Bivoltine Silkworm Research Articles

Comparative Screening of Elite Bivoltine Silkworm Breeds under Summer Conditions of Kashmir

The success of the sericulture industry largely depends upon the quality of mulberry leaf and type of silkworm breed reared on these leaves. The rearing of season specific silkworm breeds can be instrumental in the successful rearing which will yield good cocoon crop and thereby leading to enhanced silk production. Data with respect to eleven economic parameters viz., fecundity, hatching percentage, larval weight, fifth instar larval duration, total larval duration, cocoon yield by number, cocoon yield by weight, single shell weight, single cocoon weigh, shell ratio and pupation rate was recorded, analysed statistically and subjected to multiple trait evaluation index. Significant differences were recorded in economic parameters but no specific silkworm breed performed best in all the economic parameters studied except SK-6 which performed best for most of the economic parameters, SK-1 and SK-28 showed best performance with respect to single cocoon weight and fecundity respectively. Out of nineteen silkworm breeds only nine breeds viz., SK-6, SK-28, SK-30, KSO, SK-22, SK-24, SK-1, SK-13 and CSR-4 were found promising with average evaluation index of 66.7, 58.8, 57.2, 56.6, 55.5, 54.5, 53.1, 52.6 and 50.7 respectively. These breeds could be utilized in appropriate combination in evolution of new breeds/ hybrids for the region.

Influence of Natural Dyes on the Qualitative and Quantitative Parameters of Bivoltine Silkworm Breeds under Sub-Tropical Conditions of Poonch District, Jammu and Kashmir

The study on Influence of Natural Dyes on the qualitative and quantitative parameters of Bivoltine Silkworm Breeds under Sub-tropical Conditions of Poonch District, UT Jammu and Kashmir,” was conducted during the spring of 2022 at the PG, Department of Sericulture, Poonch Campus, University of Jammu. The study examined the effects of feeding bivoltine silkworm breeds CSR16 and CSR27 with two concentrations (50% and 100%) of natural dyes: madder (Rubia cardifolia) and indigo blue (Indigofera tinctoria). A comprehensive evaluation of both qualitative and quantitative parameters was undertaken, including fecundity, hatching %, larval duration, weight of 10 mature larvae, survival rate, mortality %, pupation % and cocoon quality parameters. The results indicated significant enhancements in fecundity, hatching % and cocoon yield for silkworms treated with both dyes at 100% concentration (T2). Specifically, CSR16 and CSR27 exhibited the highest values for larval weight, cocoon weight, pupation rate and shell ratio % in T2 treatments. The findings suggest that feeding silkworms natural dyes, particularly at higher concentrations, significantly improved the economic parameters of both breeds. While the cocoons produced were intrinsically coloured without compromising commercial parameters, the colour intensity was lighter than anticipated. This implies that introducing dyed mulberry leaves during the 1st instar stage may yield more favourable results. Overall, the study demonstrates that madder and indigo dyes are suitable for producing coloured silk, offering potential for large-scale applications in sustainable silk production.

Screening of Economically Sustainable Strains of Bivoltine Silkworm, Bombyx mori L. by Assessing the Comparative Fibroin Gene Expression

Screening of Economically Sustainable Strains of Bivoltine Silkworm, Bombyx mori L. by Assessing the Comparative Fibroin Gene Expression

Performance of Recently Developed Single and Double Hybrids of Bivoltine Silkworm (Bombyx mori) in India

India, contributing over 18% to global silk production, has made significant strides in sericulture through advancements in silkworm breeding. This review evaluates the performance of recently developed single and double hybrids of bivoltine silkworms (Bombyx mori) in India. These hybrids are essential for enhancing silk productivity and quality, addressing the challenges of environmental stress. This assessment reveals that these new hybrids exhibit improved growth rates, silk yields, and thermotolerance. However, limitations such as genetic stability and environmental sensitivity persist, which could impact long-term sustainability. The novelty of this work lies in its comprehensive analysis of these hybrids’ performance under varied conditions, providing insights into their potential and areas needing further improvement. Continued research, advanced breeding techniques, integrated pest and disease management, large scale evaluation at farmer’s field and supportive policies are crucial for the sustainable growth of India’s sericulture industry. By adopting these hybrids and modern rearing practices, the industry can achieve higher yields, better quality silk and substantial contributions to the rural economy and global silk market.

