Study On Medicago Sativa L. Evaluation And Embryoid Inducing For Salt-stress Breeding

Alfalfa is an excellent legumes forage, its widespread has been the promotion of the developmentof animal husbandry. The adaptability of alfalfa is accessible to cope with the salinization of the soil bybreeding fine varieties.It can alleviate the problem of the land salinization. Alfalfa is polyploid andperennial pasture, traditional breeding methods such as seed mutagenesis or the stress screening oncallus are prone to get chimera, while using tissue culture process of somatic-embryoids single cells isvery effective.With the advantage of high mutagenesis efficiency in a relatively short period, and purelines of variant,it is a high efficiency and short cycle breeding methods.The evaluation of the salt-tolerant strains ST which cultivated from callus culture and screened forsalt-resistent mutagenesis and the generation seed of ST（ST-1） were conducted for their salinitytolerance traits in comparision with Zhongmu No.1and Sanditi. And K⁺、Na⁺、Ca²⁺、Mg²⁺ion contentin leaves and stems were measured. Regeneration system were built in Xinjiangdaye、ZhongmuNo.1、ST-1et al，and the somatic cell-embryoid were cultivated twice from high frequency regrowth inXinjiangdaye.Then the somatic cell-embryoid were induced breeding by60Co-γ and EMS and selectedby NaCl. And get induced mutation plant from somatic cell-embryoid in the meantime.The results areas follows:1. Cutting seedling for salt-tolerance evaluation of ST and Zhongmu No.1were conducted for theirmorphological index and physiological indicators.The result shows no significant difference inthe two species. And salt tolerance of ST remained for long time stress which means its goodhereditary stability.In long time stress ST accumulated more K⁺and Mg²⁺in its leaves, and SK,Nain stem and leaves was higher than Zhongmu No.1. ST could take in more K⁺and discharge moreNa⁺in leaves more efficiently.2. ST-1, Zhongmu No.1and the Sanditi for seed seedling stage evaluation: morphological index andphysiological indicators were measured and analyzed under different salt stress, the results showthat Zhongmu No.1、 ST-1and Sanditi ranked No.1、No.2、No.3for15d stress and No.3、No.2、No.1for45d stress. So its important to to control the time in evaluation. ST-1has a high salttolerance and stable genetic traits.3. Regeneration system were built in Xinjiangdaye、Zhongmu No.1、ST-1et al，Xinjiangdaye washighly frequency regeneration among these species,The optimum culture for Zhongmu No.1andST-1was SH+2mg/L2,4-D+0.2mg/L KT+0.2mg/L6-BA+30g/L sucrose+0.35%phytagel.Xinjiangdaye was also suitable in it.4. Cytological observation was taken for the somatic embryoids occurring stage. It shows thatsomatic-embryoid development more in6-8weeks after subculture.and more favorable variantswould be obtained to conduct radiation mutagenesis and chemical mutagenesis in this stage.5. Combined Radiation mutagenesis with salt screening, according to the statistics of stress duringthree months, the budding rate stress did not change significantly with the salt risingconcentration in two months, while after stress for three months, the budding rate changes with the salt concentration, which reflecting the salt screening effect. Regression analysis method wasused in analyzing the radiation dose and the salt stress. The material had maximum lethal saltconcentration under5Gy radiation dose, and suitable dose of radiation for somatic-embryoid was2-8Gy. According mutant growth situation, mutants under80Gy radiation dose inducing treatmentgrow better and faster. Mutants of1.0%NaCl tolerance were obtained.6. EMS chemical mutagenesis: the budding rate of somatic-embryoid growth under EMSconcentration of0.15%and salt stress conditions is higher. The most appropriate EMSmutagenesis concentration is0.1%-0.15%（v/v）. The preferred NaCl screening concentration ofthe chemical and salt mutagenesis is0.5%.