Heterosis Effects Research Articles

Breed effects and heterosis for productivity traits at first calving of Angus, Holstein Friesian, Jersey and crossbred beef cows

Feed requirements for maintenance contribute a large proportion of the feed requirements of a beef cow so lighter cows may be more efficient producers of weaned calves, provided that such cows do not result in a comparative reduction in calf weaning weight. Beef-cross-dairy cows have increased milk yield compared with straight-bred beef cows and have the potential to wean heavier calves. Crossbred cows may also offer potential increases in production through heterosis. This experiment examined the performance of straight-bred Angus (AA), Holstein Friesian (FF) and Jersey (JJ) cows and of Angus-sired F1 crossbreds with Holstein Friesian (AF), Jersey (AJ) and Holstein Friesian-cross-Jersey (Kiwicross; AK) cows to identify breed and heterosis effects on milk intake and liveweight of calves and liveweight, reproductive performance and fatness of cows in their first lactation. Days to calving and weaning rate from first joining were similar among genotypes, but only 50% of FF cows conceived to second joining, compared with 90–98% for the other genotypes (P < 0.05). Estimated milk intake of calves was least (P < 0.05) for calves born to AA cows, and was generally similar (P > 0.05) among calves born to crossbred cows. There were positive heterosis effects between Angus and Jersey and between Angus and Holstein Friesian on milk intake of the calf. Straight-bred FF cows weaned the heaviest calves (least-squares mean + s.e.: 241 ± 5 kg; P < 0.05). Calves born to AF and AK cows were weaned at similar liveweight (229 ± 3 kg and 226 ± 4 kg, respectively; P > 0.05), and were heavier (P < 0.05) than calves born to JJ and AJ cows, which were similar (208 ± 5 kg and 215 ± 3 kg, respectively; P > 0.05). Calves born to AA cows were lightest at weaning (196 ± 3 kg; P < 0.05). Estimates of heterosis for weaning weight were 11 ± 4 kg (P < 0.01) between Angus and Holstein Friesian, and 14 ± 4 kg (P < 0.001) between Angus and Jersey. Angus-cross-dairy cows offered production advantages over straight-bred AA cows as dam lines in a terminal cross. These advantages were partially due to heterosis.

Combining ability analysis and gene effects in maize (Zea maysL.) using line × tester crosses

Determination of gene effects and combining abilities is a critical stage in maize hybrid breeding. In the present study, eight lines as female and two inbred lines (K3615.2 and A679) as tester were crossed and the resulting test cross progenies were evaluated in a randomized complete block design with three replications in 2011. During the growing period, several agronomic characters including grain yield were measured. Effects of lines and testers were significant on all the characters except for the grain yield, grains per row and days to maturity. This indicated the importance of additive gene effect in controlling most of the traits under investigation. Inbred lines L5, L10 and L14 were identified as good general combiners for grain yield because they showed significant positive GCA for this trait. L14 was superior compared with L1 and L5 because of significant positive GCA for most of the agronomic characters. These lines, especially L14, have potential additive gene effects to be utilized in the breeding programmes. T3 tester showed favourable additive gene effects for forage yield, its components, early maturity and shorter stature. Promising crosses were selected based on per se performance, standard heterosis and sca effects. The highest grain yield (107.313) belonged to L6 × A679 combination. The superiority of L6 × A679 hybrid can be attributed to its days to physiological maturity and more ears per plant. Higher grain yield and sca for forage yield were also observed in L7 × A679 and L14 × K3615.2. The cross L14 × K3615.2 had also large positive sca for grain rows per cob. Furthermore, negative sca of ear height, number of leaves above ear and grains per row were observed for L6 × A679, while positive sca of these characters was determined for L7 × A679. However, none of the scas for these combinations was significant. On the basis of grain yield, the genotypes L6 × A679, L7 × A679 and L14 × K3615.2 may be regarded as promising hybrids and should be evaluated further for grain yield and other desirable characters.

Determination of suitable microspore stage and callus induction from anthers of kenaf (Hibiscus cannabinus L.).

