The Impact of Hybrid Vigour on Commercial Traits of the Indian Tropical Tasar Silkworm, Antheraea mylitta Drury (Lepidoptera: Saturniidae)

Reddy, Rangareddygari Manohar,Suryanarayana, Nagabathula,Rai, Suresh,Sinha, Manoj Kumar,Hansda, Ganga,Ojha, Nand Gopal,Prasad, Bhagwan Chandra Korean Society of Sericultural Science 2010 International Journal of Industrial Entomology Vol.20 No.2

The bivoltine tropical tasar ecoraces of Antheraea mylitta Drury produces cocoons for seed production under seed crop rearing (July-August with $22{\sim}30^{\circ}C$ temperature and 50~70% relative humidity) and for silk production under commercial crop rearing (September-December with $17{\sim}27^{\circ}C$ temperature and 60~80% relative humidity). To consider the impact of hybrid vigour on egg, larva, cocoon and silk related commercial traits, the $F_1$ hybrids made among Daba, Jata and Raily ecoraces were assessed successively for three years. The hybrid vigour in the $F_1$ hybrid of Daba$\times$Jata ($T_7$) was positive for egg fertility (+23.1%), shell weight (+25.6%), silk yield (+79.0%) and filament length (+68.1%), with filament of high denier (11.98d) and reduced larval span (-7.1%). The Jata$\times$Daba ($T_8$) hybrid has shown negative heterosis in egg fertility (-8.0%) compared to the other F1 hybrids, Daba$\times$Raily ($T_9$) and Raily$\times$Daba ($T_{10}$), when they rise simultaneously during the commercial crop season. The better performance of parental ecoraces ($T_4$ to $T_6$) in their commercial traits during commercial crop over parents of seed crop ($T_1$ to $T_3$) and the superior performance of $F_1$ hybrids ($T_7$ to $T_{10}$) over parents of commercial crop ($T_4$ to $T_6$) during commercial crop season indicates the apparent hybrid vigour in tasar $F_1$ hybrids. As the Daba$\times$Jata ($T_7$) and Jata$\times$Daba ($T_8$) $F_1$ hybrids have shown highest hybrid vigour, their rearing during commercial crop can optimize the silk productivity and commercial sustenance of the tasar silk industry.

Basic Seed Stock Maintenance and Multiplication in Indian Tropical Tasar Silkworm Antheraea mylitta Drury-A Strategic Approach

Reddy, Rangareddygari Manohar,Suryanarayana, Nagabathula,Ojha, Nand Gopal,Hansda, Ganga,Rai, Suresh,Prakash, Nanjappa Basappa Vijaya Korean Society of Sericultural Science 2009 International Journal of Industrial Entomology Vol.18 No.2

Daba ecorace of Antheraea mylitta Drury (Lepidoptera: Saturniidae), the semi domesticated Indian tropical tasar silkworm being reared outdoor; the egg and silk yields are dependent of genotype environment interaction. The insufficient maintenance and multiplication of its P4 seed stock need a coherent as well as scientific strategy to safeguard breed potential, being commercially applied ecorace. The sort-out lines of P4 stock studied over five generations highlighting on commercial trait up gradation suits for a tropical crop season, revealed enhanced performance. The line with high pupal parents (T2) shown improved fecundity (12.9%) and the line with high shell parents (T3) recorded higher shell weight (40.0%) and silk ratio (24.1%). While, the line of high pupal female and high shell male (T4) reveal enhancement in fecundity (9.0%), egg hatching (14.1%), shell weight (50.0%), silk ratio (35.2%) and absolute silk yield (52.0%) indicating the need and role of varied basic seed stock lines. The approach could improve economically vital egg fecundity and cocoon shell weights besides balancing them in same line for commercial operation. The progressive show of lines (T1 to T4) along successive generations (G1 to G5), in spite of passing through seed crop (Jul-Aug) and commercial crop (Sep-Nov) seasons emphasize their compatibility. The study infers that the strategic plan of combining preferred parental phenotypes, methodical selection for desired commercial trait(s) through generations with best possible genotype environment interaction has enriched P4 stock with elevation in needy trait(s) besides assuring choice of suitable lines for seasons and regions and timely replenishment of basic seed of Daba ecorace.

Basic Seed Stock Maintenance and Multiplication in Indian Tropical Tasar Silkworm Antheraea mylitta Drury-A Strategic Approach

Rangareddygari Manohar Reddy,Nagabathula Suryanarayana,Nand Gopal Ojha,Ganga Hansda,Suresh Rai,Nanjappa Basappa Vijaya Prakash 한국잠사학회 2009 International Journal of Industrial Entomology Vol.18 No.2

Daba ecorace of Antheraea mylitta Drury (Lepidoptera: Saturniidae), the semi domesticated Indian tropical tasar silkworm being reared outdoor; the egg and silk yields are dependent of genotype environment interaction. The insufficient maintenance and multiplication of its P4 seed stock need a coherent as well as scientific strategy to safeguard breed potential, being commercially applied ecorace. The sort-out lines of P4 stock studied over five generations highlighting on commercial trait up gradation suits for a tropical crop season, revealed enhanced performance. The line with high pupal parents (T2) shown improved fecundity (12.9%) and the line with high shell parents (T3) recorded higher shell weight (40.0%) and silk ratio (24.1%). While, the line of high pupal female and high shell male (T4) reveal enhancement in fecundity (9.0%), egg hatching (14.1%), shell weight (50.0%), silk ratio (35.2%) and absolute silk yield (52.0%) indicating the need and role of varied basic seed stock lines. The approach could improve economically vital egg fecundity and cocoon shell weights besides balancing them in same line for commercial operation. The progressive show of lines (T1 to T4) along successive generations (G1 to G5), in spite of passing through seed crop (Jul-Aug) and commercial crop (Sep-Nov) seasons emphasize their compatibility. The study infers that the strategic plan of combining preferred parental phenotypes, methodical selection for desired commercial trait(s) through generations with best possible genotype environment interaction has enriched P4 stock with elevation in needy trait(s) besides assuring choice of suitable lines for seasons and regions and timely replenishment of basic seed of Daba ecorace.