Enzyme Response in Thermotolerant Silkworm Breeds under Beauveria bassiana Infection

A study on enzyme activity in thermotolerant bivoltine silkworm breeds under Beauveria bassiana disease was conducted at the Department of Sericulture, UAS, GKVK, Bengaluru during 2021-23. Thermotolerant bivoltine breeds viz., B1, B4 and B8, were resistant to muscardine and CSR4, a muscardine susceptible breeds were used in this study. A batch of silkworms of all the breeds were inoculated with 6.86 × 104 spores / ml of B. bassiana @ 0.5 ml per silkworm immediately after 4th moult and another batch were reared under normal condition. The haemolymph was collected from these breeds at 48, 96 and 144 hours post inoculation (hpi) with B. bassiana spores in both inoculated and control batches. Biochemical estimation of amylase, protease and trehalase enzyme activities in the haemolymph. The amylase activity increased from 48 hpi to 144 hpi in all the breeds under both control and muscardine inoculation, but being lesser under inoculation. The protease activity was found higher in B1 breed from 48 hpi to 144 hpi under both control and inoculated conditions. Trehalase activity was enhanced at all time intervals under control conditions in B1, B4 and B8 breeds and CSR4 breed shows decreased at 144 hpi under both control and inoculation conditions. Thus increased enzyme activity in B1 and B4 breeds could be associated with their better performance for survival and economic parameters under inoculated condition. The correlational studies revealed that haemolymph amylase, protease and trehalase were found to be positively corelated with cocoon weight (g) and negatively correlated with larval mortality (%). Thus, the study revealed that silkworm breeds like B1, B4 and B8 as productive breeds and hence may be used for future breeding programmes for evolution of new robust silkworm breeds.

Performance of New Bivoltine Silkworm Breeds and Hybrids for Economic Traits

Performance of New Bivoltine Silkworm Breeds and Hybrids for Economic Traits

Biochemical analysis of defensive enzymes in the hemolymph of bivoltine silkworm breeds of Bombyx mori (Lepidoptera: Bombycidae)

Biochemical analysis of defensive enzymes in the hemolymph of bivoltine silkworm breeds of Bombyx mori (Lepidoptera: Bombycidae)

Evaluation of Reproductive and Growth Performance in New Breeds and Hybrids of Bivoltine Silkworm (Bombyx mori L.)

This study aimed to evaluate the reproductive and growth performance of recently developed bivoltine silkworm parental breeds and their hybrids to improve silk production and ensure the long-term sustainability of sericulture. Utilizing five thermotolerant pure breeds (B1, B2, B4, B6 and B8) and four popular CSR breeds (CSR2, CSR27, CSR6 and CSR26), six foundation crosses and eight double hybrids were developed and evaluated for ten traits. Results showed that B1 exhibited superior performance in fecundity (524.00), hatching percentage (98.67%), dead eggs (1.33%), pupal weight (1.31 g), pupation rate (96.84%) and cumulative survival index (CSI) (93.84%). The foundation cross B1 × B2 excelled in fecundity (553.67), larval mortality (2.67%), pupal weight (1.53 g), ERR (97.33%) and CSI (93.27%) while FC2 performed better in hatching percentage (97.60%), dead eggs percentage (2.40%), fifth instar larval duration (157.21 h), fifth instar larval weight (35.64 g/10 larvae) and pupation rate (96.33%). Among the double hybrids, (B1 × B2) × (FC1) demonstrated superior performance in fecundity (614.33), larval mortality (1.41%), pupal weight (2.06 g), ERR (98.59%) and CSI (97.24%). FC2 × FC1 excelled in larval duration (141.11 h), fifth instar larval weight (51.96 g/10 larvae) and pupation rate (98.94%). Double hybrids showed significant improvements compared to parental breeds and foundation crosses, indicating potential for field testing and further development. These results indicate the potential of using the newly identified breeds and foundation crosses in silkworm breeding, particularly in developing new double hybrids as an alternative to established CSR breeds and hybrids.

Upf2-Mediated Nonsense-Mediated Degradation Pathway Involved in Genetic Compensation of TrpA1 Knockout Mutant Silkworm (Bombyx mori).

Genetic mutations leading to premature termination codons are known to have detrimental effects. Using the Lepidoptera model insect, the silkworm (Bombyx mori), we explored the genetic compensatory response triggered by mutations with premature termination codons. Additionally, we delved into the molecular mechanisms associated with the nonsense-mediated mRNA degradation pathway. CRISPR/Cas9 technology was utilized to generate a homozygous bivoltine silkworm line BmTrpA1-/- with a premature termination. Transcript levels were assessed for the BmTrpA paralogs, BmPyrexia and BmPainless as well as for the essential factors Upf1, Upf2, and Upf3a involved in the nonsense-mediated mRNA degradation (NMD) pathway. Upf2 was specifically knocked down via RNA interference at the embryonic stage. The results comfirmed that the BmTrpA1 transcripts with a 2-base deletion generating a premature termination codon in the BmTrpA1-/- line. From day 6 of embryonic development, the mRNA levels of BmPyrexia, BmPainless, Upf1, and Upf2 were significantly elevated in the gene-edited line. Embryonic knockdown of Upf2 resulted in the suppression of the genetic compensation response in the mutant. As a result, the offspring silkworm eggs were able to hatch normally after 10 days of incubation, displaying a non-diapause phenotype. It was observed that a genetic compensation response does exist in BmTrpA1-/-B. mori. This study presents a novel discovery of the NMD-mediated genetic compensation response in B. mori. The findings offer new insights into understanding the genetic compensation response and exploring the gene functions in lepidopteran insects, such as silkworms.

