Go to the main menu
Skip to content
Go to bottom
REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
International Journal of Industrial Entomology
Journal Basic Information
Journal DOI :
Korean Society of Sericultural Science
Editor in Chief :
Volume & Issues
Volume 9, Issue 2 - Dec 2004
Volume 9, Issue 1 - Sep 2004
Volume 8, Issue 2 - Jun 2004
Volume 8, Issue 1 - Mar 2004
Selecting the target year
Phylogenetic Relationships of the Fireflies Co-occurring in Korean and Japanese Territories Analyzed by Luciferase and Mitochondrial DNA Sequences
Kim, Iksoo ; Kim, Jong Gill ; Jin, Byung Rae ;
International Journal of Industrial Entomology, volume 9, issue 2, 2004, Pages 155~165
In Korean Peninsula including neighboring islands and Japanese Islands identical firefly species or the species belonging to same genera occur together in both territories. These geographic firefly species, nonetheless, have never been subject to taxonomic consideration together until recently, lacking clear species status and phylogenetic relationships. A recent serial study of these fireflies using luciferase gene and/or portions of mitochondrial DNA sequences provided some insight into these populations in terms of validity of species name, phylogenetic relationships, and speciation event. In this article, thus, we have reviewed the recent progress on phylogenetic and/or population genetic aspects of these species, i.e., Hotaria-group fireflies, Luciola lateralis, and Pyrocoelia rufa to better understand the firefly species in these regions.
Characterization of Expressed Sequence Tags (ESTs) Generated from the Bombyx mandarina Whole Larvae and Molecular Cloning of Serine Protease Homologue Gene
Hwang, Jae Sam ; Yun, Eun Young ; Goo, Tae Won ; Kim, Iksoo ; Choi, Kwang Ho ; Seong, Su Il ; Kim, Keun Young ; Lee, Sang Mong ; Kang, Seok Woo ;
International Journal of Industrial Entomology, volume 9, issue 2, 2004, Pages 167~171
We constructed an oligo-d(T) primed directional cDNA library from the Bombyx mandarina whole larvae. In an effort to isolate genes expressed in the B. mandarina, 227 expressed sequence tags (ESTs) were generated by single-pass sequencing from the cDNA library. Sequence analysis showed that 107 clones (47.1%) were classified into known genes and 120 clones (52.9%) were novel transcripts, which are unknown for their function. Of the 107 known genes, the most abundant gene was found to be actin and followed by serine protease in the expression profile. Among these clones, a serine protease homolog (BmSP) which is a class of proteolytic enzymes isolated. Full-length sequence of the BmSP cDNA clone was 922 bp in length and has an open reading frame of 276 amino acids. The conserved histidine, aspatic acid and serine residues forming the catalytic center as well as cysteine residues contributing to three disulphide bonds also were found in Bmsp gene. mRNA expression analysis revealed a high and specific expression of the gene only in midgut tissue, suggesting that BmSP gene is closely associated with the expression of digestive enzyme.
Comparative Study of Anti-Apoptotic Genes, Bcl-2 and P35 for the Suppression of Apoptosis Induced in Suspension Culture of Transformed Trichoplusia ni BTI Tn 5B1-4 Cells
Lee, Jong-Min ; Sohn, Bong-Hee ; Kang, Pil-Don ; Lee, Sang-Uk ; Chung, In-Sik ;
International Journal of Industrial Entomology, volume 9, issue 2, 2004, Pages 173~181
To delay the onset of apoptosis in the culture, transformed Tn 5B1-4 cells harboring anti-apoptotic genes, bcl-2 and baculovirus p35, have been established and analyzed for their anti-apoptotic ability in suspension culture using spinner flasks. In the suspension culture at agitation speeds of 100 rpm and 200 rpm, the cell growth of cell clone expressing Bcl-2 protein was much higher than other two clones and the maximum cell density of the clone was 6.0
cells/ml and 6.2
cells/ml at day three of the incubation. On the other hand, the cell growth of cell clone expressing baculovirus protein P35 was much higher than other two clones in suspension culture at agitation speed of 300 rpm and the maximum cell density of the clone was 6.1
cells/ml at day three of the incubation. Based on the pattern of genomic DNA laddering and the microscopic observation of apoptotic bodies, the more apoptotic bodies are induced in Tn 5B1-4 control cell clone at higher agitation speed. This result shows that the shear stress can be a main factor in inducing apoptosis in spinner flask culture. At low agitation speed, cell clone expressing Bcl-2 was more effective in delaying the onset of apoptosis than the cell clone expressing P35. On the other hand, at high agitation speed, cell clones expressing baculovirus P35 was more effective in delaying the onset of apoptosis than the cell clone expressing Bcl-2. Therefore, anti-apoptotic genes, bcl-2 and baculovirus p35, can playa distinct role depending on agitation speed in the suspension culture.
