Studies On Cultures Of Soybean Somatic Embryos And Their Genetic Stability

Soybean, Glycine max(L.) Merr., is an important crop with high oil and protein contents, however, it is one of the recalcitrant crops for in vitro culture. In our study, 61 genotypes were tested for somatic embryo induction and plant regeneration. Medium, culture temperature and a few other factors which influenced the immature cotyledons in producing somatic embryos were studied. The soybean plant regeneration was improved greatly by choosing regular somatic embryos in sub-culturring in liquid medium. We investigated the genetic stability of the somatic embryos and the regenerated plants at various sub-culture period up to more than one year, and found that the cultures were pretty stable in microsatellite DNA (SSR). The main results can be summarized as below:1. Genotype has a large effect on the somatic embryo induction from immature soybean cotyledons. The induction frequency range was 0 to 92.5% among the tested genotypes. The frequency of Nannong 90C006 was the highest while the frequency of Wei 515, 8 7. 5 % was the second.2. Factors influencing in vitro culture of the immature cotyledons were analyzed. Temperature was not a very important factor in somatic embryo induction but had significant effect on the formation of callus; medium was an important factor influencing the induction of somatic embryo but might interact with genotypes; the protein content and the frequency of somatic embryo were correlated in a degree. Other factors influencing the somatic embryo induction from soybean immature cotyledons or the regenerability of the induced somatic embryos include the physiological status of the cotyledon explants and the status of the induced somatic embryo.3. In total, we got about 50 plants regenerated directly from the induced somatic embryos and some of them set seeds. Although we induced the soybean somatic embryos and got regenerated plants successfully, it was found that the regeneration ability of the induced somatic embryos was not high.5. If we selected the more regular somatic embryos for liquid medium culture, we could set up a stable soybean somatic embryo line and improve the regeneration ability. From the somatic embryo line, we easily got more than 200 regenerated plants which could set seeds.6. We checked the somaclonal variation of the soybean somatic embryo line and the regenerated plants using 102 microsatellite DNA markers. It was found that the genetic variation was low, and the somatic embryo line was pretty stable in microsatellite DNA and had high regeneration ability. So it was a good system for genetic manipulation.