Russian (Soviet) geneticist vavilov is not only a famous scholar who studies the origin of crops, but also the founder of plant germplasm resources. During the 1920s-1930s, he organized many inspection activities on four continents, and made detailed analysis and research on the farming system, crop utilization, ethnobotany and even environmental conditions. He collected 6.5438+0.5 million germplasm resources of various crops, including some wild relatives, and studied their phenotypic diversity. Finally, vavilov put forward a set of theories about the origin of crops. In vavilov's theory of crop origin, the most important theory is the theory of crop origin center. He proposed in the article "Origin Center of Cultivated Plants" written by 1926 that the origin center of crops can be determined by studying the types of variation, and the region with the greatest genetic diversity is the origin of crops. After entering the 1930s, vavilov constantly revised his theory, and proposed that determining the origin center of crops should not only be based on the genetic diversity of this crop, but also consider the genetic diversity of its wild relatives, and also refer to archaeological and cultural materials. After years of updating, vavilov analyzed the geographical distribution of phenotypic genetic diversity of more than 600 species (including some wild relatives) in 1935, and published the World Origin Center of Main Cultivated Plants. In this famous paper, it is pointed out that the main crops have eight origin centers, plus three sub-center graphs 0- 1. These centers are usually geographically separated by deserts or mountains. They are called "primary origin centers". Wild relatives and dominant genes of crops often exist in such centers. Vavilov also found that far away from this primary origin center, sometimes there is rich genetic diversity, and there may be some variations that are not found in its primary origin center. Vavilov called this area "the second origin center". There are many recessive genes in the secondary origin center. Vavilov believes that the genetic diversity of secondary origin centers is due to natural selection and artificial selection of crops introduced from their primary origin centers under the condition of long-term geographical isolation.

The Origin Center of Cultivated Plants in vavilov

1 .China 2. India 2a. Indo-Malaya. Central Asia 4. Near East 5. Mediterranean 6. Ethiopia. Southern Mexico and Central America. South America (Peru, Ecuador, Bolivia) a. Chile 8b. Brazil and Paraguay.

Vavilov regards the Mediterranean coast of North Africa and the area around the Mediterranean as the Mediterranean center; Abyssinia (now Ethiopia) in Africa is one of the centers of crop origin in the world; Take Central Asia as another origin center independent of pre-Asia (Near East); China, the United States and South America are independent centers of origin. Together with China and India (Indo-Malaya), it is the origin center of the world's eight major crops advocated by vavilov.

The variation law of homologous series is also an important part of vavilov's theoretical system of crop origin. According to this theory, similar variations can be found in different crops in the same geographical area. That is to say, if a specific trait or phenotype is found in one crop in a certain area, the same trait or phenotype can also be found in another crop in that area. Hawkes( 1983) thinks that this phenomenon should be more accurately described as "similarity series rule" because different gene loci may be related to it. Kupzov( 1959) regards this phenomenon as that similar mutations may occur at the same site in different species, or that different adaptive gene systems have evolved to produce similar phenotypes. The research results of genomics also support this theory.

In addition, vavilov put forward the concepts of "primary crops" and "secondary crops". "Original crops" refer to those ancient crops that have been cultivated for a long time, such as wheat, barley, rice, soybean, flax and cotton. "Secondary crops" refer to those crops that are weeds in the field at first and then slowly cultivated, such as rye, oats, tomatoes and so on. Vavilov has made important conclusions on the significance of local varieties, the significance of exotic and exotic materials, and the introduction theory.

After vavilov's "Eight Origin Centers of Crops" was put forward, other researchers revised the theory. Among these researchers, zhukovsky, a student from vavilov, is the most influential. In 1975, he put forward the theory of "great centers for plant gene cultivation", and thought that there were 12 great centers in addition to Brazil, southern Argentina, Canada, northern Siberia and some marginal countries, covering almost the whole world. Zhukov also put forward the concept of "small center" of wild species that are genetically similar to cultivated species. He pointed out that there are differences in distribution between wild species and cultivated species. The distribution of wild species is very narrow, while the distribution of cultivated species is very wide and varied. He also put forward the concept of "primary gene megacenter", and thought that the primary origin center in vavilov was narrow, and the area where cultivated species spread was called "secondary gene megacenter".