Kenaf (Hibiscus cannabinus L.) is one of the important species of Hibiscus cultivated for fiber. Availability of homozygous parent lines is prerequisite to the use of the heterosis effect reproducible in hybrid breeding. The production of haploid plants by anther culture followed by chromosome doubling can be achieved in short period compared with inbred lines by conventional method that requires self pollination of parent material. In this research, the effects of the microspore developmental stage, time of flower collection, various pretreatments, different combinations of hormones, and culture condition on anther culture of KB6 variety of Kenaf were studied. Young flower buds with immature anthers at the appropriate stage of microspore development were sterilized and the anthers were carefully dissected from the flower buds and subjected to various pretreatments and different combinations of hormones like NAA, 2,4-D, Kinetin, BAP, and TDZ to induce callus. The best microspore development stage of the flower buds was about 6–8 mm long collected 1-2 weeks after flower initiation. At that stage, the microspores were at the uninucleate stage which was suitable for culture. The best callus induction frequency was 90% in the optimized semisolid MS medium fortified with 3.0 mg/L BAP + 3.0 mg/L NAA.

Effects of parental strains and heterosis of the hybrid between Clarias macrocephalus and Clarias gariepinus

The hybrid between Clarias macrocephalus female × C. gariepinus male has been cultured in Thailand for more than 20 years, but the effects of parental strains have not been studied. In the present study, differences among three strains each of C. macrocephalus and C. gariepinus were shown by the analyses of five microsatellite loci ( F ST = 0.174 ± 0.037). Pairwise F ST within species was significantly higher than zero ( P = 0.0000) for every population pair, and ranged from 0.027 to 0.041 for C. macrocephalus and from 0.087 to 0.254 for C. gariepinus . Interspecific hybridization was performed using females from C. macrocephalus and male C. gariepinus , resulting in nine hybrid crosses. Performance traits of the hybrids were compared with the offspring of three crosses each within C. macrocephalus and C. gariepinus . The experiments were done in tanks from 28 to 84 days old, and in cages fixed in an earthen pond from 85 to 175 days old. The results showed that the effects of both parental strains and their interaction on the absolute growth rate and specific growth rate (SGR) from 28 to 84 days old were significant. Absolute growth rates during 85 to 175 days were significantly affected only by strains of C. gariepinus , while neither parental strains affected SGR from 85 to 175 days old of the hybrids. The effects of the parental strains and their interaction were not significant for other traits, including the survival rate from 28 to 84 days old and 85 to 175 days old, dress-out percentage, fillet yield, phagocytic activity and phagocytic index. It was noteworthy that the difference in traits among crosses within each genetic group ( C. macrocephalus , C. gariepinus , and hybrids) was significant only for growth traits (absolute growth rates from 28 to 84 days and from 84 to 175 days among strains of C. gariepinus , and among hybrids; the SGR from 28 to 84 days old and 85 to 175 days old within C. macrocephalus , and the SGR from 28 to 84 days old within the hybrids). Mean heterosis was low and not notable (< 1%) in most cases, except for the survival rate from 28 to 84 days old and 85 to 175 days old (+ 2.43 ± 2.14 and + 10.71 ± 4.71%, respectively), absolute growth rate from 85 to 175 days (+ 10.85 ± 11.35%), and percent fillet yield (+ 1.34 ± 1.73%). Variation of heterosis among the hybrid crosses was observed. Among the nine hybrid crosses, the cross between female C. macrocephalus from Udorn Thani province (Cma-UD) × C. gariepinus from the Department of Aquaculture (Cga-AQ) showed the highest proportion of positive heterosis across ten traits (90%). • Walking catfish hybrid is important in Thailand with production > 150,000 mt/y. • Parental strain effects of hybrid walking catfishes were studied for the first time. • The study included hybrids of 3 strains each of C. macrocephalus and C. gariepinus. • The effects of strains were significant only for growth rate. • A good cross was identified base on the highest proportion of positive heterosis.

