EVALUATION OF TWO ALFALFA LANDRACES FOR SALT TOLERANCE VIA SOME MORPHOLOGICAL AND BIOCHEMICAL TRAITS

Alfalfa (Medicago sativa L.) is the most commonly grown forage crop worldwide. Salinity stress is an abiotic stress, which has harmful effects on germination, growth and yield of alfalfa. Seventeen alfalfa landraces were assessed for salt tolerance with seven salt levels 0, 5 and 10 dSm -1 of NaCl, 5 and 10 dSm -1 of CaCl2 and 5 and 10 dSm -1 mixture of NaCl + CaCl2, in a laboratory experiment to select the most salt tolerant alfalfa landrace and the most sensitive one, which were evaluated under greenhouse conditions. Regarding laboratory experiment, two alfalfa landraces, namely L12 and L3, were selected as the most salt tolerant and sensitive landraces, respectively. A significant decrease was observed in all traits with increasing salt levels. The results showed that 5 dSm -1 CaCl2 levels had the least effect on all traits, than NaCl followed by their mixture concentrations of NaCl + CaCl2. The most tolerant and the most sensitive alfalfa landraces were assessed by peroxidase (POX), polyphenyl oxidase (PPO) and alcohol dehydrogenase (ADH) systems under different salt concentrations. The POX, PPO and ADH isozyme activities showed up to 10, 11 and 10 distinct polymorphic bands, respectively. Some new bands were appeared and/or disappeared under different salt types and concentrations for the most salt tolerant and/or the most sensitive alfalfa landraces. The activity of isozymes (band intensity) increased under all salinity treatments compared with the control. The increase of band intensity and appearance or disappearance of new bands may be an indication of an increase in isozymes activities under salinity conditions.