The directional transfer of the plain silkworm variety Jingsong into a sex-limited multilunar silkworm variety
To identify the gender of the larvae in the early developmental stages of the current plain silkworm variety Jingsong,for the purpose of achieving sex-separation in rearing and differential utilization,the female of the sex-lim-ited normal marking silkworm race Yuncan 7A was crossed with the male of multilunar silkworm race Cb.Then,these hybrids were respectively crossed with the commercial plain silkworm race Jingsong A and Jingsong B.The progeny were backcrossed to the commercial plain silkworm race for several times and then selfed,combined with categorized selection for individual and batches.This process introduced sex-limited normal marking gene of Yuncan 7A and multilunar gene of Cb into the commercial plain silkworm race Jingsong,directed breeding resulted in Jing A Chaxian and Jing B Chaxian.The results showed that during the breeding process,the larval spot differentiation turned into easy-to-distinguish multilunar and non-multilunar types by color and shape.The cultivated Jing A Chax-ian and Jing B Chaxian larvae displayed clearly different color differentiation of multilunar at the beginning of the 3rd instar,allowing for accurate gender identification.The economic traits of Jing A Chaxian and Jing B Chaxian,such as the larva-pupa rate of 96.91％and 96.40％,the whole cocoon weight of 1.62 g and 1.56 g,the cocoon shell ra-tio of 23.78％and 23.26％,were slightly different from their recurrent parents,exhibiting characteristics of good health,easy rearing,and high-quality cocoons.This study laid a foundation for creating breeding materials with spe-cial traits,the differential utilization of male and female silkworms,and reducing the breeding costs of male silk-worms.
silkworm racesex-limited normal markingplainsex-limited multilunardirectional transfer
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