Heterosis For Growth Traits Research Articles

Genetic basis of negative heterosis for growth traits in chickens revealed by genome-wide gene expression pattern analysis

BackgroundHeterosis is an important biological phenomenon that has been extensively utilized in agricultural breeding. However, negative heterosis is also pervasively observed in nature, which can cause unfavorable impacts on production performance. Compared with systematic studies of positive heterosis, the phenomenon of negative heterosis has been largely ignored in genetic studies and breeding programs, and the genetic mechanism of this phenomenon has not been thoroughly elucidated to date. Here, we used chickens, the most common agricultural animals worldwide, to determine the genetic and molecular mechanisms of negative heterosis.ResultsWe performed reciprocal crossing experiments with two distinct chicken lines and found that the body weight presented widely negative heterosis in the early growth of chickens. Negative heterosis of carcass traits was more common than positive heterosis, especially breast muscle mass, which was over − 40% in reciprocal progenies. Genome-wide gene expression pattern analyses of breast muscle tissues revealed that nonadditivity, including dominance and overdominace, was the major gene inheritance pattern. Nonadditive genes, including a substantial number of genes encoding ATPase and NADH dehydrogenase, accounted for more than 68% of differentially expressed genes in reciprocal crosses (4257 of 5587 and 3617 of 5243, respectively). Moreover, nonadditive genes were significantly associated with the biological process of oxidative phosphorylation, which is the major metabolic pathway for energy release and animal growth and development. The detection of ATP content and ATPase activity for purebred and crossbred progenies further confirmed that chickens with lower muscle yield had lower ATP concentrations but higher hydrolysis activity, which supported the important role of oxidative phosphorylation in negative heterosis for growth traits in chickens.ConclusionsThese findings revealed that nonadditive genes and their related oxidative phosphorylation were the major genetic and molecular factors in the negative heterosis of growth in chickens, which would be beneficial to future breeding strategies.

Transcriptome analysis of growth heterosis in pearl oyster Pinctada fucata martensii.

Heterosis improves growth and survival of shellfish species. Although breeders have widely exploited heterosis, its underlying molecular mechanisms remain unclear. In this study, a 2 × 2 complete diallel cross was facilitated between two full‐sib families to produce two inbred families (A and D) and their reciprocal hybrid families (B and C) of pearl oyster Pinctada fucata martensii. Growth traits of the four families were compared at the adult stages. Transcriptome analysis was conducted on the four families using an Illumina sequencing platform. The results revealed that the growth traits of the four families significantly varied (P < 0.05). The mid‐parent heterosis values of shell length, shell height, shell width, shell weight, and total weight were 12.9%, 14.9%, 18.2%, 17.2%, and 33.2%, respectively. The B‐ and C‐inbred (A and D) triads had 79 and 68 differentially expressed genes (DEGs), respectively, which were dominantly nonadditive, including overdominance, underdominance, and low‐parent dominance. Gene ontology term analysis showed that the DEGs in the B‐ and C‐inbred triads were enriched for metabolic process, cellular process cell part, binding, and catalytic activity. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis indicated that the DEGs in the B‐ and C‐inbred triads were involved in focal adhesion, the P13K‐Akt signaling pathway, the mRNA surveillance pathway, and the focal adhesion pathway. The reliability of the sequencing data was confirmed by real‐time polymerase chain reaction analysis of six growth‐related genes. The findings of this study provide new insights into heterosis for growth traits and the design of genetic breeding programs for this species.

Estimates of combining ability and heterosis for growth traits in a full diallel cross of three strains of common carp, Cyprinus carpio L.

We attempted to determine the combining ability and heterosis of body weight by performing 3 × 3 complete diallel crosses derived by crossing three common carps ( Cyprinus carpio var. jian, Cyprinus carpio haematopterus Temminck et Schlegel and Cyprinus carpio haematopterus). In total, 1650 fish were tagged when they were 1.5 months of age. After five months, Jian carp (♂) × Huanghe carp (♀) attained greater weight than pure and other hybrids. By crossing with Jian, Huanghe and Heilongjiang carps have improved body weight compared to their purebred. Significant principal components (PCs) were generated from growth performance data and their statistical loadings. The first principal component had the highest Eigen value of 2.81 and accounted for 70.31% of the variability in the data set. Two crosses, Jian carp (♂) × Huanghe carp (♀) and Huanghe carp (♂) × Jian carp (♀) showed high SCA with regard to body weight. Both Heilongjiang carp (♂) × Jian carp (♀) and Heilongjiang carp (♂) × Huanghe carp (♀) had higher heterosis compared to their purebreds. Significant positive phenotypic correlations were also observed between body weight and body length, thickness and height. The aforementioned results listed were identified as the foundation for common carp selective breeding programs. Keywords : Common carp, cross-breeding, heterosis African Journal of Biotechnology Vol. 12(22), pp. 3514-3521

Evaluation of cattle breeds for beef production in New Zealand—A review

Important differences are noted between the New Zealand and European cattle industries, in terms of both breeds and farming systems. Under pasture feeding, experimental data strongly suggest that selection and genetic evaluation for growth performance should be based on weight-for-age rather than on post-weaning weight gains. Carcass merit is more appropriately measured by the yield of trimmed boneless retail cuts than by accepted commercial grades. Relative to the nationally predominant Angus beef breed, research results demonstrate an advantage in final and carcass weight per animal of 5–10% for the Hereford and 20–30% for the Friesian, with the superiority being approximately halved in crossed with the Angus. In terms of weaning performance, the Friesian dam is greatly superior, the Hereford slightly inferior, to the Angus. Heterosis for growth traits is of the order of 5%. In crosses over Jersey cows the Charolais sire is superior to the Hereford but not to the Friesian for total meat output. Carcasses from the dairy breeds and dairy x beef crosses slaughtered at the same age contain a higher bone percentage and are less acceptable on traditional export grading standards than those of the British beef breeds, but nevertheless achieve high output and quality of lean meat. Preliminary results from current large-scale trials suggest that the larger European breeds have potential for improving growth rate and meat yield in crosses with local Angus and Hereford cattle but are more prone to difficult calvings and show later sexual maturity.