Analysis of the boil-off loss in parental and different crosses of bivoltine silkworm, Bombyx mori L.
Abstract
The process of removal of gummy proteinous material (sericin) from the silk is commonly referred to as degumming loss or boil-off loss and is considered as one of the important economic traits during the course of silkworm breeding. Loss of sericin varies with breeds / hybrids, it is essential to analyze the ratio with reference to cocoon shell, as it is the basic raw material for the raw silk to estimate silk productivity of a breed / hybrid. In the present study, boil-off loss ratio in the cocoon shells of twelve bivoltine parental breeds (6 oval and 6 dumb-bell) and newly developed 21 each of different crosses (single, three-way and four-way crosses) of bivoltine hybrids along with control hybrids CSR2xCSR4 and [(CSR2xCSR27)x(CSR6xCSR26)] was analyzed to identify promising hybrids with desired boil-off loss ratio. Heterosis for boil-off loss ratio, shell ratio and raw silk percentage both in parents and all the hybrid crosses was also estimated and discussed. Among the parents, the least value of 21.50% was registered in JPN8 (oval), 22.01 % (S9) amongst dumb-bells and in the hybrids, single-cross hybrid CSR27xCSR26 (23.25%), three-way cross hybrid, (JPN8xCSR17)xCSR26 (22.51%) and four-way cross hybrid [(JPN8xCSR17)x(D13xCSR26)] (22.33%) was recorded. It was observed that some of the different crosses of the hybrids have also recorded desirable heterosis values for boil-off loss trait.
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