1, natural breeding: without artificial treatment, the natural mutation of strains is mainly used, and the method of screening ideal stra
1, natural breeding: without artificial treatment, the natural mutation of strains is mainly used, and the method of screening ideal strains is natural breeding. 2. Mutation breeding: physical mutagens (such as ultraviolet rays) are mainly used to improve the mutation rate, so as to select suitable mutants, and chemical mutagens (such as bacteriophage) can also be used to select suitable mutants. 3. Cross-breeding: it is mainly to create mutations by crossing between varieties, and then select new varieties.
First, briefly describe the method of strain breeding.
1, natural reproduction
(1) The process of screening ideal strains by natural mutation without artificial treatment is natural breeding.
(2) Without human intervention, the mutation of some microorganisms is natural mutation, which is usually divided into positive mutation and negative mutation. Among them, positive mutation is beneficial to production, such as the improvement of strain production performance, while accidental mutation is negative mutation, such as strain decline and production quality decline.
2. Mutation breeding
(1) Mutation breeding means using physical mutagens and chemical mutagens to treat the uniformly dispersed microbial cell population to improve the mutation rate, and then using convenient, rapid and efficient screening methods to select some mutant strains that meet the purpose for research and use.
(2) The common physical mutagens are mainly ultraviolet rays and fast neutrons, and the common chemical mutagens are mainly bacteriophages.
3. Cross breeding
(1) The method of crossing between varieties, then creating mutation, and then breeding new varieties is cross breeding.
(2) Cross breeding is also the most effective and commonly used breeding method at home and abroad.
Second, the advantages and disadvantages of strain breeding
1, natural reproduction
(1) Advantages: It is convenient to operate, and can purify strains, avoid strain decline, ensure the stability of production, and generally improve the yield.
(2) Disadvantages: the workload is large, the efficiency is relatively low, and the progress is relatively slow, and the probability of natural mutation is relatively small, so it is generally difficult to screen out ideal strains.
2. Mutation breeding
(1) Advantages: The mutation rate is generally high.
(2) Disadvantages: the genetic nature is unstable.
3. Cross breeding
(1) Advantages: Combining two or more excellent traits in the same species into a new variety can usually produce heterosis, thus obtaining a new variety that is stronger or better than the parent variety.
(2) Disadvantages: The breeding process is slow and complicated.