Heterosis has been exploited to enhance the yield and adaptability in various shellfish species;however,the molecular basis of it remains unclear.The Pacific oyster Crassostrea gigas is one of the most economically im...Heterosis has been exploited to enhance the yield and adaptability in various shellfish species;however,the molecular basis of it remains unclear.The Pacific oyster Crassostrea gigas is one of the most economically important aquaculture species,and its productive traits can be improved by hybridization.Here,an intraspecific cross between orange shell(O,10th generation)and‘Haida No.1’(H,13th generation)of C.gigas was performed to assess the heterosis of survival trait.Survival rates of hybrid family(OH)and inbred families(HH and OO)were compared at larval stage,and eyed-pediveliger larvae of three families were subjected to transcriptome analysis.The analysis results of best-parent heterosis and mid-parent heterosis showed that the hybrid family exhi-bited a high heterosis in survival relative to the parental families.The OH-M(OH vs.OO)and OH-P(OH vs.HH)had 425 and 512 dif-ferentially expressed genes(DEGs),respectively.Functional enrichment analysis of these DEGs revealed that the significantly enrich-ed genes function in virion binding,C-type lectin receptor signaling pathway,cellular defense response and other immune-related pro-cesses,which involves perlucin-like protein,CD209 antigen-like protein,ZNFX1,caspase-3 and acan genes.These differentially ex-pressed genes in OH-M and OH-P,together with the immune-related processes mentioned above may play an important role in the larval survival of C.gigas.In addition,three genes(CYP450,fucolectin and perlucin-like)are associated with the orange shell and low survival of maternal oyster OO.These findings provide support for the application of hybrid with superior survival and will facilitate the understanding of heterosis formation in the Pacific oyster.展开更多
Cabbage has significant heterosis and most commercial cultivars are hybrids.To explore genetic basis of cabbage heterosis and promote cabbage heterosis utilization,we constructed two populations by crossing 100 DH lin...Cabbage has significant heterosis and most commercial cultivars are hybrids.To explore genetic basis of cabbage heterosis and promote cabbage heterosis utilization,we constructed two populations by crossing 100 DH lines derived from a cabbage hybrid 01–20×96–100 with two female parents.Hybrids exhibited different extents of heterosis,the mean value of economic yield was 2.6 times bigger than parents.We identified 66 and 73 QTLs associated with mid-parent heterosis and transgressive heterosis of twelve yield-related traits,respectively.Some QTLs could be detected under the two-year experiment existed in two populations with different testers,showing relatively high phenotypic contribution rate(15.8%–20.0%).Heterosis QTLs exhibited clustered distribution in several cabbage chromosome regions.Two dominant genetic regions,mk300–316 and mk258–268,originated from the elite parent 01–20,exhibited significant genetic effects for yield-related heterosis,which were first identified.Three elite DH lines(D22,D46,D83)harboring these two dominant regions were selected as having strong heterosis in cabbage production.Candidate gene analysis revealed that some genes participating in biosynthetic processes of carbohydrates and some responses to auxin might affect cabbage yield heterosis.QTL identification and genetic dissection of yield-related traits provide new insights into the genetic effects of cabbage heterosis.展开更多
Heterosis and polyploidy have an overwhelming influence on plant evolution.Recently,polyploid rice hybrids have been used to breed new rice varieties because they combine the advantages of both heterosis and polyploid...Heterosis and polyploidy have an overwhelming influence on plant evolution.Recently,polyploid rice hybrids have been used to breed new rice varieties because they combine the advantages of both heterosis and polyploidy.In this study,we generated six rice lines:autotetraploid rice hybrids and their autotetraploid parents,diploid donors,and hybrids of the diploid donors.To investigate the molecular mechanism controlling the effects of both hybridization and polyploidization,we performed bisulfite and RNA sequencing on young panicles at the pollen meiosis stage to compare the DNA metabolomes and transcriptomes among the six rice lines.The hybrids lines were hypermethylated compared to their corresponding parents and the autotetraploid lines showed globally increased DNA methylation of their transposable elements compared to the diploid donors.The alteration in DNA methylation level corresponded to the differential gene expressions among the rice genotypes,suggesting that methylation changes induced by polyploidization and hybridization may affect gene expression.Groups of gene candidates were identified that may be associated with heterosis and polyploidy.Our results provide DNA information that can be used to investigate epigenetic modification during heterosis and polyploidy in rice.展开更多
Vine decline disease (VDD) constitutes a menace to melons worldwide. Especially, the one caused by the fungus Monosporascus cannonballus. Thus, resistant plant material must be released to help growers. Hence, our goa...Vine decline disease (VDD) constitutes a menace to melons worldwide. Especially, the one caused by the fungus Monosporascus cannonballus. Thus, resistant plant material must be released to help growers. Hence, our goal was to develop resistant plant material to VDD. More than 600 melon accessions are expected to be tested for disease resistance in M. cannonballus infested soil in Weslaco, Texas, USA, to identify resistance to VDD, and other important traits. So far, at most 7 lines were found to be resistant to VDD and some of them were used to develop elite, muskmelon inbred lines by pedigree breeding following single or double backcrosses. These elite parents were crossed to each other to develop the hybrids M3 and M4. They were also tested in the same infested field in Weslaco. The hybrids were grown using standard commercial practices followed by growers and when their fruits were ready, their roots were sampled as well as scored for disease severity to estimate high and mid-parent heterosis Our results indicate the existence of heterosis regarding resistance to VDD. Thus, resistant plant material can be developed and selection for resistance can be accomplished.展开更多
