Source-sink dynamics in field-grown durum wheat under contrasting nitrogen supplies: key role of non-foliar organs during grain filling

20 páginas, 9 figuras

The integration of high-throughput phenotyping and metabolic approaches is a suitable strategy to study the genotype-by-environment interaction and identify novel traits for crop improvement from canopy to an organ level. Our aims were to study the phenotypic and metabolic traits that are related to grain yield and quality at canopy and organ levels, with a special focus on source-sink coordination under contrasting N supplies. Four modern durum wheat varieties with contrasting grain yield were grown in field conditions under two N fertilization levels in north-eastern Spain. We evaluated canopy vegetation indices taken throughout the growing season, physiological and metabolic traits in different photosynthetic organs (flag leaf blade, sheath, peduncle, awn, glume, and lemma) at anthesis and mid-grain filling stages, and agronomic and grain quality traits at harvest. Low N supply triggered an imbalance of C and N coordination at the whole plant level, leading to a reduction of grain yield and nutrient composition. The activities of key enzymes in C and N metabolism as well as the levels of photoassimilates showed that each organ plays an important role during grain filling, some with a higher photosynthetic capacity, others for nutrient storage for later stages of grain filling, or N assimilation and recycling. Interestingly, the enzyme activities and sucrose content of the ear organs were positively associated with grain yield and quality, suggesting, together with the regression models using isotope signatures, the potential contribution of these organs during grain filling. This study highlights the use of holistic approaches to the identification of novel targets to improve grain yield and quality in C3 cereals and the key role of non-foliar organs at late-growth stages.

This study was supported by the projects AGL2016-76527-R and PID2019-106650RB-C22, funded by the Spanish Ministry of Science and Innovation, and the projects CSI260P20 and CLU-2019-05-IRNASA/CSIC Unit of Excellence funded by the Junta de Castilla y León and co-financed by the European Union (ERDF). We also acknowledge the support of FCT—Fundaçãopara a Ciência e a Tecnologia, I.P., through the R&D Unit GREEN-IT -Bioresources for Sustainability (UIDB/04551/2020 and UIDP/04551/2020). RMP was the recipient of an FPI-INIA fellowship from the Spanish Ministry of Science and Innovation (CPD2016-0107)

Peer reviewed