SILKWORM BREEDING AND GENETICS
1. Dr. N. Suresh Kumar, Scientist-D
2. Dr. A.K Verma, Scientist-C
· Development of improved multivoltine and bivoltine breeds suitable for the Eastern andNortheastern zone.
· Identification of season specific hybrids (Multi x Multi, Multi x Bi, Bi x Bi) for Eastern andNortheastern zone.
· To act as a coordinating centre for conducting hybrid trials under Race Authorization Programme.
· Maintenance of Bivoltine & Multivoltine silkworm breeds and Breeder’ stocks Supply of P3 and P2 dfls to Govt. seed organizations.
v N x (NB18 x P5) – Multi x bi hybrid with the yield potential of 50–60 kg and Shell (%) of 18–19% is authorized for Nov.–Dec. (Agrahayani) crop.
v NB18 x P5 – Bi x Bi hybrid with the yield potential of 50-60 kg/ 100 Dfls and 20.5-21.5 % shell has been authorized for rearing during Feb-Mar (Chaitra) crop.
v N x YB – Another Multi x Bi hybrid has been authorized with the yield potential of 40-50 kg/ 100 dfls with 17.6% shell for Nov-Dec. (Agrahayani); Feb.- Mar., (Chaitra); and Mar.- Apr. (Baishakhi).
v N x M12 (W) – Multi x Multi hybrid is recommended recently and at presently it is in the field with the yield potential of 35-40 kg / 100 dfls with 15.0-15.6% shell for unfavourable seasons [Jun.- Jul. (Shravani); August (Bhaduri); September (Aswina)].
Hybrids under Large scale trial
q Multi x Bi hybrid (Three way cross) M6DP(C) x (SK6 x SK7) with yield potential of 55 kg/100 dfls and 17.5% shell and multi x Multi hybrid M12(W) x M6M81 with the yield potential of 43.0 kg/ 100 dfls were identified for favourable (Oct-Apr.) and un-favourable (March–September) seasons respectively through Provincial Race Authorization Programme after testing at 10 different centres (DOS, WB & CSB) in West Bengal.Presently these hybrids are under large scale trial in collaboration with DOT (Seri), W.B and NSSO (ZSSO, Malda).
q High productive MultixMulti congenic hybrid MC1 x MC4 with yield potential of 36-45 kg/100 dfls and 16-16.7% shell for unfavourable and Multix Bi congenic hybrid MC4 x BC4 with yield potential of 55-65 kg/100 dfls and 18-18.6% shell for favourable commercial crop seasons have been identified and under authorization process.
ON GOING PROJECTS:
1. AIB3393: Development of commercial hybrids of silkworm, Bombyx mori L. by identification of bivoltine parents through screening in different seasons ofWest Bengal.
v Screening & identification of suitable bivoltine breeds & foundation crosses in both favourable & unfavourable seed crop seasons (Feb.–Mar., Sept.–Oct., & Dec.–Jan.).
v Determination of potentiality of breeds in seed crop seasons.
2. Development of Silkworm (Bombyx mori L) breeds from a gene pool with higher genetic Plasticity. (May ‘08–April 2013)
v Development of silkworm breeds from converged gene pool having genetic plasticity in tolerance and in high cocoon shell weight of target breeds.
v Development of congenic breed from the selected lines for a breed ofmultivoltine with high cocoon shell weight and bivoltine with tolerance (high survival).
v Identification of molecular / biochemical marker associated with the target traits.
3. Development of polyhybrids of Silkworm Bombyx mori L for Eastern region of India by identification of Season specific Foundation Crosses with high crop stability [Septemberl’08-December’12]
v Identification of foundation crosses with greater crop stability for unfavourable seed crop seasons
v Development of productive multivoltine & multi-bi double hybrid/s with greater egg productivity for succeeding commercial crop seasons for eastern region
1) Large scale testing of new silkworm hybrids (Dec’07-March 2010)
v Stabilization of bivoltine seed crop in West Bengal.
v Popularization of new productive silkworm hybrids at farmers’ level thereby increasing quality and quality of silk.
