New semi-dwarfing alleles with increased coleoptile length by gene editing of gibberellin 3-oxidase 1 using CRISPR-Cas9 in barley (Hordeum vulgare L.)

The green revolution was based on genetic modification of the gibberellin (GA) hormone system with "dwarfing" gene mutations that reduces GA signals, conferring shorter stature, thus enabling plant adaptation to modern farming conditions. Strong GA-related mutants with shorter stature often have reduced coleoptile length, discounting yield gain due to their unsatisfactory seedling emergence under drought conditions. Here we present gibberellin (GA) 3-oxidase1 (GA3ox1) as an alternative semi-dwarfing gene in barley that combines an optimal reduction in plant height without restricting coleoptile and seedling growth. Using large-scale field trials with an extensive collection of barley accessions, we showed that a natural GA3ox1 haplotype moderately reduced plant height by 5-10 cm. We used CRISPR/Cas9 technology, generated several novel GA3ox1 mutants and validated the function of GA3ox1. We showed that altered GA3ox1 activities changed the level of active GA isoforms and consequently increased coleoptile length by an average of 8.2 mm, which could provide essential adaptation to maintain yield under climate change. We revealed that CRISPR/Cas9-induced GA3ox1 mutations increased seed dormancy to an ideal level that could benefit the malting industry. We conclude that selecting HvGA3ox1 alleles offers a new opportunity for developing barley varieties with optimal stature, longer coleoptile and additional agronomic traits.

Validation of SNP markers for selection of semi-dwarf and peduncle extrusion in barley

This study aimed to validate the use of two SNP markers associated to a sdw1 allele identified previously in a short barley genotype (ND23049) with an adequate peduncle extrusion which reduces predisposition to fungal disease development. First, the GBS SNP were converted in a KASP marker but only one of them, named TP4712, correctly amplified all allelic variations and had a Mendelian segregation in a F2 population. To corroborate the association between TP4712 allele with plant height and peduncle extrusion, a total of 1221 genotypes were genotyped and evaluated for both traits. Out of the 1221 genotypes, 199 were F4 lines, 79 were a diverse panel, and 943 were two complete breeding cohorts of stage 1 yield trials. To corroborate the association between the sdw1 allele and the short plant height with adequate peduncle extrusion, contingency tables were created, grouping the 2427 data points into categories. Based on the contingency analysis, it was demonstrated that the higher proportion of short plants with adequate peduncle extrusion were present in genotypes carrying the SNP allele of ND23049 regardless the population and the sowing date. This study develops a marker-assisted selection tool to accelerate the introgression of favourable alleles for plant height and peduncle extrusion in adapted germplasm.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11032-023-01371-7.

Identification of QTL underlying the main stem related traits in a doubled haploid barley population

Lodging reduces grain yield in cereal crops. The height, diameter and strength of stem are crucial for lodging resistance, grain yield, and photosynthate transport in barley. Understanding the genetic basis of stem benefits barley breeding. Here, we evaluated 13 stem related traits after 28 days of heading in a barley DH population in two consecutive years. Significant phenotypic correlations between lodging index (LI) and other stem traits were observed. Three mapping methods using the experimental data and the BLUP data, detected 27 stable and major QTLs, and 22 QTL clustered regions. Many QTLs were consistent with previously reported traits for grain filling rate, internodes, panicle and lodging resistance. Further, candidate genes were predicted for stable and major QTLs and were associated with plant development and adverse stress in the transition from vegetative stage to reproductive stage. This study provided potential genetic basis and new information for exploring barley stem morphology, and laid a foundation for map-based cloning and further fine mapping of these QTLs.