Effects of cassava leaves'nutrient components on eri-silkworm breeding

【Objective】 To reveal the effects of feeding different cassava leaves to eri-silkworms on their growth，development and morphological structure of their silk fiber for screening cassava varieties suitable for feeding eri-silkworms，so as to provide a reference for cassava feeding.【Method】 Cassava leaves of 4 genotypes，South China 9（SC9），Manibot esculenta cv.Variegata，petiole-free cassava and purple-leaf cassava were used as materials，and castor leaves were taken as control（CK）.Nutritional indexes，soluble sugar，crude protein ，dry matter rate，hydrocyanic acid，total carotenoid，anthocyanin and total flavonoids were determined.Body length，body weight pupa weight and total cocoon weight of fifth instar larvae fed on different cassava leaves were measured and morphological structure of silk was observed by scanning electron microscope.【Result】Contents of total carotenoid，anthocyanin，hydrocyanic acid and dry matter rate in the 4 varieties of cassava leaves were higher than that of castor leaves.Contents of anthocyanin，total flavonoids，dry matter and hydrocyanic acid content in the leaves of purple-leaf cassava were significantly higher than those of 4 other materials（P<0.05，the same below）.Correlation analysis showed that significant correlations existed between carotene and chlorophyll，between carotene and total carotenoids，between total flavonoids and anthocyanin，between soluble sugar and hydrocyanic acid（P<0.01）.Principal component analysis showed that the cumulative contribution rate of the first two principal components was 87.632%；the first principal component was determined by dry matter rate，chlorophyll and soluble sugar；and the second principal component was determined by lutein and crude protein.Cassava leaves of different genotypes had significant effects on the growth and development of eri-silkworm，and they can significantly increase body length of eri-silkworms.The whole cocoon weight of eri-silkworms fed on SC9 and purple-leaf cassava leaves was bigger than that of eri-silkworms fed on castor leaves；the pupa weight and cocooning rate of eri-silkworms fed on purple-leaf cassava leaves were the highest.Silk width of eri-silkworms fed on cassava leaves of 4 genotypes was increased，among which eri-silkworms fed on purple-leaf cassava leaves had the highest silk width and comparatively complete silk surface.【Conclusion】 Difference of nutrient components between castor leaves and cassava leaves of 4 varieties was significant，and cassava leaves feeding can significantly promote the growth of eri-silkworm.Pupa weight of eri-silkworms fed on purple-leaf cassava is the heaviest，with high cocooning rate and complete silk surface.Body weight，body length and whole cocoon weight of eri-silkworms fed on SC9 cassava leaves are the highest，their silk had more impurities.Therefore，leaves of purple-leaf cassava，suitable for feeding eri-silkworms，has great potential to be developed as feed.