Asked what kind of varieties the farmers had ever planted, and I believe that I can say a few things out of my mouth. This situation reflects the production of a common "variety update" phenomenon. Farmers always want to replace old varieties with better ones; research units must constantly cultivate new varieties to meet the demands of farmers' friends. So, how is the new breed bred?

The research of breeding new varieties, like other scientific research, is conducted under the guidance of certain scientific theories. Its central content is the use of biological variability and heredity, and the purpose of changing varieties' characteristics through artificial selection. Variability refers to the phenomenon of dissimilarity between parents and children. As the saying goes, "a mother has nine children and nine children are different from each other." Hereditary refers to the similar phenomenon between parents and children, as the saying goes The phenomenon of melons, beans, beans, etc.; artificial selection is artificially selecting the best ones, and constantly selecting the fine variations that people need. Due to biological variability, we have the opportunity to choose relatively better individuals. Due to the heredity of the organism, the good traits we have chosen can be passed on to the next generation.

The selection and breeding work has been going on for thousands of years. Domestic pigs have faster flesh than wild boars, there are more domestic ducks than wild ducks, and cultivated soybeans have higher yields than wild soybeans. These are the results of our ancestors constantly changing the original wild animals and plants in accordance with the needs of humans. Modern breeding is guided by more scientific theories, methods and methods are greatly improved, and breeding is faster. The varieties we use now are obviously different from those used 20 years ago.

Corn is a “cross-pollination” crop in which progeny are propagated through the pollen of different flowers to breed offspring. Differences among plants are large. Even if people can select good mutations, they cannot naturally reproduce completely in offspring, so its breeding program needs It is more complex than self-pollination crops such as soybeans and rice. Divided into three sections:

The first paragraph: Inbred breeding. First, create a group with large differences between plants and adopt a method of artificially controlling pollination. Grant the pollen on the tassel to the same ear, which is often referred to as “self-interesting”. Accompanied by self-interesting, the bad traits that have been concealed in the past are reproduced, giving us the opportunity to eliminate the bad traits. After repeated five or six generations, the offspring of the same plant no longer continue to separate, and they are relatively neat and consistent. We call it the stable line. Through the measurement, valuable stable strains are screened out. This is the inbred line. This process requires 7-8 generations.

The second paragraph: preparation of hybrids. The inbreeding plants produced by continuous self-crossing of corn become shorter and the ear becomes smaller, which is called the phenomenon of "self-inferiority recession" and is difficult to use directly in production. The two inbred lines were used as female parents and one as the father, so that the female seeds of the female parent only received the seeds produced from the pollen of the father and were called “hybrid seeds”. When they were planted in the ground, they were growing and yielding. The stress resistance, resistance and growth and development status are better than those of parents. This is the phenomenon of "heterosis". The hybrids of two inbred lines are called "single crosses"; the hybrids of one single cross and one inbred line are called "three crosses"; the hybrids of two single crosses are called " Double cross species." The single cross is a stable inbred line because its parents are generally stable and superior to other hybrids. Therefore, at present, the vast majority of hybrids used in production in China are single-crossed species.

Although hybrids of two inbred lines can produce heterosis, the advantages and disadvantages vary greatly. The advantage of a large number means that the yield of single crosses is high. In order to obtain a strong single-crossing type, according to the matching principle of the parental inbred lines, a scheme for the combination and breeding of single-bred lines should be established, including which inbred line is crossed with which inbred line, who is the father and who is the mother. And artificial bagging, pollination control method to obtain a single cross seeds. This paragraph only takes 1 year.

The third paragraph: trait identification and yield comparison. Plant single-cross seeds, use the variety as a reference, conduct comparative test of yield and resistance of small-scale varieties for 2 to 3 years, select some excellent combinations to participate in regional tests at multiple locations and larger production trials. Demonstration 3~4 years. Finally, it is submitted to the Variety Approval Committee, which can be promoted after passing the validation. After the above procedures, new varieties are bred. Under normal circumstances, the entire process takes 12 to 14 years. The use of winter conditions in the southern region can save years.

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