Cloning of Small Plasmids from Bacillus thuringiensis Subsp. israelensis Using Plasmid Capture System
Choi, Jae Young ; Roh, Jong Yul ; Li, Ming Shun ; Shim, Hee Jin ; Kang, Joong Nam ; Woo, Soo Dong ; Jin, Byung Rae ; Je, Yeon Ho ;
International Journal of Industrial Entomology, volume 9, issue 2, 2004, Pages 183~186
Recently, we have developed an easy, simple and convenient circular DNA cloning system named plasmid capture system (PCS). To investigate usefulness of PCS in cloning of plasmids from Bacillus thuringiensis strains, PCS donors, pPCS-S and pPCS-L were applied to clone plasmids of B. thuringiensis subsp. israelensis by in vitro transposition using
transposase. In result, 3 small plasmids were cloned, and these were consistent with pTX14-1, pTX14-2 and pTX14-3 reported previously from B. thuringiensis subsp. israelensis. Therefore, the PCS can be successfully applied to clone small plasmids from B. thuringiensis strains.
Cloning and mRNA Expression of an Actin cDNA from the Mulberry Longicorn Beetle, Apriona germari
Gui, Zhongzheng ; Lee, Kwang Sik ; Wei, Yadong ; Yoon, Hyung Joo ; Kim, Iksoo ; Guo, Xijie ; Sohn, Hung Dae ; Jin, Byung Rae ;
International Journal of Industrial Entomology, volume 9, issue 2, 2004, Pages 187~191
Actin is a ubiquitous and highly conserved protein found in eukaryotic organisms. In this study, we describe the cDNA cloning and mRNA expression of an actin gene from the mulberry longicorn beetle, Apriona germari. The A. germari actin cDNA is 1524 bp containing a complete 1128 bp open reading frame that encodes a polypeptide of 376 amino acid residues with a predicted molecular weight of about 41.5 kDa. The deduced amino acid sequence of the A.germari actin cDNA showed 99% protein sequence identity to Homalodisca coagulata actin, differing at only two amino acid positions, and 92-98% protein sequence identity to known insect species actins. The predicted three-dimensional structure of A. germari actin revealed the four residue hydrophobic pulg loop characteristic of the actin family. Northern blot analysis showed that A. germari actin is highly expressed in epidermis and muscle, and less strongly in midgut, but not in the fat body of A. germari larva.
Seasonal Effects on the Performance of Newly Evolved Bivoltine Hybrids of the Silkworm (Bombyx mori L.) Under Tropics
Rao, P.Sudhakara ; Datta, R.K. ; Palit, A.K. ; Haque Rufaie, S.Z. ;
International Journal of Industrial Entomology, volume 9, issue 2, 2004, Pages 193~198
Seasonal effects of the newly evolved bivoltine hybrid namely CSR
and control hybrid KA
along with their parents SR
KA and NB
were evaluated during different seasons of the year to understand genotype and environment interactions. Data were collected on five economic importance namely, pupation rate, cocoon yield, cocoon weight, cocoon shell ratio and filament length of the lines, hybrids and the control breeds/hybrid in three different seasons i.e., Pre-Monsoon, Monsoon and post-monsoon and subjected to relevant statistical methods. Seasonal performance of CSR
revealed superiority over control breeds KA and NB
. Both the hybrids i.e., CSR
performed well under diversified environmental conditions of tropical climate in a year indicating overall stability. These hybrids revealed highly significant (P < 0.01) variations for majority of the traits studied over the control hybrid KA
Evaluation of F
Hybrids Between RD
and Bivoltine Breeds of the Silkworm (Bombyx mori L.) for Exploitation in Dry Zones
Singh, Ravindra ; Rao, D.Raghavendra ; Baro, Pranakrishna ; Choudhary, Nazia ; Gangopadhyay, Debnirmalya ; Kariappa, B.K. ; Dandin, S.B. ;
International Journal of Industrial Entomology, volume 9, issue 2, 2004, Pages 199~205
With the main objective to know the feasibility of exploitation of F
hybrids in semi arid and arid climatic conditions of India, the present study was carried out by utilising RD
as female parent and six bivoltine silkworm breeds viz., CSR
along with NB
as male parents. Different hybrids exhibited their superiority for various economic characters during different seasons. Among F
was adjudicated as the best hybrid in terms of expression of significant positive hybrid vigour over mid parental value for five economic characters namely hatching %, cocoon yield, cocoon weight, cocoon shell weight and filament size, highest multiple trait average evaluation index value of 56.77 and comparatively uniform cocoon size with coefficient of variation (CV%) of 3.80 and Standard Deviation (SD) of 7.99 during September - October 2003. Results of the present study revealed that the F
can be successfully exploited on commercial in semi arid and arid climatic conditions in India. India.dia.
