Discussion on breeding principle from wheat and corn breeding methods

The most basic basis for breeding is genetics, which is very easy to understand, that is, the dragons and dragons and phoenixes that people often say. Second is the law of survival and inferiority in nature. Breeding is the process of keeping good quality and throwing out inferior quality. Crossbreeding allows individuals of different breeds of the same species to intersect, and concentrates the good traits scattered among different breeds into a new breed. This is often referred to as heterosis. Breeding is to select individuals who meet the breeding objectives in the hybrid progeny to further cultivate until a new variety with good traits is obtained.

In the case of wheat breeding, if there are two varieties, one has a large ear, good quality and high yield, but it is easy to fall and has poor disease resistance. In addition, one has a very low yield and poor quality, but the root system is developed and resistant to lodging. Strong disease resistance, can you complement the advantages of the two? In theory, if the two wheat varieties can hybridize, they can select new varieties that have high yield, high quality, developed roots, disease resistance, and dwarfing plants. We first hybridize these two varieties, and then broadcast the seeds harvested after hybridization . The second generation of wheat that has been planted may have many differentiations, some of which are better than the two parents, and some are poor; Then choose the dominant population with good growth, then plant and harvest, and repeat until the seeds are kept high, high quality, disease resistance, lodging resistance and other good traits remain stable. This kind of seed is an excellent variety that we use for promotion in Daejeon.

This kind of breeding method is the most basic and basic method. Simply put, the breeding process is self-crossing after hybridization. The flower of wheat is a bisexual flower, that is, a small flower has both stamens and pistils. Wheat is a strictly self-pollinated crop, and the flowers are very small, which means that the amount of work required to achieve artificial hybridization of wheat is very large. In practice, a typical, robust main stem ear is selected from the maternal population according to the determined hybridization combination, and the dysplastic florets are removed, and then the retained florets are emascated (ie, the stamens are removed), and then the male parent is removed. The pollen was given to the female parent, thus completing the first step of breeding: hybridization. Similarly, the rice breeding of Gramineae is difficult to obtain hybrids by artificial emasculation. The main reason is that the structure of rice flowers is different from that of wheat. It is difficult to achieve emasculation, even if the seeds obtained by emasculation are often poorly developed and cannot be obtained. Excellent seed. Therefore, the rice male sterile plants discovered by Academician Yuan Longping became a milestone in the history of rice breeding.

　　 Maize breeding is the opposite of wheat. It is the first cross-breeding. The common point is to breed excellent genetic homozygotes through continuous self-crossing for many years. The difference is that wheat breeding is homozygous after hybridization, and maize breeding is Hybrid after homozygous. The flower of corn is a single flower, that is, a flower has only pistils or only stamens. Maize is a cross-pollinated crop with a cross-pollination rate of 20%-50%, so the hybridization of corn is much simpler than wheat. At the time of breeding, the inbred lines of the male parent and the female parent should be prepared at the same time. After several years of homozygous, the two inbred lines are planted together, one parent, two females, and the female tassel Remove and give the father's pollen, the mother will produce the first generation of single cross. This is the hybrid generation (F1) that we promoted in Daejeon.

Therefore, wheat varieties can be kept, and the seeds harvested this year are planted, and the same seeds are harvested in the coming year. Corn species can't be kept, and the seeds harvested this year will not only grow uneven, but also have different grain shapes and lower yields.

In short, all breeding methods are inseparable from these basic principles, either first or first self-crossing, self-crossing is to obtain homozygous genes that control certain traits, and hybridization is to reflect the complementary advantages of parents. Modern breeding has greatly accelerated the breeding process due to the adoption of more advanced physical and chemical treatment methods.