Sélection et évaluation de lignées de cals stables et tolérantes vis-à-vis du stress salin chez le citrange ‘Troyer’ [Citrus sinensis(L.) ×Poncirus trifoliata(L.) Raf.

Abstract

Selection and evaluation of stable salt-tolerant callus cell lines of the Troyer citrange. Abstract -- Introduction. Citrus fruits are sensitive to salinity. Our study aimed at selecting cellular lines tolerant to NaCl of citrange Troyer and assessing the characters involved in salt stress responses in callus cultures. Materials and methods. Calli were cultivated on a culture medium containing NaCl whose concentration was gradually increased until it reached 8 g NaCl·L -1 . They were then transferred onto a medium without NaCl to test their independence with respect to the salt, then placed in the presence of 8 g NaCl·L -1 to test their stability. Dosages of the content in soluble Na + , K + , proline and sugars contained in the calli were carried out at the end of the experiment. Results and discussion. Salinity stopped the calli from growing and caused the majority of the explants (sensitive calli) to become brown. Tolerant calli presented a growth comparable with the growth of the controls. The transfer of these calli onto medium without NaCl followed by their transfer onto saline culture medium showed the independence and the stability of the selected character of tolerance. The content in K + of the tolerant calli was close to that of the control calli, but it was greater than that of the sensitive calli. On the other hand, the content in Na + ions in the tolerant and sensitive calli was relatively higher than that of the control calli. Sodium would thus be accumulated in two cellular levels according to the type of callus: invasion of the cytosol (toxic effect) for the sensitive calli or vacuolar partitioning for the tolerant calli. Salinity caused the accumulation of proline and soluble sugars in the tolerant calli but not in the sensitive calli. Conclusions. Stable and tolerant cellular lines in NaCl were obtained starting from embryos of citrange Troyer. This tolerance could be related to changes in the properties of ion migration and in the regulation capacity and ionic partitioning. Accumulation of proline and soluble sugars constitutes a metabolic character to adaptive value that could be an indicator of tol- erance to salinity. Morocco / Citrus / citranges / in vitro culture / callogenesis / salt tolerance