In the first three years after returning to China, he introduced Japanese silkworm eggs to cross with local yellow cocoon varieties, and cultivated new varieties such as Xue 14 and Xue 16 (later renamed as10/4,10/6), which are in China. Its cocoon and raw silk samples were sent to the Paris World Expo for exhibition in 1933, which was well received by the international silkworm industry.
Guangdong is located in the subtropical zone, with an annual average temperature of 2 1.6℃, a monthly average temperature of 3℃(65438+ 10 month) and a maximum temperature of 28.3℃ (July and August). Mulberry has the advantages of early germination, fast growth, late defoliation, long growth period and high yield. If pruning and fertilizer and water management are proper, sericulture with leaves can reach seven or eight times a year. However, due to the rainy weather and high temperature, it also brings unfavorable factors to sericulture. In the history of South China, the original species is a multi-chemical silkworm called "Yue Lun", which can be raised all year round, but the cocoon is small and the silk yield is low. In Guangdong, the first silkworm can be bred into a bisexual silkworm variety, called "Da Zao". Its cocoon is bigger than Yue Lun's, and its silk is also heavy. Farmers are willing to raise jujube in the first crop, but if they continue to raise jujube in the second and third crops, the yield will decrease because they are not suitable for the high temperature and high humidity climate. In order to improve silkworm eggs, Yang Bangjie selected more than 10 varieties by pure line separation, such as Dazao line No.56, Tuda line and Yue Lun line Zhong Kai 258, 560, 369 and 4000. Cooperate with Guangxi to improve 258, improve its vitality, and achieve the advantages of uniform cocoon shape, less cocoon cotton, good relaxation, less water condensation and high silk yield. This variety was popularized in Guangdong and Guangxi for more than 20 years until the early 1950s. In addition, a hybrid fixed species 1053A2 with good vitality and silk quality was bred through hybridization, which has been popularized in Xijiang River basin of Guangdong Province for many years.
1930 The book "Improvement of Silkworm Eggs in Guangdong-Two or Three Achievements Made by Applying Genetic Laws" summarizes his work and achievements in this period.
First, the improvement of native (original) silkworm eggs in Guangdong-the results obtained by pure line separation method. That is, after the pure lines of local varieties are separated, large-sized silkworms, large-sized silkworms, white cocoon-shaped silkworms, white cocoon-shaped silkworms, yellow cocoon-shaped silkworms and black cocoon-shaped silkworms are obtained. After selecting pure species, its cocoon shape, crepe, cocoon color, cocoon shape size and silkworm body markings are consistent, and the number of cocoon layers is greatly improved compared with the original native species.
2. The results of the first generation hybrid obtained from the above six Guangdong local varieties show that the number of cocoon layers has been greatly improved. Judging from the number of cocoons needed for reeling 1 kg of raw silk, Rongqi and Guanshan have 8 142 cocoons and 9,374 cocoons respectively, while Zhong Kai A&M has only 3,968-5,200 cocoons, of which about 4,330 cocoons are the most.
3. The weight of cocoon layer of hybrid obtained by mating improved local varieties with improved exotic varieties (I and II) increased obviously. At the same time, these hybrids have strong resistance. Even if it is raised according to the old method, it can be raised at least three times a year, that is, spring silkworm 1 time and autumn silkworm twice. Its cocoon harvest is also the most in these three times, and the quality of silk is better than that of unmodified local varieties.
Yang Bangjie was in a leading position in sericulture in China at that time by using pure line separation and hybridization based on genetic theory. After the publication of its application results, silkworm schools all over the country have inquired from Zhong Kai A&M School for reference. Guangdong is used to soaking silkworm eggs in soup (bath eggs) to promote hatching, and it can also kill those weak and sick silkworm eggs, so it is also a method to prevent silkworm diseases. It has always been based on the experience of the soaking master to master the temperature and soaking time of the soup. If the soup is too hot or soaked for too long, the silkworm eggs will die; If the soup is not hot enough or the soaking time is too short, silkworm eggs will not hatch or hatch unevenly. 1933, Yang Bangjie published the experiment of soaking silkworm eggs in warm water, and 1959 published the experiment of soaking white cocoons in warm water (forecast), which made the soup soaking method scientific and quickly applied to silkworm egg production. At that time, Guangdong produced millions of seeds every year, and the problem of hatching uniformity was well solved, which played an important role in developing sericulture production.
1933- 1936 published "Guangdong Special Silkworm Line 23", "Morphological and Genetic Studies of Special Silkworm Species in Guangdong" and "Study on the Relationship between Special Silkworm Line 23 and Black Silkworm 18, 48".
1933 published the article "The Relationship between Silkworm Variety, Sex, Weight and Maturation Speed", which discussed the laws of female and male silkworm weight, cocoon shell weight and maturity of local varieties, exotic varieties and their hybrids from the genetic point of view, and had important guiding significance for the improvement of local varieties at that time and the promotion of first-generation hybrids, ternary hybrids and quaternary hybrids. This paper also puts forward an important hypothesis that there are at least two Q factors inferred from genetic form and genetic quality. However, due to the lack of in-depth research, it has not been confirmed so far.
Yang Bangjie also published many papers on the anatomy and physiology of silkworms in the Research Report of Zhong Kai A&M School, which provided a meaningful reference for the physiological anatomy of silkworms.