. Evaluation of field and laboratory predictors of drought and heat tolerance in winter cereals. Can. J. Plant Sci 77: 523-531. In Mediterranean regions, plant breeding programs are being conducted to select genotypes having high and stable yields. Screening techniques that are able to identify desirable genotypes based on the evaluation of physiological traits related to stress tolerance could be useful, particularly if they are rapid, simple and inexpensive. The objectives of this study were: i) to evaluate the validity of four laboratory screening tests to discriminate among bread wheat (Triticum aestivum L.), durum wheat (Triticum turgidum L.) and barley (Hordeum vulgare L.) cultivars differing in adaptation to the Mediterranean climate; ii) to evaluate the repeatability of determinations performed on cultivars grown in different locations and years, and iii) to evaluate relationships among the tests and yield performance under stress. The tests were: cellular membrane stability after heat (CMS-HS) and drought stress (CMS-DS), tolerance to leaf water loss (LWL), and translocation capacity after the chemical desiccation (CD) of the photosynthetic apparatus. The CMS-HS and CMS-DS tests revealed genetic variability in all the three species. The LWL test did not differentiate genotypes at some sites. Genetic differences for grain yield, kernel weight and harvest index after chemical desiccation were evident for wheat genotypes but the test did not differentiate barley genotypes. The test performed under laboratory controlled conditions (CMS-HS, CMS-DS and LWL) was less affected by environment compared with the test based on the evaluation of the translocation capacity after chemical desiccation carried out in the field. We concluded that, when good standardization of procedures are obtained, the tests investigated can be regarded as possible tools in breeding programs for tolerance to heat and drought stress. ) selon leur adaptation au climat de la Méditerranée, ii) d'évaluer la répétabilité des déterminations faites sur un certain nombre des cultivars cultivés à des emplacements et en des années différents et iii) d'évaluer les rapports existant entre les tests et le rendement en condition de stress. Les tests portaient i) sur la stabilité de la membrane cellulaire après un stress thermique (SMC-st) et hydrique (SMC-sh), ii) sur la tolérance aux déperditions d'eau par les feuilles (DEF) et iii) sur la capacité de transport après dessiccation chimique (DC) de l'appareil photosynthétique. Les tests SMC-st et SMC-sh ont permis de mettre à jour l'existence de variabilité génétique au sein des trois espèces. A certains endroits, il etait pas été possible de différencier les génotypes selon les DEF. Des différences génétiques quant au rendement grainier, au poids des grains et à l'indice de moisson, à la suite d'une dessiccation chimique ont pu être constatées chez le blé, mais pas chez l'orge. Les tests réalisés en milieu contrôlé (SMC-st, SMC-sh et DEF) étaient moins sensibles aux conditions environnementales que l...

Among the cultivars of bread wheat, durum wheat and barley grown in the South of Italy, genetic variation for adaptation to the high temperature and drought stress conditions typical of the Mediterranean environment has been found.The basic data have been extrapolated from 5 years of Italian national network cultivar trials, where 20-30 cultivars were grown in replicated plot trials in 30-50 locations per year, including some where stress strongly affected grain yield.After careful identification of the most representative years and testing sites it was possible to characterise the cultivars on the basis of the grain yield in stress conditions and the Fischer & Maurer (1978) susceptibility index and to find genotypic differences sufficiently repeatable in years.The cultivars giving the best yield under stress associated with low susceptibility indices were in bread wheat:

Breeding for heat and drought tolerance in bread wheat by means of field and laboratory screening procedures by Basilio BORGHI(l), Maria CORBELLINI(l), Pia GAVUZZI(l), Gaetano BOGGINI(2) and Abdellah OUASSOU(3) (1) Experimentalln.