Relationships between early vigour, grain yield, leaf structure and stableisotope composition in field grown barley

Fast growth and early development in barley are used in breeding programmes to improve the water use efficiency and transpiration efficiency of this c rop in Mediterranean conditions. Here, we examine the use of several simple traits based on the structure and stable isotope composition of seedling l eaves to assess differences in early vigour, phenology and grain yield, and also the interaction with low temperatures in barley. A set of 260 F-8 lin es of two-row barley (Hordeum vulgare L.) derived from the cross of Tadmor and WI 2291 were cultivated in two locations in northwest Syria. Total chlo rophyll content on an area basis (SPAD) and specific leaf dry weight (SLDW) were measured in recently fully expanded intact leaves of seedlings. Total leaf area and total dry weight per seedling were evaluated in the same see dlings. The stable isotope compositions of carbon and nitrogen (delta(13)C and delta(15)N, respectively) were analyzed in the same leaves on a subset of 75 genotypes. Number of days from planting to heading and grain yield we re recorded at both sites. The grain yield measured at both locations was p ositively correlated with the SPAD value of seedlings, but showed no relati onship with SLDW. Days to heading was negatively correlated with SPAD value s. Regarding early vigour, a negative relationship between the SLDW and the total leaf area of seedlings was observed. However, no relationship betwee n the delta(13)C of seedlings and early vigour was observed, except when on ly the genotypes most resistant to low temperatures (i.e. showing the highe st SPAD values) were considered. This subset of genotypes showed negative r elationships between delta(13)C and either total leaf area or total dry wei ght. In addition, delta(15)N was negatively correlated with SPAD only withi n the high-SPAD genotypes. This suggests that within the genotypes resistan t to low temperatures, those with higher chlorophyll content assimilate mor e nitrogen from nitrate. (C) Elsevier, Paris.