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 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. Key words: Wheat, barley, drought screening