• International Journal of Industrial Entomology and Biomaterials
• /
• v.7 no.2
• /
• pp.209-219
• /
• 2003

An experiment was initiated to evaluate hybrid vigour in twelve F$_1$ hybrids and seven three-way crosses of multivoltine ${\times}$ bivoltine silkworm between newly evolved multivoltine breed BL67 with productive bivoltine CSR breeds and hybrids. Analysis of variances computed for different characters among F$_1$hybrids and three-way crosses showed highly significant differences among them indicating presence of both additive and non-additive gene actions for the expression of these characters. Among twelve F$_1$ hybrids, two F$_1$ hybrids viz., BL67${\times}$CSR$_4$and BL67${\times}$CSR$_{5}$ have expressed significant heterosis for nine characters and two hybrids viz., BL67${\times}$NB$_4$D$_2$and PM${\times}$NB$_4$D$_2$ for eight characters whereas out of nine three-way crosses, three hybrids viz., BL67${\times}$ (CSR$_3$${\times}$CSR$_{6}$), BL67${\times}$(CSR$_{16}$${\times}$CRS$_{17}$) and BL67${\times}$(CSR$_{18}$ ${\times}$CSR$_{19}$) expressed significant heterosis for eight characters. In the present study, it is observed that the cocoons of two hybrids viz., BL67${\times}$CSR$_4$and BL67${\times}$CSR$_{19}$ were found to be uniform as these hybrids showed lowest CV％ (5.35 and 5.38) among twelve F$_1$ hybrids and seven three way crosses between multivoltine ${\times}$ bivoltine hybrids. Four F$_1$ hybrids viz., BL67${\times}$CSR$_4$, BL67${\times}$CSR$_{5}$, BL67${\times}$ (CSR$_3$${\times}$CSR$_{6}$), BL67${\times}$(CSR$_{16}$${\times}$CRS$_{17}$) and BL67${\times}$(CSR$_{18}$ ${\times}$CSR$_{19}$) showed superiority in expressing hybrid vigour and are considered as best heterotic hybrids for commercial exploitation.ion.ation.ion.ation.ion.

• International Journal of Industrial Entomology and Biomaterials
• /
• v.2 no.1
• /
• pp.79-81
• /
• 2001

A study was conducted to establish the degree of genetic divergence between different hybrid forms and rearing conditions through estimation of the minimum number of genes (allelic pairs) differentiating parents in terms of specific quantitative traits. It was established that the minimum gene numbers differentiating parental lines in the inheritance of cocoon was 1, of cocoon shell weight- between 1 and 2, and of silk filament length- between 2 and 3. The variability in the specific genetic parameter could be explained by the reliability of the statistical-and-genetic method used and the expression of genes affecting the formation of each of the characters tested. Gene expression, in its turns is conditioned both by the gene interaction within the genotypes and the different genotype response to environmental change. To go deep in the problem, experiments should be conducted under strictly controlled conditions, reducing the mathematical-and-genetic analysis to a physiological levels and hence to analyse the genetic nature of the specific quantitative character formation and its genetic control.

• Journal of Sericultural and Entomological Science
• /
• v.10
• /
• pp.67-72
• /
• 1969

In order to analyse the correlation between the parents and their hybrids in the silkworm, which were reared in spring, the author has surveyed the various quantitative characters which are significant in genetics, and the hybrid vigor rate. The duration of larvae life is shorter in F1 Value an in the mid parents value, cocoon size biffer, pupa rate, cocoon crop from ten thousand silkworms just molted in the fourth instar, total cocoon weight and cocoon layer weight increases in comparison with the mid parents value. Although cocoon layer ratio only shows increasing by 0.3％ or so, it is too little to admit the effect. F1 value is nearly equal to parent value and there is no correlation between F1 hybrids value and their mid parents value.

