Destructive sampling for TDM assessment is tedious and time-consuming, and reduces the area available for Future wheat yield improvements may be gained by increasing determining final grain yield in small research plots. total dry matter (TDM) production. Vegetation indices (VI) based on spectral reflectance ratios have been proposed as an appropriate Also, sampling errors often hinder the detection of gemethod to assess TDM and leaf area index (LAI) in wheat. This study notypic differences (Whan et al., 1991). In the last years, was undertaken to determine whether VI could accurately identify VI based on spectral reflectance measurements have TDM and LAI in durum wheat {Triticum turgidum var. durum (Desf.) been proposed as a reliable nondestructive method for Bowden [ϭ T. turgidum subsp. durum (Desf.) Husn.]} and serve as quickly estimating TDM (Tucker, 1979; Asrar et al., indirect selection criteria in breeding programs. Total dry matter and 1984) and LAI in wheat and barley (Elliott and Regan, LAI were determined from destructive sampling from booting to 1993). Total dry matter is mainly determined by two milk-grain in seven field experiments conducted under Mediterranean processes: (i) the interception by the canopy of incident conditions. Each experiment included one of two sets of 20 or 25 solar irradiance, which depends on the photosynthetic genotypes. Field reflectance values were collected using a portable area of the canopy; and (ii) the conversion of the interfield spectroradiometer. Two VI, the normalized difference vegetation index (NDVI) and the simple ratio (SR), were derived from spectral cepted radiant energy to potential chemical energy, measurements and their predictive value for TDM and LAI was evalu-which relies on the overall photosynthetic efficiency of ated. The best stages for growth trait appraisal were Stages 65 and the crop (Hay and Walker, 1989). A rapid, nondestruc-75 of the Zadoks scale. The power of VI for assessing TDM was lower tive simultaneous estimation of both processes may be than their predictive value for LAI. The suitability of VI for the provided by VI based on reflectance values at specific assessment of growth traits depended on the range of variability existwavelengths or formulations using simple operations ing within the experimental data. Vegetation indices accurately between reflectances at given wavelengths (Field et tracked changes in LAI when data were analyzed across a broad range al., 1994). of different growth stages, environments, and genotypes. However,Research to develop applications for VI has focused their value as indirect genotypic selection criteria for TDM or LAI was on wide bandwidths (Blackmer et al., 1996). High speclimited, since they lacked predictive ability for specific environment/ growth stage combinations.

No abstract

Carbon isotope discrimination (∆) was determined for kernels of six-row barley and durum wheat cultivated in the western Mediterranean basin during the last seven millennia. Samples came from different archaeological sites in Catalonia (north-east Spain) and in the south-east of Spain (mainly eastern Andalusia). Samples from the present were also analysed. Mean values of ∆ for barley and durum wheat grains decreased slightly from Neolithic (7000-5000 BP) to Chalcolithic-Bronze (5000-3000 BP) and Iron ages (3000-2200 BP) both in Catalonia and in south-east (SE) Spain. Values were consistently lower in SE Spain than in Catalonia throughout these five millennia, which suggests that Catalonia was less arid than SE Spain in this period. Within a given region, current discrimination values for kernels of the same cereal species cultivated under rainfed conditions were lower than those of archaeological grains, which implies more arid conditions at present. Furthermore, an empirical relationship between ∆ of mature kernels and total precipitation (plus irrigation where applicable) during grain filling (r 2 ϭ 0.73, N ϭ 25) was established for barley, currently cultivated at different locations in the western Mediterranean basin in Spain. The resulting relationship was applied to the ∆ data for barley kernels from 10 archaeological sites in Catalonia and 10 sites in SE Spain, to estimate the precipitation during grain filling at the time the kernels were produced. For both regions, current climatic conditions are consistently more arid than those inferred for the Neolithic, Bronze and Iron ages. In addition, although Catalonia was estimated to have had consistently wetter conditions (about 20% more precipitation) than SE Spain throughout these millennia, differences in precipitation between these two regions have recently increased, with 79% more precipitation in Catalonia. Results indicate a more rapid increase in aridity in SE Spain than in Catalonia, probably produced during the last few centuries, and due to anthropogenic causes.Abbreviations ∆, stable carbon isotope discrimination; δ 13 C, ratio of CO 2 ; WUE, water-use efficiency; BP, before present; NE Spain, north-east of Spain; SE Spain, south-east of Spain; 13 C/ 12 C relative to PeeDee belemnite standard; p i /p a, ratio of intercellular to atmospheric partial pressure of VPD, vapour pressure deficit.

This study addresses the sustainable use of water resources in the Mediterranean basin, particularly in the Southern and Eastern parts of the region, and the many problems generated by water scarcity and misuse. Water economy in the region is beset by two specific problems: high irrigation needs and changes in consumer demands (especially after population shifts from rural to urban areas and because of increasing tourism and industrialisation). The challenges presented by the water crisis are even greater because of growing populations and estimated future climatic changes in the region. The integrated management of limited water resources in the Southern and Eastern parts of the Mediterranean involves several areas of research. Those most directly related with agriculture concern improving water (and nutrient) use in agriculture through the management and breeding of irrigated and rain-fed crops. However, these fields of research address only one face of a multi-factorial equation that affects water sustainability in the region. Thus, other research fields include the design of comprehensive water policies and integrated planning, and technologies for advanced water treatment and re-use. Moreover, local problems and socio-economic aspects must be considered when addressing research issues.