Study On The Salt Tolerant Mutant Selection Of Three Alfalfa (Medicago Sativa) Varieties And Physiological Characteristics Of Regenerative Plantlets

Alfalfa is high quality pasture which has most growth area and great using value. It's now facing important research task how to improve salt-tolerant characteristic and extend growth area. Calli were induced from mature embryos of Millenium, Victoria,CW787,Sodium Chloride(Nacl) were used as selective reagent,Nacl-tolerant calli variant were obtained from embryogenic calli by positive selection methods(direct selection and continuous selection). Plantlets were regenerated from those tolerant calli and grew well on the soil. Compared some physiological and biochemical characterization of the Nacl-tolerant Variants and controls after irrigation by saline water. The result showed that:1. Nacl had remarkable influence on germination rate; The presence of Nacl clearly decreased the frequency of callus formation, relative growth rate of callus, survival rate of callus and regenerated rate of allus.2. Nacl tolerant calli were subculture in salt free medium for two passes, and then transferred into saline medium, and they could grow well. It demonstrated its Nacl tolerant stability.3. In this paper selected 5 plantlets of Millennium which could tolerant up to 1.0% Nacl, and 3 plantlets of Victoria, and 1 plantlets of CW787 which could tolerant up to 1.0% Nacl.4. Physiological and biochemical analysis showed that: The content of chlorophyll and the TTC deoxidize capacity increased first and then decreased follow by the content of Nacl, the variant were higher than the control on the whole; In both the variant and the control, the content of Malondialdehyde(MDA) decreased first and then increased, the variant were lower than the control under the same Nacl stress; The content of Proline(PRO) in the variant were equal to the control without Nacl stress, in both the variant and the control, the content of PRO increased follow by the content of Nacl, the variant had higher accumulation of PRO than the control; The activity of Peroxidase(POD), Polyhphenol oxidase(PPO), Superoxide dismutase(SOD) increased first and then decreased on the whole both in the variant and the control, the variant were much higher than the control under the same Nacl stress; The transition in the change curve appeared at 0.8% concentration of Nacl on the whole.5. Nacl-tolerant variants of Millennium had great accumulation capability to PRO, the activity of SOD increased stably follow by the content of Nacl, so we educed these had the most tolerance to Nacl.