Analysis of growth characteristics in short-term divergently selected Japanese quail lines and their cross

SUMMARY The current study was conducted to investigate the effect of short-term selection for 4 wk BW (BW) on the performance of divergent lines of Japanese quail and their crosses. The mean of BW at 1, 2, 3, and 4 wk of age in each group (2 lines and their crosses) were compared to investigate the maternal and heterosis effects. There were significant differences (P < 0.05) between the mean of BW in each group. Moreover, the reciprocal effect (maternal effect) was significant (P < 0.05) for all BW measured at different ages except for 4-wk BW in males and 3- and 4-wk BW in females. However, the effect of heterosis was not significant for all BW measured. The description of growth curves in each group and control line was compared with 3 mathematical models (Gompertz, logistic, and Richard). Based on the error variance, the logistic model described the growth pattern of Japanese quail and their crosses better than other models.

Inheritance of a darkened caudal peduncle and yellow body coloration in the gilthead sea bream (Sparus aurata L.)

Summary This study presents data on inheritance of a darkened caudal peduncle (ebony) and yellow body coloration (yellow) in the gilthead sea bream (Sparus aurata). Fifteen progeny groups, obtained by crossing fish with three color phenotypes and of known origin, were analyzed. Analyzes of segregation in F1 progeny involving groups from parental crosses of wild-type colored × wild-type colored; ebony × ebony; yellow × yellow, showed that the parents produced the offspring only with the same phenotypes (true breeding). Crosses involving F1 wild-type colored parents (that resulted from crosses of wild-type parents with either ebony or yellow fish) showed in their F2 progeny groups of which their phenotypic segregations did not differ significantly from a 3 : 1 Mendelian ratio. The progeny of back-cross of ebony × (F1 wild-type colored × ebony) showed phenotypic segregations that did not differ significantly from the 1 : 1 Mendelian ratio. Overall, the results of the crossing experiments demonstrated that, similar to albinism described in a number of aquacultured species, ebony and yellow body coloration in S. aurata are both due to a single recessive allele. However, the yellow mutation of a gene controlling yellow pigment synthesis affects the yellow color of the whole fish body, whereas the ebony mutation causes production of melanin only in a specific area of the fish body, resulting in the development of a black coloration of the caudal peduncle. Experiments to assess culture performance showed that the color genes controlling ebony and yellow coloration had significant detrimental pleiotropic effects on growth, survival and body shape. Color mutations in the gilthead sea bream may be used as models for the study of: (i) genetic and physiological mechanisms of sterility, (ii) stress and disease resistance, (iii) effects of heterosis, (iv) genetic polymorphism in populations, and (v) methods of genetic protection in selected sea bream strains as well as in experiments on chromosome set manipulation.

Maize ARGOS1 (ZAR1) transgenic alleles increase hybrid maize yield

Crop improvement for yield and drought tolerance is challenging due to the complex genetic nature of these traits and environmental dependencies. This study reports that transgenic over-expression of Zea mays AR GOS1 (ZAR1) enhanced maize organ growth, grain yield, and drought-stress tolerance. The ZAR1 transgene exhibited environmental interactions, with yield increase under Temperate Dry and yield reduction under Temperate Humid or High Latitude environments. Native ZAR1 allele variation associated with drought-stress tolerance. Two founder alleles identified in the mid-maturity germplasm of North America now predominate in Pioneer's modern breeding programme, and have distinct proteins, promoters and expression patterns. These two major alleles show heterotic group partitioning, with one predominant in Pioneer's female and the other in the male heterotic groups, respectively. These two alleles also associate with favourable crop performance when heterozygous. Allele-specific transgene testing showed that, of the two alleles discussed here, each allele differed in their impact on yield and environmental interactions. Moreover, when transgenically stacked together the allelic pair showed yield and environmental performance advantages over either single allele, resembling heterosis effects. This work demonstrates differences in transgenic efficacy of native alleles and the differences reflect their association with hybrid breeding performance.

ANALYSIS OF GENETIC PARAMETERS FOR BEAN PHYSICAL QUALITY CHARACTERS AND CLUSTERIZATIONS OF ELEVEN GENOTYPES OF ROBUSTA COFFEE (Coffea canephora)

