Breeding at KSSRDI

CURRENT BREEDING APPROACH FOR THE DEVELOPMENT OF MULBERRY SILKWORM BREEDS AT KSSRDI, BANGALORE

Karnataka State Sericulture Research and Development Institute (KSSRDI) is involved in sericulture developmental activities covering all the aspects from mulberry cultivation to silk fabric since 1982. From the inception, the institute has made many attempts and succeeded in evolving several races and their hybrids suitable to different seasons and regions. Based on the socio- economic conditions of local farmers and the requirement of the silk industry, the silkworm breed strategies were formulated from time to time. With the result many cross breeds and the bivoltine single hybrids were developed, field tested in association with Department of Sericulture, Government of Karnataka and got authorized.

KSSRDI has been maintained its own working Germplasm for their utilization in breeding programmes and adding promising parental sources to its list from time to time. In KSSRDI, Silkworm breeding related activities are being executed in four different locations, namely, Thalaghattapura, Bidadi, B.R.Hills and Ooty. The silkworm breeding activities along with maintenance of working germplasm and also maintenance of basic parental races of double hybrids are being carried out at Silkworm Breeding and Genetics Section, Thalaghattapura. In race maintenance and multiplication center at Bidadi, IMH improved polyvoltine pure race maintenance and field popularization of an improved crossbreed “Bengaluru Belli” IMH x CSR2 related activities are being carried out. Besides, sixteen polyvoltine germplasm accessions and forty five bivoltine germplasm accessions are maintained at substation, B.R.Hills of Chamarajanagara district and sub station, Ooty of Nilgiri district in Tamil Nadu respectively.

Objectives of Silkworm Breeding at KSSRDI

· Development of Bivoltine hybrid combinations for the promotion and production of quality bivoltine raw silk

· Development of races as alternative to Pure Mysore in cross breed combination

· Development of races to replace male parent in cross breed

· Development of robust silkworm races suitable for region and seasons of

Karnataka

· Hill rejuvenation programme to restore the vigour in basic stocks

· Combining ability studies to identify suitable combination for field trail

· Large scale field popularization

The list of both authorized cross breeds and bivoltine hybrids developed at KSSRDI are tabulated here under.

Sl. No.

Bivoltine hybrids

Multi-bivoltine hybrids

Multivoltine hybrids

1

NP2 x KSO-1

SLKSPM x NB4D2

MH1 x C-Nichi

2

SP2 x KSO1

SLKSPM x CSR2

PM x CN2

3

NTCM x CTM

MH1 x NB4D2

PM x C110

4

NK2 x NP4

MH1 x CSR2

5

KSO1 x NP4

CSR2 x KS10

6

HND x NK2

PM x NK2

7

NK2 x HND

8

BRO2 x NP4

During the past three years, the following breeding related projects were implemented.

1. Strategies for development of productive multivoltine breeds and exploitation of Improved Cross Breeds

KSSRDI, Bengaluru has developed few promising multivoltine breeds viz., RP9, RP10, IMH etc. The breed IMH has been renamed after improvement of MH1 breed through line breeding/directional selection. Combining ability studies were conducted to identify the suitable cross breed for commercial exploitation in Karnataka. Using IMH the institute has developed an improved cross breed “Bengaluru Belli” (IMH x CSR2) which can be reared during all seasons of a year and different sericulture zones in Karnataka. This improved race gives good cocoon yield and tolerant to variability in the environmental conditions of tropics. The quality of silk produced by Bengaluru Belli race is on-par to bivoltine silk. It is anticipated that, rearing of this improved cross breed fetches more income to the sericulturists in Karnataka. It possesses good cocoon qualities like Higher ERR, good pupation rate, higher shell percentage, neatness and longer filament length. It has good dye absorbability due to its’ lesser gum content (sericin) in the silk filament. This race can be reared as an alternate to ‘Kolar Gold’. Hence, the large scale rearing of “Bengaluru Belli” has been taken–up as a flagship programme of the KSSRDI and implemented with the financial assistance by Govt. of Karnataka under the “Punaschetana/PSFA and RKVY programme”