Evaluation of ISSR and RAPD Markers for the Detection of Genetic Diversity in Mulberry (Morus spp.)
Venkateswarlu, M. ; Nath, B.Surendra ; Saratchandra, B. ; Urs, S.Raje ;
International Journal of Industrial Entomology, volume 9, issue 2, 2004, Pages 207~215
The present study was carried out to evaluate the ISSR and RAPD markers for their efficiency as genetic marker systems to establish the relationships between 18 mulberry genotypes. A total of 36 from 56 (64%) RAPD primers and 12 from 48 (25%) ISSR primers produced reproducible amplification patterns. A high proportion of polymorphic bands ranging from 44 to 91% was observed respectively with RAPD and ISSR markers. The average Resolving Power (Rp) of ISSR primers was higher than RAPD primers. The ISSR primers, UBC 825, 868 and 873, and RAPD primers, UBC 712, 720 and 729, possessed the highest Rp values and could in each instance distinguish all the 18 genotypes. Similarity matrix values were estimated based on Jaccards coefficient, considering 109 polymorphic ISSR and 212 polymorphic RAPD bands and two dendrograms were constructed. The dendrograms obtained with ISSR and RAPD markers distinguished the eight exotic genotypes from the ten indigenous (Indian) genotypes. A significant correlation value (r=0.959; p=0.001) for the cophenetic matrix between the RAPD and ISSR matrices was observed. The results indicated that the ISSR and RAPD markers could assist in the differentiation of genotypes and permit the determination of genetic distances that might be exploited by mulberry breeders in improvement programs.
Characterization of the v-cath Gene of Bombyx mori Nuclear Polyhedrosis Virus K1
Lee, Kwang Sik ; Li, Jianhong ; Je, Yeon Ho ; Woo, Soo Dong ; Sohn, Hung Dae ; Jin, Byung Rae ;
International Journal of Industrial Entomology, volume 9, issue 2, 2004, Pages 217~223
A cathepsin L-like cysteine protease, v-cath, encoded by the baculovirus has been shown to playa role in host liquefaction. We have identified a v-cath gene in the silkworm virus, Bombyx mori nuclear polyhedrosis virus (BmNPV) K1 strain. The 969 bp v-cath has an open reading frame of 323 amino acids. A putative cleavage site and catalytic sites were conserved in BmNPV-K1 v-cath. The predicted three-dimensional structure of BmNPV-K1 v-cath revealed that the overall fold of BmNPV-K1 v-cath is similar to that of other proteases of the papain family. The deduced amino acid sequence of BmNPV-K1 v-cath showed 98% and 97% protein sequence identity to BmNPV T3 strain and to Autographa californica nuclear polyhedrosis virus, respectively. The BmNPV-K1 v-cath differed at 4 amino acid positions from BmNPV T3. The v-cath gene in BmNPV-K1 genome is located on the EcoRV 6 kb and XhoI 9 kb fragments. Northern hybridization analysis of BmNPV K1 v-cath gene revealed that it is expressed late in infection.