Exploring the indica-japonica differentiation in parents of hybridization can provide theoretical bases for utilizing inter-subspecific heterosis. In this study, 5 sterile lines and 18 self-bred restorer lines were us...Exploring the indica-japonica differentiation in parents of hybridization can provide theoretical bases for utilizing inter-subspecific heterosis. In this study, 5 sterile lines and 18 self-bred restorer lines were used as female parents and male parents respectively. Then 90 combinations were constructed by incomplete diallel cross followed by relationship analysis between parental Cheng’s index difference value and Euclidean distance and heterosis. The results showed a significant correlation between several phenotype values, super male parent heterosis and control heterosis and Euclidean distance or Cheng’s index difference value. However, it was no significant correlation for yield. Further analysis found a common interval, 3.41 - 3.46 for Euclidean distance and 3 - 4 for cheng’s index difference value of parents, which was significant or high significant positive correlated with phenotype value, super male parent and control heterosis of main yield traits. This illustrates that the larger the genetic difference of parents was, the stronger the heterosis combinations were, when the genetic differences of parents were in an appropriate range.展开更多
The Asian cultivated rice(Oryza sativa L.) grown worldwide is divided into two subspecies, indica and japonica. It is well known that the heterosis of inter-subspecies is usually stronger than that of intra-subspecies...The Asian cultivated rice(Oryza sativa L.) grown worldwide is divided into two subspecies, indica and japonica. It is well known that the heterosis of inter-subspecies is usually stronger than that of intra-subspecies. Since the 1970 s, indica hybrid rice, an intra-subspecific hybrid rice, has being widely used in China and even in the world. However, the inter-subspecific hybrid rice between indica and japonica is still unavailable. The major obstacle is the hybrid sterility of the inter-subspecies. In recent decades, the genetic and molecular basis of indica-japonica hybrid sterility was understood more and more clearly. Some breeding approaches for overcoming inter-subspecific hybrid sterility were proposed and used to develop the indicajaponica hybrid rice. The updated understanding will offer new approaches for development of breeding lines for overcoming indica-japonica hybrid sterility, which facilitates developing of inter-subspecific hybrid rice.展开更多
Despite the great success achieved by the exploitation of heterosis in rice,the genetic basis of heterosis is still not well understood.We adopted an advanced-backcross breeding strategy to dissect the genetic basis o...Despite the great success achieved by the exploitation of heterosis in rice,the genetic basis of heterosis is still not well understood.We adopted an advanced-backcross breeding strategy to dissect the genetic basis of heterosis for yield and eight related traits.Four testcross(TC) populations with 228 testcross F1 combinations were developed by crossing57 introgression lines with four types of widely used male sterile lines using a North Carolina II mating design.Analysis of variance indicated that the effects of testcross F1 combinations and their parents were significant or highly significant for most of the traits in both years,and all interaction effects with year were significant for most of the traits.Positive midparent heterosis(HMP) was observed for most traits in the four TC populations in the two years.The relative HMPlevels for most traits varied from highly negative to highly positive.Sixty-two dominant-effect QTL were identified for HMPof the nine traits in the four TC populations in the two years.Of these,22 QTL were also identified for the performance of testcross F1.Most dominant-effect QTL could individually explain more than 10% of the phenotypic variation.Four QTL clusters were observed including the region surrounding the RM9–RM297 region on chromosome 1,the RM110–RM279–RM8–RM5699–RM452 region on chromosome 2,the RM5463 locus on chromosome 6 and the RM1146–RM147 region on chromosome 10.The identified QTL for heterosis provide valuable information for dissecting the genetic basis of heterosis.展开更多
Heterosis,which describes the superior vigor and yield of F_1 hybrids with respect to their parents,is observed in many rice hybrid crosses.The exploitation of heterosis is a great leap in the history of rice breeding...Heterosis,which describes the superior vigor and yield of F_1 hybrids with respect to their parents,is observed in many rice hybrid crosses.The exploitation of heterosis is a great leap in the history of rice breeding.With advances in genomics and genetics,high-resolution mapping and functional identification of heterosis-associated loci have been performed in rice.Here we summarize advances in understanding the genetic basis of grain yield heterosis in hybrid rice and provide a vision for the genetic study and breeding application of rice heterosis in the future.展开更多