The genetic parameters of coffee related to their bean physical quality characters are important for breeder to improve the bean quality. Eleven genotypes of robusta coffee were identified and their genetic relationship to the bean physical quality were characterized. The research was conducted at coffee plantation of the Association of Indonesian Coffee Exporters in West Lampung, altitude of 800 m above sea level, Latosol type of soil, and A type of climate, starting from 2010 to 2012. The objectives of this study were to estimate the genotypic coefficient of variation, heritability and genetic advance of the bean physical quality characters, and clusterization analysis of eleven genotypes of robusta coffee. A randomized complete block design with eleven treatments of coffee genotypes and three replications was used in this study. The results showed that the estimated values of genotypic coefficient of variation, heritability and genetic advance for small-size normal bean characters of robusta coffee were very high, so the genetic improvement for these characters has a high probability of success by direct selection. Clusterization of the genotypes resulted three clusters with their respective characteristics. The study implies that future breeding program especially for hybridization should be conducted between genotypes arising from different clusters to obtain the possible high heterosis effects.&lt;br /&gt;&lt;br /&gt;

ANALYSIS OF GENETIC PARAMETERS FOR BEAN PHYSICAL QUALITY CHARACTERS AND CLUSTERIZATIONS OF ELEVEN GENOTYPES OF ROBUSTA COFFEE (Coffea canephora)

The genetic parameters of coffee related to their bean physical quality characters are important for breeder to improve the bean quality. Eleven genotypes of robusta coffee were identified and their genetic relationship to the bean physical quality were characterized. The research was conducted at coffee plantation of the Association of Indonesian Coffee Exporters in West Lampung, altitude of 800 m above sea level, Latosol type of soil, and A type of climate, starting from 2010 to 2012. The objectives of this study were to estimate the genotypic coefficient of variation, heritability and genetic advance of the bean physical quality characters, and clusterization analysis of eleven genotypes of robusta coffee. A randomized complete block design with eleven treatments of coffee genotypes and three replications was used in this study. The results showed that the estimated values of genotypic coefficient of variation, heritability and genetic advance for small-size normal bean characters of robusta coffee were very high, so the genetic improvement for these characters has a high probability of success by direct selection. Clusterization of the genotypes resulted three clusters with their respective characteristics. The study implies that future breeding program especially for hybridization should be conducted between genotypes arising from different clusters to obtain the possible high heterosis effects.&lt;br /&gt;&lt;br /&gt;

From nursery into nature: A study on performance of cultivated varieties of native plants used in re-vegetation, their wild relatives and evolving wild × cultivar hybrids

Cultivated varieties may have life-history traits which are very different to those of their wild progenitors. Changes in life-history traits due to cultivation may not be desirable for plant material used for re-vegetation, as these plants may be adapted to constant human care and lack the finely tuned trade-off that allows wild plants to cope with the often harsh and heterogeneous environmental conditions outside of nurseries. Research is needed to identify differences in life-history traits between cultivated varieties used in re-vegetation and restoration and their wild relatives. If such traits are changed by cultivation, it is necessary to examine if they will persist also at the re-vegetation site and may be transferred to wild relatives by hybridization as that may reduce their survival or lead to undesirable changes on local ecosystems.In this study we examined whether cultivated varieties of Plantago lanceolata and Lotus corniculatus, two species frequently used in re-vegetation and restoration projects, differ from their wild relatives in morphology or flower phenology and whether differences could be transferred into wild relatives by hybridization. We tested if cultivated varieties are bred for high vegetative and generative yield in greenhouse studies. In common garden experiments we studied if the detected enhanced biomass production is persistent under the climatic conditions of the wild plant's natural habitat in Central Europe. Additionally, we tested if hybrids show effects of outbreeding depression or heterosis.The cultivated varieties of both species grew very vigorously and showed a more erect growth pattern than their wild relatives. The cultivated varieties seem to be selected toward high vegetative and generative yield. However, if exposed to local climatic conditions, cultivated varieties suffered a fitness loss with a complete mortality for the L. corniculatus cultivar and a reduced vegetative biomass production for P. lanceolata cultivars. On the other hand, we detected heterosis effects in hybrids for survival and generative biomass production in L. corniculatus and number of leaves in P. lanceolata. As it remains possible that the use of cultivated varieties may result in strongly competitive genotypes or reduced local adaptation of wild plant populations (via hybridization), large-scale use of cultivated varieties of native plants should be avoided in re-vegetation and restoration.

