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Sericulture Research & Development Council

Species of Silkworm

Earlier attempts to rear bivoltine hybrids resulted only a sporadic success and that too confined only to some seasons of the year, when climatic conditions are not hostile to silkworms The bivoltine breeds developed earlier were with an objective to have higher pupation rate and all the other characters balanced at a moderate level for enabling easy rearing by the farmers. Therefore, limited hybrid vigour could be realized when two such breeds are crossed because both the breeds are on par in almost all the characters. This is one of the reasons for lack of productive bivoltine hybrids in India. Therefore, in CSR&TI, Mysore new breeding programmes were formulated for the development of productive hybrids . This has resulted in the evolution of a series of productive bivoltine breeds (CSR) with high survival and cocoon shell percentage. By systematic evaluation of large number of crosses involving these parents, highly productive hybrids with high quality silk could be identified with cocoon shell percentage of 23-24%; raw silk recovery of 18-19% and 2A-3A grade silk.

Success in sericulture depends largely on major factors like, breed, seed and feed. Concurrently, appropriate technological supports like disease free environment during rearing and cocooning also play an important role. If the cocoons, which form the basic raw material for raw silk, are from bivoltines will definitely be superior with high silk content. Besides, they possess longer filament length, higher neatness, cleanness, less size deviation, low boil-off ratio, higher tensile strength and less variation in evenness. Hence, bivoltine cocoons form suitable raw material for the production of gradable raw silk as compared to polyvoltine x bivoltine cocoons. Keeping the requirement of the industry in view, various countries have developed breeds / hybrids to suit their local agro climatic conditions to increase the quality and productivity. In this context, silkworm breeds / hybrids play a very important role in the development of sericulture industry. In tropical countries, high temperature, low humidity, poor rearing management poor mulberry quality, high incident of diseases etc are mainly responsible for partial success of crops at the farmers level. To suit the prevailing conditions, robust breeds / hybrids are required. Among various factors that are attributed to the poor performance of the bivoltine strains under tropical conditions the important aspect is that many quantitative characters such as viability and cocoon traits decline sharply when temperature is higher than 28°C.

The ultimate success of identification of promising silkworm hybrids is assessed by the superiority of the commercial traits of the parental strains that appears in F1 hybrid. Hybrid vigour in silkworm has received a considerable attention because of marked effect of the yield components. It is well documented that F1 hybrids are superior to their parents in many qualitative and quantitative characters. The superiority of the hybrids is judged by their cocoon yield and yield attributes as compared to their parents. Among various genetic principles and breeding techniques, the utilization of hybrid vigor was one of the major breakthroughs which contributed to the success. Depending upon various factors, different cross-breeding techniques have been employed. Multivoltine (MV) x MV, (ex: PM x C Nichi, PM x C110) mainly for rain fed, low input conditions; MV x Bivoltine (BV) (ex: PM x CSR2, MH1 x CSR2) for average climatic and input conditions and BV x BV (ex: CSR2 x CSR4) for favorable season and/or better input conditions. Research institutes have developed suitable robust BV x BV hybrid combinations (ex: KSO-1xSP2, CSR18 x CSR19) for average conditions and double hybrids (BV x BV) x (BV x BV) for high input conditions.

Authorization of silkworm hybrids grants recognition to silkworm hybrids for commercial exploitation. The co-ordinated hybrid test is conducted by Central Silk Board (CSB), Bangalore, Government of India, in each year in different seasons at different test centres all over India simultaneously. Based of performance, several hybrids have been authorized at national level and the list of hybrids authorized in recent years is given below:

S.No. Combination Hybrid Recommended for Season Authorization Date
1 CSR2 × CSR4 BV South India, Temperate Spring, Rainy 8-5-1997
2 CSR6 × CSR26 × CSR2 × CSR27 Double hybrid Throughout India Spring, Rainy 15-09-2005
3 CSR48 × CSR5 BV South India, Temperate Spring, Rainy 15-09-2005
4 DUN6 × DUN22 BV North India Spring, Rainy 15-09-2005
5 CSR2A × CSR4A BV South India, Temperate Spring, Rainy 15-09-2005
6 BL67 × CSR19 CB Throughout India All Seasons 15-09-2005
7 MYSORE × CSR2 CB South India,Temperate All Seasons 15-09-2005
8 N × YB CB WB All Seasons 15-09-2005
9 BL67A × CSR101A CB South India,Temperate All Seasons 15-09-2005
10 Varuna (BL24 × C.NICHI) CB South India,Temperate All Seasons 15-09-2005
11 N × M12(W) MH WB Summer 15-09-2005
12 APS105 × APS126 BV AP, TN, WB All Seasons 18-04-2010
13 APS45 × APS12 BV TN, JK All Seasons 18-04-2010
14 CSR46 × CSR47 BV UK , HP, UP, KR, AP, OR, WB, AS All Seasons 18-04-2010
15 DUN17 × DUN18 BV HP,KR,WB,AS All Seasons 18-04-2010
16 GEN3 × GEN2 BV AP,TN,WB,AS,JK All Seasons 18-04-2010
17 KSO1 × NP4 BV KR,HP,JK All Seasons 18-04-2010
18 NK2 × NP4 BV AS,JK All Seasons 18-04-2010
19 SLD4 × SLD8 BV KR,AP,TN,WB,AS,JK All Seasons 18-04-2010
20 APDR15 × APDR115 CB KR,WB All Seasons 18-04-2010
21 APM2 × APDR105 CB KR,AP,TN,WB All Seasons 18-04-2010
22 APM3 × APS12 CB KR,WB All Seasons 18-04-2010
23 MCON1 × BCON4 CB KR,AP,TN,WB,JR All Seasons 18-04-2010
24 MCON4 × BCON4 CB WB,OR,JR,AS All Seasons 18-04-2010
25 MH1 × CSR2MH1 × CSR2MH1 × CSR2 CB UP,KR,AP,TN,OR All Seasons 18-04-2010
26 PM × CSR2(SL) CB KR,AP,TN,AS,MN All Seasons 18-04-2010
27 MCON1 × MCON4 MH KR,AP,TN,WB All Seasons 18-04-2010
28 N × MCON4 MH AP,TN,WB All Seasons 18-04-2010
29 PM × C110 MH WB All Seasons 18-04-2010

Source:

Central Sericulture Research & Training Institute, Mysore, Karnataka

Package of Practices of Mulberry Sericulture for Eastern and North Eastern Region, Central Sericultural Research & Training Institute, Berhampore, West Bengal