At present, plant tissue culture has been widely used in crop breeding at home and abroad, and great progress has been made in the following aspects:
1, haploid plants in haploid breeding often fail to bear fruit. When treated with colchicine in culture, chromosomes can be doubled and become homozygous diploid plants. The application of this culture technique in breeding is called haploid breeding. Haploid breeding has the advantages of high speed, high efficiency and obtaining homozygous genotypes at one time. Therefore, haploid breeding by anther or pollen culture is a brand-new breeding method. And began to cultivate new crop varieties planted in large areas. In haploid breeding, scientists in China have made outstanding contributions. 1974, the first new crop variety in the world-Shan Yu 1 tobacco variety was successfully selected. Later, new crop varieties such as Zhonghua No.8 rice, Jinghua 1 and single crystal 92-2097 wheat were bred. A large number of new flower cultivation strains of various crops have also been obtained. Henan Province has made great achievements in anther culture and breeding, and cultivated excellent varieties (lines) such as Pei Hua 28, Pei Hua 232 1, Summer Wheat 1, Yumai 1, Yumai 37, Huatai Zao and Yumai 60, which have been popularized for 700 years.
2. Embryo culture In interspecific hybridization or distant hybridization, hybrid sterility brings many difficulties to distant hybridization. Early embryo culture in vitro can make embryos develop normally and successfully cultivate hybrid offspring, and a large number of populations with the same characteristics can be obtained through cloning and reproduction. Embryo culture has been successful in more than 50 families and genera. In distant hybridization, unfertilized ovules can be separated and fertilized with heterogeneous pollen in test tubes. The hybrid embryos produced develop into complete plants in test tubes, which is called "in vitro fertilization". Triploid plants can be obtained by endosperm culture, which opens up a new way for inducing triploid plants. After triploid doubling, hexaploid plants can be obtained and new polyploid varieties can be cultivated.
3. Cell fusion: Through protoplast fusion, the incompatibility of sexual hybridization can be partially overcome, and somatic hybrids can be obtained, thus creating new species or breeding excellent varieties, which is the most attractive aspect of tissue culture application. At present, more than 40 somatic hybrids, calli and some of them have been obtained, and some of them have further differentiated into seedlings. At present, protoplast fusion technology has been applied to plants that have never hybridized, such as tomatoes and potatoes, tobacco and dragons. Mustard seed and others have obtained interspecific hybrids, but these hybrids have no practical application value. With the continuous maturity and development of protoplast fusion, selection and culture technology, more somatic hybrids and new varieties of economic crops with certain application value are expected to be obtained in the future.
4. Genetic Engineering With the method of genetic engineering, the target gene can be completely cut off and the foreign gene can be integrated into the plant genome through the vector. If this research is successful, it will overcome the blindness in crop breeding and turn into manipulating the genetic variation of crops according to people's needs and cultivating excellent varieties. At present, this research has just started, and the genetic background of plants is more complicated than that of prokaryotes. Therefore, using genetic engineering to improve crop yield and quality will be 260.
5. Mutants of cultured cells, whether callus culture or cell culture, are in the state of unchanged meristem, and are easily induced by the influence of culture conditions and external pressure (such as rays and chemicals), so as to screen out mutants useful to people and cultivate new varieties. Especially for some traits that are not easy to induce mutation and have low mutation rate, cell culture is used for induction, screening and identification. The number of cells treated is far more than the number of individuals treated, so it is possible to select some traits with extremely low mutation rate. Such as inducing plant resistance to diseases and insect pests, cold resistance, salt tolerance, herbicide toxicity and physiological and biochemical variation, which provides rich mutant materials for further screening and breeding. At present, mutants with disease resistance, salt tolerance, high lysine, high protein and high yield have been screened by this method, and some of them have been used in production.
(2), the application in plant detoxification and rapid propagation.