Deletion of Superoxide Dismutase Gene of Bombyx mori Nuclear Polyhedrosis Virus Affects Viral DNA Replication
Wang, Wenbing ; Song, Zhixiu ; Ji, Ping ; Wu, Jun ; Zhang, Zhifang ; He, Jialu ; Wu, Xiangfu ;
International Journal of Industrial Entomology, volume 9, issue 2, 2004, Pages 225~228
Superoxide dismutase (SOD) is an important enzyme which catalyzes superoxide radicals to hydrogen peroxide. A Cu, Zn sod-like gene was found in Bombyx mori nuclear polyhedrosis virus encoding 151 amino acids. To demonstrate its function, a recombinant virus named dsBmNPV with deleted sod gene was constructed. It was discovered that the sod gene was not essential for viral replication. Studies on growth of budded virus in BmN cells and superoxide dismutase and catalase activities in vivo after dsBmNPV infection showed that the titer of dsBmNPV decreased obviously comparing to wild type BmNPV, the sod gene was effective on genomic DNA replication of baculovirus, the peak of SOD activity of silkworm infected with wt-BmNPV appeared between 36 and 48 hrs post infection, and with dsBmNPV, it did not appear. And the changes of CAT activity after infection were similar to SOD activity.
Taxonomic Characteristics of Six Species of Entomopathogenic Fungi Isolated from the Silkworm, Bombyx mori
Nguyen, Mau Tuan ; Nam, Sung Hee ; Park, Hyun Ro ; Han, Myung Sae ;
International Journal of Industrial Entomology, volume 9, issue 2, 2004, Pages 229~234
Six entomopathogenic fungus isolates, Beauveria bassiana J57A, Nomuraea rileyi J125A, Paecilomyces farinosus J3A, Paecilomyces fumosoroseus J50A, Metarhizium anisopliae J88, Aspergilius sp. J64A, causing muscardine disease and aspergillosis in the silkworm, Bombyx mori were investigated for their cultural and morphological characteristics (on PDA culture media within 14 days at
). The results showed that they differ each other from the features of cultural characteristics (colony elevation, colony color, colony growth rate) or morphological characteristics (conidiogenous cell structure, phialides, conidia size and shape). Among cultural characteristics, colony color is the easiest recognizable character between isolates. The morphological characteristics of each fungal isolate correspond to the descriptions of current system of classification.
The Homologous Region 3 from Bombyx mori Nucleopolyhedrovirus Enhancing the Transcriptional Activity of Drosophila hsp70 Promoter
Tang, Shun-Ming ; Yi, Yong-Zhu ; Zhou, Ya-Jing ; Zhang, Zhi-Fang ; Li, Yi-Ren ; He, Jia-Lu ;
International Journal of Industrial Entomology, volume 9, issue 2, 2004, Pages 235~239
Drosophila melanogaster heat shock protein 70 gene promoter (Dhsp70p) is widely used in transgenic insect to drive exogenous gene, and the homologous region 3 from Bombyx mori nucleopolyhedrovirus (BmNPVhr3) functions as an enhancer for several promoters. To test whether BmNPVhr3 can enhance the Dhsp70ps transcriptional activity, the reporter plasmids, which contain the Dhsp70p, the reporter
-galactosidase gene with SV40 terminator and BmNPVhr3 fragment, are constructed and transfected into the insect cell lines (Bm-N cells and Sf-21 cells) by lipofectin-mediated method. The results from the transient expression assay show that BmNPVhr3 significantly increases transcriptional activity of Dhsp70p both under the normal condition and under the heat-shock treatment, although the effects are significantly different between in Bm-N cells and in sf-21 cells. The enhancing behavior of BmNPVhr3 on the Dhsp70p is in an orientation-independent manner. Meanwhile, the effects of heat-shock treatment on Dhsp70p alone or Dhsp70p/BmNPVhr3 combination present no significant difference, indicating that BmNPVhr3 only enhances the transcriptional activity of Dhsp70p, but cant alter its characteristic of the response to the heat-shock stress. The above results suggest that the Dhsp70p/BmNPVhr3 combination is more effective one to drive exogenous gene for transgene or stable cell expression system in insects.