Increased productivity in sorghum has been achieved in the developed world using hybrids.Despite their yield advantage,introduced hybrids have not been adopted in Ethiopia due to the lack of adaptive traits,their shor...Increased productivity in sorghum has been achieved in the developed world using hybrids.Despite their yield advantage,introduced hybrids have not been adopted in Ethiopia due to the lack of adaptive traits,their short plant stature and small grain size.This study was conducted to investigate hybrid performance and the magnitude of heterosis of locally adapted genotypes in addition to introduced hybrids in three contrasting environments in Ethiopia.In total,139 hybrids,derived from introduced seed parents crossed with locally adapted genotypes and introduced R lines,were evaluated.Overall,the hybrids matured earlier than the adapted parents,but had higher grain yield,plant height,grain number and grain weight in all environments.The lowland adapted hybrids displayed a mean better parent heterosis(BPH) of19%,equating to 1160 kg ha-1and a 29% mean increase in grain yield,in addition to increased plant height and grain weight,in comparison to the hybrids derived from the introduced R lines.The mean BPH for grain yield for the highland adapted hybrids was 16% in the highland and 52%in the intermediate environment equating to 698 kg ha-1and 2031 kg ha-1,respectively,in addition to increased grain weight.The magnitude of heterosis observed for each hybrid group was related to the genetic distance between the parental lines.The majority of hybrids also showed superiority over the standard check varieties.In general,hybrids from locally adapted genotypes were superior in grain yield,plant height and grain weight compared to the high parents and introduced hybrids indicating the potential for hybrids to increase productivity while addressing farmers' required traits.展开更多
The relationship between the indica-japonica differentiation of parents and heterosis of hybridin rice was studied with 10 sterile lines, 10 maintainer lines of the sterile lines, 38 restorer lines of Dian typehybrid ...The relationship between the indica-japonica differentiation of parents and heterosis of hybridin rice was studied with 10 sterile lines, 10 maintainer lines of the sterile lines, 38 restorer lines of Dian typehybrid rice and 40 hybrids derived from the sterile lines and restorer lines. The results indicated that there wasa parabolic correlation between the indica-japonica differentiation of parents detected by RAPD markers andheterosis of hybrid rice. When certain indica-japonica differentiation of parents exists, the percentage of com-binations with positve heterosis and the mean heterosis of hybrids were high. But that didn't mean too muchdifference of parents could lead to stronger hetesosis, that meant overdiffernt parents seldom bring positve het-erotic hybrids. Suitable difference of percent of indica alleles of parents of stronger heterotic hybrid was 12 -16%.展开更多
Background:Heterosis 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 impa...Background:Heterosis 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.Results:We 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.Conclusions:These 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.展开更多
66 F1 hybrids, produced by 3 double low self-incompatible lines and 22 varieties with a North Carolina Ⅱ (NCⅡ) crossing design, were tested for their heterosis in Wuhan, China during two growing seasons from 1999- 2...66 F1 hybrids, produced by 3 double low self-incompatible lines and 22 varieties with a North Carolina Ⅱ (NCⅡ) crossing design, were tested for their heterosis in Wuhan, China during two growing seasons from 1999- 2001. The results showed that significant differences were found between F1s and their parents for yield per plant and seed oil content. Mid-parent heterosis of these two characters ranged from 5.50%-64.11% and from 1.55% -7.44% respectively. Heterosis for seed yield per plant was greater than that of seed oil content. For yield components, heterosis of total number of siliques per plant was the highest, followed by seed number per silique and 1 000 seeds weight. Significant genotype-by-year interaction was found for seed yield per plant. Results from correlation and combining ability analysis indicated that parental effects on its F1 hybrid depended on characters, seed yield per plant was affected by both additive and non-additive effects, and seed oil content was affected mainly by additive effect. When designing hybrid programme, parents might be selected by GCAs and variances of SCAs of parents for the characters affected by both additive and non-additive effects, and by the sum of GCAs of female and male parents for the characters mainly affected by additive effects.展开更多
Genetic distance among 36 cotton cultivars measured by molecular markers of RAPDs, ISSRs,and SSRs was from 0.0701 to 0.4255 with the mean of 0.2844, and from 2.18 to 12.60 with the mean of 7.04 based on the genotype p...Genetic distance among 36 cotton cultivars measured by molecular markers of RAPDs, ISSRs,and SSRs was from 0.0701 to 0.4255 with the mean of 0.2844, and from 2.18 to 12.60 with the mean of 7.04 based on the genotype performance in two-year field experiments, which has a significant positive correlation (r = 0.3350). The correlative coefficients for boll number per plant, boll weight, yield per plant, lint percent and lint yield per plant were 0. 8035,0. 8877,0. 7135,0. 9640 and 0. 8956 between F1 and F2 hybrid performance assessed by three-environment field experiments, respectively. The mean of F1 and F2 hybrid heterosis of yield per plant and lint yield per plant were 13.62%, 16.31%, 7.90% and 9.02%, and the correlative coefficients between them were 0.3689 and 0.3787, respectively. The correlation between the genetic distance and heterosis was low, and influenced directly by the selected parents.展开更多
