Comparison of different multi-trait selection strategies for genetic improvement of economic traits in six Iranian commercial lines of the silkworm, Bombyx mori (Lep.: Bombycidae)

In this study, the genetic parameters and economic weights of some important economic traits in six Iranian commercial varieties (110, 107, 101433, Xinhong1, Koming1 and Y) of the silkworm were estimated and selection indices for these traits constructed. Individual recording of cocoon weight, shell weight and shell ratio were carried out during six generations. Heritabilities and genetic correlation between traits were estimated by restricted maximum likelihood method. The heritability of cocoon weight and shell weight were higher than that of shell ratio. Genetic improvement of cocoon weight and shell weight were high in the line 101433 due to higher heritability and genetic correlation between them. Therefore, the restriction of genetic gain of cocoon weight in this line is expected to cause a severe decrease in improvement of shell weight, and subsequently a decrease of selection efficiency. The genetic improvement of cocoon shell percentage increased in restricted indices due to low genetic correlation with cocoon weight, and selection accuracy in these indices decreased significantly compared to other indices. Considering the difference in genetic parameters and economic values of traits in commercial lines of the silkworm, it would be necessary to define a separate breeding goal and selection strategy in each line

Asymmetric growth-limiting development of the female conceptus

IntroductionSex differences in prenatal growth may contribute to sex-dependent programming effects on postnatal phenotype. MethodsWe integrated for the first time phenotypic, histomorphological, clinico-chemical, endocrine and gene expression analyses in a single species, the bovine conceptus at mid-gestation. ResultsWe demonstrate that by mid-gestation, before the onset of accelerated growth, the female conceptus displays asymmetric lower growth compared to males. Female fetuses were smaller with lower ponderal index and organ weights than males. However, their brain:body weight, brain:liver weight and heart:body weight ratios were higher than in males, indicating brain and heart ‘sparing’. The female placenta weighed less and had lower volumes of trophoblast and fetal connective tissue than the male placenta. Female umbilical cord vessel diameters were smaller, and female-specific relationships of body weight and brain:liver weight ratios with cord vessel diameters indicated that the umbilico-placental vascular system creates a growth-limiting environment where blood flow is redistributed to protect brain and heart growth. Clinico-chemical indicators of liver perfusion support this female-specific growth-limiting phenotype, while lower insulin-like growth factor 2 (IGF2) gene expression in brain and heart, and lower circulating IGF2, implicate female-specific modulation of key endocrine mediators by nutrient supply. ConclusionThis mode of female development may increase resilience to environmental perturbations in utero and contribute to sex-bias in programming outcomes including susceptibility to non-communicable diseases

Maternal and paternal genomes differentially affect myofibre characteristics and muscle weights of bovine fetuses at midgestation

Postnatal myofibre characteristics and muscle mass are largely determined during fetal development and may be significantly affected by epigenetic parent-of-origin effects. However, data on such effects in prenatal muscle development that could help understand unexplained variation in postnatal muscle traits are lacking. In a bovine model we studied effects of distinct maternal and paternal genomes, fetal sex, and non-genetic maternal effects on fetal myofibre characteristics and muscle mass. Data from 73 fetuses (Day153, 54% term) of four genetic groups with purebred and reciprocal cross Angus and Brahman genetics were analyzed using general linear models. Parental genomes explained the greatest proportion of variation in myofibre size of Musculus semitendinosus (80–96%) and in absolute and relative weights of M. supraspinatus, M. longissimus dorsi, M. quadriceps femoris and M. semimembranosus (82–89% and 56–93%, respectively). Paternal genome in interaction with maternal genome (P<0.05) explained most genetic variation in cross sectional area (CSA) of fast myotubes (68%), while maternal genome alone explained most genetic variation in CSA of fast myofibres (93%, P<0.01). Furthermore, maternal genome independently (M. semimembranosus, 88%, P<0.0001) or in combination (M. supraspinatus, 82%; M. longissimus dorsi, 93%; M. quadriceps femoris, 86%) with nested maternal weight effect (5–6%, P<0.05), was the predominant source of variation for absolute muscle weights. Effects of paternal genome on muscle mass decreased from thoracic to pelvic limb and accounted for all (M. supraspinatus, 97%, P<0.0001) or most (M. longissimus dorsi, 69%, P<0.0001; M. quadriceps femoris, 54%, P<0.001) genetic variation in relative weights. An interaction between maternal and paternal genomes (P<0.01) and effects of maternal weight (P<0.05) on expression of H19, a master regulator of an imprinted gene network, and negative correlations between H19 expression and fetal muscle mass (P<0.001), suggested imprinted genes and miRNA interference as mechanisms for differential effects of maternal and paternal genomes on fetal muscle.Ruidong Xiang, Mani Ghanipoor-Samami, William H. Johns, Tanja Eindorf, David L. Rutley, Zbigniew A. Kruk, Carolyn J. Fitzsimmons, Dana A. Thomsen, Claire T. Roberts, Brian M. Burns, Gail I. Anderson, Paul L. Greenwood, Stefan Hiendlede