2) Validation cum Multilocational trial of new silkworm breed/ hybrids at farm level (April’08-March 2010)
v To test the potentiality of the newly developed bivoltine silkworm breeds and identified season specific silkworm hybrids at farm level
Maintenance of Germplasm:
A total of 24 multivoltine and 24 bivoltine silkworm genetic stocks are maintained.
1. AIB001: Improvement of silkworm (1990-2000)
v A total of 15 multivoltine breeds have been evolved. Of which M12 (W), M6M81, and M6DP(C) showed 18.6 to 29.2 % more in respective of yield and 13.5 to 21 % more in respective of shell (%) in compare to Nistari.
v Three hardy bivoltine viz., BHR-1, BHR-2 and BHR-3 developed through inducting thermal stress. They showed 21.6 to 30.9% more survival during Seed crop (September) of Agrahayani in comparison to check P5.
v Four hardy bivoltine viz., YB, BG (W), MJI and MC3 were developed through incorporating multivoltine genes. During unfavourable seasons, YB showed 60.52% survival with shell (%) of 17.0, BG(W) showed 40.15% survival with shell (%) of 16.39, whereas MJ1 and MC3 showed 61.2 % , 51.5% survival with shell % of 17.52 and 18.0 respectively.
v Out of 12 bivoltine evolved, SK3, SK4, O3, O4, D6 (P) showed higher shell (%) (22.0, 19.85, 22.45, 21.60, 22.0% respectively) and filament length (935, 850, 1175, 1012, 1207 respectively).
v Identified two multi x multi hybrids viz., M6M81 x M12 (W) and M6DP(C) x M12 (W) with the yield potential of 36-39 kg / 100 layings for rearing during adverse climatic conditions (June-September).
v Identified two multi x Bi hybrids for favourable seasons viz., N x YB and M12 (W) x KPG-B with the yield potential of 50 kg and 60 kg / 100 layingsrespectively.
v Identified two multi x Bi hybrids (three way cross) for Agrahayani crop (Nov) viz., M12 (W) X (SK3 x SK4) & M6DP (C) x (SK6 x SK7) with the yield potential of 51 kg and 65 kg / 100 layings respectively.
2.AIG002: Utilization of syngenic lines for improvement of shell weight and survival in silkworm Bombyx mori L. (Dec. 1998 – Dec. 2004)
§ Isozyme based seven multivoltine and three bivoltine syngenic lines were developed.
§ Four high cocoon shell weight multivoltine congenic breeds (M.Con.1, MCon.2, M Con.3 & MCon.4) were developed by using bivoltine Syngenic breed JPN and D6p.Two numbers of bivoltine congenic breeds (BCon1; BCon 4) with high survival were developed by using multivoltine syn. line as a donor for survival.
§ Identified two multi x multi hybrids viz.,N x MCon 4, MCon1 x MCon 4 ; Two multi x bi viz., MCon1 x BCon4 , MCon4 x BCon4 for unfavourable and favourable seasons respectively. One Bi x Bi hybrid namely BCon1 x BCon4 was developed for favourable seasons.
§ Identified two apparent native proteins i.e., 224 & 182 kDa are the esterase isozymepossessor and associated with high survival & high cocoon shell weight.
3. CSIR Scheme: Introgression of higher shell weight, higher survival character(s)/ gene(s) through the development of multivoltine & bivoltine congenic breeds and identification of bio-chemical markers in silkworm Bombyx mori L. (April 2002 – March 2005)
§ Four enzymes (Amylase-a, b, Est, Acph, Mdh) were considered to develop Nistaribased syngenic lines.
§ Developed two Nistari based high cocoon shell weight congenic breeds and two high survival bivoltine congenic breeds (one flesh color) were developed.
§ Existence of the two biochemical markers ( 224 and 182 kDa) associated with high survival and high cocoon shell weight were confirmed
4. AIB3237: Utilization of polyvoltine breeds for improvement of survival in bivoltine silkwormB. mori L. (March 2002 – February 2007)
§ Two promising bivoltine breeds viz., D6(P) N & SK4C were developed. D6 (P) N and SK4C showed 68.0 & 54.5% survival respectively against 11.5% in control (NB4D2) during adverse seed crop season (Sep-Oct). In favourable seed crop season (Feb-Mar), D6 (P) N and SK4C showed 90.13 & 85.0% survival respectively against 74.0% in control, NB4D2.
