Elevated CO2 (eCO2) concentrations can stimulate crop growth, but little is known about intraspecific variability in the response to eCO2 and the underlying genetics in cereals. Field experiments over two years with 98 barley genotypes were conducted in open‐top chambers (OTCs) under ambient CO2 (400 ppm) and eCO2 (700 ppm) concentrations. At crop maturity, different fractions of aboveground biomass (AGB) were measured, and genome‐wide association studies (GWASs) were conducted to identify quantitative trait loci (QTL). Averaged across all genotypes, eCO2 significantly enhanced AGB by 15%, while the increase in culm and ear biomass alone was not significant. The AGB response to eCO2 of the individual genotypes ranged from c. −36% to +95% compared with ambient CO2 (aCO2), showing a large variability of growth responses. In GWAS, 51 associations between SNP markers and the relative changes (eCO2/aCO2) in biomass were detected on different chromosomes. Loci potentially involved in biomass alterations under eCO2 were identified. The wide range of variability in responses might be exploited by marker‐based breeding for climate‐resilient barley.
The effect of elevated atmospheric CO
2 concentration [CO
2] on the diversity and composition of the prokaryotic community inhabiting the rhizosphere of winter barley (Hordeum vulgare L.) was investigated in a field experiment, using open‐top chambers. Rhizosphere samples were collected at anthesis (flowering stage) from six chambers with ambient [CO
2] (approximately 400 ppm) and six chambers with elevated [CO
2] (700 ppm). The V4 region of the 16S rRNA gene was PCR‐amplified from the extracted DNA and sequenced on an Illumina MiSeq instrument. Above‐ground plant biomass was not affected by elevated [CO
2] at anthesis, but plants exposed to elevated [CO
2] had significantly higher grain yield. The composition of the rhizosphere prokaryotic communities was very similar under ambient and elevated [CO
2]. The dominant taxa were Bacteroidetes, Actinobacteria, Alpha‐, Gamma‐, and Betaproteobacteria. Elevated [CO
2] resulted in lower prokaryotic diversity in the rhizosphere, but did not cause a significant difference in community structure.
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