Selection indices for cocoon traits in six commercial silkworm (Bombyx mori L.) lines

Genetic parameters and economic values of cocoon traits in six commercial silkworm varieties (110, 107, 101433, Xinhong1, Koming1 and Y) were analyzed and selection indices for these traits were constructed. Cocoon weight, shell weight and shell ratio for each silkworm were carried out for four generations. Heritability and correlation coefficients were estimated by the REML method. Heritability of cocoon weight and cocoon shell weight were higher than the heritability of cocoon shell ratio. Using a deterministic model, the economic weights of the traits were calculated. In each variety, two conventional indices (family and individual indices), two restricted indices (family and individual restricted indices) and two base indices (individual and phenotypic base indices) were constructed. The expected economic efficiency resulting from family index selection was the highest. Thus, family index is suggested for selection. The maximum and minimum selection accuracy, expected economic gain and relative efficiency of individual to family index belonged to Xinhong1 and 107, respectively

Estimation of Some Nutritional Indices in Commercial Hybrid of Silkworm at Five Larval Instar

Nutritional incides have important role in economical efficiency of silkworm rearing. In order to estimate nutritional indices six silkworm hybrids including 103×104, 31×32, 107×110, 104×103, 32×31 and 110×107 which were commercially used in Iran for cocoon production were tested. These hybrids were reared in spring 2003, spring 2004 and autumn 2004. The studied parameters were amount of ingestion and facea, digested food, percentage of ingestibility and digestibility, reference ratio (ingested feed/produced feces), larva weight gain, efficiency of conversion of ingested (ECI) and digested (ECD) food into larva weight. The obtained results clearly indicate that ingestion, digestion and utilization of food were mostly dependent upon genotype and hybrid's instars. Hybrids E and F at instars 1-3 and instars 4-5 duration ingested less food. Food ingestion was different at the same season of different years. Meanwhile this index have many alteration upon rearing season. At spring season, the first and third instar larvae obtained the most ingested foods. At autumn season, other instars obtained the most ingested food. Ingested food amount affected by larval duration and also by climatic conditions especially rearing season. Hybrids E and F had the highest digestibility in comparison with other hybrids. Comparisons of common hybrids (A, C and E) against the reciprocal hybrids (B, D and F) for percentage of ingestibility and digestibility is showed Japanese hybrids have nutritional indices higher than Chinese hybrids. But at instars 4-5 these results were reverse i.e. Chinese-maternal based hybrids have nutritional indices higher than Japanese-maternal based hybrids. Obtained results are showed nutritional indices were different in various silkworm hybrids and it must be noticed to hybrid production based on nutritional characteristics

Estimation of Performance and Genetic Parameters of Ten Chinese and Japanese Silkworm Hybrids in a Crisscrossing System

Performance of five Chinese commercial lines of silkworm like 32, 104, 110, 152, 154 and five Japanese ones such as 31, 103, 107, 151, 153 were investigated at four rearing periods of two spring and two summer seasons. Total hatch, rearing steps, recording and experimental activities were conducted under standard conditions of ESCAP (1993). The results indicated that maternal base effect all of effects in model (generation, genus and hybrid group) was significant (