With the application of hybrid wheat, lodging is becoming one of the major factors limiting high yield in its production. However,few studies have focused on combining ability and heterosis analysis of stem-related tr...With the application of hybrid wheat, lodging is becoming one of the major factors limiting high yield in its production. However,few studies have focused on combining ability and heterosis analysis of stem-related traits. In this study, 24 crosses were made according to NCII genetic design, using the three(photo-sensitive male sterile lines)×eight(restorer lines) incomplete diallel crosses. The length of basal second internode(LBSI) and breaking strength of basal second internode(BSBSI)as well as other stem-related traits were used to perform the principal component analysis(PCA), combining ability and heterosis analysis. The PCA results showed that the variables could be classified into two main factors, which were named as the positive factor(factor 1) and the negative factor(factor 2), and accounted for 52.3 and 33.2%, respectively, of the total variance in different variables, combined with the analysis for index weight indicated that the factor 1-related traits play positive roles in lodging resistance formation of hybrids. Combining ability variance analysis indicated that its genetic performance was mainly dominated by additive gene effects, and the hybrid combinations with higher lodging resistance can be selected by using of 14 GF6085(R1), 14 GF6343-2(R4), 14 GF6937(R6), 14 GF7433-1(R7), and BS1086(M3),which are with the features with lower general combining ability(GCA) effects of factor 2-related traits whereas higher GCA effects of factor 1-related traits. The heterosis analysis showed that the wide range of heterosis varied with the traits and combinations, and GCA or specific combining ability(SCA) effects of factor 1-related traits except wall thickness of basal second internode(WTBSI) were positively and closely related to the heterosis of lodging resistance. Generally, the correlation coefficients of heterosis to GCA effects of sterile lines(GCAm) of factor 1-related traits are significantly higher than that to GCA of restorer lines(GCAr) and SCA, combined with the higher GCAm variance values of factor 1-related traits compared to GCAr, the GCAm of factor 1-related traits should be particularly considered when breeding hybrid combinations.The heritability analysis showed that the narrow-sense heritability of the diameter of basal second internode(DBSI) and the center of gravity height(TCGH) were obviously lower(<60%) than other traits, suggesting that these two traits were suitable for selection in higher generation for parental breeding. These could provide a theoretical basis for parental breeding and heterosis utilization of lodging resistance.展开更多
Development of hybrid rice with high yield and grain quality is a goal of rice breeding.To investigate the genetic mechanism of heterosis for rice milling and appearance quality in indica/xian rice,QTL mapping was con...Development of hybrid rice with high yield and grain quality is a goal of rice breeding.To investigate the genetic mechanism of heterosis for rice milling and appearance quality in indica/xian rice,QTL mapping was conducted using 1061 recombinant inbred lines(RILs)derived from a cross of the xian rice cultivars Quan 9311B(Q9311B)and Wu-shan-si-miao(WSSM),and a backcross F_(1)(BC_(1)F_(1)) population developed by crossing the RILs with Quan 9311A(Q9311A),combined with phenotyping in two environments.The F_(1) hybrid(Q9311A×WSSM)showed various degrees of heterosis for milling and appearance quality.A total of 142 main-effect QTL(M-QTL)and 407 pairs of epistatic QTL(E-QTL)were identified for five milling and appearance quality traits and grain yield per plant(GYP)in the RIL,BC_(1)F_(1) and mid-parental heterosis(H_(MP)) populations.Differential detection of QTL in three populations revealed that most additive loci detected in the RILs did not show heterotic effects,but some of them did contribute to BC_(1)F_(1) trait performance.Unlike heterosis of GYP,single-locus overdominance and epistasis were the main contributors to heterosis for milling and appearance quality.Epistasis contributed more to the heterosis for milling quality than to that for appearance quality.Three(four)QTL regions harboring opposite(consistent)directions of favorable allele effects for GYP and grain quality were identified,indicating the presence of partial genetic overlaps between GYP and grain quality.Three strategies are proposed to develop hybrid rice with high yield and good grain quality:1)pyramiding favorable alleles with consistent directions of gene effects for GYP and grain quality at the M-QTL on different chromosomes;2)introgressing favorable alleles for GYP and grain quality into the parents and then pyramiding and fixing these additive effects in hybrids;and 3)pyramiding overdominant and dominant loci and minimizing or eliminating underdominant loci from the parents.展开更多
Heterosis has historically been exploited in plants;however,its underlying genetic mechanisms and molecular basis remain elusive.In recent years,due to advances in molecular biotechnology at the genome,transcriptome,p...Heterosis has historically been exploited in plants;however,its underlying genetic mechanisms and molecular basis remain elusive.In recent years,due to advances in molecular biotechnology at the genome,transcriptome,proteome,and epigenome levels,the study of heterosis in vegetables has made significant progress.Here,we present an extensive literature review on the genetic and epigenetic regulation of heterosis in vegetables.We summarize six hypotheses to explain the mechanism by which genes regulate heterosis,improve upon a possible model of heterosis that is triggered by epigenetics,and analyze previous studies on quantitative trait locus effects and gene actions related to heterosis based on analyses of differential gene expression in vegetables.We also discuss the contributions of yield-related traits,including flower,fruit,and plant architecture traits,during heterosis development in vegetables(e.g.,cabbage,cucumber,and tomato).More importantly,we propose a comprehensive breeding strategy based on heterosis studies in vegetables and crop plants.The description of the strategy details how to obtain F_(1) hybrids that exhibit heterosis based on heterosis prediction,how to obtain elite lines based on molecular biotechnology,and how to maintain heterosis by diploid seed breeding and the selection of hybrid simulation lines that are suitable for heterosis research and utilization in vegetables.Finally,we briefly provide suggestions and perspectives on the role of heterosis in the future of vegetable breeding.展开更多