The Flight of the Bumblebee Queen, Bombus terrestris, After Diapause Termination Affects to Oviposition and Colony Development
Yoon, Hyung Joo ; Lee, Sang Beom ; Kim, Sam Eun ; Seol, Kwang Youl ;
International Journal of Industrial Entomology, volume 9, issue 2, 2004, Pages 241~247
It was investigated whether or not flight has any effects on oviposition and colony development of the artificially hibernated Bombus terrestris queen and ,
-treated queen. Flight periods were defined as 0 days (control), 1 day, 3 days and 6 days. The weights of queens after flight were 1.5-8.9% lower than those before flight depending on the flight periods. The oviposition and colony development of artificially hibernated and
-treated B. terrestris queen were affected by the flight. Among flight periods tested, in particular, the queens start to flight for 3 days showed better flight effect than those other flight periods in the colony development, rate of colony foundation, rate of progeny-queen production, the number of worker and queen produced. But, the longer the flight periods is, the worse the oviposition and colony development of the queens hibernated artificially and
-treated are (i.e., the 6 days-flight queen).
Influence of Sodium Nitrate (NaNO
) of Different Feeds on Growth and Bioenergetics of Bivoltine NB
Race of the Silkworm, Bombyx mori L.
Pallavi, V.P. ; Kaliwal, B.B. ;
International Journal of Industrial Entomology, volume 9, issue 2, 2004, Pages 249~254
Dietary supplementation of sodium nitrate with different concentrations 50, 100, 200, 500, 700 and 1000
/ml of single, two, three and four feeds to fifth instar larvae of biovoltine NB
race of the silkworm, B. mori resulted in significant increase in the food conversion, conversion rate and conversion efficiency
. However, there were significant decrease in the food assimilation, assimilation rate and assimilation efficiency in the sodium nitrate treated groups as compared with that of the corresponding parameters of the carrier control. This indicates that the administration of sodium nitrate may stimulate metabolic activities, thereby influencing conversion of food into body weight in the bivoltine silkworm, B. mori.
Post-Infectional Biochemical Changes in Mulberry Due to Xanthomonas campestris pv. mori Induced Bacterial Leaf Spot
Maji, M.D. ; Sengupta, T. ; Das, C. ; Urs, S.Raje ;
International Journal of Industrial Entomology, volume 9, issue 2, 2004, Pages 255~259
Post-infectional biochemical changes due to Xanthomonas campestris pv. mori (Xcm) infection in five elite mulberry varieties viz.,
and JRH was studied under inoculated condition. It was revealed that total soluble sugar and protein content was significantly declined in all the varieties due to X. campestris infection. Total phenol content was at par prior to inoculation in all varieties, but it was significantly increased in
and JRH 7 days after inoculation. The correlation coefficient (r) between total soluble sugar and total phenol content was found positive (r = 0.825) and statistically significant. Similarly, correlation coefficient (r) between total soluble protein and phenol content was found positive (r = 0.897) and statistically significant. The present study indicates that X. campestris infected leaves are nutritionally inferior in quality and the duration of phenol production in a mulberry variety play decisive role on disease resistance.nce.
Some Observations on Phenotypic Variations in Mulberry Silkworm, Bombyx mori L.
Patil, Rajashekhargouda R. ; Ankad, Ganga ; Klusugal, Sunita ;
International Journal of Industrial Entomology, volume 9, issue 2, 2004, Pages 261~264
Kolar gold (PM
CSR2) is the most popular cross breed of India, especially in Karnataka. During January - February 2004 we observed several phenotypic variations leading to poor survival. Though occurrence of morphologically abnormal individuals is common, the extent of occurrence in the present report was on the higher side (upto 6 percent). It is unwarranted and not desirable in commercial silkworm rearing. The variations exhibited might be due to change in the environmental conditions like incubation temperature during embryonic stage or spontaneous mutation resulting out of environmental stress.
Preliminary Study on a Microsporidian Isolate Occurring in the Lamerin Breed of the Silkworm Bombyx mori L. in India
Bhat, Shabir Ahmad ; Nataraju, B. ;
International Journal of Industrial Entomology, volume 9, issue 2, 2004, Pages 265~267
The silkworm, Bombyx mori L. is prone to infection of various pathogenic organisms. Pebrine, one of the deadliest disease of silkworm caused by highly virulent parasitic microsporidian, Nosema bombycis has been understood since long. Infections of the disease range from chronic to highly virulent and can result in complete lose to the sericulture industry. Several strains and species of microsporidians have since been isolated from the infected silkworms. A new microsporidian spore was isolated from Lamerin breed of the silkworm B. mori have been studied under scanning electron microscope, found to be different in spore size (length 4.36
, width 2.14
) and shape (ova cylindrical with slight depression) from standard strain N. bombycis (length 3.08
, width 2.01
and ovidal respectively). In immunological test, the silkworm breed Lamerin isolated micrisporidian spore does not react to different antibody (N. bombycis, M
) sensitized latex particle and thus appeared to be a different strain of microsporidian parasitic to the Lamerin breed of the silkworm B. mori.i.i.