Assessment of the effect of heterosis on semen parameters of two-breed crosses of Duroc, Hampshire and Pietrain boars

Abstract. The study was performed on 4 609 ejaculates obtained from 32 boars, including 14 purebred and 18 two-breed crosses. The ejaculates were collected manually every 4–5 days. The study involved ejaculates collected from each boar from the first day of its insemination use until the day of semen depletion. Each ejaculate was assessed for the following physical parameters: ejaculate volume, sperm concentration, percentage of spermatozoa with correct motility, total sperm count per ejaculate and number of insemination doses obtained from one ejaculate. The effect of heterosis was calculated on the physical parameters of the boar crosses ejaculates in relation to the mean value of a given parameter for the parent breeds. Positive and well pronounced heterosis effects were identified in the majority of the physical ejaculate parameters of the cross boars for all the cross-breeding variants. A negative effect of heterosis was only identified in the ejaculate sperm concentration of the Hampshire × Pietrain crosses. The highest ejaculatory efficiency was identified in the hybrids produced on the basis of the Hampshire breed. These breeders were also found to feature significant heterosis effects on ejaculate volume, total ejaculate sperm count and number of insemination doses prepared from one ejaculate.

Genetic Variation and Combining Ability Analysis of Bruising Sensitivity in Agaricus bisporus

Advanced button mushroom cultivars that are less sensitive to mechanical bruising are required by the mushroom industry, where automated harvesting still cannot be used for the fresh mushroom market. The genetic variation in bruising sensitivity (BS) of Agaricus bisporus was studied through an incomplete set of diallel crosses to get insight in the heritability of BS and the combining ability of the parental lines used and, in this way, to estimate their breeding value. To this end nineteen homokaryotic lines recovered from wild strains and cultivars were inter-crossed in a diallel scheme. Fifty-one successful hybrids were grown under controlled conditions, and the BS of these hybrids was assessed. BS was shown to be a trait with a very high heritability. The results also showed that brown hybrids were generally less sensitive to bruising than white hybrids. The diallel scheme allowed to estimate the general combining ability (GCA) for each homokaryotic parental line and to estimate the specific combining ability (SCA) of each hybrid. The line with the lowest GCA is seen as the most attractive donor for improving resistance to bruising. The line gave rise to hybrids sensitive to bruising having the highest GCA value. The highest negative SCA possibly indicates heterosis effects for resistance to bruising. This study provides a foundation for estimating breeding value of parental lines to further study the genetic factors underlying bruising sensitivity and other quality-related traits, and to select potential parental lines for further heterosis breeding. The approach of studying combining ability in a diallel scheme was used for the first time in button mushroom breeding.

Evaluasi Penampilan dan Efek Heterosis Hasil Persilangan Beberapa Aksesi Jarak Pagar (Jatropha curcas L.)

Agronomic performance and heterosis effect of progeny are important criteria for selection of parental hybrid. The agronomic performance evaluation of Jatropha progeny which was derived from crossing of some Jatropha accessions has been carried out for those goals. The study was conducted at Agro Techno Park, Indralaya South Sumatra. The crossing combinations were Pidie x Medan, Curup x Lampung, Pidie x Lampung, Lampung x Pidie, Curup x Medan, Indralaya x Pontianak, Medan x Palembang, Curup x Pidie, and Jogya x Komering. Oil production, nitrate reductase enzyme activity, leaf chlorophyll content and relative plant growth rate were evaluated. The result showed that the relative plant growth rate could be used as early detection parameter for yield potential. Progenies of Pontianak x Indralaya, Palembang x Indralaya and Pidie x Lampung were selected as promising hybrids based on high productivity and heterosis effect. Keywords: Jatropha curcas, heterosis, relative plant growth rate, nitrate reductase activity

СТЕРИЛЬНОСТЬ ПРИ МЕЖПОДВИДОВОЙ ГИБРИДИЗАЦИИ РИСА Oryza sativa L. В СВЯЗИ С ПОИСКОМ ГЕНОВ ШИРОКОЙ СОВМЕСТИМОСТИ И ОТНЕСЕНИЕМ ОБРАЗЦОВ К ПОДВИДАМ indica И japonica