During the year 2018-19 and 2019-20 a total of 1,65,000 DFLs of Bengaluru Belli were distributed to farmers and cocoons made over to reelers in different GCMs of Karnataka and one ARM at Haveri. It is proposed to take up large scale field trial of 1,50,000 dfls of ‘Bengaluru Belli’/year during 2020-21 with the identified farmers in different zones of Karnataka. More than fifty farmers are to be identified to rear B. Belli over a period of two years. The total requirement of layings is 1,50,000 DFLs/year. The Breeder’s stock maintenance and P₃ maintenance will be taken-up at Silkworm Crop Improvement Section of KSSR&DI. Simultaneously, the P₃ stock maintenance will be carried out at Silkworm Breeding unit and layings produced will be distributed to ASRs of Mysore Seed area. The layings will be distributed to the identified seed farmers. The RSPs who are identified under this programme will purchase P1 seed cocoons from ASRs for further processing. From these P1 cocoons the DFLs of ICB of Bengaluru Belli will be produced by identified RSPs. Crop monitoring will be taken-up by scientists of the institute who are part of the project document. The ICB DFLs of B. Belli will be supplied to identified owners of RCRCs. The third instar larvae of ‘Bengaluru Belli’ will be distributed to commercial rearers. Requisite rearing inputs and technical guidance will be given to the identified farmers. The rearing and reeling data will be collected and project report will be submitted.

2. Breeding studies to evolve new robust and productive bivoltine races

To increase the farmer income and quality of rawsilk, different bivoltine breeds suitable for tropical best are essential. Futher, Governmnet of Karnataka has contemplated to establish an additional 110 Automatic Reeling Machines(ARMS) with an objective to produce gradable quality silk. This indirectly helps to reduce the foreign exchequers to reduce import of bivoltine silk from china. Keeping this in view, breeding experiments were formulated. In our institute, Breeding studies were continued by adopting hybridization and selection method. Promising bivoltine lines, namely JKDB, KSO-2, 8KDC, J2, NK-4, KDR, and K9D(O) were continued for further improvement by directional selection.

Further, four new robust and productive bivoltine lines, namely, T1(P),T1(M), T6(P) and T6(M) were isolated. These isolated lines have showed high cocoon shell ratio of 22-23% and pupation rate of above 90%. Inbreeding and selection process was continued. Presently these lines are under different generation of selection.

In addition to the above, breeding program is being initiated for the evolution of races for favorable season. Under this programme, three KCR lines are under different generations of selection. These lines have exhibiting high cocoon shell ratio of 23% and moderate resistance suitable for favorable season.

3. Identification of suitable bivoltine double hybrid for commercial exploitation by using pure races evolved by different institutions

The promising bivoltine pure races such as BRO-2, KDR, NK-2, JKDB and K9D(MD) (KSSRDI), two races namely, APS101M, APS46TMP (APSSRDI) and CSR2, CSR27, CSR6 and CSR26 (CSRTI) were selected for the preparation of foundation crosses.

From the pure races listed above, seven oval foundation crosses and seven dumbbell foundation crosses were prepared and reared. Based on the evaluation index value, the foundation crosses spinning oval and dumbbell cocoons were ranked.

Using foundation crosses the following double hybrids were prepared. They are (BRO-2 X JKDB) X (APS46TMP X CSR-6), (BRO-2 X NK2) X (APS46TMP X CSR-6), (CSR-2 X CSR-27) X (APS46 X K9D(MD)), (BRO-2 X JKDB) X (CSR-6 X CSR-26), (BRO-2 X NK-2) X (CSR-6 X CSR-26), (CSR-2 X CSR-27) X (APS46TMP X CSR-6) and (CSR-2 X CSR-27) X (CSR-6 X CSR-26). These hybrids were reared and data was collected, analyzed and ranked. From this data it is clear that the hybrid (BRO-2 x NK-2) X (CSR-6 x CSR-26), which is released as Adithya stood first and the other hybrid Kasturi (CSR-2 x CSR-27) X (APS46TMP x K9D(MD)) stands second.

