Strategies for rice salinity tolerance in Mediterranean France

Salinity constraints for rice cultivation in Camargue mainly concern short periods (5-10 days) during the first cropping month (from germination to 5th leaf stages). Because of unfavourable climatic conditions, it is impossible to directly undertake breeding lines field screening. So greenhouse tests have been performed in order to specifically screen for varietal salt tolerance according to the Rice critical stages in Camargue: germination (comparison of germination ratio in salted/unsalted conditions), sprouting (evolution of dry matter weight in function of increased salt concentration) and 5th leaf stage (transpiration and photosynthesis activities evolution in function of increased salt concentration). Another type of test attempt to consider the effect of cumulated constraints; the varietal behaviour when salted and cold environment give a good image of that really occurs in Camargue. Then, fields trials only concerns the better genotypes in order to confirm greenhouse tests characterisation. Another way to improve salt tolerance try to profit by the presumed 'seeds hardness' phenomenon. Using three seeds samples coming from cropping in very different situation of salt constraint (weakly, moderately or strongly salted conditions) and three type of conditions for germination (distilled water, 2.54 g/l NaCI and 10.2 g/l NaCI), it is possible to measure "the hardness seed effect". Whatever the salt concentration, the germination rates are so much higher so was the importance of salt constraint in the seed multiplication paddyfield. Prospective for Rice salt tolerance improvement, based on the knowledge of salt adaptation cells physiological mechanism is discussed. (Resume d'auteur)