Bivoltine Race Research Articles

Studies on the biological traits of multivoltine and bivoltine races and their F1 hybrids of mulberry silkworm

Studies on the biological traits of multivoltine and bivoltine races and their F1 hybrids of mulberry silkworm

Comparative Haemolymph Protein Content in Gen-3 Bivoltine Race of Bombyx Mori L. with Supplementation of Vitamin-C , E

Comparative Haemolymph Protein Content in Gen-3 Bivoltine Race of Bombyx Mori L. with Supplementation of Vitamin-C , E

Silk Productivity and Yield Related Characters of Selected Pure Races of Mulberry silkworm, Bombyx mori L.

Experiment was conducted to study the cocoon, biological and yield related characters of selected pure races of Bombyx mori L. Among the multivoltine races, significantly higher cocoon, biological and yield related characters were observed in AGL3 and low in Pure Mysore. Among the bivoltine races, significantly higher characters were observed in CSR2 and low in NN6D. The silk productivity had significant positive correlation with the cocoon and yield related characters whereas fifth instar larval duration, cocoon length and breadth ratio, and renditta were negatively correlated, among all the 10 pure races tested.

Changes in the Activity of Digestive Enzymes in Response to Chemical Mutagen Diethyl Sulfate in the Silkworm Bombyx mori L. (Lepidoptera: Bombycidae)

The silkworm Bombyx mori L. is a economic sericigenous insect show a high degree of sensitivity towards chemical mutagens and have drastic physiological and biochemical effects during its larval stages. In the present study a bivoltine race of silkworm NB 4D 2 was treated with chemical Mutagen Diethyl Sulfate (DES). The larvae were used for the treatment with different concentrations of DES orally as well as injected through body wall. In F 1 generation, the larvae of 4th and 5th instar were used to study the activity of prominent digestive enzymes amylase and protease for evaluation of the mutagenic response in haemolymph and midgut tissues. The enzyme activity was found to be higher in treated sets, particularly in 8 mM injection sets. Further, maximum enzyme activity was noticed during middle part of both the instars with a few variations among the treated sets. The data were statistically analysed using One-way ANOVA and discussed. © 2012 Knowledgia Review, Malaysia.

Genetic Distance and Heterosis through Evaluation Index in the Silkworm, Bombyx mori (L.)

Problem statement: Synthesis of new-gene combinations by genetic manipulation is one of the powerful tools in exploiting the commercial qualities of plants and animals. Hybrid performance is evaluated from extensive yield trials that are costly and time consuming. Approach: Four silkworm races belonging to two different voltine groups (two multivoltine races namely Pure Mysore and Nistari and two bivoltine races namely C108 and NB4D2) and the twelve regular and reciprocal hybrids derived from them were reared under standard laboratory condition analyzing six quantitative traits namely cocoon weight, shell weight, shell ratio, filament length, denier and renditta. The data of the pure races was analysed for the estimation of evaluation index to study the genetic divergence between the races, where as evaluation index, heterosis and overdominance effects were studied in twelve hybrid combinations. Results: Varied heterotic effects were observed for different traits for hybrid combination. Cocoon weight and shell weight has maximum heterosis over the mid parent in Pure Mysore × Nistari (27 and 42% respectively), whereas C108 × Nistari have shown maximum shell ratio (30%) among the hybrids. The maximum filament length for heterosis was observed in the Nistari × Pure Mysore. Heterosis for cocoon weight, shell weight, shell ratio, filament length, denier and renditta based on evaluation index confirmed the above results. Conclusion: The investigation indicates that optimum level of genetic divergence between parents is necessary to obtain heterosis in F1 generation.

C/N RATIO OF MULBERRY LEAVES FED TO SILKWORM, Bombyx mori L. LARVAE AS AN INDEX FOR ITS PRODUCTIVITY.

