Rut Sanchez-Bragado

The pine nut, the seed of the stone pine, is highly valued in local cuisine and dietetics for its nutritional qualities. These nuts still come from forest stands, which results in their limited and irregular presence on the market. Domesticating the species through orchard management practices could increase its production. In this context, two irrigation schedules were tested in a grafted stone pine orchard that was planted in 2009 and has been under drip irrigation since 2011. Water needs were calculated weekly using the water balance method (ETc-P). The treatments considered were as follows: T₁, irrigation from April to the end of summer; T₂, irrigation from April to the end of June; and T₀, rainfed as the control. Monitoring of the pines, considering vegetative and reproductive responses, was carried out from 2015 (7th leaf) to 2023. T₁ and T₂ increased primary and secondary growth and resulted in higher strobili production compared to T₀. The tree’s ability to sustain the reproductive load was enhanced under irrigation versus rainfed treatment. The longest irrigation schedule increased productivity. However, when the environmental cost of supplying twice as much water in the Mediterranean region—an annual average of 900 m³ ha⁻¹ (T₂) versus 1900 m³ ha⁻¹ (T₁)—is considered, the overall assessment changes. The irregularity of stone pine mating was not prevented by a regular water supply, but it was mitigated, promoting sustainable production.

Increasing the speed of breeding to enhance crop productivity and adaptation to abiotic stresses is urgently needed. The perception that a second Green Revolution should be implemented is widely established within the scientific community and among stakeholders. In recent decades, different alternatives have been proposed for increasing crop yield through manipulation of leaf photosynthetic efficiency. However, none of these has delivered practical or relevant outputs. Indeed, the actual increases in photosynthetic rates are not expected to translate into yield increases beyond 10–15%. Furthermore, instantaneous rates of leaf photosynthesis are not necessarily the reference target for research. Yield is the result of canopy photosynthesis, understood as the contribution of laminar and non-laminar organs over time, within which concepts such as canopy architecture, stay-green, or non-laminar photosynthesis need to be taken into account. Moreover, retrospective studies show that photosynthetic improvements have been more common at the canopy level. Nevertheless, it is crucial to place canopy photosynthesis in the context of whole-plant functioning, which includes sink–source balance and transport of photoassimilates, and the availability and uptake of nutrients, such as nitrogen in particular. Overcoming this challenge will only be feasible if a multiscale crop focus combined with a multidisciplinary scientific approach is adopted.

High-throughput phenotyping platforms provide valuable opportunities to investigate biomass and drought-adaptive traits. We explored the capacity of traits associated with drought adaptation such as aerial measurements of the Normalized Difference Vegetation Index (NDVI) and carbon isotope composition (δ¹³C) determined at the leaf level to predict genetic variation in biomass. A panel of 248 elite durum wheat accessions was grown at the Maricopa Phenotyping platform (US) under well-watered conditions until anthesis, and then irrigation was stopped and plot biomass was harvested about three weeks later. Globally, the δ¹³C values increased from the first to the second sampling date, in keeping with the imposition of progressive water stress. Additionally, δ¹³C was negatively correlated with final biomass, and the correlation increased at the second sampling, suggesting that accessions with lower water-use efficiency maintained better water status and, thus, performed better. Flowering time affected NDVI predictions of biomass, revealing the importance of developmental stage when measuring the NDVI and the effect that phenology has on its accuracy when monitoring genotypic adaptation to specific environments. The results indicate that in addition to choosing the optimal phenotypic traits, the time at which they are assessed, and avoiding a wide genotypic range in phenology is crucial.

The stable carbon (δ¹³C) and oxygen (δ¹⁸O) isotope compositions in plant matter reflect photosynthetic and transpirative conditions in plants, respectively. However, the nature of hydrogen isotope composition (δ²H) and what it reflects of plant performance is poorly understood. Using durum wheat (Triticum turgidum var durum), this study evaluated the effect of different water and nitrogen growing field conditions on transpiration and how this effect influenced the performance of δ²H in autotrophic (flag leaf), mixotrophic (ears), and heterotrophic (grains and roots) organs. Moreover, δ²H was compared with the δ¹³C and δ¹⁸O in the same organs. Isotope compositions were analyzed in dry matter, the water-soluble fraction, and in water from different tissues of a set of genotypes. Similar to δ¹³C, the δ²H correlated negatively with stomatal conductance, whereas no correlation was observed for δ¹⁸O. Moreover, δ²H was not only affected by changes in transpiration but also by photosynthetic reactions, probably as a consequence of NADPH formation in autotrophic organs. Compared with the δ²H of stem water, plant δ²H was strongly diminished in photosynthetic organs such as the flag leaves, whereas it strongly increased in heterotrophic organs such as grains and roots. In heterotrophic organs, δ²H was associated with postphotosynthetic effects because there are several processes that lead to ²H-enrichment of carbohydrates. In summary, δ²H exhibited specific features that inform about the water conditions of the wheat crop, together with the photosynthetic characteristics of the plant part considered. Moreover, correlations of δ²H with grain yield illustrate that this isotope can be used to assess plant performance under different growing conditions.