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Abstract Taking introduced trimolter varieties 853 Bai and 543B with stable moltinism as male parents, and tetramolter varieties 932, 7532, Furong, Xianghui with excellent comprehensive economic characters in current production as female parents, the trimolter varieties San, Long, Hui and Yuan with excellent comprehensive economic characters and stable moltinism were bred using cross breeding and systematic breeding methods, and healthy trimolter four-way cross combination "San * Long x Hui * Yuan" (Yuecanxixian No. 1) was assembled. Provincial laboratory and rural production and identification results showed that the variety had strong vitality, stable moltinism (trimolt rate over 98%) and short duration; laboratory identification results were as follows; cocoon filament size 1.853 dtex, cocoon filament length 1 146 m, reelability percentage 73.04%, neatness 95.38 points, strength 4.63 mN/dtex, elongation rate 23.3%, cohesion 116 times. The variety was approved by Guangdong Crop Variety Approval Committee in December 2010, which can be used as raw cocoon for reeling high-grade fine size raw silk.
Key words Yuecanxixian No. 1; Trimolter; Four-way cross combination; Healthy; Fine size
Compared to tetramolter, trimolter has healthy body, short developmental duration, high leal-silk conversion rale, fine size of cocoon filament and high silk quality, which is suitable for reeling high-grade fine size raw silk. Therefore, production technology of trimolter varieties and their raw cocoon with special purpose has been one oí the important topics in sericultural scientific research. To achieve diversification and superiority of silk products and enhance competitiveness and adaptability ol our silk in international market, Lu Xuefang et, al. ['! had successfully developed artificially-induced trimolter ultra-fine size silk technology using SM - 1 and "Jinlu" early in 1985. He Simei et, al. at The Sericultural Research Institute, Chinese Academy of Agricultural Sciences successfully bred two-way crossbred fine size trimolter varieties 853 Bai and 543 B from 1996 to 2002 2-41.
Guangdong Province is located in tropical and subtropical regions, with more hot and humid climate. Due to overlapping silkworm rearing for a few7 times and multiple harvesting of mulberry throughout the year, silkworm varieties for popularization and application must have strong resistance to stress, diseases and crude feed. The research on fine size silkworm variety started relatively late in Guangdong, and there are healthy problems if varieties suitable for silkworm areas...