The present study was conducted to evaluate the performance of five mulberry varieties used for rearing the bivoltine race (EJ) of mulberry silkworm. Nutritional composition of the leaves was determined. Carbohydrate/protein (C/N) ratios were focused. Also, leaf/cocoon ratios and its suitability for judging the mulberry leaves efficiency were determined. The results show significant differences between varieties. Kokuso-27 and Kearyang-Seoban-3 show higher nutritional components followed by Josaengrok-2. While the lowest value were recorded in Morittiana and Kokuso-20 varieties. Kokuso-27 and Kearyang-Seoban-3 recorded lowest values in C/N ratio and in leaf/cocoon ratio, and therefore, Kokuso-27 and Kearyang-Seoban-3 give more superiority over other varieties, they can be used as criteria for comparing the different mulberry varieties. The biological and economic characters of silkworm were reflection of higher values of leaf nutritional contents, lower values of carbohydrate/ protein ratio and leaf /cocoon ratio.

Molecular cloning and characterization of Bombyx mori CREB gene

The cAMP response element binding protein (CREB), as one of the best characterized stimulus-induced transcription factors, plays critical roles in activating transcription of target genes in response to a variety of environmental stimuli. To characterize this important molecule in the silkworm, Bombyx mori, we cloned a full-length cDNA of CREB gene from B. mori brains by using RACE-PCR. The sequence of B. mori CREB (named BmCREB1) gene contains a 88 bp 5' UTR, a 783 bp open reading frame (ORF) encoding 261 amino acids and a 348 bp 3' UTR. The deduced BmCREB amino acid sequence has 56.7% and 37.2% homology with CREB from Apis mellifera carnica and Drosophila melanogaster, respectively. The primary structure of the deduced BmCREB1 protein contains a kinase-inducible domain (KID) and a basic region/leucine zipper (bZIP) dimerization domain which exists in all CREB family members. Genomic analysis showed there are 9 exons and 5 introns in B. mori CREB genome sequences. We identified three different isoforms of BmCREB (BmCREB1, BmCREB2 and BmCREB3) through alternative splicing in C terminal. In addition, the expression of BmCREB in different developmental stages was investigated by using quantitative real-time PCR in both diapause and non-diapause type of B. mori bivoltine race (Dazao). BmCREB transcripts showed two peaks in embryonic stage and pupal stage in both types of bivoltine race. However, consistently higher expression of BmCREB was found throughout the developmental stages in the diapause type than in the non-diapause type. These results suggest that BmCREB is involved in the process of diapause induced by environmental factors.

Effect of Fenvalerate-20EC on Sericigenous Insects: I. Food Utilization in the Late-Age Larva of the Silkworm, Bombyx mori L.

The effect of the common pyrethroid insecticide fenvalerate-20EC (Sumicidine-20EC) on food utilization parameters in the pure multivoltine (Pure Mysore) and pure bivoltine (NB 4D 2) races of silkworm, Bombyx mori, fed ad libitum with Morus alba, was studied in the final two instars. Insecticide treatment was found to reduce the rates of feeding, assimilation, and conversion along with the efficiencies of conversion of ingested and digested food into body substance. This was due to the toxic effects, which interfered with the silkworms' feeding behavior, and physiology of digestion, and the magnitude of changes increased with the increase in the concentration of fenvalerate used. To overcome the deleterious effects of such pyrethroid insecticides, it has been suggested that the safe periods for use of mulberry leaves contaminated with fenvalerate for summer and winter.

Enhancement of cocoon yield in silkworm, Bombyx mori.L. by protein supplementation in shoot rearing

Two laboratory experiments were conducted during winter 2000 to study the effect of fortification of mulberry leaves and shoot with soyaflour on the larval and cocoon characters in a bivoltine race NB4D2 and a cross breed, PMXNB4D2 of silkworm, Bombyx mori. Soyaflour @ 5 g and 10 g kg of shoot was compared with 10 g kg' of leaves.

Neuroendocrine regulation of seasonal morph development in a bivoltine race (Daizo) of the silkmoth, Bombyx mori L.

