Senescence was evaluated at different stages of the grain‐filling period in eight durum wheat varieties using numerical image analysis (NIA). The varieties were grown under early, severe drought conditions on the high plains of Sétif in Algeria. After flowering, three different irrigation treatments were applied. Treatment effect was small, while a genotypic effect was noted for most of the senescence parameters. Senescence correlated to biomass, while the maximal rate of senescence, Vsmax, correlated to thousand‐kernel weight. The potential of the method of numerical image analysis for monitoring flag leaf senescence, detecting genotypic variability and selecting genotypes with delayed senescence is discussed.

Les relations entre la senescence foliaire, la discrimination isotopique du carbone et la performance du rendement, sont examinées chez le Blé dur (Triticum durum Desf.), au niveau des hautes plaines sétifiennes. Dix variétés de Blé dur à haut potentiel ont été conduits durant deux saisons agricoles successives caractérisées par une faible pluviométrie (217 et 162 mm, respectivement), des températures gélives au stade épiaison et un stress thermique en fin de cycle. La sénescence a été évaluée par le traitement numérique de l'image (NIA). La discrimination isotopique du carbone de la feuille drapeau a été analysée pour les différentes variétés aux stades anthèse et maturité du grain respectivement. La sénescence a été corrélée significativement et négativement au rendement grain pour la première saison mais pas pour la deuxième. Il n'y a pas eu de relations significatives entre Δ et le rendement pour les deux saisons. L'absence d'association entre Δ (la discrimination isotopique du carbone) et le rendement grain est probablement dû à une forte contribution des assimilats au rendement au stade pré-anthèse avec une limitation du puits (fertilité de l'épi).Mots clés : discrimination isotopique du carbone, sécheresse, sénescence, blé dur (Triticum durum Desf.) Abstract:The relationships between leaf senescence, carbon isotope discrimination and yield performance were examined in durum wheat (Triticum durum Desf.), in the high plains of Setif, eastern Algeria. Ten CIMMYT highyielding cultivars were grown during two cropping seasons characterized by low rainfall (217 and 162 mm, respectively), freezing temperatures at heading stage and terminal heat stress. Senescence was assessed using numerical image analysis (NIA). Carbon isotope discrimination was analyzed in flag leaves at anthesis and grain at maturity. Senescence was significantly negatively correlated to grain yield in season 1, but not in season 2. There was no relationship between Δ and grain yield in both seasons. The absence of association between Δ and grain yield is likely to be due a strong contribution of pre-anthesis assimilates to yield together with a sink limitation of yield.

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Drought, one of the abiotic stresses, is the most significant factor restricting crop production in large agricultural fields of the world. Wheat is generally grown on arid-agricultural fields. Drought often causes serious problems in wheat production. Ten durum wheat (Triticum durum Desf.) genotypes were tested under rain-fed (T 0 ) and three irrigated treatments (T 1 = 50 mm at Booting stage, T 2 = 50 mm at Booting and 15 mm at heading stages and T 3 = 50 mm at Booting and 30 mm at heading stages) in semi-arid conditions of Eastern Algeria. Grain Yield, components of yield, heading evolution, leaf relative water content, leaf specific weight, grain filling rate and duration and chlorophyll content were measured. The irrigation treatments affect significantly all characters. Application of 50 mm of irrigation at booting stage increased significantly grain yield by 23%, compared to rain-fed treatment. Another supplementary irrigation of 15 or 30 mm, at heading, increased significantly grain yield by 45 and 61%, respectively. Stressed condition affects negatively thousand kernel weights (105%). In addition, combined analysis of variance showed high genetic variation for all parameters measured, excepted leaf relative water content and leaf specific weight, when measured at heading stage suggesting the possibility of selecting tolerant genotypes for drought tolerance under semi arid condition.

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