• International Journal of Industrial Entomology and Biomaterials
• /
• v.8 no.2
• /
• pp.181-187
• /
• 2004

Polyvoltine silkworm breeds/hybrids play an important role in tropical sericulture. In the process of synthesizing more potential polyvoltine hybrids(polyvoltine${\times}$bivoltine) of superior quantity and quality, the Andhra Pradesh State Sericulture Research and Development Institute (APSSRDI) has developed 8 promising polyvoltine breeding lines (SDMG2, APM16, APM15, APM14, APM5, RM2, APM3, APM13). In order to study their hybrid vigour and performance, these breeds were crossed with 4 potential bivoltine testers (SDD1, SDD2, SDD3, APS8), and 32 different hybrid combinations were prepared and evaluated for their mid parent heterosis (MPH) and better parent heterosis (BPH) of silk productivity. Since silk is the ultimate product required for commercial purpose, based on silk productivity and its heterosis, three superior polyvoltine hybrid combinations namely RM2${\times}$APS8 (24.3%), APM3${\times}$APS8 (12.4%) and APM15${\times}$SDD2 (10.8%) were adjudicated as potential heterotic hybrid combinations of superior silk yield and hence recommended for further large scale field trails and commercial exploitation.

• International Journal of Industrial Entomology and Biomaterials
• /
• v.9 no.1
• /
• pp.41-46
• /
• 2004

A breeding programme was initiated by utilizing a robust bivoltine breed CSR$_{18}$ and a polyvoltine breed Cambodge with the main objective of developing robust polyvoltine silkworm breeds/hybrids. At F$_1$ and F$_2$, parthenogenetic development was induced following warm water treatment of eggs at 46$^{\circ}C$ for 18 min followed by two backcrosses with Bl$_{67}$, an evolved polyvoltine breed. The newly developed breed was subjected for hybrid study using eight hybrid combinations in the laboratory at F$_{8}$ generation. F$_1$ hybrids between newly developed breed Bl$_{67}$ (Pg) and promising bivoltine breeds exhibited their superiority by expressing significant hybrid vigour for several economic characters like cocoon yield/10,000 larvae, cocoon weight, cocoon shell weight, cocoon shell ratio and denier. Study on cocoon shape variability revealed that cocoons of all the F$_1$ hybrids except BL$_{67}$ (Pg)${\times}$NB$_4$D$_2$ were found comparatively uniform in shape.pe.

• International Journal of Industrial Entomology and Biomaterials
• /
• v.7 no.2
• /
• pp.221-229
• /
• 2003

Ten multivoltine female parental lines were crossed with popular bivoltine male silkworm breed NB$_4$D$_2$. Three types of heterosis parameters viz., heterosis over mid-parental value (hybrid vigour), heterobeltiosis (useful heterosis) and standard heterosis (standard check) were estimated for 15 economically important quantitative traits. The interaction among the hybrids and parents indicated significant effect for maximum characters. The heterotic effect of new hybrid combination was compared with popular hybrids viz., Pure Mysore${\times}$NB$_4$D$_2$ and Nistari${\times}$NB$_4$D$_2$. Varied heterotic effect was observed for different traits for different hybrid combination. The results inferred that the crosses viz., BL$_{23}$${\times}$NB$_4$D$_2$ ranked top for 14 traits followed by Hosa Mysore${\times}$NB$_4$D$_2$ for 11 traits; PA$_{12}$${\times}$NB$_4$D$_2$ for 9 traits; BL$_{24}$${\times}$NB$_4$D$_2$ for 8 traits; Kolar Gold${\times}$NB$_4$D$_2$ for 7 traits; WAI$_1$${\times}$NB$_4$D$_2$ for 6 traits and MU$_{11}$${\times}$NB$_4$D$_2$ for 5 traits. Among these, the best hybrids Kolar Gold${\times}$NB$_4$D$_2$ and MU$_{11}$${\times}$NB$_4$D$_2$ were identified for longer filament length and fine denier. Similarly for higher cocoon yield and silk productivity BL$_{223}$${\times}$NB$_4$D$_2$ and BL$_{24}$${\times}$NB$_4$D$_2$ were found to be superior. These hybrid combinations are suitable for commercial exploitation at large scale.e.e.e.

