Spectral phenotyping of agronomic and NUE traits in bread and durum wheat genotypes grown under two contrasting Mediterranean environments and different N fertilization strategies

Climate variability and nitrogen (N) management are two of the main challenges facing wheat production. In this study, the effects of Mediterranean climate conditions, different N rates and sources on yield, quality and nitrogen use efficiency (NUE) have been investigated in relation to spectral phenotyping. NDVI measurements at different growing stages were carried out and data were put in relation to agronomic and NUE traits in a GxExM experimental framework including both bread and durum wheat. Plot experiments were carried out over two seasons (2019/2020 and 2021/2021) in two locations (North and South Italy), evaluating two durum (Antalis and Saragolla) and two bread (Solehio e Bologna) wheat varieties under four N rates (0, 80, 130 and 180 kg N ha− 1) and three N source (AN, ammonium nitrate; ASN, ammonium sulphate nitrate; ASNi, ammonium sulphate nitrate with nitrification inhibitor). Findings: show that environmental factors, particularly related to rainfall and temperatures, significantly impact agronomic traits. Higher yields were found in North Italy compared to the South (6.0 > 4.4 t ha− 1 on average), where a better durum wheat genotypes adaptation and a higher protein content are highlighted (15.1 > 10.7 %). NUE, higher in North Italy, is not influenced by N source, while high yield cultivars showed an increased N efficiency. This suggests that the potential benefits of the previous factors may depend on specific local conditions, with strong interaction with weather conditions. For these reasons, the selection of the appropriate genotypes for the specific environment represents one of the key points in wheat cultivation. Also, the higher yield in the North is associated with longer grain filling that influenced the number of grains per spike and the grain weight, together with a higher harvest index and allowed for better genotypic discrimination by grain protein deviation. Finally, NDVI at booting (about 1000 ◦C d) resulted a good predictor of grain yield and N uptake, while at later stages it better fitted with protein content. These observations obtained in a range of different growing conditions might be useful to define suitable indicators to be used to face climate change future challenges.