The Impact of Hybrid Vigour on Commercial Traits of the Indian Tropical Tasar Silkworm, Antheraea mylitta Drury (Lepidoptera: Saturniidae)

( Rangareddygari Manohar Reddy ),( Nagabathula Suryanarayana ),( Suresh Rai ),( Manoj Kumar Sinha ),( Ganga Hansda ),( Nand Gopal Ojha ),( Bhagwan Chandra Prasad ) 한국잠사학회 2010 International Journal of Industrial Entomology Vol.20 No.2

The bivoltine tropical tasar ecoraces of Antheraea mylitta Drury produces cocoons for seed production under seed crop rearing (July-August with 22~30˚C temperature and 50~70% relative humidity) and for silk production under commercial crop rearing (September-December with 17~27˚C temperature and 60~80% relative humidity). To consider the impact of hybrid vigour on egg, larva, cocoon and silk related commercial traits, the F1 hybrids made among Daba, Jata and Raily ecoraces were assessed successively for three years. The hybrid vigour in the F1 hybrid of Daba×Jata (T7) was positive for egg fertility (+23.1%), shell weight (+25.6%), silk yield (+79.0%) and filament length (+68.1%), with filament of high denier (11.98d) and reduced larval span (-7.1%). The Jata×Daba (T8) hybrid has shown negative heterosis in egg fertility (-8.0%) compared to the other F1 hybrids, Daba×Raily (T9) and Raily×Daba (T10), when they rise simultaneously during the commercial crop season. The better performance of parental ecoraces (T4 to T6) in their commercial traits during commercial crop over parents of seed crop (T1 to T3) and the superior performance of F1 hybrids (T7 to T10) over parents of commercial crop (T4 to T6) during commercial crop season indicates the apparent hybrid vigour in tasar F1 hybrids. As the Daba×Jata (T7) and Jata×Daba (T8) F1 hybrids have shown highest hybrid vigour, their rearing during commercial crop can optimize the silk productivity and commercial sustenance of the tasar silk industry.

Silk Filament Progression with Backcross Breeding Generations in Tropical Tasar Silkworm, Antheraea mylitta D

Reddy, Rangareddygari Manohar,Suryanarayana, Nagabathula,Sinha, Manoj Kumar,Gahlot, Nand Singh,Hansda, Ganga,Ojha, Nand Gopal,Prakash, Nanjappa Basappa Vijaya Korean Society of Sericultural Science 2009 International Journal of Industrial Entomology Vol.19 No.1

Silk filament progression study applying backcross breeding with recipient parent Jata and donor parent Daba ecoraces of tropical tasar silkworm, Antheraea mylitta Drury conducted during 2006 to 2008, revealed introgression of filament denier (10.2 d) superior to both parents at BC4 level. Also, the silk waste (0.35%) and filament breaks (2.6 nos) were reduced compared to both parents, while the filament length (973 m) and non break filament (296 m) improved over donor and could attain closer to recipient parent. The best performance of Jata $\times$ Daba at F1 level, with highest silk filament length (1646 m) of 12.5 d denier, denotes heterosis impact on silk trait with parental heterogenousity, an advantage to exploit silk filament yield. The progression of quality in terms of finer filament denier, less silk waste and least number of filament breaks over both parents and improvement in filament length and non break filament over donor parent except for a marginal shortage against recipient at BC4 level indicates the prospects of Jata and Daba ecoraces as source of breeding material for qualitative improvement of tasar silk filament. The study suggests that the commercially important finer denier of tasar silk filament can be attained with minor reduction in silk yield of wild Jata ecorace by adopting repeated backcrossing for four generations with semi domesticated Daba ecorace.

Silk Filament Progression with Backcross Breeding Generations in Tropical Tasar Silkworm, Antheraea mylitta D

Rangareddygari Manohar Reddy,Nagabathula Suryanarayana,Manoj Kumar Sinha,Nand Singh Gahlot,Ganga Hansda,Nand Gopal Ojha,Nanjappa Basappa Vijaya Prakash 한국잠사학회 2009 International Journal of Industrial Entomology Vol.19 No.1

Silk filament progression study applying backcross breeding with recipient parent Jata and donor parent Daba ecoraces of tropical tasar silkworm, Antheraea mylitta Drury conducted during 2006 to 2008, revealed introgression of filament denier (10.2 d) superior to both parents at BC4 level. Also, the silk waste (0.35%) and filament breaks (2.6 nos) were reduced compared to both parents, while the filament length (973 m) and non break filament (296 m) improved over donor and could attain closer to recipient parent. The best performance of Jata x Daba at F1 level, with highest silk filament length (1646 m) of 12.5 d denier, denotes heterosis impact on silk trait with parental heterogenousity, an advantage to exploit silk filament yield. The progression of quality in terms of finer filament denier, less silk waste and least number of filament breaks over both parents and improvement in filament length and non break filament over donor parent except for a marginal shortage against recipient at BC4 level indicates the prospects of Jata and Daba ecoraces as source of breeding material for qualitative improvement of tasar silk filament. The study suggests that the commercially important finer denier of tasar silk filament can be attained with minor reduction in silk yield of wild Jata ecorace by adopting repeated backcrossing for four generations with semi domesticated Daba ecorace.