蚕分子育种的研究

蚕分子育种的研究黄君霆（中国农业科学院蚕业研究所）国际蚕分子育种计划（ＩｎｔｅｒｎａｔｉｏｎａｌＳｉｋｗｏｒｍＰｒｏｊｅｃｔ）是ＲｈｏｄｅＩｓｌａｎｄ大学的Ｍ·Ｒ．Ｇｏｌｄｓｍｉｔｈ在１９９１年提出来的，也叫基因标记育种（ＧｅｎｅＴａｇｇｉｎｇＢｒｅ...

外磁场作用下蚕体物理效应与机制的研究

运用磁场及统计物理的相变相关理论,分析了家蚕在磁场作用于下物理特性的变化及其变化原因。通过实验发现,经磁场处理后蚕体生长活力有所变化,蚕体发育匀正,食桑旺盛。

Screening and Cloning of RAPD Marker of Fluoride Tolerance Gene in Silkworm,Bombyx mori

In this study,silkworm strain T6,tolerant to fluoride,and silkworm strain 733xin,highly sensitive to fluoride,were used to construct the near-isogenic lines.300 random primers were used in RAPD amplification to DNAs of these lines.A molecular marker named S207 was found linked to the fluoride tolerance gene.Examination to F 2 segregated individuals of the above lines verified that this molecular marker was reliable.Subsequently,the molecular marker was cloned into a T vector (pUCm-T) for sequencing.Comparing with sequences available in the GenBank showed that this molecular marker was novel.We plan to convert it into a SCAR marker to facilitate establishment of a molecular marker assisted breeding system.

The Construction of Heat-resistant Near Isogenic Line (NIL) of Bombyx mori and the Development of Molecular Marker Breeding Technique

[Objective] The study aimed to provide theoretical basis for development and application of molecular marker breeding technique to obtain Bombyx mori near-isogenic lines （NILs）. [Method] Thermotolerance gene was introduced into sensitive variety Ou17 by developing NILs and recurrent backcross,then through six generations of backcross,thermotolerance-assisted selection,and two generations of self-cross. [Result] Bombyx mori NILs carrying thermotolerance gene （new germplasm） were produced. Meanwhile,thermotolerance level of progenies of each backcross and molecular markers of NILs were determined,and then attempts were made to produce practical thermotolerance hybrids by using thermotolerance varieties whose thermotolerance gene is linked to SSR markers. [Conclusion] The study successfully construct thermotolerance NILs,monitor thermotolerance level and breeding results of progenies of each backcross,and determine molecular marker of NILs.

Molecular Detection of Healthiness of Bombyx mori

[Objective] The paper was to explore the regularity between heat shock protein expression and the healthiness changes of Bombyx moil materials. [Method] The representative heat shock protein gene Bmhsp24.3 was screened by bioinfor- matic analysis method, and carried out real-time PCR expression analysis. [Result] The target gene Bmhsp24.3 expressed in different B. mori materials, but the expres- sion level in different materials significantly varied. The relative expression level of the gene had different degrees of changes under different rearing conditions. With the increase of rearing temperature, the gene expression was upregulated. The ma- terials with better healthiness had remarkable increase in expression of target gene, while the materials with poorer healthiness had less increase in expression of target gene. The expression difference of target gene Bmhsp24.3 was exactly consistent with the healthiness of breeds. [Conclusion] The healthiness of materials had rela- tionship with expression of target gene Bmhsp24.3. the higher the expression of tar- get gene Bmhsp24.3 was, the better the healthiness of materials was; conversely, the lower the expression of target gene Bmhsp24.3 was, the poorer the healthiness of materials was.

Relationship between Biological Characteristics of Beauveria bassiana (Bals.) Vuill and Pathogenicity to Bombyx mori L.

[Objective] This study was to investigate the relationship between biological characteristics of Beauveria bassiana （Bals.） Vuill and pathogenicity to Bombyx rnori L, with the aim to provide scientific basis for the control of white muscardine in Bombyx mori L. [Method] The strains isolated and purified from the 6 Beauveria bassiana biocontrol agents from all over the country and the 3 white muscardine silkworms collected from Guangxi provincial silkworm rearing areas were identified by the morphological observation and molecular biology technology. The pathogenicity of B. bassaina to silkworms was determined, and the biological characteristics such as growth diameter, sporulation and the extracellular protease activity of the different B. bassiana strains were compared. [Result] The isolated 9 strains were all B. bassaina （Bals.） Vuillemin, and all strains had high pathogenicity to silkworm, but with different pathogenicities. The growth diameter, sporulation and extracellular protease activity of different B. bassiana strains were also different, and showed correlation with the patheogenicity to silkworms. [Conclusion] B. bassiana spores production amount and exocellular protease activity had significant positive correlation with their pathogenicity to silkworm.

Analysis of bulked segregants to identify molecular markers linked with cocoon weight and cocoon shell weight in the silkworm Bombyx mori L

Two silkworm strains viz, B20 A (high cocoon shell ratio) and C.Nichi (low cocoon shell ratio) were sib mated for 10 generations to determine the homozygosis. Both bulked segregant analysis(BSA) and near isogenic lines (NIL) studies were done to identify the RFLP markers closely linked to cocoon shell parameters. Three hundred and fifty two random clones were identified as the low copy number sequence and used for identification of Restriction Fragment Length Polymorphic (RFLP) marker linked to cocoon weight and cocoon shell character. In the bulk segregant analysis, DNA from the parents (B20 A, C.Nichi), F 1 and F 2 progeny of high shell ratio (HSR) and low shell ratio (LSR) were screened for hybridization with the random clones. Polymorphic banding pattern achieved through southern hybridization with different probes indicated the probable correlation of polymorphism with high and low cocoon shell character which are possible landmarks in identifying the putative marker(s) for the cocoon shell character. Out of the 100 probes tried with parents, F 1, F 2 and their bulks, 10 probes were found to be closely linked to cocoon shell characters.

Phylogeny and evolutionary history of the silkworm

The silkworm,Bombyx mori,played an important role in the old Silk Road that connected ancient Asia and Europe.However,to date,there have been few studies of the origins and domestication of this species using molecular methods.In this study,DNA sequences of mitochondrial and nuclear loci were used to infer the phylogeny and evolutionary history of the domesticated silkworm and its relatives.All of the phylogenetic analyses indicated a close relationship between the domesticated silkworm and the Chinese wild silkworm.Domestication was estimated to have occurred about 4100 years ago(ya),and the radiation of the different geographic strains of B.mori about 2000 ya.The Chinese wild silkworm and the Japanese wild silkworm split about 23600 ya.These estimates are in good agreement with the fossil evidence and historical records.In addition,we show that the domesticated silkworm experienced a population expansion around 1000 ya.The divergence times and the population dynamics of silkworms presented in this study will be useful for studies of lepidopteran phylogenetics,in the genetic analysis of domestic animals,and for understanding the spread of human civilizations.