Oryza glaberrima response strategies to salinity : distinction between osmotic and ionic components

Salinity is an important environmental constraint which strongly reduces crop yield in several areas in the world. Rice (Oryza sativa) is considered as a salt-sensitive species and improvement of salt resistance is a major goal for plant breeders. Some species in the Oryza genus may constitute an interesting source of genes for rice improvement. Comparatively to the classical Asian rice species (Oryza sativa), the African rice Oryza glaberrima is poorly described for its response to salt stress. Our aims were 1-) to identify salt-tolerant varieties of O. glaberrima, 2-) to discriminate between the osmotic and the ionic components of salt stress and 3) to precise the impact of individual ions on salt deleterious impact. Plants were exposed to stress in nutrient solution or in soil culture. Then, a set of parameters related to photosynthesis, mineral nutrition, plant water status, yield, and antioxidative properties were recorded. Our results showed that one accession such as the cultivar TOG5307 was able to maintain a higher net photosynthesis under salt conditions and exhibited a higher level of tolerance to accumulated Na+ ions and a higher capacity for osmotic adjustment comparatively to the salt-sensitive cultivar TOG5949. The salt-resistant cultivar TOG5307 was also less affected by salinity than TOG5949 for yield-related parameters. Na+ ions appeared more toxic than Cl-, although an additive effect was recorded when both ions were simultaneously present in NaCl. The use of non-penetrating osmotic agent PEG demonstrated that osmotic and ionic components of salt stress acted in an additive way in the salt-sensitive cultivar but not in the salt-resistant one where an antagonist action was recorded for several parameters. Data were analyzed in relation to the expression of genes coding for ions transporters.
(SC - Sciences) -- UCL, 2021