Effect of Different Periods of Cold Storing of Bivoltine Eggs on Subsequent Generation Rearing Performance
Venkatesh, H. ; Raghuraman, R. ; Katti, S.R. ;
International Journal of Industrial Entomology, volume 9, issue 2, 2004, Pages 269~272
Different methods of cold storing of bivoltine eggs are in practice to postpone hatching. Bivoltine eggs undergo hibernation if they are not acid treated within 20 - 24 hrs of oviposition, which depends on race, ambient temperature and humidity. The schedules adopted for cold storing include hibernation schedule (Hib), ordinary chilling (OC), short term chilling (STC) and acid treated layings (AT). Peanut cocooning race
has been subjected for the present assessment. Cocoons harvested from the crop pertaining to all the four methods of cold storing have been used for producing different combinations and acid treated followed by rearing. The performance in respect of chawki loss, maximum larval weight
, yield/ 10,000 larvae (no), cocoon and shell weight showed maximum values for hibernation
hibernation combination followed hibernation with OC and hibernation with AT. Lowest performance was recorded when STC batch source females were used.
Studies on Cocoon Filament Size Deviation in Multivoltine Breeds and Multivoltine
Bivoltine Hybrids of Silkworm, Bombyx mori L.
Rao, D.Raghavendra ; Singh, Ravindra ; Kariappa, B.K. ; Dandin, S.B. ;
International Journal of Industrial Entomology, volume 9, issue 2, 2004, Pages 273~277
Variation in the size of the silk filament will determine the uniformity and quality of the silk reeled. In the present study, an attempt has been made to study the filament size variation in 6 multivoltine parental breeds and 9 multivoltine
bivoltine hybrids in all three seasons of a year. All multivoltine breeds and multivoltine
bivoltine hybrids showed variation in filament size throughout its length from the outer layer to inner layer. Results of the present study indicated that the size of the filament decreased from outer to inner layer. The decrease in filament size was sudden in some breeds/hybrids whereas it was gradual in other. Relationship between filament length to that of slope, average filament size to slope, and maximum filament size to slope was determined based on regression analysis. Regression analysis revealed significant positive correlation between slope vs average filament length (r=0.92
) in multivoltine
bivoltine hybrids. Among parental breeds, 96C showed lowest slope of the curve (b-value: -0.00428) and 96A showed highest slope of the curve (b-value: -0.00269). Among 9 hybrids, PM
recorded lowest slope value (b-value: -0.00328) and BL24
showed highest value for slope of the curve (b-value: -0.00234). The breed 96C, which showed lowest slope value can be utilized for future breeding programmes to breed strains with less size deviation. Three multivoltine
bivoltine hybrids viz., PM
CSR19 and BL67
, which showed less slope values (b-values: -0.00328, -0.00300 and -0.00297 respectively) can be utilized for commercial exploitation to produce uniform silk.k.
Estimation of Genetic Components of Variance in Biparental Progenies of Bivoltine Silkworm (Bombyx mori L.)
Malik, Gulam Nabi ; Sofi, Abdul Majeed ; Haque Rufaie, Syed Zia ; Singh, Tejender Paul ; Aijaz, Mohammad ; Malik, Manzoor Ahmad ; Dar, Habib Ullah ;
International Journal of Industrial Entomology, volume 9, issue 2, 2004, Pages 279~281
Components of genetic variation were estimated for five metric traits using 24 biparental progenies (N. C. Design III) generated from F
generation of a commercial bivoltine silkworm hybrid, SH
. Variance due to additive (
A) and dominance (
D) gene effects was significant for single cocoon weight and shell weight. However, magnitude of former was greater than latter indicating preponderance of additive gene action in the inheritance of these two traits. Average degree of dominance was in the range of partial dominance for all the traits. High estimates of heritability (ns) indicated operation of genes with large additive effects, hence, scope exists for improvement of present populations through a few cycles of selection.n.