The experiment was conducted at the experimental field of Olericulture Division, Horticulture Research Centre (HRC), Bangladesh Agricultural Research Institute (BARI), Gazipur, Bangladesh during the winter season of 2...The experiment was conducted at the experimental field of Olericulture Division, Horticulture Research Centre (HRC), Bangladesh Agricultural Research Institute (BARI), Gazipur, Bangladesh during the winter season of 2018-2019 to study the genetic architecture of yield in a seven parent half diallel cross of bottle gourd. The values of mean square for GCA (general combining ability) and SCA (specific combining ability) were highly significant which suggested the presence of both additive and non-additive genetic variance in the population. But the higher magnitude of GCA compared to SCA indicated predominance of additive genetic variance. In most of the cases, the cross between poor and poor parents showed positive SCA effect for fruit yield, which indicated the higher yield. The estimates of significant positive better parent heterosis ranged from 6.27 to 49.72 percent. Analysis of genetic components of variation suggested that additive components were more important in the inheritance of fruit yield. This character was observed being controlled by two to three pairs of genes or groups of genes. Narrow sense heritability was 23 percent indicating probability of selection in generations. The graphical analysis also indicated wide genetic diversity among the parents.展开更多
Hybrid millet Zhang and its parental cultivars were studied for their potassium (K) uptake and accumulation characteristics and related physiological mechanisms. Hydroponic culture was performed with two K levels (i.e...Hybrid millet Zhang and its parental cultivars were studied for their potassium (K) uptake and accumulation characteristics and related physiological mechanisms. Hydroponic culture was performed with two K levels (i.e., high and low) set up. At high K level, hybrid millet showed heterobeltiosis in K accumulation and leaf K content, and it also had higher H+-ATPase activity, respiration rate, root oxidant activity and root K+ influx rate than its parental cultivars. All these lay the physiological foundation of heterosis for potassium uptake of hybrid millet. At low K level, the hybrid millet had a lower H+-ATPase activity and a higher K efflux rate than its parental cultivars, thus heterobeltiosis in K accumulation or leaf K content was not observed. Therefore, high level K fertilizer application is recommended for hybrid millet cultivation as it is favorable for hybrid millet to display heterosis in K uptake and K accumulation.展开更多
13 normal maize inbred lines with quite different quantitative traits were used as experimental materials in this paper. The results showed that there was significantly positive correlation between genetic distance an...13 normal maize inbred lines with quite different quantitative traits were used as experimental materials in this paper. The results showed that there was significantly positive correlation between genetic distance and plot yield,mid-parent heterosis,super heterosis,or SCA of yield. In a certain range,the longer the genetic distance between parental inbred lines,the stronger the heterosis. Therefore,in genetic practice,it was necessary to take the molecular genetic distance between inbred lines as an important reference.展开更多
Although heterosis is widely utilized in crop production, its genetic and molecular basis is still elusive. It is arguably that heterosis arises in crosses between genetically and/or epigenetically distinct individual...Although heterosis is widely utilized in crop production, its genetic and molecular basis is still elusive. It is arguably that heterosis arises in crosses between genetically and/or epigenetically distinct individuals. Various genetic models have been proposed to explain heterosis, such as dominance and overdominance hypothesis. With the recent advancements in functional genomics, epigenetics, transcriptomics, proteomics, and metabolomics-related technologies, systems-level approaches have been adopted to understand the molecular basis of heterosis. In this review, we gather a brief account of findings from various studies in order to better understand the genetic and molecular basis of heterosis.展开更多
基金supported by the grants from the China Agriculture Research System Project(No.CARS-49)the Earmarked Fund for Agriculture Seed Improvement Project of Shandong Province(No.2020LZGC016).
文摘Heterosis has been exploited to enhance the yield and adaptability in various shellfish species;however,the molecular basis of it remains unclear.The Pacific oyster Crassostrea gigas is one of the most economically important aquaculture species,and its productive traits can be improved by hybridization.Here,an intraspecific cross between orange shell(O,10th generation)and‘Haida No.1’(H,13th generation)of C.gigas was performed to assess the heterosis of survival trait.Survival rates of hybrid family(OH)and inbred families(HH and OO)were compared at larval stage,and eyed-pediveliger larvae of three families were subjected to transcriptome analysis.The analysis results of best-parent heterosis and mid-parent heterosis showed that the hybrid family exhi-bited a high heterosis in survival relative to the parental families.The OH-M(OH vs.OO)and OH-P(OH vs.HH)had 425 and 512 dif-ferentially expressed genes(DEGs),respectively.Functional enrichment analysis of these DEGs revealed that the significantly enrich-ed genes function in virion binding,C-type lectin receptor signaling pathway,cellular defense response and other immune-related pro-cesses,which involves perlucin-like protein,CD209 antigen-like protein,ZNFX1,caspase-3 and acan genes.These differentially ex-pressed genes in OH-M and OH-P,together with the immune-related processes mentioned above may play an important role in the larval survival of C.gigas.In addition,three genes(CYP450,fucolectin and perlucin-like)are associated with the orange shell and low survival of maternal oyster OO.These findings provide support for the application of hybrid with superior survival and will facilitate the understanding of heterosis formation in the Pacific oyster.
