VOL. 4, NO. 4, JULY 2009 ISSN 1990-6145 ARPN Journal of Agricultural and Biological Science © 2006-2009 Asian Research Publishing Network (ARPN). All rights reserved. www.arpnjournals.com SYNTHESIS OF PROMISING BIVOLTINE BREED UP 1 OF THE SILKWORM (Bombyx mori L.) FOR UTTAR PRADESH S. K. Gangwar 1 , K. Jaiswal 1 , P. Dwivedi 2 and V. Gupta 2 1 Department of Applied Animal Sciences, Babasaheb Bhimrao Ambedkar University, Lucknow, India 2 Department of Zoology, Lucknow University, Lucknow, India E-Mail: gangwar_shishir@yahoo.com ABSTRACT In silkworm Bombyx mori L. for high productivity and narrow range of adaptability in fluctuating environmental condition depends upon genetic stability of the breed. In tropical climate especially for Uttar Pradesh climatic conditions, it is necessary to synthesize silkworm breed with suitable genetic constitution. A breeding experiment was initiated to isolate robust bivoltine line of silkworm (Bombyx mori L.) by utilizing bivoltine breed CSR 2 , NB 4 D 2 and white multivoltine C. nichi by inbreeding the hybrids of the above pure breeds, recurrent back crossing followed by selection at each and every generation, a hardy bivoltine breed with white oval cocoon was isolated. This bivoltine line herein referred as UP 1 (Uttar Pradesh-1) has been bred through over 25 generations and revealed significant improvement in regard to viability and productivity compared to the control breed. Keywords: silkworm, Bombyx, bivoltine breeding, viability, productivity. INTRODUCTION Hybridization coupled with selection as an important tool has been exploited by many breeders in the improvement of breed for their maximum economic grains in silkworm, Bombyx mori L. Breeders have extensively studied the silkworm breeds for recognition of their economic importance for the desirable traits through inbreeding. However continuous inbreeding results in the accumulation of many deleterious genes leading to inbreeding depression, thereby resulting in the deterioration of some commercial characters. However, the overall combination of beneficial traits could be achieved in a reasonable way by employing inbreeding techniques coupled with selection, as the silkworm breeder has at his disposal a diversified array of gene combination to manipulate and isolate new silkworm breeds having desirable qualities for commercial exploitation (Raju and Krishnamurty, 1993). The improvement of indigenous breed could be achieved through hybridizations utilizing exotic breeds (Koalov, 1970). Harada (1956) viewed that new silkworm breed has been evolved through hybridization followed by selection. India has many indigenous breeds but, it suffers for new silkworm breeds in competing with other Sericulturally advanced countries like china and Japan have commendable progress has been achieved in evolving robust and productive breed through hybridization (Yokoyama, 1956). Until the 1970s, Indian sericulture was mostly multivoltine-oriented and bivoltine rearing was restricted only for maintenance and multiplication of foreign breeds imported from other countries (Raju, 1990). During this period, Indian breeders evolved few bivoltine breeds like Kalimpong- A, Nan Nung 6D and new bivoltine series (NB), including NB 7 , NB 18 and NB 4 D 2 breed (Narasimhanna et al., 1976; D. Gangopadhyay, 2003 and D. Raghavendra Rao, 2003). However, these breeds were mostly used for producing commercial crossbreed’s cocoons with that of pure multivoltine pure Mysore female, but are not fully satisfied for the production of pure bivoltine silk in view of their poor adaptability to the fluctuating agro-climatic conditions of the tropics specially for Uttar Pradesh climatic conditions. Hence there is a necessity to formulate a need bases breeding programme to evolve robust bivoltine hybrid breeds to improve the productivity and viability traits. MATERIALS AND METHODS The present studies initiated during the year 2003 involve two bivoltine CSR 2 and NB 4 D 2 and a white multivoltine breed C. nichi. The breeding plan of the present experiment represents the production of progeny from a cross between NB 4 D 2 x CSR 2 . The F1 was inbred and F2 hybrid female emerged were out crossed to C. nichi to obtain the F3 progeny, which was further inbred for analyzing cocoon shape till the 5 th generation. The F5 females emerged from the white oval cocoons were backcrossed to NB 4 D 2 males, during the course of inbreeding from F6 onwards, careful selection was made to isolate oval white cocoon with good productivity and viability. The following selection parameters were applied at different stages of development to select the parent at every generation. Egg Stage During the course of breeding programme robust and fertilized female moth were placed on egg sheet for oviposition to replace around 50 layings at every generation. A definite period of 3 hours mating time of moth was followed at every generations as suggested by petkov et al., 1979 only the disease free layings (Dfls) exhibiting complete hibernation features were selected at every generation, in order to prevent the eggs from entering diapauses they were acid treated following the method of Yokoyama (1963) and incubated at 25 ± 1°C temperature and 60% to 70% relative humidity on the ninth day of incubation composite laying comprising approximately 1000 eggs were prepared in 3 replicates. 8