In rice ( Oryza sativa L.) between indica and japonica subspecies a number of transitional forms both on phenotype and on physiological determinants present, which have the characteristic features in their development and adaptation to stress. The heterosis effect in intersubspecific hybrids ( japonica/indica ) can be of 100 % and more. The superhigh heterosis can be used during intersubspecific hybridization on conditions that the genes of wide compatibility (WC), which ensure a grain content more of 70 %, will be involve in breeding. The authors made the crossings between the samples of domestic and foreign breeding from japonica subspecies. The analysis of grain formation in the hybrid combinations did not allow to reveal WC genes in studied varieties of Russian selection defining high fertility of hybrids. The molecular scanning of hybrids and their parental forms was made with the use of 11 polymorphous SSR-markers, typical for subspecies. A possibility to obtain the fertile intersubspecific hybrids of rice and the list of trait used for differentiating samples to subspecies japonica and indica are discussed. The obtained results show that it is necessary to include additional characteristics into the list of trait for the taxonomic attributing samples to indica and japonica subspecies.

English

The aim of this experiment is to investigate the effect of crossbreeding pure breeds on reproductive traits and the effective costs in pigs. The study was conducted on 21,431 records concerning the reproductive traits of 4 pure breeds Large Yorkshire&nbsp;(LY), Swedish&nbsp;Landrace (SL),&nbsp;Duroc&nbsp;(D),&nbsp;and Hampshire&nbsp;(H) and their reciprocal F1&nbsp;crosses. Data processing&nbsp;method&nbsp;was by the least squares&nbsp;for&nbsp;testing in animal. The improvement&nbsp;of reproductive&nbsp;traits&nbsp;by crossing&nbsp;pure breeds was shown in the results. The improvements were more pronounced in the Three ways crossing and Back way crossing. By using the crossing&nbsp;breeds, the number&nbsp;of live births and&nbsp;weaned&nbsp;piglets increased&nbsp;while the number of&nbsp;stillborn&nbsp;piglets&nbsp;decreased compared to pure&nbsp;breeds. It can be seen that, there are differences&nbsp;in terms&nbsp;of fertility&nbsp;between pure breeds&nbsp;which can be&nbsp;successfully&nbsp;used&nbsp;by crossing&nbsp;selected&nbsp;(specialized) or&nbsp;breed&nbsp;lines. Heterosis&nbsp;effect&nbsp;was manifested&nbsp;in&nbsp;reproductive&nbsp;traits, depending on the&nbsp;choice of&nbsp;crossing&nbsp;scheme involving&nbsp;one of 3 types&nbsp;of heterosis and breed selection for cross. &nbsp; Key words:&nbsp;Pigs, sows, litter size, heterosis.

The effect of breed and individual heterosis on the feed efficiency, performance, and carcass characteristics of feedlot steers1

This study was conducted to evaluate maternal breed effects, direct breed effects, and individual heterosis on subsequent steer performance, carcass, and feed efficiency traits. This was a consecutive 2-yr trial using 158 steers. The same dam breeds, Angus (AN) and purebred Simmental (SM), were used both years. Also, the same AN and SM sires (n=11) were used both years. Steers were AN, SM, or AN×SM breed composition. Steers were managed similarly before weaning and early weaned at 56±9 d of age. Steers were then randomly allotted to pens and fed a common finishing ration. Contrasts were written to evaluate direct and maternal breed effects and individual heterosis in the PROC MIXED procedure of SAS (SAS Inst. Inc., Cary, NC) using dam breed, sire breed, and year as fixed effects. Simmental direct breed effect resulted in a 26 kg heavier initial BW (P<0.05) and a 46 kg heavier final BW (P<0.05). Simmental maternal breed effect increased initial BW by 43.5 kg (P<0.05). Dry matter intake was not impacted by direct breed effects, maternal breed effects, or individual heterosis. Individual heterosis did improve G:F 3.4% (P<0.05) and residual BW gain 0.048 kg/d (P<0.05). Residual intake and BW gain tended (P=0.07) to improve as a result of individual heterosis. Residual feed intake (RFI) was impacted by direct breed effect with SM cattle having a more desirable RFI (P=0.05). Angus direct breed effect increased backfat (P<0.05) and improved marbling score by 126 units (P<0.05). Simmental direct breed effect increased LM area (P<0.05), had the highest HCW at 410 kg (P<0.05), and had the most desirable yield grade at 2.74 (P<0.05). Individual heterosis improved marbling score (P=0.05). Maternal breed effect increased HCW (P<0.05) as a result of the SM dam. Direct breed effects were present for performance, feed efficiency measures, and carcass traits. Overall, heterosis impacted feedlot performance, carcass characteristics, and feed efficiency, which impacts beef production.

