Studies On Creating Silkworm (Bombyx Mori.L) Asexual Reproductive Lines And Its Hereditary Feature

Sexual reproduction of animals was wildIy distributed in nature and also was the main reproductiveway As an important economic insect, the reproductive way of silkworm was similar to other animals.Sexual reproduction provided variation for the siIkworm breeding. By cross breeding, many fine si1kwormraces had been bred out, which promoted the race regeneration, cocoon and silk quality improvement.Along the utilization of limited genetic resources repeatedly, making progress in siIkworm breeding wouIdbecome more and more difficuIt, the economic characters of commercial races would also become verynearly Besides, as the silkworm breeding deeply and different productive needs, sex controI would becomevery important. Compared with the femaIe silkworm, the male has higher raw silk rate, silk quality littleamount of ingested leaves and cost rearing. So popularizing the male silkworm races in rural, the economicbenefits wouId be increased l0 percent. But in silkworm egg station, more female silkworms should bereared to increase the breeding benefits. So reaIizing maIe silkworms reared in rura1 instead of commercialraces and more female silkworms reared in egg station had become an important study Many researchersfrom China, Japanese and Russia had been carrying out studying on silkworm sex control. In l996,Sericultural Research Institute, Zhejiang Academy of Agricultural Sciences introduced the balanced Iethallines from Russia and cariied out trans-breeding. Up to now several fine male silkworm races had beenbred out and were successful to be used in rural. But the cost of the male silkworm hybrids production wasvery high because of its productive mechanism, which had limited its populariZaion. If breeding out femaleline, which had high hatching rate and fine economic characters, it could be crossed with the balancedletha1 male silkworm to produce the hybrids and decrease the productive cost greatly. So we catried outstudies on creating siIkworm asexual reproductive lines and its hereditary featUre. The results of this studyshould improve the technique of silkworm asexual reproduction and enrich the genetic resources in China.On the other hand, the results of this study should also provide a new breeding method and new studyingway on gene expression, character formation and hybrid vigor mechanism.In this study, nine aspects had been carried out, which included the condition optimization of inducingsilkworm asexuaI reproduction; the effective technique of obtaining unfertilized eggs from virginal moth;the investigation of asexual reproductive genetic resources on bivoltine siIkworm races; the creating ofbivoItine female asexuaI reproductive Iines; the genetic effect analysis of silkworm asexual reproductivecharacter; the eggs protein study on different fema1e lines; growing and developing comparison betweenasexual reproductive line and its sexuaI parent; RAPD. study on aSexual reproductive character;. thel45utiliZaion of asexual reproductive lines. The main results are as follow:1 .The asexuaI reproductive eggs and 1arvae were obtained when 50 commercial and bivoltine races inducedby hot water. But the rate of asexual developed eggs varied markedIy among these races, the range was1 1 .99~88.88 percent. About one-third races, their rates of asexual developed eggs at'tained 70~80 percent.The rate of asexual developed eggs about hybrid was higher than its parent. From above, fine geneticresources of asexual reproduction had been found from commercial and bivoltine genetic races.2.During hot water treatment to bivoltine races, the temperature effect on rate of asexual developed eggs. was more significant than that of soaking time. When the unfertilized eggs were treated with 40~50'Cwatet, many asexual developed eggs could be obtained, but if the temperatUre was low 40'C or above 50C,the rate of asexua1 developed eggs would decrease greatly So the optimum treating temperature tobivoltine races was from 44~46...