Study on plant regeneration of 3 cultivars of Medicago sativa

The study was conducted on plant regeneration in vitro of 3cultivars of Medicago sativa(Gannong No.1,Gannong No.3,Xinjiang Daye),widely cultivated in the northwest region.The results showed that genotype of alfalfa,explant resource and different exogenous hormone level,hormone induction time and sucrose concentration had obvious effect on cell development and plant regeneration of alfalfa.The frequency of callus induction and somatic embryogenesis from hypocotyls of‘Gannong No.1'was 97.2%and 70.9%respectively.‘Xinjiang Daye'took the second place.‘Gannong No.3'had lower frequency of callus induction and somatic embryogenesis.The former 2cultivars were optimum for plant regeneration in vitro.Hypocotyl was the optimum donor tissues for rapid and higher frequency induction of callus.It was better to induct callus from hypocotyl on solidified MS medium supplemented with 2.0mg/L 2,4-D or 2.0mg/L 2,4-D and 0.5mg/L KT,the highest rate of callus induction reached 97.2%,and to develop somatic embryogenesis on solidified MS medium supplemented with 2 mg/L 6-BA and 0.5 mg/L NAA,its highest frequency was 70.9%.It took 20minutes to finish the callus induction and initiate devel-opment of somatic under hormone treatment mentioned above.The plants rooted in 1/2MS medium supplemented with 1.0mg/L IBA,1 % sucrose and 0.7 % agar.It is suggested that solidified MS medium supplemented with 25~30g/L sucrose would be good for somatic embryogenesis.