基金financially supported by the Major State Research Development Program(Grant No.2016YFD0101702)the National Natural Science Foundation of China(Grant No.31872948)the Science and Technology Innovation Program of the Chinese Academy of Agricultural Sciences(CAAS-ASTIPIVFCAAS)。
文摘Cabbage has significant heterosis and most commercial cultivars are hybrids.To explore genetic basis of cabbage heterosis and promote cabbage heterosis utilization,we constructed two populations by crossing 100 DH lines derived from a cabbage hybrid 01–20×96–100 with two female parents.Hybrids exhibited different extents of heterosis,the mean value of economic yield was 2.6 times bigger than parents.We identified 66 and 73 QTLs associated with mid-parent heterosis and transgressive heterosis of twelve yield-related traits,respectively.Some QTLs could be detected under the two-year experiment existed in two populations with different testers,showing relatively high phenotypic contribution rate(15.8%–20.0%).Heterosis QTLs exhibited clustered distribution in several cabbage chromosome regions.Two dominant genetic regions,mk300–316 and mk258–268,originated from the elite parent 01–20,exhibited significant genetic effects for yield-related heterosis,which were first identified.Three elite DH lines(D22,D46,D83)harboring these two dominant regions were selected as having strong heterosis in cabbage production.Candidate gene analysis revealed that some genes participating in biosynthetic processes of carbohydrates and some responses to auxin might affect cabbage yield heterosis.QTL identification and genetic dissection of yield-related traits provide new insights into the genetic effects of cabbage heterosis.
基金supported by the Key Research and Development Program of Hubei Province(2020BBA032)the Wuhan Science and Technology Major Project “Development and application of polyploid rice”,the Open Research Fund of State Key Laboratory of Hybrid Rice(Hunan Hybrid Rice Research Center)(19KF06)the Youth Grant of Hubei University.
文摘Heterosis and polyploidy have an overwhelming influence on plant evolution.Recently,polyploid rice hybrids have been used to breed new rice varieties because they combine the advantages of both heterosis and polyploidy.In this study,we generated six rice lines:autotetraploid rice hybrids and their autotetraploid parents,diploid donors,and hybrids of the diploid donors.To investigate the molecular mechanism controlling the effects of both hybridization and polyploidization,we performed bisulfite and RNA sequencing on young panicles at the pollen meiosis stage to compare the DNA metabolomes and transcriptomes among the six rice lines.The hybrids lines were hypermethylated compared to their corresponding parents and the autotetraploid lines showed globally increased DNA methylation of their transposable elements compared to the diploid donors.The alteration in DNA methylation level corresponded to the differential gene expressions among the rice genotypes,suggesting that methylation changes induced by polyploidization and hybridization may affect gene expression.Groups of gene candidates were identified that may be associated with heterosis and polyploidy.Our results provide DNA information that can be used to investigate epigenetic modification during heterosis and polyploidy in rice.
文摘Vine decline disease (VDD) constitutes a menace to melons worldwide. Especially, the one caused by the fungus Monosporascus cannonballus. Thus, resistant plant material must be released to help growers. Hence, our goal was to develop resistant plant material to VDD. More than 600 melon accessions are expected to be tested for disease resistance in M. cannonballus infested soil in Weslaco, Texas, USA, to identify resistance to VDD, and other important traits. So far, at most 7 lines were found to be resistant to VDD and some of them were used to develop elite, muskmelon inbred lines by pedigree breeding following single or double backcrosses. These elite parents were crossed to each other to develop the hybrids M3 and M4. They were also tested in the same infested field in Weslaco. The hybrids were grown using standard commercial practices followed by growers and when their fruits were ready, their roots were sampled as well as scored for disease severity to estimate high and mid-parent heterosis Our results indicate the existence of heterosis regarding resistance to VDD. Thus, resistant plant material can be developed and selection for resistance can be accomplished.
文摘Exploring the indica-japonica differentiation in parents of hybridization can provide theoretical bases for utilizing inter-subspecific heterosis. In this study, 5 sterile lines and 18 self-bred restorer lines were used as female parents and male parents respectively. Then 90 combinations were constructed by incomplete diallel cross followed by relationship analysis between parental Cheng’s index difference value and Euclidean distance and heterosis. The results showed a significant correlation between several phenotype values, super male parent heterosis and control heterosis and Euclidean distance or Cheng’s index difference value. However, it was no significant correlation for yield. Further analysis found a common interval, 3.41 - 3.46 for Euclidean distance and 3 - 4 for cheng’s index difference value of parents, which was significant or high significant positive correlated with phenotype value, super male parent and control heterosis of main yield traits. This illustrates that the larger the genetic difference of parents was, the stronger the heterosis combinations were, when the genetic differences of parents were in an appropriate range.
基金supported by the National Natural Science Foundation of China (91435207 and 91735304)the Project of Science and Technology of Guangzhou, China (201607020040)
文摘The Asian cultivated rice(Oryza sativa L.) grown worldwide is divided into two subspecies, indica and japonica. It is well known that the heterosis of inter-subspecies is usually stronger than that of intra-subspecies. Since the 1970 s, indica hybrid rice, an intra-subspecific hybrid rice, has being widely used in China and even in the world. However, the inter-subspecific hybrid rice between indica and japonica is still unavailable. The major obstacle is the hybrid sterility of the inter-subspecies. In recent decades, the genetic and molecular basis of indica-japonica hybrid sterility was understood more and more clearly. Some breeding approaches for overcoming inter-subspecific hybrid sterility were proposed and used to develop the indicajaponica hybrid rice. The updated understanding will offer new approaches for development of breeding lines for overcoming indica-japonica hybrid sterility, which facilitates developing of inter-subspecific hybrid rice.