• International Journal of Industrial Entomology and Biomaterials
• /
• v.3 no.1
• /
• pp.31-35
• /
• 2001

Ten newly evolved bivoltine hybrids of silkworm (Bombyx mori L) were evaluated with control hybrid KA${\pm}$NB4D2 during three seasons of a year for their seasonal performance. Analysis of variance and other statistical methods were employed and the performance was observed in respect of 10 quantitative traits. The results showed significant genotype${\pm}$environment interaction with respect to four quantitative characters viz. fecundity, yield/10,000 larvae, filament length and raw silk (%). Environmental effects were significant for nine characters out of ten characters evaluated. A 105${\pm}$J2 and B${\pm}$NB4D2 were considered as highly adaptable hybrids to local conditions with high mean for maximum characters studied and found suitable to rear in all seasons.

• International Journal of Industrial Entomology and Biomaterials
• /
• v.4 no.1
• /
• pp.37-41
• /
• 2002

Heterosis studies on rearing performance of 25 Fl Polyvoltine $\times$ bivoltine (sex-limited cocoon colour) hybrids revealed that manifestation of heterosis was highly significant for majority of the economic traits contributing to more silk yield. Five hybrids namely BL24${\times}$ CSR 19 (SL), BL24${\times}$${\times}$${\times}$${\times}$${\times}$

• International Journal of Industrial Entomology and Biomaterials
• /
• v.14 no.1
• /
• pp.63-68
• /
• 2007

The response of silkworm, Bombyx mori L. to phytoecdysteroid (PE) when administered at different ages of $5^{th}$ instar was studied in the popular bivoltine ($CSR2{\times}CSR4$) and multi${\times}$bivoltine ($PM{\times}CSR2$) silkworm hybrids, reared on the Victory-1 variety of mulberry leaves. PE was administered to $5^{th}$ instar silkworm per os at a rate of $250{\mu}g$ per 100 larvae to different batches of silkworm at 0, 24, 48, 72, 96, 120, 144 hrs and at the onset of cocoon spinning when a few larvae were ripe. The larval and mounting duration, cocoon yield and cocoon characters were influenced by PE. The intensity of influence was dependent on the time of application. The larvae treated at the beginning of the instar, improved the economic traits significantly with a marginal increase in larval duration. In the larvae treated at the middle of the instar, larval duration was shortened remarkably but the economic traits were adversely affected. This particular treatment can become a good management strategy in the case of mulberry leaf shortage or disease incidence. In the larvae treated at the onset of cocoon spinning, the mounting duration was substantially reduced without much effect on the cocoon traits which would be a big benefit in commercial sericulture. The physiological significance of varied response of silkworm to PE administration is discussed.

• International Journal of Industrial Entomology and Biomaterials
• /
• v.9 no.1
• /
• pp.53-58
• /
• 2004

Studies on heterotic expression in the silk productivity of 66 thermo-tolerant bivoltine hybrids reared under high temperature $(36{\times}1^{\circ}C)$ and low humidity (60${\times}$5%) conditions revealed that manifestation of heterosis was highly significant for majority of the quantitative traits contributing to more cocoon productivity. Observations were made on 8 economically important traits such as fecundity, pupation rate, cocoon yield, cocoon weight, cocoon shell weight, cocoon shell ratio, cocoon filament length and raw silk. Analysis of variance results revealed great deal of variability indicating significant (P < 0.001) variations. Out of 66 hybrids, 7 hybrids exhibited positive heterosis for seven traits and 4 hybrids expressed significant hetero-beltiosis for 6 traits, out of 8 traits evaluated. Based on results, the hybrids ${SR_1} {\times} {SR_5}and {CSR_2} {\times} {SR_5}$ are adjudged as most promising ones and can be exploited commercially in tropical climates to increase the cocoon productivity.