What are the functions of agricultural germplasm resources in crop genetics and breeding?

Grain crop germplasm resources have played a great role in crop genetics and breeding in China. In the worldwide "green revolution", China independently used different dwarf gene resources to carry out this "green revolution" with the world, shouldering the responsibility of feeding 22% of the world's population with 10% of the world's cultivated land, reaching the miracle of agricultural science and technology revolution at the same level as the world. Among them, China's grain crop germplasm resources,

In the second half of the 20th century, China's 50-year breeding work mainly went through four stages. The first stage was the middle and early 1950s, which was the period of breeding and popularizing local varieties and early breeding varieties, which changed the phenomenon of excessive, chaotic and miscellaneous agricultural production and increased the national grain yield by 654.38+00% ~ 20%. In addition, with the expansion of arable land, by the end of 1950s, the total grain output of China was close to 200 billion kilograms. The second stage, from the late 1950s to the early 1970s, mainly focused on cultivating and popularizing short and high-yield varieties. The third stage, from the early 1970s to the mid-1980s, is mainly the breeding and popularization of hybrid rice, with the cultivation and popularization of high-yield and disease-resistant varieties as the main goal. The second and third stages coincided with the "Green Revolution" in the world, and China also made remarkable achievements. The total grain output increased from 65,438+197.7 billion kg in 0958 to 407.3 billion kg in 0984, and the per capita grain share also increased from 299 kg to 390 kg. . The fourth stage is from the mid-1980s to the end of 20th century. Crop breeding and variety promotion take "two highs and one excellent" (high yield, high resistance and high quality) as the main goal, which will make China's total grain output go up a big step and break through the 500 billion kg mark, thus making China step into a well-off level as a whole, realizing a basic balance of grain supply and having more than a bumper year.

In the first stage of local variety breeding in China, excellent local varieties were selected as the main ones, which replaced many disorderly general local varieties. Through early breeding and popularization of introduced varieties, the first variety renewal of main crops in China was realized. A number of rice varieties, such as Nante and Shengli indica, have replaced most of the original varieties in South China (Lin Shicheng, 19 1). On the other hand, most of the varieties in the former northern wheat region (Jinshanbao, 1983) were replaced by a number of wheat varieties represented by Liaozi wheat, grasshopper wheat, Bima 1 and Nanda 24 19.

In the second stage of dwarf breeding in China, China adopted dwarf germplasm resources different from international agricultural research institutions and independently carried out the "green revolution" work. For example, the wheat in China was developed by using the germplasm from red wheat, with Rht8 and Rht9 dwarf genes, Zhongnong 28, Alido, Nanda 24 19, Afu, Apo and Oulu (this variety comes from Chile and has Italian wheat origin) (Jin Shanbao, 1983). Another example is rice. In China, the dwarf from Nantes was used as the dwarf source (Lin Shicheng, 199 1), while the Philippine International Rice Research Institute used the dwarf black tip from China as the dwarf source. On the other hand, the development and utilization of excellent germplasm plays a key role in this stage of breeding. The backbone parents, such as Nante, Aizhan and Shengli Indica, are 17 (Lin Shicheng, 199 1), which play a key role in southern rice-growing areas and 1 in northern wheat-growing areas.

In the third breeding stage, represented by hybrid rice in China, most of the cytoplasm sources of indica hybrid rice sterile lines in China came from wild rice, and the nuclear sources mainly came from dwarf Zhan, Nante and Shengli indica. The parental relationship of the corresponding maintainer lines is basically derived from two dwarf species, Dwarf Zhanzhan and Dwarf Cross Nantes. The original parents of the corresponding restorers were Wujiaojian, CPSL0 17 and Cina (Lin Shicheng, 199 1). In the hybrid breeding of wheat region in northern China, in addition to the original 14 backbone parents, cattle and dwarf Meng cattle were created by multi-parent aggregation method. These two new germplasm have played a recognized role and won the first prize of national invention, which shows their great contribution.

In the fourth breeding stage (after the mid-1980s) with the comprehensive goal of "two highs and one excellent", the breeding of new varieties in China and even major countries in the world is in a difficult "climbing" stage. The output of grain crops is stagnant, and there are few breakthroughs in quality and resistance. The main reason is that the genetic basis of parental materials is narrow. For example, hundreds of wheat varieties have been bred, and most parents are inseparable from 14 backbone parents. What's more, 70% ~ 80% of the wheat varieties used in production in 1980s have pedigrees of IB/IR addition/translocation lines (Jin Shanbao, 1996). According to statistics, 1995, there are 24 single-cross species with corn planting area exceeding133,000 hm2 in China, among which 9 inbred lines (Wu Jingfeng, 1998) were used in 2/kloc-0. At present, hybrid rice accounts for half of China's rice planting area, and most of the sterile lines of hybrid rice are wild abortion systems, and most of the restorers have pedigrees of IR varieties.