UTTAR PRADESH JOURNAL OF ZOOLOGY

The som, Persea bombycina Kost major food plant of muga silkworm shows various morphotypes within the species. Eight (PB 001, PB 002, PB 003, PB 004, PB 005, PB 006, PB 007, PB 008) morphotypes of som food plant maintained at Regional Muga Research Station, Boko were evaluated for rearing performance of muga silkworm, Antheraea assamensis Helfer during Kotia commercial (October - November 2012) and Chotua seed crop (February - March 2013) rearing seasons. Among the eight morphotypes higher moisture percent was recorded in the tender leaves of PB 003 (69.70%) followed by PB 006 (67.50%) and least in PB 002 (61.02%) during Kotia commercial crop rearing. The mature larva weight (11.30 g), effective rate of rearing (59.66%) and cocoon yield (61 cocoons/ g) recorded were highest in muga silkworm fed on PB 003 morphotype of som followed by batch of larvae fed on PB 006 morphotype and least in larvae fed on PB 002. Data of important cocoon characters like single cocoon weight, single shell weight and silk ratio of muga silkworm fed on different morphotypes were different. The single cocoon weight was ranged from 5.31g to 5.45 g, Shell weight 0.42 to 0.46g and Silk Ratio percent 8.02 to 8.66%. The rearing parameters i.e. mature larva weight, Effective rate of rearing and cocoon yield per/dfl and cocoon parameters i.e. single cocoon weight, single shell weight and silk ratio were observed higher during Kotia commercial crop than that of Chatua seed crop of muga silkworm fed on different morphotypes of Som. The score of evaluation index of rearing and cocoon parameters indicated that PB 003 was more suitable for muga silkworm rearing as received highest score of 411.21 which was followed by PB 006 having score 408.24 during Kotia commercial crop. Similar trend was observed during Chotua seed crop.