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Nitrogen (N) is one of the most important macronutrients for crop growth and development. Large amounts of N fertilizers are applied exogenously to improve grain yield and quality, which has led to environmental pollution and high cost of production. Therefore, improvement of N use efficiency (NUE) is a very important aspect for sustainable agriculture. Here, a pilot experiment was firstly conducted with a set of barley genotypes with confirmed NUE to validate the fast NUE screening, using chlorate as an analogue to nitrate. High NUE genotypes were susceptible to chlorate-induced toxicity whereas the low NUE genotypes were tolerant. A total of 180 barley RILs derived from four parents (Compass, GrangeR, Lockyer and La Trobe) were further screened for NUE. Leaf chlorosis induced by chlorate toxicity was the key parameter observed which was later related to low-N tolerance of the RILs. There was a distinct variation in chlorate susceptibility of the RILs with leaf chlorosis in the oldest leaf ranging from 10 to 80%. A genome-wide association study (GWAS) identified 9 significant marker-trait associations (MTAs) conferring high chlorate sensitivity on chromosomes 2H (2), 3H (1), 4H (4), 5H (1) and Un (1). Genes flanking with these markers were retrieved as potential targets for genetic improvement of NUE. Genes encoding Ferredoxin 3, leucine-rich receptor-like protein kinase family protein and receptor kinase are responsive to N stress. MTA4H5468 which exhibits concordance with high NUE phenotype can further be explored under different genetic backgrounds and successfully applied in marker-assisted selection.

Nitrogen (N) is one of the most important macronutrients for crop growth and development. Large amounts of N fertilizers are applied exogenously to improve grain yield and quality, which has led to environmental pollution and high cost of production. Therefore, improvement of N use efficiency (NUE) is a very important aspect for sustainable agriculture. Here, a pilot experiment was firstly conducted with a set of barley genotypes with confirmed NUE to validate the fast NUE screening, using chlorate as an analogue to nitrate. High NUE genotypes were susceptible to chlorate-induced toxicity whereas the low NUE genotypes were tolerant. A total of 180 barley RILs derived from four parents (Compass, GrangeR, Lockyer and La Trobe) were further screened for NUE. Leaf chlorosis induced by chlorate toxicity was the key parameter observed which was later related to low-N tolerance of the RILs. There was a distinct variation in chlorate susceptibility of the RILs with leaf chlorosis in the oldest leaf ranging from 10 to 80%. A genome-wide association study (GWAS) identified 9 significant marker-trait associations (MTAs) conferring high chlorate sensitivity on chromosomes 2H (2), 3H (1), 4H (4), 5H (1) and Un (1). Genes flanking with these markers were retrieved as potential targets for genetic improvement of NUE. Genes encoding Ferredoxin 3, leucine-rich receptor-like protein kinase family protein and receptor kinase are responsive to N stress. MTA4H5468 which exhibits concordance with high NUE phenotype can further be explored under different genetic backgrounds and successfully applied in marker-assisted selection.

The introduction of semi-dwarf cereal crop varieties in the 1960s enabled extensive increases in global food production. Semi-dwarf barley cultivars have shorter stature and improved stress resistance, grain yield and quality than tall varieties. The major semi-dwarf genes, sdw1 and ari-e, have been widely used in barley breeding programmes worldwide. In this study, we identified a novel sdw1 allele in cv. Lockyer and investigated the effect of sdw1 and ari-e and their interactions on plant height, flowering time and grain yield using a Multi-parent Advanced Generation Inter-cross (MAGIC) population generated from four elite barley cultivars. Allele-specific markers combined with Kompetitive Allele Specific Polymerase Chain Reaction (KASP) assays were used for fast and accurate screening of plants with different allele combinations. The results showed that the novel sdw1 allele from cv. Lockyer had similar effects on plant growth and phenology as the known sdw1.d allele. The two semi-dwarf genes sdw1 and ari-e had an additive effect for plant height with height reductions up to 27 cm. The ari-e gene triggered earlier flowering up to 6 days compared to WT and reduced the delay in flowering time caused by the sdw1 gene. The two semi-dwarf genes boosted grain yields by 20% in the sdw1 plants and up to 28% in plants with the two combined semi-dwarf genes. The results presented will benefit the development of higher-yielding and better-adapted barley cultivars.

The introduction of semi-dwarf cereal crop varieties in the 1960s enabled extensive increases in global food production. Semi-dwarf barley cultivars have shorter stature and improved stress resistance, grain yield and quality than tall varieties. The major semi-dwarf genes, sdw1 and ari-e, have been widely used in barley breeding programmes worldwide. In this study, we identified a novel sdw1 allele in cv. Lockyer and investigated the effect of sdw1 and ari-e and their interactions on plant height, flowering time and grain yield using a Multi-parent Advanced Generation Inter-cross (MAGIC) population generated from four elite barley cultivars. Allele-specific markers combined with Kompetitive Allele Specific Polymerase Chain Reaction (KASP) assays were used for fast and accurate screening of plants with different allele combinations. The results showed that the novel sdw1 allele from cv. Lockyer had similar effects on plant growth and phenology as the known sdw1.d allele. The two semi-dwarf genes sdw1 and ari-e had an additive effect for plant height with height reductions up to 27 cm. The ari-e gene triggered earlier flowering up to 6 days compared to WT and reduced the delay in flowering time caused by the sdw1 gene. The two semi-dwarf genes boosted grain yields by 20% in the sdw1 plants and up to 28% in plants with the two combined semi-dwarf genes. The results presented will benefit the development of higher-yielding and better-adapted barley cultivars.