Sun Benzhong's career (before the founding of the People's Republic of China)

1928, Sun Ben Middle School returned to China as the silk technical director of Jiangsu Provincial Department of Agriculture and Mining, responsible for silk improvement in the province. 1929 concurrently serves as the director of Jiangsu sericulture experimental field. Being withdrawn and lacking in administrative ability, Zou Bingwen (then Dean of Agricultural College of Central University) introduced him to Central University as a professor and head of sericulture department at 1930. Two years later, introduced by Liang, he was hired as a professor and director of sericulture department of Agricultural College of Zhejiang University. 1933, then the president of Zhejiang University was overbearing, oppressing and crowding out the dean of the prestigious Agricultural College, and even being forced to leave, causing public anger. Most of the faculty and staff later left him. Together with Zhu, he was employed by the Central Agricultural Research Office of the Ministry of Industry of the National Government, and Sun was also the director of the sericulture department. At this time, he was in the prime of life and determined to improve silkworm varieties as his lifelong career. So in Nanjing Xiaolingwei, mulberry fields were opened, silkworm houses were built, equipment was purchased, and silkworm eggs were regularly selected. Besides raising silkworms and selecting seeds in the laboratory, he is also very concerned about the development of the silk industry in the motherland. He once broadcast a speech "There is hope for the revival of sericulture in China" on the radio, saying that "China people don't know how to improve the management of silk industry with the progress of the times, and so far the international market has been occupied by Japanese and Italian silkworms." He pointed out that China has unique conditions suitable for sericulture and mulberry, and cited the data of the synchronous growth of rayon and natural silk over the years, pointing out that the consumption of rayon and raw silk in the world is parallel, which has swept away all kinds of pessimism in China and demonstrated that there is indeed hope for the revival of silk industry in China. At that time, when China's silk industry was dying, it played an enlightening role.

He paid attention to absorbing foreign advanced experience, such as publishing the translation of "Study on the Improvement of European Silkworm Varieties" and introducing in detail the single moth breeding selection method initiated by G. Cotagne of France. Through his own seed selection work, he established breeding methods such as pure line selection, moth area selection and individual selection, which laid the foundation for systematic breeding methods of silkworm in China. 1937 published the paper "research on experimental techniques in silkworm breeding", pointing out that foreign papers on silkworm breeding focused on genetic analysis, but lacked research on how to improve the efficiency of silkworm breeding and improve the experimental techniques of silkworm varieties. According to the principle of biostatistics, he studied the positioning of silkworm foil, the sampling method of silkworm cocoon and the scale of seed selection in the moth area experiment, and pointed out that the environmental errors caused by different positions of silkworm rooms can be eliminated without frequent adjustment of the plaques. In this paper, the sampling standard of 25 male and female cocoons from each moth area and the scale of rearing moths in different feeding experiments were put forward. 1937 War of Resistance against Japanese Aggression broke out and moved in with China Agricultural College. Successively borrowed silkworm houses from Changsha Agricultural School of Hunan Province, Beibei Seed Production Farm of Sichuan Silk Industry Company, Nanchong Silk Experimental Farm and Xichong Seed Production Farm to continue the breeding work. At this time, his breeding work has developed. In addition to continuing to carry out soil species tests, we should pay attention to the utilization of good species such as Hua 6 and Qiagui, and the research on hybrid identification technology has developed from pure line breeding. He used a single-parent hybridization test (now usually called top crossing method) to select the varieties with excellent general mating ability from many silkworm varieties, and then selected the best hybrid combination for production and application through the determination of special mating ability. During his stay in War of Resistance against Japanese Aggression, his main achievement was to breed a new variety "Zhongnong 29" with the characteristics of yellow-skinned silkworm through cross breeding.

1933, he found a native yellow-skinned silkworm different from ordinary white-skinned silkworm in Jianqiao Farmhouse, Hangzhou. After feeding observation, the cocoon layer amount is only 0. 15g, and the cocoon layer rate is only 13.6%, but it is extremely heat-resistant. We chose the rich silk variety Ou 8 to cross with it. When the second generation of summer silkworm was exposed to the high temperature of 40.5℃, all other silkworm varieties died, but half of them still cocooned. Therefore, the hybrid improvement was continued, and several silk lineages such as Japanese 1 10 and China 107 were introduced successively, so as to keep the resistance of Bombyx mori as much as possible. After 7 years and 20 generations of breeding, the yellow-skinned silkworm variety "Zhongnong 29" was bred in 1940 (29 years of the Republic of China). Compared with the imported variety Hua 6× Qiagui 16-20%, the hybrid between this variety and the improved variety Qiagui (white-skinned silkworm) has the characteristics of low silkworm reduction rate and excellent silkworm relaxation. However, the body color of wampee is a recessive trait. After crossing with white-skinned silkworm, the first generation hybrid is white-skinned. Therefore, according to Mendel's genetic principle, body color and markings are recessive, and then Qiagui was changed into wampee species, and the second generation wampee species was bred at 1 1. In this way, the first generation hybrid of Zhongnong 29×30 1 1 fully possessed the characteristics of yellow-skinned silkworm when raised. This species has been sent to rural areas of Jiangsu, Zhejiang, Sichuan and Singapore for a small amount of promotion. The breeding of yellow-skinned silkworm varieties can be said to be the beginning of his career in skin spot breeding.

