Abstract
In the context of population growth and global climate change, crop stress tolerance studies are of great importance. We have analysed the responses to salt and water stress in three Phaseolus vulgaris and one P. coccineus cultivars. Leaf ion (Na+, K+, Cl-) and osmolyte (proline, glycine betaine, total soluble sugars) contents, as well as individual soluble carbohydrates, separated by HPLC, were quantified after 3-week treatments, and correlated with the relative tolerance to stress of the cultivars, established from the degree of growth inhibition; this allowed to identify the stress responses that are the most relevant for tolerance in Phaseolus. Salt resistance is mostly dependent on inhibition of Na+ transport to shoots and accumulation of myo-inositol for osmotic adjustment; the increase of myo-inositol content is also important under water stress conditions. Glycine betaine may also contribute to drought tolerance in P. coccineus, but not in P. vulgaris. Responses to salt and water stress appear to be more efficient in P. vulgaris cv. Maxidor, the most tolerant of the tested Phaseolus genotypes. Proline accumulation is a reliable stress marker, but is not directly related to stress tolerance
