Differential response to water deficit stress in alfalfa (Medicago sativa) cultivars: Growth, water relations, osmolyte accumulation and lipid peroxidation

The present study was fixed as objective to compare the response to water deficit (33% of field capacity, FC) stress of eight cultivars of Medicago sativa, originating from the Mediterranean basin. Comparison was performed on some key parameters such as growth, relative water content, leaf water potential, MDA tissue content, electrolyte leakage and proline and soluble sugar tissue concentrations. In all cultivars, water deficit stress reduced the whole plant growth, increased the root/shoot DW ratio and led to a significant decrease in leaf relative water content and leaf water potential. In water-stressed plants and for the majority of cultivars, proline and soluble sugar concentrations increased significantly. The Tamantit cultivar originating from Algeria showed the better tolerance to water deficit stress. Some criteria are concomitant with this tolerance: (1) a high biomass production under stress conditions when compared to other cultivars (2) the root preferential development, (3) the better ability to accumulate proline and soluble sugars, and (4) the aptitude to protect its photosynthetic apparatus against the oxidative stress generated by the water deficit stress. Ecotipo Siciliano, originating from Italy was the most sensitive cultivar. The increase of proline and soluble sugars concentrations upon water deficit stress particularly in the most tolerant cultivar suggested their involvement in the osmotic adjustment.