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Background and Aims: Barley breeding has increased yield over the last century, but the associated changes in the phenotype are largely unknown. Our aim was to quantify the rate of genetic gain in a collection of Australian barley cultivars representing seven decades of breeding, and the associated changes in the phenotype. Methods: Thirteen barley cultivars were grown in the field at Roseworthy and Mintaro, South Australia, to evaluate shifts in phenology, yield, and its components. A subset of five cultivars was grown under controlled conditions to probe for changes in root traits and nutrient uptake. Results: Grain yield increased at 16.0 ± 5.3 kg ha−1 yr−1 or 0.43 ± 0.15% yr−1 at Roseworthy, where average yield was 3.1 t ha−1. There was no relation between yield and year of registration at Mintaro, where severe, extended frost disrupted reproduction. Changes in phenology with year of registration were not apparent. The main drivers of yield gain were grain number per m2 and harvest index, with a minor contribution of shoot biomass. Root length density, specific root length, root extension rate, and nutrient uptake per cm of root length increased with year of registration. Conclusions: The rate of genetic gain of Australian barley aligned with rates reported for other breeding programs worldwide and compared to 21.0 ± 2.3 kg ha−1 yr−1 for actual yield in Australian farms between 1961 and 2019. Changes in the growth and functionality of the root system highlight the indirect effects of selective pressure for yield and agronomic adaptation. [ABSTRACT FROM AUTHOR]

Background and Aims: Climate change in the Mediterranean-climate region of Australia is reducing growing season rainfall and delaying first autumn rain or the onset of ‘autumn break’. We tested the hypothesis that selection for yield and agronomic traits has favored adaptation to early season drought in Australian wheat (Triticum aestivum L.). Methods: Ten wheat varieties released between 1958 and 2012 were grown in a glasshouse. After sowing in dry soil, the equivalent of 25 mm rainfall was supplied, with no subsequent watering provided for 32 days to induce an early season drought treatment (ESD) while a well-watered treatment (WW) was planted on a wet soil that was water-saturated 48 h before sowing. We measured soil and plant water status, gas exchange, shoot and root traits at the end of drought (32 days after sowing) and at anthesis, and grain yield per plant at maturity. Results: Grain yield increased with year of release at 0.43% yr–1 under well-watered conditions and at 0.35% yr–1 under drought. The improved yield under drought was associated with a shorter time to flowering, and a change from isohydric behavior (maintained Ψleaf, reduced gs, leaf photosynthesis and transpiration rates in response to drought) in older varieties to anisohydric behavior (decreased Ψleaf and increased gs, leaf photosynthesis and transpiration in response to drought) in newer varieties that reduced leaf area and maintained higher gs, and higher photosynthesis per unit leaf area. Conclusions: Direct selection for yield and agronomic traits between 1958 and 2012 has improved adaptation to early-season drought. Our collection of varieties is an interesting model to probe for variation in drought tolerance. [ABSTRACT FROM AUTHOR]

We used a water-centred framework (yield = transpiration × transpiration efficiency × harvest index) to investigate the effect of soil salinity on growth and yield of wheat and barley. Our working hypothesis is that salinity reduces transpiration proportionally more than transpiration efficiency. We established a glasshouse experiment with the factorial combination of four varieties (wheat: Janz, Krichauff; barley: Mundah, Keel) and three soil treatments: a control with no NaCl added, and NaCl added to achieve soil EC 0.75 dS m and 1.5 dS m. Pot-grown plants were watered to weight to determine transpiration and shoot dry matter was determined using a non-destructive image analysis system. Consistent with our hypothesis, salinity reduced transpiration (30-60%) proportionally more than transpiration efficiency (0-35%); transpiration accounted for 90% of the variation in shoot growth across varieties and treatments. Against this pattern, there were time- and variety-dependent responses. The rate of leaf appearance and the transpiration efficiency of Janz, Krichauff and Keel showed a two-stage response to salinity. In stage 1, salt-stressed plants maintained rate of leaf appearance and transpiration efficiency close to or slightly below those of the controls. After a clear break point where the slope changed, stage 2 was characterised by a substantial reduction in both traits. Stage 2 was not evident in salt-stressed Mundah, which maintained a relatively high rate of leaf appearance and transpiration efficiency. Across species, harvest index increased from 0.40 in controls to 0.47 at 0.75 dS m. Harvest index of plants grown at 1.5 dS m was unaffected in wheat, and was reduced in barley. We propose that an understanding of the effect of salinity on crop development, growth and yield requires integration of low-level traits in a framework of resource capture, resource-use efficiency and plant allocation. Osmotic stress tolerance, Na exclusion, and tissue tolerance to accumulated Na would improve yield of salt-stressed crops to the extent that these traits contribute to the maintenance of water uptake and harvest index. [ABSTRACT FROM AUTHOR]