The Adithya and Kasturi bivoltine double hybrid were released in State Level Sericulture Farmers and Entrepreneurs Meet “Pragatiyatta Reshme Krishi” held on 24/02/2018 for field trial. The post cocoon parameters were also collected

4. Feeler Field trial of identified Bivoltine double hybrid Adithya and Kasturi

During the year 2018-19 and 2019-20, Adithya and Kasturi double hybrids were field tested and during the 2019-20 onwards only Adithya was field popularized. For field trial, Cellular rearing of pure races was conducted in Silkworm Breeding and Genetics Section and foundation crosses BRO-2 X NK-2(AFC2),CSR-6 X CSR-26 (FC1), APS46X K9D ( KFC1) and CSR-2 XCSR27 (FC2) were prepared and supplied to Adopted Seed Preparers (ASPs). The rearing performance data of foundation crosses with the ASPs was recorded. The foundation crosses AFC2 and KFC1 have showed more yield compare to FC1 and FC2. The Foundation cross cocoons were purchased through the Government Bivoltine Seed Cocoon Market, Tumkur on the basis of buy-back. The purchased cocoons were processed at Government Model Grainage, Tumkur. During the preparation of the double hybrid layings, the egg recovery percentage was found to be more in FC1XAFC2 (Adithya) and APS46X K9D ( Kasturi) compare to FC1X FC2

The layings were supplied to identified Registered Chawki Rearing Centers (CRCs) free of cost. After second moult, larvae were distributed to the farmers. The crops were inspected and the data pertaining to cocoon harvest, cocoon yield/100dfls, cocoon rate was collected and tabulated. The details of field performance of both Aditya and Kasturi during the year 2018-21 is presented in table below.

Field performance of bivoltine double hybrid Aditya and Kasturi during 2018-21

Sl. No.

Hybrid

Year

No. of DFLs brushed

Avg.yield

Avg. rate

1

Aditya

2018-21

73000

78.56

333/-

2

Kasturi

2018-19

2850

83.15

302/-

The following observations were made during field trial.

Ø Foundation crosses AFC2 (BRO2 x NK2) and KFC1 (APS46 x K9D) are easy to rear

Ø Egg recovery is more

Ø Less number of meltage cocoons

Ø Consistency in crop success is more

Ø Cocoons produced generate 2A grade silk

Ø As an alternate to the existing double hybrid

5. Molecular characterization of diapauses inhibiting factor in race KS-10 of

silkworm Bombyx mori L.

KS10 is a unique silkworm breed with anti-diapause ability. KS10 as male crossed with any bivoltine female triggers hatching in the eggs laid by these bivoltine females, a special phenomenon hitherto unknown to tropical sericulture. Conventional breeding crosses proved that KS10 has a inhibitory new gene nomenclature as Id by our institute. Several brainstorming sessions were conducted to find the way to validate the claim. The brainstorming session chaired by Prof. H.A. Ranganath held on 27.2.2016 at KSSRDI, Bangalore recommended that transcriptome of the eggs of 2 to 20 hrs age has to be studied and compared with other normal controls, namely, Pure Mysore, CSR2 and CSR2 x KS10 eggs immediately after egg laying. Further, Dr. Upendra Nongthomba, Associate Prof. IISc also opined the same.

Accordingly the project has been formulated under internal funding. The work of transcriptome sequencing of zygotes from silkworm breeds/hybrids to identify transcripts responsible for shifting of diapause embryos to non-diapause embryos was out sourced. The eggs of identified races/hybrid were supplied duing specific period of egg laying as advised by the experts. From the interim summary of the completed project, the following results were summarized.

1. The present project work supports the hypothesis of KSSRDI that “The KS-10 has a unique transcript/transcripts which is not present in any other strains analyzed in this study (PM, CSR2).

2. This transcript, along with the other unannotated novel transcripts identified in KS10 and CSR2xKS10 strains might have a role in switching the diapausing embryo to non-diapausing embryo.

6. Isolation of first Indian non diapause red egg mutant of silkworm Bombyx

mori .L

During the process of preparation of cross breeds in Silkworm Breeding and Genetics section, KSSRDI, Thalaghattapura an unique non-diapause red mutant few eggs were observed. This is probably the first natural red egg mutant observed in Indian sericulture. When IMH x BRO2 cross breed layings were kept under incubation, some of the eggs turned red after 72 hours of post oviposition. For the isolation of this mutant hybridization and selection method was adopted. With the result ,One non-diapause red egg producing polyvoltine line and another diapause egg producing bivoltine line are under development. Presently these lines are under different generations of selection (F10-F11). The studies on the hybrid performance, rearing performance and expression of heterosis will be initiated after stabilization of the line. The colour of the red eggs laid by polyvoltine line ‘PNR’ is shown in the Figure below. This line is probably the first new non diapause natural red egg mutant in the sericulture industry in India.

