Mise au point d’un test in vitro de comportement au sel de quatre génotypes d’agrumes

Introduction : La salinite des sols et des eaux d’irrigation constituent une contrainte abiotique dont les consequences impactent autant la production que la qualite des agrumes. L’utilisation d’un porte-greffe resistant a ces conditions apparait la solution la plus adaptee. Objectifs : Cette etude est la comparaison de comportement de  genotypes d’agrumes, en termes de resistance a la salinite in vitro au niveau des cals et des cellules cultivees parallelement sur milieu liquide et solide. Methodologie et resultat : A cet egard, des cals de quatre genotypes d’agrumes : mandarinier Cleopâtre (citrus reshni hort ex Tan), mandarinier commun (citrus delicosa Ten.), pomelo Star Ruby ruby (citrus paradisi Macfad.cv Star Ruby) et orange Shamouti (citrus sinensis) ont ete maintenus sur des milieux MT renfermant des doses de NaCl 0, 50, 100, 150 et 200 mM. Les resultats ont montre que les differents niveaux de stress de salinite ont eu un effet significatif sur la croissance des cellules. En outre, la salinite a augmente de facon significative le niveau de chlorures des genotypes testes. Conclusions et application des resultats : Un comportement differentiel sur les niveaux de tolerance a la salinite a ete revele, entre genotypes d’une part, et entre types de milieu d’autre part. Le mandarinier Cleopâtre et le pomelo Star Ruby ont montre la meilleure reponse sous stress salin. La culture des suspensions cellulaires peut etre un outil efficace pour etudier le comportement des genotypes d'agrumes vis-a-vis la salinite. Mots clefs : Agrumes, salinite, tolerance, cals, suspension cellulaire Introduction : Soil and water salinity is an important abiotic stress that can affect both production and quality of citrus fruits. The use of tolerant rootstocks under these conditions would be a promising solution. Objectives: The aim of this study was to compare in vitro behaviour of four citrus genotypes in terms of salt tolerance using callus and cells grown in parallel on liquid and solid media. Methodology and Results : In this regard, calluses of four genotypes of citrus: Cleopatra mandarin (Citrus reshni hort ex Tan), Willow leaf mandarin (Citrus delicosa Ten.), ‘Star Ruby’ grapefruit ( Citrus paradisi Ruby ), and ‘Shamouti’ sweet orange (Citrus sinensis) were maintained on MT media containing different NaCl doses, i.e.: 0, 50, 100, 150, and 200 mM. The results showed that the different salt levels used had a significant effect on cell growth, resulting in a decrease in fresh and dry weights. In addition, salinity increased considerably Chloride concentrations in the tested genotypes. Conclusions and application of findings : A differential behaviour of salt tolerance was found between citrus calluses used depending on genotype on one hand, and type of medium on other hand. Compared to the other genotypes, Cleopatra mandarin and Star Ruby grapefruit showed the best performance under salt stress conditions. These results suggest that  culture cell suspensions can be an effective tool for studying the behaviour of citrus species under salinity. Keywords : Citrus, salinity, tolerance, callus, cell suspension