§ Identified one bivoltine foundation cross [D6(P)N x SK4C] for adverse seed crop season (Sep-Oct) ( 85.56 % pupation against 48.75% pupation in the control, NB18 x P5)
§ Three multi x bi hybrids viz., M6DP (C) x D6(P)N , M6DP ( C) x SK4C and M6DP (C) x [D6 (P) N x SK4C] were developed with yield potential of 9.5 to 15.9 kg / 10000 Larv,9.0 to 15.0 kg kg / 10000 Larv and 10 to 14.38 kg / 10000 Larvae respectively and the same were recommended autumn (Nov-Dec), spring (Feb-Mar) and early summer (Mar-Apr) seasons. Yield potential of N x NB4D2 (Control) was 7.0-13.5 kg / 10000 Larva.
· One bi x bi hybrid D6 (P) N x SK4C recommended for autumn (Nov-Dec), and spring (Feb-Mar) seasons.
· Est-3(a-esterase) with Rm value of 0.247 can be used as an indicator for introgressionof multivoltine genes/characters for increase of survival in bivoltine. This band may have role in increase of survival in bivoltine lines.
5. AIB3291: Development of viable sex-limited bivoltine & multivoltine breeds of B. mori L.(April 2003 – March 2008)
Ø Five sex-limited Bivoltine Breeds have been developed as per milestone in March, 07. Among the new breeds, 3 breeds viz. SK7+P, SK7Di & NB4D2+P developed byintrogression of sex-limited marker for larval body markings (+p & Di) and 2 breeds VIZ. SK6Y & SK7Y by sex-limited marker for yellow blood gene (Y) for effective sex discrimination during larval & cocoon stage. Larval marking line SK7Di was found most promising with highest fecundity (588), pupation rate (84.44), yield/10,000 larvae (16.278 kg), SCW (1.947 g) and SSW (0.405 g).
Ø Five Sex-limited multivoltine breeds i.e., N+P, NDi, M12 (W)+P, M12 (W) Di and M12 (W) Y were developed by introgression of sex-limited markers for larval marking traits normal( +P) & Dirty(Di) and yellow blood colour gene (Y) in ruling multivoltine breedsNistari (P) and M12(W). The new sex-limited breeds are found to be statistically at par with their recurrent parents, Nistari & M12(W).
6. AIB 3349: On Farm Trials of Evolved Bivoltine and Multivoltine Congenic Breeds and Their Hybrids Performance at Farmers Level
v The performance of Congenic hybrids viz., M Con.1 x M Con.4 & N x M Con4 as Multi x Multi for unfavourable seasons and M.Con.1 x B Con.4 & M Con.4 x B Con.4 as Multi x Bi showed significant performance (5.0% level) on yield than their respective control. So, all the congenic hybrids could be exploited for commercial purpose in West Bengal.
1. Provincial Race authorization programme in West Bengal (Sep 2000-Dec 2002):
Though improved breeds and hybrids were evolved / identified, their potentiality was not tested during different crop seasons of West Bengal .In order to achieve this a total of seven hybrids (Two multi x multi and Five multi x bi) were selected and tested at 10 different centres (Three CSB farms and 7 DOS farms) for four seasons. [Chaitra (Feb-Mar), Jaista (May), Badhuri (Aug), Agrahayani (Nov).
Considering the performance of hybrids in commercial seasons and their parents in seed crop seasons, the following three hybrids were recommended for different seasons
1. M12 (W) x KPG-B (Multi x Bi) for Chaitra (Feb.- Mar) crop
2. M6DP(C) x (SK6xSK7) (Multi x Bi) for Agrahayani (Oct-Nov) crop
3. M12 (W) x M6M81 (Multi x Multi) for Shravani (Jun-Jul.), Bhaduri (August) &
Aswina (Sep) crops.
2. TAVT: Screening of high temperature and humidity tolerant silkworm hybrids developed by various institutes suitable for different crop seasons of West Bengal. (June 2002 – March 2005)
Out of 10 breeds/ hybrids were tested, N x M12 (W) found best during unfavourable seasons. CSN x YB and CSN x (SK6 x SK7) performed better during early summer (April) and summer (June-July) respectively.