Heritability of beef tenderness at different aging times and across breed comparisons

Zwambag, A., Kelly, M., Schenkel, F., Mandell, I., Wilton, J. and Miller, S. 2013. Heritability of beef tenderness at different aging times and across breed comparisons. Can. J. Anim. Sci. 93: 307–312. The heritability of shear force at 7, 14 and 21 d was estimated from a crossbred population of beef cattle. The population consisted of approximately 1400 crossbred cattle that were predominantly the offspring of Angus, Simmental, Gelbvieh and Piedmontese sires bred to predominantly Angus and Simmental females. Significant breed effects on tenderness were found within each aging time and no effect of heterosis was detected. The heritability of shear force declined from 0.194 to 0.048 as aging time increased from 7 to 21 d, highlighting the effectiveness of aging as a tool to improve tenderness. The repeatability of shear force was also found to be moderate (0.53). However, as energy prices increase it may be attractive to reduce aging times, thus breeding animals that are more tender at shorter aging times would be beneficial. The heritability of tenderness found at shorter aging times would indicate that improvement in this trait would be possible within a population where phenotypes are available.

Combining Ability and Heterosis Effects between 12 Exotic Maize Populations and Domestic Germplasm

The introgression of exotic maize (Zea mays L.) germplasm with abundant genetic variation from International Maize and Wheat Improvement Center (CIMMYT) and the United States could be an important approach for broadening the genetic basis of maize germplasm used in China. The objectives of this study were to evaluate combining ability and heterosis effects between exotic and domestic maize populations by Miranda Filho-Geraldi model. Twelve populations from the United States and CIMMYT were test-crossed with three domestic populations (Csyn 5, Csyn 6, and Csyn 7) in an NCII mating design. Thirty-six crosses and one commercial hybrid (Zhengdan 958) were evaluated in 2009 and 2010 at Shunyi in Beijing, Jinan in Shandong province, and Xinxiang in Henan Province. The results showed that the populations Pob43, La Posta, Pob21, Pob32, Pob49, and Pob501 had a good performance in GCA of yield and related traits. Pob49 and Pob501 were closer to PA germplasm; Pob32 and BS29 were closer to PB germplasm; Pob43 and La Posta were closer to Sipingtou germplasm. Therefore, on the based of exotic germplasm adaptation, we recommended to compose populations or composites between Pob21, Pob49, Pob501, and domestic heterotic group A, Pob32 and domestic heterotic group B, as well as Pob43, La Posta, and domestic heterotic group D germplasm, in order to broaden genetic basis of domestic germplasm groups.

Combining Ability and Heterosis Effects between 12 Exotic Maize Populations and Domestic Germplasm

Combining Ability and Heterosis Effects between 12 Exotic Maize Populations and Domestic Germplasm

A Computational Workflow to Identify Allele-specific Expression and Epigenetic Modification in Maize

Allele-specific expression refers to the preferential expression of one of the two alleles in a diploid genome, which has been thought largely attributable to the associated cis-element variation and allele-specific epigenetic modification patterns. Allele-specific expression may contribute to the heterosis (or hybrid vigor) effect in hybrid plants that are produced from crosses of closely-related species, subspecies and/or inbred lines. In this study, using Illumina high-throughput sequencing of maize transcriptomics, chromatic H3K27me3 histone modification and DNA methylation data, we developed a new computational framework to identify allele-specifically expressed genes by simultaneously tracking allele-specific gene expression patterns and the epigenetic modification landscape in the seedling tissues of hybrid maize. This approach relies on detecting nucleotide polymorphisms and any genomic structural variation between two parental genomes in order to distinguish paternally or maternally derived sequencing reads. This computational pipeline also incorporates a modified Chi-square test to statistically identify allele-specific gene expression and epigenetic modification based on the Poisson distribution.