Phenotype and Molecular Analysis of M_1 Generation of Stylosanthes Irradiated by ~(60)Co

The seeds of Stylosanthes guianensis SW.'Reyan No.13' were irradiated by 60Co at 0,325,487 and 974 Gy.Phenotype and molecular variations of Stylosanthes M1 generations were studied.Germination percentage,plant height,leaf length and stem diameter of M1 seedlings were determined using SRAP-PCR.Results showed that biological character indices of treatments were significantly lower than that of control(CK).Irradiation inhibited plant growth.Growth indices of 974 Gy treatment,except leaf length,were significantly lower than CK and other two treatments.Eight effective primers selected from 24 primers combination were used for SRAP-PCR.SRAP analysis revealed that the 57 of 88 DNA fragments were amplified showing polymorphisms.The average percentage of polymorphic bands was 64.77%.The effects of 60Coγ irradiation on DNA variation of seedlings were varied from different treatments.Numbers of polymorphic bands changed after irradiation.Coefficient of variation was in direct proportion to irradiation doses.Variation rates of 325 Gy,487 Gy and 974 Gy treatments were 22.0%,38.1% and 41.5%,respectively.The Nei's genetic similarity coefficient of all treatments was ranged from 0.585 to 0.780 by software NTSYSpc 2.1 based on SRAP results and the average Nei's coefficient was 0.678.The Nei's genetic similarity coefficient of 974 Gy treatment was 0.585 and variation degree was highest among all treatments,487 Gy treatment was second and 325 Gy treatment was the lowest one.Based on present bands,four irradiated treatments were classified into two major groups by UPGMA cluster analysis.GroupⅠincluded CK,325 Gy and 487 Gy treatment and groupⅡincluded 974 Gy.SRAP analysis determinedvariationof Stylosanthes after irradiation and the results of SRAP analysis were consistent with their biological indexes in some extent.