Mafirakurewa, TariroMathema, NdabanyeMutanda, Maltase2026-08-212026-08-212026-06-09Mafirakurewa, T., Mathema, N. and Mutanda, M. (2026) ‘Carbon Isotope Discrimination: A Gateway to Smarter Water Use and Drought-resilient Cereals’, International Journal of Food Science and Agriculture, 10(2), pp. 131–145 DOI: 10.26855/ijfsa.2026.06.0032578-3467DOI: 10.26855/ijfsa.2026.06.003https://ir.gsu.ac.zw/handle/123456789/1082Carbon isotope discrimination (Δ¹³C) is widely used as an integrative physiological trait for assessing intrinsic water use efficiency (iWUE) in cereals under water limited conditions. This review synthesizes the physiological basis linking Δ¹³C to iWUE through intercellular-to-atmospheric CO₂ ratios (cᵢ/cₐ), emphasizing sto matal conductance, photosynthetic capacity, and genotype × environment interactions. Environmental drivers, including drought, temperature, vapor pressure defi cit, and atmospheric CO₂, are evaluated alongside differences between C₃ and C₄ cereals. Analytical approaches such as isotope ratio mass spectrometry (IRMS), near-infrared spectroscopy (NIRS), and laser-based methods are compared in terms of precision and scalability. Evidence shows a strong inverse relationship between Δ¹³C and iWUE in C₃ species, while C₄ responses are weaker due to CO₂ concentrating mechanisms. Despite limitations related to environmental sensitivity and inconsistent trait-yield relationships, integrating Δ¹³C with complementary traits, multi-environment testing, and genomic tools enhances its application in breeding. Δ¹³C remains a valuable tool for developing drought-resilient cereal ideotypes.enWheatdrought toleranceC₃ photosynthesiscrop improvementclimate resiliencecarbon isotopic signaturesArticle