Virus-free seedlings and rapid propagation in vitro are the most widely used and effective aspects in plant tissue culture at present. Many agricultural products carry viruses, especially asexual plants, such as potatoes, sweet potatoes, strawberries and garlic. However, not every part of infected plants carries the virus. As early as 1943, White found that the virus concentration near the growing point of plants was very low, or even there was no virus. If tissue culture is adopted, shoot tips of a certain size are taken for culture, and the regenerated plants may be virus-free, so as to obtain virus-free seedlings, and then the virus-free seedlings are used for propagation, so that the planted crops will not or rarely produce viruses. At present, tissue culture has been successfully applied to sugarcane, pineapple, banana, strawberry and other major cash crops. The explants used are not limited to stem tips, and other explants can also be used, such as lateral buds, scales, leaves, bulbs and roots.
Because the prominent feature of tissue culture is the rapid propagation of crops, it is of greater significance for the propagation of some "famous, excellent, special, new and strange" crop varieties with low propagation coefficient. Virus-free seedlings, newly bred, newly introduced, rare breeding, excellent individual plants, endangered plants and genetically engineered plants can be propagated rapidly in test tubes, and at the same time, they can be free from the influence of regions and climate. Timely provide a large number of high-quality seed potatoes and seedlings. Virus-free potato stalks, virus-free seedlings and miniature virus-free seed potatoes are widely used in potato production, which fundamentally solves the problem of potato degradation. At present, some or most of ornamental plants, horticultural crops, economic trees, asexual crops and so on provide seedlings through in vitro rapid propagation, and test-tube seedlings have appeared in the international market and formed industrialization.
(3) Application in plant useful products
Through large-scale culture of tissues or cells, it is possible to produce all natural organic compounds needed by human beings, such as protein, fat, sugar, drugs, spices, alkaloids and other active compounds. Therefore, this field has aroused great interest in recent years, and many industrial departments have invested in research. At present, there are more than 20 kinds of effective substances in plant culture tissues higher than the original plants, and more than one patent has been obtained in the world. The research on the production of microorganisms and drugs or effective components that cannot be synthesized artificially by tissue culture is deepening, and some of them have been put into industrial production, and it is expected that there will be greater development in the future.
(d) Application in conservation and exchange of plant germplasm resources.
Agricultural production is carried out on the basis of existing germplasm resources. Due to the competition between natural disasters and organisms and the influence of human activities on nature, a considerable number of plant species have disappeared or are disappearing on the earth. The extinction of biological species with unique genetic characteristics is an irreparable loss. Using plant tissues and cells to preserve germplasm at low temperature can greatly save manpower, material resources and land, and also facilitate the exchange and transfer of germplasm resources. Preventing the artificial spread of harmful diseases and insect pests brings hope for the preservation and rescue of useful genes. For example, the cell suspensions of plants such as carrots and tobacco can resume growth and regenerate plants after being stored at a low temperature of -20℃ to-196℃ for several months.
(e) in genetic, physiological, biochemical and pathological research.
Tissue culture has promoted the study of plant genetics, physiology, biochemistry and pathology, and has become a routine method of plant science research. Haploid and homozygous diploid plants obtained from anther and pollen culture are excellent materials for cytogenetics research. In cell culture, it is easy to cause variation and chromosome change, thus obtaining new crops such as addition lines, substitution lines and translocation lines, which opens up a new way for studying dyeing engineering.
Cell culture and tissue culture provide a very powerful means for studying plant physiological activities. Plant tissue culture has done a lot of research on mineral nutrition, organic nutrition and growth active substances, which is helpful to understand plant nutrition problems. It is very ideal to study the photosynthetic metabolism of plants by single cell culture, and photoautotrophic culture is also very effective in recent years. Cell tissue culture is also very useful in cell biosynthesis research. For example, finding out the position of nicotine in tobacco, cell culture provides convenience for studying pathology. For example, the disease resistance of plants can be identified by single cell or protoplast culture, and the results can be produced within a few days.