Since then, he has bred several pairs of practical new silkworm varieties. He thinks that selecting new silkworm varieties is the simplest and quickest breeding method, and points out that some purebred varieties have outstanding characters, but they are not necessarily the best after hybridization. Because the first generation hybrid is used in production, the hybrid combination with the best general mating ability and special mating ability can be directly selected from ready-made varieties through hybrid combination identification (including top crossing test), which can be directly used in production application. Zhenjiang 1× Zhenjiang 2 was selected by this method. After breeding, the pure line was continuously improved, and after years of regional experiments, it was popularized in rural areas of East China, which played a role in increasing production and won the reward of the Ministry of Agriculture. 1945 victory in the anti-Japanese war. 1946 Zhongnong Institute moved back to Nanjing Xiaolingwei. 1947, Sun Benzhong continued the two-hybrid experiment. 1948 published the paper "Two-hybrid Experiment of Silkworm" in the Journal of China Agricultural Society, and pointed out that using two-hybrid is beneficial to improve the reproductive coefficient of silkworm eggs. At the end of 1948, as Jiaxing workstation of China Academy of Agricultural Sciences, we borrowed Jiaxing Silkworm Farm of China Silk Company to raise silkworms. Jiaxing was liberated in May 1949. At that time, four academic groups, including the Chinese Science Society, initiated the establishment of the Preparatory Committee for the National Congress of Natural Science Workers in Beijing and hired him as a member. In July, I went to Beijing to attend the preparatory meeting. In his speech, Zhou Enlai expounded the relationship between politics and science, theory and practice, popularization and improvement, which inspired him greatly. In the same year, sericulture moved back to Nanjing. 1950 In February, Zhongnong Institute was renamed East China Institute of Agricultural Sciences.

From 1949 to 1950, Sun Benzhong has carried out cross breeding between brown spot restricted species and common restricted species, that is, brown spot Wulong Sanmian white silkworm crossed with common restricted species 1 16 and new improved varieties Hua 8, Guan Han and Guan Wen. At that time, he thought that farmers could abandon female silkworms and exclusively raise male silkworms in the young silkworm period after the limited variety of brown round skin spot was bred, because the male cocoon had high silk yield, long silk length and good silk quality, which could increase the raw silk output by about 10%. At the same time, the breeding of limited varieties with skin spots can improve the accuracy of male and female identification, improve the identification efficiency and reduce the production cost of silkworm eggs. From his breeding history to the later breeding of limited skin spots "Zhen 3" and "Zhen 4", the improvement of silkworm varieties with limited eggs (black and white eggs), and the experiment of changing the sex ratio of male and female silkworms by adding drugs in order to produce more male silkworms, it can be seen that he constantly innovated hybrid breeding techniques, from skin color breeding (yellow-skinned silkworms) to stripe breeding (brown round spots and ordinary spots), and then to egg color limited breeding. His main experience of constantly innovating hybrid breeding techniques and methods can be summarized as follows:

1. The method of variety pairing utilization was pioneered in parent selection. In other words, the selected varieties have excellent combining ability and can still maintain good combining ability after hybridization.

2. By crossing the original variety 1 16 with the same band-limited, many new band-limited varieties with economic and practical value were bred, and the economic performance of the new varieties was continuously improved by backcross improvement. Around 1963, the double-limited silkworm variety "Zhen 3 × Zhen 4" was popularized in rural areas of Jiangsu and Zhejiang, many years earlier than Japan.

3. Cross between strains, make a double cross hybrid, and popularize it, so as to improve the physique of silkworm and increase the reproductive coefficient of silkworm eggs. The application of two-hybrid method to silkworm egg reproduction is Sun Benzhong's original creation, which not only has stronger anti-hybrid ability, is easier to raise and lays more eggs, but also can solve the problem of autumn reproduction in fine seed farms. It is still used in production.