We investigated the neuroendocrine regulation of the development of seasonal morphs in a bivoltine race (Daizo) of the silkmoth, Bombyx mori, by decerebration, the transplantation of brain–suboesophageal ganglion (Br-SG) complexes and the injection of active neuropeptides. When brains were removed from fresh pupae destined to develop into summer morphs (SD pupae) by embryonic and larval exposures to short days at low temperature, the pupae developed into autumn or intermediate morphs. However, in pupae destined to develop into autumn morphs (LD pupae), the operation did not show an effect on seasonal morph development. Br-SG complexes were excised from fifth-instar LD and fifth-instar SD larvae 2 days after larval ecdysis and were transplanted into the abdomen of SD larvae of the same age. The Br-SG complexes of LD larvae, but not the Br-SG complexes of SD larvae, shifted the host's seasonal morph development toward the autumn morph. Furthermore, when treated with crude pupal SGs extract and diapause hormone (DH), fresh SD pupae developed into autumn or intermediate morphs, respectively. Possibly the development of seasonal morphs in the silkmoth, B. mori, is regulated by a novel function of DH. Alternatively, DH may act on the imaginal wing disks at an earlier stage than on the ovaries.

Effects of photoperiod and temperature on seasonal morph development and diapause egg oviposition in a bivoltine race (Daizo) of the silkmoth, Bombyx mori L.

A bivoltine race (Daizo) of the silkmoth, Bombyx mori, has two types of adults which are classified on the basis of the number of dark-brown and brown scales distributed along the outer lines of the anterior wings. Development of these two types of adults is determined by photoperiod and temperature experienced during the embryonic and larval stages. The two types of adults are thought to be seasonal (summer and autumn) morphs. All adults developed under short days at low temperature (15°C and 23°) were classified as summer morphs and oviposited only nondiapause eggs (ND-eggs), and those that developed under long days at high temperature (28°C and 25°C) were autumn morphs ovipositing only diapause eggs (D-eggs), only ND-eggs or a mixture of D- and ND-eggs. Larval exposure to long days at 25°C shifted the wing pattern towards the autumn morphs and decreased the incidence of female adults ovipositing only D-eggs. Larval exposure to long days elicits an opposite effect on D-egg oviposition to that observed when long days are received only during the embryonic stage.

Free nucleotides related to the induction of diapause in the silkworm, Bombyx mori

Free nucleotides in pupal brains were examined in a bivoltine race (Daizo) of the silkworm, Bombyx mori, using high pressure liquid Chromatography (HPLC). Concentrations were nearly the same level as observed in rat brains. Major differences in monophosphates, diphosphates and triphosphates of purine and pyrimidine nucleotides, and an unidentified nucleotide derivative were observed between silkworms which were exposed to regimens of continuous light and warm conditions (27 °C) and those exposed to continuous darkness and cold conditions (15 °C) throughout maternal embryonic development. In particular, concentrations of ADP, ATP, GDP, GTP, IDP, ITP, UDP and UTP were more abundant in the pupal brains of insects exposed to continuous light and warm conditions. When brain-subesophageal ganglion complexes from non-diapause egg producers were cultured with mixtures of nucleotides, the resulting culture medium was highly effective in eliciting diapause in non-diapause egg producers. These results suggest that brain nucleotides have a role in diapause induction.

