SILKWORM BREEDING AND GENETICS

 

Scientists:

1. Dr. N. Suresh Kumar, Scientist-D

2. Dr. A.K Verma, Scientist-C

 

 

Mandate:

·        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.

 

ACHIEVEMENTS:      

Hybrids Authorized

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.

 

Objective: 

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)

 

Objective:

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]

 

Objective:

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

 

PROGRAMMES:

 

1) Large scale testing of new silkworm hybrids (Dec’07-March 2010)

 

Objectives:

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)

 

Objectives:

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.

 

CONCLUDED PROJECTS:

 

1.                AIB001: Improvement of silkworm (1990-2000)

 

 Findings:

 

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)

 Findings:

 

§    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)

 

Findings

 

§        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)

 

 Findings:

§        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)

 

Findings

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


 

       Findings:

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.

 

 

CONCLUDED PROGRAMMES:

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). 

        

Findings:

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) 

Findings

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.