In order to determine the best determination stage and organ of the carbon isotope discrimination(Δ13C)used to breed high-yield and water saving varieties,2local wheat landraces,14bred varieties(lines)and 2introduced varieties were grown with different irrigation treatments in Ningxia.The correlation between theΔ13 C in leaf,stem and grain with yield of wheat were analyzed.The results showed that there were bigger variation for theΔof the same variety in different organs,theΔ13C of wheat grain was lower tha...