Heat shock response in mulberry silkworm races with different thermotolerances

The thermal sensitivity and heat shock response of the different races of the mulberry silkworm Bombyx mori have been analysed. The multivoltine race, strains C. Nichi and Pure Mysore showed better survival rates than the bivoltine race, strain NB4D2 exposed to 41 degrees C and above. In general, the fifth instar larvae and the pupae exhibited maximum tolerance compared to the early larval instars, adult moths or the eggs. Exposure up to 39 degrees C for 1 or 2 h was tolerated equally whereas temperatures above 43 degrees C proved to be lethal for all. Treatment of larvae at 41 degrees C for Ih resulted in a variety of physiological alterations including increased heart beat rates, differential haemocyte counts, enlargement of granulocytes and the presence of additional protein species in the tissues and haemolymph. The appearance of a 93 kDa protein in the haemolymph, fat bodies and cuticle, following the heat shocking of larvae in vivo was a characteristic feature in all the three strains examined although the kinetics of their appearance itself was different. In haemolymph, the protein appeared immediately in response to heat shock in C. Nichi reaching the maximal levels in 2-4 h whereas its presence was noticeable only after 2-4 h recovery time in Pure Mysore and bivoltine races. The fat body from both C. Nichi and NB4D2 showed the presence of 93 kDa, 89 kDa and 70 kDa proteins on heat shock. The haemocytes, on the other hand, expressed only a 70 kDa protein consequent to heat shock. The 93 kDa protein in the haemolymph, therefore could have arisen from some other tissue, possibly the fat body. The 93 kDa protein was detected after heat shock in pupae and adult moths as well, although the presence of an additional (56 kDa) protein was also apparent in the adults. The presence of 46 kDa and 28 kDa bands in addition to the 93 kDa band in the cuticular proteins immediately following heat shock was clearly discernible. The 70 kDa band did not show much changes in the cuticular proteins on heat shock. In contrast to the changes in protein profiles seen in tissues and haemolymph following heat shock in vivo, the heat treatment of isolated fat body or haemolymph in vitro resulted in protein degradation.

Spore replication rate of Nosema bombycis (Microsporidia: Nosematidae) in the silkworm Bombyx mori L. in relation to pupal development and age of moths

The spore replication rate of the parasitic microsporidian, Nosema bombycis, was investigated in the pupal and adult stages of two popular tropical silkworm races of India, Pure Mysore (multivoltine race) and NB18 (bivoltine race). The rate was assessed in terms of spore yield per unit weight of tissue. In pupae, spore replication in the bivoltine race was higher than that in the multivoltine race. Spore replication in both races followed a logistic pattern. Spore production increased substantially with age of moths in both races. The cephalothoracic region of each race had the highest spore concentration, especially around the wing and wing muscles.

New pathway of utilization of ammonia nitrogen for the synthesis of amino acids through NADH dependent transaminases in Bombyx mori L.

. NADH dependent transamination was recorded for the first time in silkworm Bombyx mori(L.) eggs and in larval tissues. L-Glutamine:2–oxoglutarate amino transferase (GOGAT) and L-asparagine:2–oxoglutarate amino transferase (AOGAT) were determined in embryonic and also in larval tissues of multi-and bivoltine races. The presence of these two enzymes coupled to glutamine synthetase indicated efficient utilization of metabolic ammonia hitherto unknown in higher organisms. It is proposed that these transfer enzymes help in building the free amino acid pool seen during the diapause and also in the fibroin synthesis in the last larval stadium.

Evaluation of bivoltine single and double cross hybrids of silkworm, Bombyx mori L. for grainage parameters

Grainage parameters, viz. pupal weight, rate of moth emergence, fecundity and hatching were studied among four bivoltine pure races and their five single and four double cross hybrids of silkworm Bombyx mori L. The significant increase in double cross hybrids over pure races was 11.72, 7.43,19.45 and 12.26% for pupal weight, rate of moth emergence, fecundity and hatching, respectively. The fecundity in double cross hybrids improved significantly over single cross hybrids to the extent of 16.03% whereas pupal weight, rate of moth emergence and hatching increased to the extent of 4.38, 5.90 and 5.76%, respectively. The extent of standard heterosis and heterobeltiosis was maximum in double cross hybrids and the heterosis was more pronounced for fecundity.

