EVALUATION OF FIELD AND LABORATORY PREDICTORS OF DROUGHT AND HEAT TOLERANCE IN WINTER CEREALS

In Mediterranean regions, plant breeding programs are being conducted to select genotypes having high and stable yields. Screening technique s that are able to identify desirable genotypes based on the evaluatio n of physiological traits related to stress tolerance could be useful, particularly if they are rapid, simple and inexpensive. The objective s of this study were: i) to evaluate the validity of four laboratory s creening 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 g rown in different locations and years, and iii) to evaluate relationsh ips 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 capacit y after the chemical desiccation (CD) of the photosynthetic apparatus. The CMS-HS and CMS-DS tests revealed genetic variability in all the t hree species. The LWL test did not differentiate genotypes at some sit es. Genetic differences for grain yield, kernel weight and harvest ind ex after chemical desiccation were evident for wheat genotypes but the test did not differentiate barley genotypes. The lest performed under laboratory controlled conditions (CMS-HS, CMS-DS and LWL) was less af fected by environment compared with the test based on the evaluation o f 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 tool s in breeding programs for tolerance to heat and drought stress.