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 bred the world's first new crop variety-tobacco variety Shan Yu 1, and then bred new crop varieties cultivated in areas such as Zhonghua No.8 rice, Jinghua 1 and single crystal 92-2097 wheat. A large number of new flower cultivation strains of various crops have also been obtained. Pei Hua 28, Pei Hua 232 1, Xiamai 1, Yumai 37, Huahua 9, Huatezao, Yumai 60 and other excellent varieties (lines) have been cultivated in Henan Province, and have been popularized for more than 7 million mu, ranking among the best in the country.
(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 used for different flowers in test tubes.
Pollen germinates and fertilizes on ovules, and the hybrid embryos produced develop into complete plants in test tubes. This method 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 is doubled, hexaploid 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 and calli between species, genera and even families have been obtained, some of which further differentiated into seedlings. Intergeneric hybrids, such as tomatoes and potatoes, tobacco and nightshade, mustard and rape, can be obtained from plants that do not cross, 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) It is completely possible to cut off the target gene through the vector and integrate the foreign gene into the plant genome. If this research is successful, it will overcome the blindness in crop breeding and manipulate the genetic variation of crops according to people's needs to become excellent varieties. At present, this research has just started, and the genetic background of plants is more complicated than that of prokaryotes. Therefore, it is necessary
Improving crop yield and quality through genetic engineering will be a problem to be solved in 2 1 century.
(5) Mutants of cultured cells, whether in callus culture or cell culture, are in a constant meristem state, 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. In particular, some traits with low mutation rate and difficult to induce mutation were induced, screened and identified by cell culture.
At present, the number of cells processed is far more than the number of individuals processed, so it is possible to select some traits with extremely low mutation rate. Such as inducing plants to be resistant to pests, cold, salt, herbicides and physiological and biochemical mutants, and providing 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.
2.2 Application in Plant Virus-free 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 the tissue culture method is used, shoot tips with a certain size are taken for culture, the regenerated plants can be virus-free 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. Other crops, such as lateral buds, scales, leaves, bulbs and roots, can be applied. Because the prominent feature of tissue culture method is the rapid propagation of crops, it is of great significance for the propagation of some "famous, excellent, special, new and strange" crop varieties with low propagation coefficient, and for virus-free seedlings, new breeding, new introduction, rare breeding, excellent single plants, endangered plants and genes. At the same time, it can propagate tens of thousands to millions times faster than the conventional method, and provide a large number of high-quality seed potatoes and seedlings in time. Virus-free potato stalks, virus-free seedlings and miniature virus-free seed potatoes have been widely used in potato production, which fundamentally solved 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.
2.3 Application in the production of 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, biological seals and other active compounds. Therefore, this field has aroused great interest in recent years, and many industrial departments have invested in research. At present, about 20 species of plants have higher effective substances in their culture tissues than the original plants. More than 100 patents have been obtained in the world. In recent years, the production of protein by single cell culture will provide broad raw material production prospects for feed and food industries. 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.
2.4. Application in conservation and communication 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 germplasm.
The exchange and transfer of resources prevent the artificial spread of harmful diseases and insect pests, and bring hope for the preservation and rescue of useful genes. For example, cell suspensions of plants such as carrots and tobacco can be stored for several months at a low temperature of -20℃ to-196℃, but they can still grow again and regenerate plants.
2.5 application 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. It is easy to cause variation and chromosome changes in cell culture, thus obtaining new crops such as addition lines, substitution lines and translocation lines. It 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 carried out many studies 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. In recent years, the research on photoautotrophic culture is also very effective. In the study of cell biosynthesis, cell tissue culture is also very useful, such as finding out the position of nicotine in tobacco. Cell culture provides convenience for pathological research, such as identifying plant disease resistance by single cell or protoplast culture, and the results can be obtained within a few days.
2.6. Study the open tissue culture technology to solve the worldwide problems.
Using disposable plastic drinking cups and food preservative films as culture containers and sealing materials, and adding bacteriostatic agents to inhibit the pollution of culture medium, qualified and robust plant tissue culture seedlings can be quickly cultivated in a greenhouse with natural light. Recently, the project passed the evaluation of nine experts and scholars, including Chen Junyu, a famous academician of China Academy of Engineering. Experts believe that in view of the limitation that plant tissue culture must be operated in strict aseptic environment, an efficient bacteriostatic agent has been developed in this study. After adding bacteriostatic agent to the culture medium, the culture medium can inhibit the growth of fungi and bacteria, and has no adverse effect on plant growth within a limited bacteriostatic concentration range. Therefore, in the process of plant tissue culture, the high-pressure sterilization procedure of culture medium can be omitted, and inoculation can be carried out without clean workbench, which is a major breakthrough in the history of plant tissue culture technology and the first at home and abroad. The technology of replacing traditional high-temperature and high-pressure glass and polypropylene plastic products with ordinary polyethylene plastic cups and replacing sealing film with food preservative film is also the first at home and abroad. The perfect open plant tissue culture regulations put forward by the institute and the commercial culture medium developed by traditional Chinese medicine bacteriostat have greatly reduced the cost of plant tissue culture, made the advanced technology of plant tissue culture go to the general public, and will certainly accelerate the pace of tissue culture industrialization in China and promote the development of tissue culture.