基金funded by the National High Technology Research and Development Program of China (No.2014AA10A604)the Shenzhen Municipal Peacock Plan for introducing high-level overseas talents
文摘Despite the great success achieved by the exploitation of heterosis in rice,the genetic basis of heterosis is still not well understood.We adopted an advanced-backcross breeding strategy to dissect the genetic basis of heterosis for yield and eight related traits.Four testcross(TC) populations with 228 testcross F1 combinations were developed by crossing57 introgression lines with four types of widely used male sterile lines using a North Carolina II mating design.Analysis of variance indicated that the effects of testcross F1 combinations and their parents were significant or highly significant for most of the traits in both years,and all interaction effects with year were significant for most of the traits.Positive midparent heterosis(HMP) was observed for most traits in the four TC populations in the two years.The relative HMPlevels for most traits varied from highly negative to highly positive.Sixty-two dominant-effect QTL were identified for HMPof the nine traits in the four TC populations in the two years.Of these,22 QTL were also identified for the performance of testcross F1.Most dominant-effect QTL could individually explain more than 10% of the phenotypic variation.Four QTL clusters were observed including the region surrounding the RM9–RM297 region on chromosome 1,the RM110–RM279–RM8–RM5699–RM452 region on chromosome 2,the RM5463 locus on chromosome 6 and the RM1146–RM147 region on chromosome 10.The identified QTL for heterosis provide valuable information for dissecting the genetic basis of heterosis.
基金funded by the National Key Research and Development Program of China(2016YFD0100902)。
文摘Heterosis,which describes the superior vigor and yield of F_1 hybrids with respect to their parents,is observed in many rice hybrid crosses.The exploitation of heterosis is a great leap in the history of rice breeding.With advances in genomics and genetics,high-resolution mapping and functional identification of heterosis-associated loci have been performed in rice.Here we summarize advances in understanding the genetic basis of grain yield heterosis in hybrid rice and provide a vision for the genetic study and breeding application of rice heterosis in the future.
基金AusAID (Australian Agency for International Development) for a scholarship supporting TTM,Queensland Alliance for Agriculture and Food Innovation (QAAFI)the Ethiopian Institute of Agricultural Research (EIAR) for financially supporting the research activities
文摘Increased productivity in sorghum has been achieved in the developed world using hybrids.Despite their yield advantage,introduced hybrids have not been adopted in Ethiopia due to the lack of adaptive traits,their short plant stature and small grain size.This study was conducted to investigate hybrid performance and the magnitude of heterosis of locally adapted genotypes in addition to introduced hybrids in three contrasting environments in Ethiopia.In total,139 hybrids,derived from introduced seed parents crossed with locally adapted genotypes and introduced R lines,were evaluated.Overall,the hybrids matured earlier than the adapted parents,but had higher grain yield,plant height,grain number and grain weight in all environments.The lowland adapted hybrids displayed a mean better parent heterosis(BPH) of19%,equating to 1160 kg ha-1and a 29% mean increase in grain yield,in addition to increased plant height and grain weight,in comparison to the hybrids derived from the introduced R lines.The mean BPH for grain yield for the highland adapted hybrids was 16% in the highland and 52%in the intermediate environment equating to 698 kg ha-1and 2031 kg ha-1,respectively,in addition to increased grain weight.The magnitude of heterosis observed for each hybrid group was related to the genetic distance between the parental lines.The majority of hybrids also showed superiority over the standard check varieties.In general,hybrids from locally adapted genotypes were superior in grain yield,plant height and grain weight compared to the high parents and introduced hybrids indicating the potential for hybrids to increase productivity while addressing farmers' required traits.
文摘The relationship between the indica-japonica differentiation of parents and heterosis of hybridin rice was studied with 10 sterile lines, 10 maintainer lines of the sterile lines, 38 restorer lines of Dian typehybrid rice and 40 hybrids derived from the sterile lines and restorer lines. The results indicated that there wasa parabolic correlation between the indica-japonica differentiation of parents detected by RAPD markers andheterosis of hybrid rice. When certain indica-japonica differentiation of parents exists, the percentage of com-binations with positve heterosis and the mean heterosis of hybrids were high. But that didn't mean too muchdifference of parents could lead to stronger hetesosis, that meant overdiffernt parents seldom bring positve het-erotic hybrids. Suitable difference of percent of indica alleles of parents of stronger heterotic hybrid was 12 -16%.
基金supported by the National Natural Science Foundation of China(No.31930105)China Agriculture Research Systems(CARS-40)China Postdoctoral Science Foundation(No.2020 M680028).
文摘Background:Heterosis 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.Results:We 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.Conclusions:These 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.
基金supported by the National Key Basic Research Special Foundation of China(2001CB10807)European Union Project(IC-18-CT97-0172)China-Sweden Cooperation Project(Plan for breeding SI hybrids).
文摘66 F1 hybrids, produced by 3 double low self-incompatible lines and 22 varieties with a North Carolina Ⅱ (NCⅡ) crossing design, were tested for their heterosis in Wuhan, China during two growing seasons from 1999- 2001. The results showed that significant differences were found between F1s and their parents for yield per plant and seed oil content. Mid-parent heterosis of these two characters ranged from 5.50%-64.11% and from 1.55% -7.44% respectively. Heterosis for seed yield per plant was greater than that of seed oil content. For yield components, heterosis of total number of siliques per plant was the highest, followed by seed number per silique and 1 000 seeds weight. Significant genotype-by-year interaction was found for seed yield per plant. Results from correlation and combining ability analysis indicated that parental effects on its F1 hybrid depended on characters, seed yield per plant was affected by both additive and non-additive effects, and seed oil content was affected mainly by additive effect. When designing hybrid programme, parents might be selected by GCAs and variances of SCAs of parents for the characters affected by both additive and non-additive effects, and by the sum of GCAs of female and male parents for the characters mainly affected by additive effects.