Selected Thermotolerant Bivoltine Hybrids of Bombyx mori L. Exhibit Desirable Heterosis for Quantitative Traits under Beauveria bassiana Infection

Four thermotolerant bivoltine silkworm parents viz., B1, B4, B6 and B8 and their 12 hybrids viz., B1×B4, B1×B6, B1×B8, B4×B1, B4×B6, B4×B8, B6×B1, B6×B4, B6×B8, B8×B1, B8×B4 and B8×B6 were used in the experiments. One set of the parents and their hybrids were inoculated with Beauveria bassiana spore suspension (9.04 × 104 spores / ml), on the first day of the fifth instar before first feed and another set were exposed to high temperature (36 ± 1o C temp. & 85 ± 5 % RH) and their responses were studied in terms of heterotic expression of quantitative traits. Significantly highest positive relative heterosis under normal condition was recorded in B1×B4 hybrid for five characters (fifth instar larval weight, cocoon yield by weight, single cocoon weight, shell weight and filament length) and under muscardine inoculation significantly highest positive relative heterosis was recorded in the hybrid B4×B6 for ten characters (ERR, cocoon yield by number, fifth instar larval weight, cocoon yield by weight, single cocoon weight, shell weight, shell ratio, pupal weight, filament length and filament weight). Heterosis scoring over all the traits under muscardine inoculation revealed that the hybrid B4 × B6 scored high overall status of heterotic effects across the characters. Thus, B1 and B8 among parents and B1 × B8 and B4 × B6 among hybrids could be selected for dual stress tolerance against high temperature and muscardine disease.

Field evaluation of multi-viral diseases tolerant bivoltine silkworm hybrid of Bombyx mori l. (Lepidoptera: Bombycidae)

Bombyx mori Densonucleosis virus (BmDV), Bombyx mori Infectious flacherie virus (BmIFV) and Bombyx mori nuclear polyhedrosis virus (BmNPV) infection to silkworms causes major sericulture crop loss. The multi-viral diseases tolerant bivoltine silkworm double hybrid, RDIN1, developed through marker-assisted selection was field evaluated by rearing 20,000 dfls at different location and season. RDIN1, had better pupation (94.8%) compared to control, FC1 X FC2 (91.5%) at farmers’ level with 4 % significant improvement. Average Cocoon yield of RDIN1 (71.2%) was better compared to FC1 X FC2 (69.3%) in unfavourable conditions. Other parameters such as cocoon weight, shell weight, shell percentage, reelability, filament length, raw silk, denier, neatness had also significant difference between RDIN1 and FC1 x FC2. The RDIN1 is expected to reduce cocoon crop losses invariably due to viral infection and fetch more profit to sericulture farmers.

Effect of Spermidine Supplementation on Testicular And Ovarian Development in Sex-limited and Non-sex-limited Bivoltine Silk Worm Breeds of <i>Bombyx mori</i> L

Silk worm Bombyx mori L is a holometabolous, lepidopteran model for investigating the effect of various molecules. The sex-limited character of cocoon color is useful for the separation of male and female pupae during commercial seed production. Fecundity is the major limitation of cocoon colour sex-limited breeds. Spermidine is a polyamine, present in all living cells involved in the growth and reproduction of many organisms. The effect of spermidine on testicular and ovarian development in the selected bivoltine sex-limited breed; APS27SL and non-sex-limited hybrid; APS45 x APS12 is studied in the present work. Results showed that foliar feeding of spermidine significantly increased pupal growth, testicular and ovarian growth, number of ovarioles and ovules in the sex-limited breed. Moreover, increased expression of Bm-tektin was observed in the testes of spermidine fed groups. Thus, the study suggests that foliar feeding of spermidine can be used to overcome the limitation of reproductive potential in sex-limited breeds.

Investigating the performance of thermotolerant bivoltine silkworm breeds and hybrids infected with Beauveria bassiana

Investigating the performance of thermotolerant bivoltine silkworm breeds and hybrids infected with Beauveria bassiana

Comparative assessment of growth and performance of bivoltine silkworm races fed on mulberry (Morus alba) against biological and commercial parameters of Bombyx mori Linn.

Comparative assessment of growth and performance of bivoltine silkworm races fed on mulberry (Morus alba) against biological and commercial parameters of Bombyx mori Linn.