Establishment of Various European Corn Borer (Lepidoptera: Pyralidae) Races on Selected Cultivars of Snap Beans

Cultivars of snap beans, Phaseolus vulgaris L., previously evaluated for levels of resistance to larvae of a single race of European corn borer, Ostrinia nubilalis (Hubner), were infested in greenhouse and field experiments with eggs from laboratory cultures of three races and an interracial hybrid. In the greenhouse, fewer larvae survived on the cultivars‘ Volare’ and‘ BBL-94’ (1.3 and 6.4%, respectively) than on‘ 77063’ and‘ BBL-92’ (11.8 and 11.7%, respectively). Although the establishment of larvae was very low for all experiments, particularly in the field (0-0.46%), we noted significant differences among the races. A bivoltine race of European corn borer, producing a pheromone blend of primarily (E)-11-tetradecenyl acetate, had the highest establishment, and a second hivoltine race and a univoltine race that shared a pheromone blend of primarily (Z)-11-tetradecenyl acetate had lower establishment rates. An interracial hybrid population that resulted from crossing the two parental bivoltine races had low to intermediate levels of establishment.

Comparative analysis of sex-pheromone-response antagonists in three races of European corn borer

Behavioral responses of males from three New York races of European corn borer,Ostrinia nubilalis (Hübner), to various suspected sexpheromone-response antagonists were investigated with a flight tunnel protocol. Males from a bivoltine (Z) race and from a univoltine (Z) race utilizing a natural pheromone blend of 98∶2 (Z)-∶(E)-11-tetradecenyl acetates and males from a bivoltine (E) race utilizing a 1∶99 (Z)-∶(E)-11-tetradecenyl acetate ratio were flown to their natural blends and to blends containing 1 % of one of the following additional compounds: Z9-12∶OAc,E9-12∶OAc,Z9-14∶OAc, andE9-14∶OAc. In each race, the added components lowered significantly the number of individuals completing the behavioral sequence. The only exception was bivoltineE males flown to a blend withE9-12∶OAc added. The number completing the sequence in this case was statistically not significantly lower than the number that completed the sequence to the standard blend. In all three races, theZ9-14∶OAc produced the most dramatic reduction in completed flights, and in the univoltineZ race, this added component was significantly more effective in reducing completed flights than any other added component. The response to the Z9-14∶OAc is understandable given recently published findings of an electrophysiological study of single sensilla in the European corn borer.

Damage to Apple Cultivars by Races of European Corn Borer (Lepidoptera: Pyralidae)

Experiments were conducted in a growth chamber, greenhouses, and orchards to determine the level of infestation, behavior, and survival of larvae from European corn borer, Ostrinia nubilalis (Hubner), races and a population on apple cultivars. Field infestations of apple shoots with either eggs or first instars of three races yielded no establishment. In a greenhouse test with potted scions, however, a bivoltine race responding to a predominately E pheromone mix, produced significantly more dead shoots than other infestations. Greatest shoot mortality in the greenhouse was caused by infestations with fourth instars. In growth-chamber tests, neonate larvae displayed a low degree of establishment on fruits, but where there was establishment, fruit entry increased proportionately with instar. Cultivars in both the orchard and the growth chamber were not equally susceptible to larval entry into fruits. Bivoltine races responding to E or Z pheromone blends entered orchard fruits to a greater degree and caused more damage than did a univoltine race responding to a Z pheromone blend.

Photoperiodic induction in the silkworm, Bombyx mori, reared on artificial diet: Evidence for extraretinal photoreception

When a bivoltine race of the silkworm, Bombyx mori, was reared on artificial diets, the silkworm became photoperiodically responsive during larval development. The response curve for the embryonic-diapause induction of the next generation was of the long-day type, showing a sharply defined critical day-length of 16.5 hr. Complete blindness caused by covering the larval stemmata with black paint was confirmed electrophysiologically. It did not influence the diapause incidence. Vitamin A deficiency, which produced a similar defect in visual function in the stemmata, was also without effect on diapause. These observations show that extraretinal photoreception is involved in photoperiodic induction in the silkworm.