Study On The Pigment Of Natural Colored Cocoon Of Silkworm, Bombyx Mori

Silkworm Bombyx mori(B.mori) colored cocoon varieties are special resources,whose cocoon color controlled by genes.Silkworm colored cocoon varieties can mainly be classified into two families:yellow-red cocoon series that include yellow,pink, golden-yellow and flesh cocoons,and green cocoon series.Pigments in them are absorbed from its host plant,mulberry tree(Morus alba) and from the diet then subsequently modified within the silkworm.At home and abroad,there are many scientific studies on silkworm colored cocoon races,which have come to many valuable theories and practical applied research results.In recent years,Silkworm Inheritance and Breeding Lab of Soochow University have improved practical silkworm natural colored cocoon varieties. However,for the number of the genes that control cocoon color is about 20,the types and formation mechanisms of pigment are unclear.In order to investigate the differences of pigments,metabolism and inheritance mechanism between different cocoon colours of silkworm colored cocoon varieties,we used different silkworm races and their filial generation as material to analysis carotenoids and flavonoids content in fresh and dried cocoons,inside and outside cocoon and different tissues of silkworm.Furthermore,we used the UV-VIS and FTIR spectrum and HPLC techniques to analyse pigment content and types between different materials.1.Analysis results of cocoons color and the pigment content in cocoon shell of diff(?)rent cocoon color varieties and their reciprocal cross and backcross generations showed that parts filial generations show hybrid vigor,green cocoons are controlled by major genes,genes control two kinds of pigments are independent of each other, interaction happens between cocoon color genes locate on euchromosome so that types and contents of pigments have charged in the filial generations.W chromosome of Y_{深虎} show very powerful regulation on cocoon color sex-limited inheritance,whose contribution on yellow cocoon do not influenced by green-cocoon genes from Daizo.Spectrum and HPLC analysis showed that interaction between cocoon color genes on euchromosome may make part of filial generations inherit the material of 200～4 000 nm selectively from their parents, and generate new material at the same time.It appeared that parents and filial generations almost have the same color,but the contents and types of pigments are different between them.2.Both the contents of carotenoids and flavonoids are low in white cocoon.In green cocoon series,the cocoon colour depth is positive correlation with the contents of flavonoids.The content of flavonoids is significantly higher than that of carotenoids in yellow-red cocoon series,while their cocoons show yellow,pink,golden-yellow and flesh. Although inside cocoon seems white,the contents of pigments are higher than that of white cocoon.Therefore,we supposed that carotenoids and flavonoids play crucial roles in cocoon pigmentation to yellow-red and green cocoon series respectively,but flavonoids are less important than carotenoids in yellow-red cocoon series.There are also lots of flavonoids in cocoon shell which are not visible at natural light,and have other physiological activities.3.The capabilities of uptaking of carotenoids from the midgut epithelium into the hemolymph or modifying pigment shows better in filial generations of G_1白 than their parents,but that of uptaking carotenoids from the hemolymph to the silk gland and combining pigment of fibroin and sericine are opposite.It is supposed that the contribution major dominant green-cocoon genes and recessive green-cocoon genes make are different on combining and uptaking pigment.4.The analysis of pigment content and spectrum in green,yellow and red cocoon shells showed that there were not notably differences of pigment contents and types in yellow and red cocoons between fresh and dried cocoon shells,but flavonoids content of green cocoons is reduce.These datas are useful for colorful cocoon industrialization.The color of cocoon shell inside is different with outside cocoon,and their pigments contents are different too.But material absorbance of 200～4 000 nm between inside and outside are almost the same.5.After analysis by determination,spectrum and HPLC,difference of cocoon color between Y_{深虎},which is sex-limited yellow cocoon race,depends on whether having the material of absorbance at 404 nm,425 nm,446 nm and 474 nm or not.HPLC analysis showed the pigment types are significantly different between C₁₀₈ and N₄,a yellow cocoon race. 6.Spectrum analysis showed that in addition toβ-carotene,there is at least one other carotenoids in part of cocoon shell.One or two kind hydroxy position on C-5,C-7 of quercetin and kaempferol may present in some cocoon shells and there are other unknown flavonoids.The FTIR spectrum showed the presence of carbonyl,NH and OH group at 1 650 nm and 3 100 nm to 3 700 nm,respectively.It is supposed that pigments contain these groups.Further research should be done to determine the existence of these groups.7.By using acetonitrile,dichloromethane and methanol(85:10:5,v/v) as the mobile phase of HPLC,we found that the absorption peaks appeared earlier,which indicate that these compounds might have aglycone.