Conversion Of Somatic Embryos To Plantlets And Genetic Stability During Somatic Embryogenesis In Quercus Variabilis

Quercus variabilis, a hardwood species belonging to the Fagaceae, is an important species for afforestation with great economic value in China. Plant regeneration by somatic embryogenesis is of great significance for mass production, genetic improvement and germplasm conservation. In this paper, immature zygotic embryos were used as explants to induce embryogenic calli. The effect of carbohydrates, ABA concentrations, organic compounds on maturation of somatic embryos as well as the effect of chilling and desiccation, culture methods, GA3 concentration on germination of somatic embryos were investigated. In addition, the genetic stability of regeneration plants was assessed with molecular marker. It will lay the foundations for establishing an efficient regeneration plantlets system in Q. variabilis. The main results were as follows:1. Carbohydrates adding into the medium has a significant influence on maturation of somatic embryos. When adding both sucrose and sorbitol or maltitol into the medium, maturation rate of somatic embryos increased significantly, mature somatic embryos obtained is bigger and greener than that obtained by adding any one single source. The rate of maturation is up to 72% when adding 3% sucrose and 6% sorbitol into the medium. Adding 0.5mg·L-1 ABA can significantly increase the maturation rate of somatic embryos, going up to 50%. But high levels of ABA will lower the quality of somatic embryos. PEG can significantly enhance somatic embryos’ tolerance of dehydration. When the concentration of PEG is 20g·L-1, the rate of maturation is up to 32%, almost twice as control. Therefore, the most suitable maturation medium for Q. variabilis was: 1/2MS+3%Sucrose+6%sorbitol+ 0.6% Agar +0.5mg·L-1 ABA +20g·L-1 PEG.2. Chilling and desiccation treat before germination can effectively improve the germination rate. The germination rate of the embryos experiencing chilling is 65% higher than the control. After 20 days desiccation, germination rate has increased and reached the maximum, which is 88%. The germination rate on the liquid germination medium is much higher than that on solid medium, but liquid culture can only increase the speed of radicle elongation, its effect on the rooting rate was not significant. Adding GA3 into the medium can significantly increase germination rate of embryos. When the concentration of GA3 was 2.0mg·L-1, the germination rate of somatic embryos reached 80%.3. ISSR amplification pattern in different stages from the same cell line is consistent and polymorphic fragments were not appeared, indicating that there is no genetic variation throughout the process of somatic embryogenesis and regeneration plants can maintain the stability of gene.