The effect of environment on the relationship between grain carbon isotope discrimination (Δ) and grain yield was studied for eight durum wheat (Triticum turgidum L. var. durum) under Mediterranean conditions. Trials were carried out in Sétif (low rainfall) and El Kroub (moderate rainfall), in the Eastern high plains of Algeria over 2 successive years (2002-2004). In Sétif, grain yield ranged from 2.08 to 3.35 t ha^-1 and grain carbon isotope discrimination (Δ) ranged from 16.05 to 17.91 ‰. In El Khroub, yield ranged from 4.44 to 7.82 t ha^-1 and grain Δ from 16.38 to 18.03 ‰. Environmental conditions were responsible for 61 and 43 % of the variability observed in grain yield and grain Δ. The main environmental factor affecting yield and grain Δ was total rainfall during the growth cycle. A significant correlation was noted between grain yield and grain Δ in each environment.

Keywords: Durum wheat, carbon isotope discrimination, drought.