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Understanding the interaction between genotype performance and the target environment is the key to improving genetic gain, particularly in the context of climate change. Wheat production is seriously compromised in agricultural regions affected by water and heat stress, such as the Mediterranean basin. Moreover, wheat production may be also limited by the nitrogen availability in the soil. We have sought to dissect the agronomic and physiological traits related to the performance of 12 high-yield European bread wheat varieties under Mediterranean rainfed conditions and different levels of N fertilization during two contrasting crop seasons. Grain yield was more than two times higher in the first season than the second season and was associated with much greater rainfall and lower temperatures. However, the nitrogen effect was rather minor. Genotypic effects existed for the two seasons. While several of the varieties from central/northern Europe yielded more than those from southern Europe during the optimal season, the opposite trend occurred in the dry season. The varieties from central/northern Europe were associated with delayed phenology and a longer crop cycle, while the varieties from southern Europe were characterized by a shorter crop cycle but comparatively higher duration of the reproductive period, associated with an earlier beginning of stem elongation and a greater number of ears per area. However, some of the cultivars from northern Europe maintained a relatively high yield capacity in both seasons. Thus, KWS Siskin from the UK exhibited intermediate phenology, resulting in a relatively long reproductive period, together with a high green area throughout the crop cycle. [ABSTRACT FROM AUTHOR]

The regulation of plant transpiration was proposed as a key factor affecting transpiration efficiency and agronomical adaptation of wheat to water-limited Mediterranean environments. However, to date no studies have related this trait to crop performance in the field. In this study, the transpiration response to increasing vapor pressure deficit (VPD) of modern Spanish semi-dwarf durum wheat lines was evaluated under controlled conditions at vegetative stage, and the agronomical performance of the same set of lines was assessed at grain filling as well as grain yield at maturity, in Mediterranean environments ranging from water stressed to good agronomical conditions. A group of linear-transpiration response (LTR) lines exhibited better performance in grain yield and biomass compared to segmented-transpiration response (STR) lines, particularly in the wetter environments, whereas the reverse occurred only in the most stressed trial. LTR lines generally exhibited better water status (stomatal conductance) and larger green biomass (vegetation indices) during the reproductive stage than STR lines. In both groups, the responses to growing conditions were associated with the expression levels of dehydration-responsive transcription factors (DREB) leading to different performances of primary metabolism-related enzymes. Thus, the response of LTR lines under fair to good conditions was associated with higher transcription levels of genes involved in nitrogen (GS1 and GOGAT) and carbon (RCBL) metabolism, as well as water transport (TIP1.1). In conclusion, modern durum wheat lines differed in their response to water loss, the linear transpiration seemed to favor uptake and transport of water and nutrients, and photosynthetic metabolism led to higher grain yield except for very harsh drought conditions. The transpiration response to VPD may be a trait to further explore when selecting adaptation to specific water conditions. [ABSTRACT FROM AUTHOR]

Identifying traits conferring high yield in target environments has become a main concern of wheat breeders. This is particularly relevant for the current Mediterranean conditions as well as for the expected scenarios driven by climate change for central and northern Europe. The objective of this study was to identify breeding traits conferring adaption of high-yielding European wheat cultivars to actual Mediterranean conditions. Twelve elite winter wheat cultivars from different European (northern, central and southern) regions were grown under Mediterranean continental conditions across three consecutive crop seasons and three different topdressing nitrogen fertilization levels. Phenology was assessed throughout the crop cycle. At maturity, grain yield (GY), grain number and thousand kernel weight (TKW) were determined. Further, carbon (δ13C) and nitrogen (δ15N) stable isotope compositions and nitrogen concentration (N) were analyzed in mature grains as proxies for water and nitrogen status, respectively. The nitrogen fertilization effect was minor for GY compared with the season and genotypic effects. Concerning genotypic performance, the effect of phenology varied across seasons, with longer crop durations being associated with higher GY under the wettest season (2017–2018), no effect under mildly wet conditions (2019–2020) and being negatively associated with GY under dry conditions (2018–2019). Furthermore, the relative duration of each phenological stage had an effect on genotypic performance, particularly during the dry season (2018–2019). Moreover, regardless of the season considered, the highest-yielding genotypes were associated with better water status (lower δ13C). Under wet season conditions, northern European genotypes had 6 % higher yields, whereas in the dry season, southern European genotypes had 2 % higher yields. The differences in GY among the top wheat cultivars originating from different European regions were fairly minor across the seasons and across the N fertilization levels recommended in the region. The study suggests that, depending on the season, selection for the high-yielding conditions of central and northern Europe also delivers genetic increases in grain yield under Mediterranean conditions. • Recommended N topdressing levels place wheat fertilization in the saturation zone. • Genotypic yield performance is associated with higher grain number rather than weight. • Crop duration and phenology are key to adapting genotypes to Mediterranean conditions. • Regardless of the season, the best genotypes exhibit better water status (lower δ13C). • Some northern European wheat cultivars are well adapted to Mediterranean conditions. [ABSTRACT FROM AUTHOR]