or grain quality traits in barley was detected.

Keywords: Functional polymorphism; Grain protein content; Heading date; Plant height; QTL; Semi-dwarf barley; Thousand grain weight; sdw1/denso.

Fig. 1

7-bp deletion detected in exon 1 of HvGA20ox2 in Barke (KX611232), Triumph (KX611233) and Franklin (KX789375) semi dwarf barley. Medium tall barley Morex (KX611234) has the intact exon 1. Numbers in parenthesis are GenBank accession numbers. a – multiple alignments include morex_contig_40861 (abbreviated as C_40861) that contains the coding sequence of HvGA20ox2 gene (MLOC_56462.1). The start codon is highlighted in gray. Primers positions are indicated by boxes. b – the predicted protein sequence resulting from 7 bp deletion in exon 1 of HvGA20ox2. The black box indicates 34 amino acids that are in common between intact and altered protein sequence

Fig. 2

Genotyping of DHLs derived from Morex and Barke cross with CAPS marker to detect DHLs with the 7-bp deletion in exon 1 of HvGA20ox2 gene (sdw1/denso allele, undigested fragment of 488 bp). DHLs with the intact exon 1 (Morex allele): lines 1–6, 11. DHLs with sdw1/denso allele: lines 7–10, 12. M - DNA size marker

Fig. 3

Influence of sdw1.d allele on plant height segregation in Morex/Barke barley mapping populations. a – bimodal distribution of plant height observed among the progeny of Morex/Barke cross; black bars correspond to the DHLs with 7-bp deletion in exon 1 of HvGA20ox2. b – LOD scans of Composite Interval Mapping (CIM) for plant height in Morex/Barke population in Pushkin (59°59′39″ N) in 2015. Barley chromosomes are designated 1H through 7H. HvGA20ox2 gene-specific CAPS is the closest marker to the QTL on 3H

Fig. 4

LOD scans of Composite Interval Mapping (CIM) for days to heading in 90 DH progeny lines derived from the Barke and Morex cross in two geographical locations: Pushkin (59°59′39″ N) in 2011, 2012, 2013 and Krasnodar (45°02′55″N) in 2011, 2013. Additive effect is shown by the gray fill path along the X axis. Barley chromosomes are designated 1H through 7H. HvGA20ox2 gene-specific CAPS is the closest marker to the QTL on 3H in all environments tested

Fig. 5

LOD scans of Composite Interval Mapping (CIM) of thousand grain weight in Morex/Barke barley population in three geographical locations: Pushkin (59°59′39″ N) in 2011, 2013, and Krasnodar (45°02′55″ N) in 2011. Additive effect is shown by the gray fill path along the X axis. SNP 3_0896 (VRS1) is the closest marker to the QTL on 2H in all environments tested. The position of the sdw1/denso gene is marked by the black arrows