A Brief Introduction to Mass Propagation Technologies for

 Superior Forest Tree Varieties by Somatic Embryogenic

 Engineering  and Large-scale Application in Reforestation

    Forest tree fine species are the cornerstone of forestry industry development and ecological construction. The Jisen Shi team of Nanjing Forestry University focuses on the important tree species that are in great demand and difficult to propagate with traditional technology, realize the rapid propagation of improved tree species through using cell engineering technology, and effectively solves the problem of efficient and large-scale propagation of improved tree species. Their work is of great significance to promote the development of modern forestry and the construction of ecological civilization. The great breakthroughs have been made in high-efficiency breeding and industrialization production of improved seedlings from cell engineering technology through the systematic study to eight important species of coniferous and broad-leaved species such as Cunninghamia lanceolata and Liriodendron hybrid.

    The somatic embryogenesis system with high induction rate and good synchronization was established, which realized the rapid and efficient propagation of improved tree species. The Shi team achieved some key technologies including the high frequency induction and proliferation of embryogenic cells, the regulation of high frequency induction and synchronous development, the acceleration of the development process of somatic embryogenesis and the long-term maintenance of the ability of somatic embryogenesis, and realized somatic embryogenesis and plant regeneration with high frequency and synchronization.

    The integration innovation in application of forest cell engineering technology will expand the utilization scope of forest excellent germplasm. The Shi team breaks through the limitation of explant sources, solving the problem of rejuvenation and plant regeneration of mature and excellent trees, and develops the somatic embryogenesis and organogenesis technology of vegetative organs from several adult tree species respectively, realizes efficient regeneration; breaks through the limitation of genotypes and different tree species, successfully establishes the general platform of forest cell engineering technology, and improves the breeding level of improved tree species.

    The Shi team innovatively put forward the theory of forest cell engineering breeding, which combines conventional breeding with modern biotechnology. Based on the conventional breeding technology system such as hybrid breeding, they revealed the mechanism of somatic embryogenesis and optimized the system of somatic embryogenesis through the theories and methods of molecular biology, proteomics and physiology and biochemistry, and developed the cell engineering technology into the technological platform of modern genetic breeding innovation such as genetic transformation and germplasm innovation.

    The project establishes a large-scale breeding technology system of cell engineering seedlings, and realizes the industrialization of scientific and technological achievements; establishes mature cell engineering seedling breeding and large-scale application system, and formulates standards for somatic embryo production and seedling quality detection. Three production lines of hybrid Liriodendron with a total capacity of 21.1 million and four production lines of Cunninghamia lanceolata with a total capacity of 26.1 million were established. This is the largest successful application of cell engineering technology in the breeding of improved tree species at home and abroad.

    Compared with similar technologies at home and abroad, The core technology of this project has obvious advantages in induction efficiency of somatic embryo, plant regeneration efficiency and production scale. Among of them, the induction rate of hybrid Liriodendron somatic embryo is 60%, the synchronization rate of somatic embryo development is 95%, the regeneration cycle is 2 months, and the germination rate of somatic embryo is 95%; the induction rate of Cunninghamia lanceolata somatic embryo is 30%, the synchronization rate is 90%, the regeneration cycle is 3 months, and the germination rate of somatic embryo is 90%. 1 L liquid culture cells of hybrid Liriodendron could induce 400000 improved seedlings, and the embryogenic cells in one culture dish of Cunninghamia lanceolata could induce about 200 somatic embryos.

    This achievement has fundamentally changed the traditional breeding mode with "one seed for one seedling", and promotes the transformation and upgrading of China's traditional forest seed industry to industrialization. Since the application of the achievement aboved, 72.96 million seedlings have been produced and planted in the forest area of 350000 mu. Cell engineering seedlings of hybrid Liriodendron and Cunninghamia lanceolata have been popularized and applied in southern forest areas of Fujian, Jiangxi, Guangdong, Hubei, etc., and get remarkable economic and social benefits. This achievement won the first prize of Science and Technology of Jiangsu Province in 2015 and the second prize of National Science and Technology Progress in 2016.