RELATIONSHIP BETWEEN REGENERATION AND PRODUCTIVITY OF SOMATIC EMBRYOS IN ALFALFA (MEDICAGO-SATIVA L)

Relationship between the ratio of regenerable plants (regeneration frequency) and productivity of somatic embryos was studied for three different genetic sources of alfalfa (Medicago sativa L.), including (i) four commercial cultivars and three breeding populations, (ii) five selfed and (iii) three crossed progenies of regenerants. Number of somatic embryos, stability of embryo formation and days to embryo formation were referred to as the productivity of somatic embryos in this study. The regeneration frequency of each line ranged from 14 to 70 % in the cultivars and breeding populations, 12 to 92 % in the selfed progenies and 14 to 58 % in the crossed progenies of the regenerants. In the cultivars and breeding populations the increase of the regeneration frequency was independent of the increase of the productivity of somatic embryos. This result indicates that regeneration and the productivity of somatic embryos are controlled by different genetic factors. In the selfed and crossed progenies the regeneration frequency was correlated with the average number of embryos and the average stability of embryo formation (r = 0.906 and r = 0.882, respectively, significant at 1 % level). In the relationships among the three characteristics of the productivity of somatic embryos, genotypes which produced many embryos showed a higher stability. In the genotypes which showed a higher stability of embryo formation the score of the number of embryos and the days to embryo formation varied. It was concluded that the production of somatic embryos in alfalfa was controlled sequentially by the following factors, regeneration competency. stability of embryo formation and number of embryos. Furthermore the correlation in the selfed and crossed progenies may suggest that the productivity factor could increase the regeneration frequency.