Performance of new double hybrids of bivoltine silkworm derived from high temperature and muscardine tolerant foundation crosses

Performance of new double hybrids of bivoltine silkworm derived from high temperature and muscardine tolerant foundation crosses

Evaluation of New Foundation Crosses of Thermotolerant Bivoltine Silkworm (Bombyx mori) for their Tolerance to Muscardine Disease

Evaluation of New Foundation Crosses of Thermotolerant Bivoltine Silkworm (Bombyx mori) for their Tolerance to Muscardine Disease

Storage duration of bivoltine Silkworm (Bombyx mori L.) hybrid cocoons: its effect on reeling performance and cocoon characteristics

Storage duration of bivoltine Silkworm (Bombyx mori L.) hybrid cocoons: its effect on reeling performance and cocoon characteristics

Differential adult lifespan and starvation stress responses in laboratory evolved bivoltine silkworm breeds of Bombyx mori l.

Silkworm breeding is majorly focused on balancing the progress of productive trait to generate profitability.However, with recurrent commercialization and utilization of such productive trait through heterosis may decline with drastic climatic variations. In order to achieve and generate profitability in sericulture, paradigm shift is essential through transition from balanced breeding to sustainable breeding via selection of breeding lines with better adult moth longevity which confers the benefits by coping with stressful environment. In the present investigation, CSR bivoltine silkworm breeds were screened to understand the adult moth longevity among them which have attained two decades of evolution. Differential longevity was recorded among the selected breeds. The maximum and minimum longevity was observed in CSR 51 and CSR17 respectively than other breeds. The short-listed breeds were exposed to starvation stress, wherein, interestingly, the CSR51 was highly tolerant compared to other breeds and CSR17 being short-lived was susceptible to starvation stress. The data obtained suggest that the relatively longer lifespan may be rendering more tolerance towards the starvation stress mediated lethality, as evident by the induced starvation stress assay. This would help us to focus on the generation of long-lived breeding lines with better longevity which could intrinsically determine for better abiotic and biotic stress tolerance.

Comparative analysis of gut bacteria of silkworm Bombyx mori L. on exposure to temperature through 16S rRNA high throughput metagenomic sequencing

Global warming is one of the serious threats that adversely affects the development and reproduction of silkworms. The ideal temperature for silkworms to carryout normal life activities is 20–30 °C. Certain bivoltine silkworms that are raised in tropical regions are thermotolerant. But, prolonged exposure to high temperatures may be fatal. In the present study, fifth instar larvae of bivoltine silkworm were exposed to heat shock at 40 ± 2 °C for a short period of one hour per day to examine the changes in the gut microflora. The study used high throughput sequencing to evaluate the impact of intestinal microbes of silkworms in response to high temperature. The findings demonstrated that elevated temperature has a negative impact on the intestinal microbes of silkworm compared to the control which were reared under the optimum temperature (25 ± 3° C). Four hundred and fifty eight (458) species of microbes were reported in the control group whereas only 434 species were reported in the temperature exposed group. The digestive process of silkworms may also be impaired by heat shock due to their effect on digestive enzymes. So, the results indicated that heat shock has an impact on the intestinal microflora of silkworms that control the activity of associated digestive enzymes which affects the digestion and nutritional intake, eventually impacting the growth and development of silkworm larvae and cocoons produced. The morphometric parameters of silkworm larvae and cocoons also showed a considerable drop when exposed to heat shock.

RNA N6-methyladenosine of DHAPAT and PAP involves in regulation of diapause of Bombyx mori via the lipid metabolism pathway.

Environment-induced epigenetics are involved in diapause regulation, but the molecular mechanism that epigenetically couples nutrient metabolism to diapause regulation remains unclear. In this study, we paid special attention to the significant differences in the level of N6-adenosine methylation (m6A) of dihydroxyacetone phosphate acyltransferase (DHAPAT) and phosphatidate phosphatase (PAP) genes in the lipid metabolism pathway of the bivoltine silkworm (Bombyx mori) strain Qiufeng developed from eggs incubated at a normal temperature (QFHT, diapause egg producer) compared to those from eggs incubated at a low temperature (QFLT, non-diapause egg producer). We knocked down DHAPAT in the pupal stage of the QFLT group, resulting in the non-diapause destined eggs becoming diapausing eggs. In the PAP knockdown group, the colour of the non-diapause destined eggs changed from light yellow to pink 3 days after oviposition, but they hatched as normal. Moreover, we validated that YTHDF3 binds to m6A-modified DHAPAT and PAP mRNAs to promote their stability and translation. These results suggest that RNA m6A methylation participates in the diapause regulation of silkworm by changing the expression levels of DHAPAT and PAP and reveal that m6A epigenetic modification can be combined with a lipid metabolism signal pathway to participate in the regulation of insect diapause traits, which provides a clearer image for exploring the physiological basis of insect diapause.