In vitro morpho-physiological characterization of cassava accessions according to salinity tolerance

Description of the subject. In Senegal, manioc tuber production targets are increasing every year. However, salinization is a major constraint to its cultivation due to salt-affected land and irrigation water. Objectives. The objective of this study was to evaluate in vitro the physiological and morphological response to salinity stress (NaCl) of cassava accessions in order to identify the most tolerant and their tolerance threshold. Method. In vitro cultured explants were exposed to different concentrations of NaCl (0, 1, 1.5, 2, 2.5, and 3 g.l(-1)) to determine the most tolerant accessions and their tolerance threshold. The stress impact was measured by the height of vitroplants, the rooting ability of vitroplants, the fresh and dry biomass, and the leaves' chlorophyll content. Results. The results showed that NaCl significantly reduced in vitro plant growth and biosynthesis of chlorophylls a, b and total in in vitro plant leaves. The leaves of the vitroplants were more sensitive to the depressive effects of salinity than the roots. Two critical sensitivity thresholds to the adverse effects of salinity were identified at 1.5 and 2 g.l(-1) NaCl for physiological and morphological parameters, respectively. The salinity index (SI) is a relevant morphological criterion for assessing the salinity tolerance of cassava vitroplants. The method used can be adopted for rapid, large-scale screening of cassava varieties and/or accessions for salinity tolerance. Conclusions. In vitro micropropagation is a technique that can be adopted for rapid, large-scale screening of cassava accessions for salinity tolerance. The levels of chlorophylls biosynthesized by in vitro plants can be considered as relevant biochemical indicators for determining the sensitivity of in vitro plants to salt (NaCl).