Abstract Purpose: To evaluate the responses of seven citrus rootstocks, including five new genotypes (US942, US802, B11R3T27, B11R5T64, and B11R5T36) and two references (Cleopatra mandarin, tolerant; Carrizo citrange, sensitive), to iron (Fe) deficiency induced by carbonate (CaCO 3 ) and alkaline pH, and its interaction with phosphorus (P) nutrition. Methods: Six-month-old seedlings were grown in pots under four treatments: (i) complete absence of Fe, (ii) Fe supplied with CaCO 3 at pH 8, (iii) Fe supplied with CaCO 3 at pH 9, and (iv) Fe-sufficient control. Chlorophyll content, biomass, and tissue nutrient concentrations were determined. Results: Fe deficiency reduced root Fe in all rootstocks, whereas leaf Fe decreased only under total absence of Fe. Leaf Fe was most affected in B11R3T27, B11R5T64, and Carrizo citrange, indicating higher sensitivity, while US942, B11R5T36, and Cleopatra mandarin maintained leaf Fe through efficient root-to-shoot transport. A significant negative correlation between Fe and P accumulation indicated an antagonistic interaction between these nutrients. Carbonate treatments impaired biomass accumulation and reduced leaf P but did not significantly alter leaf Fe, suggesting growth inhibition was linked to broader nutrient constraints rather than Fe alone. Conclusion: Rootstocks studied differed in their ability to maintain leaf Fe accumulation under Fe limiting conditions, which depended on both Fe mobilization and transport efficiency. US942 and B11R5T36 exhibited greater tolerance to Fe deficiency than B11R3T27 and B11R5T64. Our results highlighted the importance of considering overall nutrient status and rootstock-specific transport traits in the management of Fe deficiency in citrus grown on calcareous soils.
Moreno-Lora et al. (Tue,) studied this question.