Characterization of cucumber response to Fe and P deficiency

In alkaline condition, both Iron (Fe) and Phosphorus (P) are scarcely available for plant acquisition leading to nutritional stresses in crops. In recent years, strong cross-connections between plant responses induced by Fe and/or P deficiency have been reported in the literature, suggesting a close interplay in the regulation and functionality of Fe- and P-acquisition mechanisms. Indeed, some genes induced in response to low-available P are also upregulated in low-Fe conditions and conversely, some components of the P acquisition are enhanced in Fe deficiency. This synergism between Fe- and P-deficiency responses might be taken advantage to improve the acquisition of these poorly bioavailable nutrients. To investigate the interplay between Fe- and P-nutritional pathway Cucumis sativum plants were hydroponically grown under Fe and/or P deficiency (+Fe+P, +Fe-P, -Fe+P, -Fe-P; for three weeks). In roots, the transcriptomic profiles indicated that when plants were exposed to -Fe-P, more than 5500 genes were differentially modulated compared to +Fe+P of which about 17% exclusively modulated by -Fe-P and not shared with -Fe+P or +Fe-P. Metabolomic analyses showed also an induction of secondary metabolites’ and amino acids’ and hormone synthesis. Using hyperspectral imaging analysis, we discriminate between Fe deficiency and P deficiency focusing on reflection intensity changes in specific wavelength bands. Key wavelength bands were selected using Competitive Adaptive Reweighted Sampling (CARS) algorithm. Using these wavelengths and two different classification algorithms, Support Vector Machine (SVM) and Linear Discriminant Analysis (LDA), it was possible to develop a classification model to discriminate between the two deficiencies with an accuracy of the model up to 100% of the test data. Next soluble form of either Fe or P were resupplied, first results indicated that -P and -Fe-P plants exhibited an enhanced accumulation of Fe, and the reciprocal is also enhanced (P in -Fe and -Fe-P). These findings confirm that there is a significant interplay between the responses of the plant to Fe and P deficiency. Furthermore, the transcriptomic data suggest that the double deficient plants have a specific response that it is not display by either single deficient plant. Fundings CEDRIC project is funded by Interreg Italia Austria, DM1062/2021-Tomasi, DM737/2021-Tomasi and Agritech National Research Center are funded by European Union Next-GenerationEU (PIANO NAZIONALE DI RIPRESA E RESILIENZA (PNRR)–MISSIONE 4 COMPONENTE 2, INVESTIMENTO 1.4–D.D. 1032 17/06/2022, CN00000022) and the Departmental Strategic Plan (PSD) of the University of Udine - Interdepartmental Project on Artificial Intelligence (2020-25)