7. Utilization of foundation cross BRO2XNK2 (AFC2) as male parent in the cross breed PMXCSR2

The rearing of pure bivoltine race CSR2 seed cocoons for the purpose of using it as male component for the cross PMXCSR-2 is found to be quite difficult especially during summer in the field. Further grainuers are being met with little success in achieving expected egg recovery. But the rearing of foundation cross BRO2X NK2 is easy as observed in the field trial. Keeping these prevailing field problems, studies have been initiated to study the feasibility of using BRO2X NK2 (AFC2) as male parent in the cross PMX CSR2. Since the rearing of foundation cross (AFC2) rearing is easy. This will enable the rearer and granuier to use BRO-2X NK-2 as an alternate to the race CSR-2 during summer season. The rearing of PMX CSR-2 and PM X (BRO2X NK2) hybrids was conducted under standard rearing conditions. The PM X (BRO2XNK-2) rearing performance showed significant improvement with regard to cocoon yield and pupation rate compare to PMXCSR2 hybrid during summer season. Except for the trait pupation rate remaining all the traits showed no significant difference between two hybrids during rainy and winter. During 2020-21, preliminary field trial of the cross breed PM X(BRO2X NK2) will be conducted to study the rearing performance and also the grainage performance in the field level under RKVY project. In parallel, reeling parameters will be collected for both PMXCSR-2 and PM X (BRO2X NK2) cross breeds.

8.Utilisation of diapausing inhibiting sex limited race HNID as male parent

Combining ability studies were conducted to study the performance of the diapausing inhibiting race HNID as male component with the bivoltine female. (BRO-2X NK-2)X HNID hybrid, which is found to be promising, will be field tested in small scale. Parallely, reeling data will be collected

9.Inter institutional programme

During the year 2018-19 and 2019-20, the layings of authorized bivoltine hybrid KSO-1X SP2 was supplied for the project entitled “ Evaluation and identification of suitable productive bivoltine hybrids for odisha” implemented by RSRS,CSB,GOI at Landiguda Koraput.

APPSRDI, Hindupur has included KSSRDI for its collaborative work for the project entitled “Contained trials of transgenic silkworm hybrid CSR(T) X CSR-4 and PMX CSR(T)( Phase –II) at farmers level”. The farmers near the vicinity of the institute were selected and their profile was collected. The committee for examining the silkworm rearing places at selected farmer’s premises was also visited for the multilocational trial to be taken up.

Future plan of action

1. Breeders’ stock of new bivoltine races will be maintained and evolution of elite robust bivoltine lines for high cocoon shell ratio will be continued for few more generation till stabilization for subsequent combining ability studies.

2. The promising bivoltine hybrid “Adithya” will be popularized in large scale and performance collected will be submitted for race authorization.

3. Popularisation of improved cross breed ‘Bangaluru Belli’ in the field for the production of quality silk

4. Small scale field trial of BRO-2 X NK2 as male parent in the cross breed PMX CSR2 during summer.

5. The sex- limted line HNID, which is showing antidiapausing character, will be field tested both as male and female parent with other bivoltines after collecting the reeling data in small scale under RKVY project.

Summary

KSSRDI is succeeded in evolving suitable bivoltine hybrids based on the socio-economic conditions of the farmers and to fulfill the requirement of Department of Sericulture, Government of Karnataka from time to time. Since from the establishment of the institute under the world bank assistance, breeders are continuously working for the development of the races / hybrids which can sustain with the farmers having improper adoptability of technology, maderate quality leaf and fluctuating climatic conditions. Over the past two decades, with the development of chawki rearing concept for the supply of quality chawki larvae and farmers awareness about technology of the rearing of productive breeds, the polyvoltine and bivoltine breeds developed and also hybrids identified for large scale field trial will increase the farmers income and also help in producing good quality silk .