文摘Genetic distance among 36 cotton cultivars measured by molecular markers of RAPDs, ISSRs,and SSRs was from 0.0701 to 0.4255 with the mean of 0.2844, and from 2.18 to 12.60 with the mean of 7.04 based on the genotype performance in two-year field experiments, which has a significant positive correlation (r = 0.3350). The correlative coefficients for boll number per plant, boll weight, yield per plant, lint percent and lint yield per plant were 0. 8035,0. 8877,0. 7135,0. 9640 and 0. 8956 between F1 and F2 hybrid performance assessed by three-environment field experiments, respectively. The mean of F1 and F2 hybrid heterosis of yield per plant and lint yield per plant were 13.62%, 16.31%, 7.90% and 9.02%, and the correlative coefficients between them were 0.3689 and 0.3787, respectively. The correlation between the genetic distance and heterosis was low, and influenced directly by the selected parents.
基金supported by the National Key R&D Program of China(2016YFD0101601)the Beijing Natural Science Foundation,China(6194035)the Training Programme Foundation for the Beijing Municipal Excellent Talents,China(2017000020060G130)。
文摘With the application of hybrid wheat, lodging is becoming one of the major factors limiting high yield in its production. However,few studies have focused on combining ability and heterosis analysis of stem-related traits. In this study, 24 crosses were made according to NCII genetic design, using the three(photo-sensitive male sterile lines)×eight(restorer lines) incomplete diallel crosses. The length of basal second internode(LBSI) and breaking strength of basal second internode(BSBSI)as well as other stem-related traits were used to perform the principal component analysis(PCA), combining ability and heterosis analysis. The PCA results showed that the variables could be classified into two main factors, which were named as the positive factor(factor 1) and the negative factor(factor 2), and accounted for 52.3 and 33.2%, respectively, of the total variance in different variables, combined with the analysis for index weight indicated that the factor 1-related traits play positive roles in lodging resistance formation of hybrids. Combining ability variance analysis indicated that its genetic performance was mainly dominated by additive gene effects, and the hybrid combinations with higher lodging resistance can be selected by using of 14 GF6085(R1), 14 GF6343-2(R4), 14 GF6937(R6), 14 GF7433-1(R7), and BS1086(M3),which are with the features with lower general combining ability(GCA) effects of factor 2-related traits whereas higher GCA effects of factor 1-related traits. The heterosis analysis showed that the wide range of heterosis varied with the traits and combinations, and GCA or specific combining ability(SCA) effects of factor 1-related traits except wall thickness of basal second internode(WTBSI) were positively and closely related to the heterosis of lodging resistance. Generally, the correlation coefficients of heterosis to GCA effects of sterile lines(GCAm) of factor 1-related traits are significantly higher than that to GCA of restorer lines(GCAr) and SCA, combined with the higher GCAm variance values of factor 1-related traits compared to GCAr, the GCAm of factor 1-related traits should be particularly considered when breeding hybrid combinations.The heritability analysis showed that the narrow-sense heritability of the diameter of basal second internode(DBSI) and the center of gravity height(TCGH) were obviously lower(<60%) than other traits, suggesting that these two traits were suitable for selection in higher generation for parental breeding. These could provide a theoretical basis for parental breeding and heterosis utilization of lodging resistance.
基金funded by the Key Research and Development Project of Hainan Province(ZDYF2021XDNY128)the Hainan Yazhou Bay Seed Lab Project(B21HJ0216)+1 种基金the Agricultural Science and Technology Innovation Programthe Cooperation and Innovation Mission(CAAS-ZDXT202001)。
文摘Development of hybrid rice with high yield and grain quality is a goal of rice breeding.To investigate the genetic mechanism of heterosis for rice milling and appearance quality in indica/xian rice,QTL mapping was conducted using 1061 recombinant inbred lines(RILs)derived from a cross of the xian rice cultivars Quan 9311B(Q9311B)and Wu-shan-si-miao(WSSM),and a backcross F_(1)(BC_(1)F_(1)) population developed by crossing the RILs with Quan 9311A(Q9311A),combined with phenotyping in two environments.The F_(1) hybrid(Q9311A×WSSM)showed various degrees of heterosis for milling and appearance quality.A total of 142 main-effect QTL(M-QTL)and 407 pairs of epistatic QTL(E-QTL)were identified for five milling and appearance quality traits and grain yield per plant(GYP)in the RIL,BC_(1)F_(1) and mid-parental heterosis(H_(MP)) populations.Differential detection of QTL in three populations revealed that most additive loci detected in the RILs did not show heterotic effects,but some of them did contribute to BC_(1)F_(1) trait performance.Unlike heterosis of GYP,single-locus overdominance and epistasis were the main contributors to heterosis for milling and appearance quality.Epistasis contributed more to the heterosis for milling quality than to that for appearance quality.Three(four)QTL regions harboring opposite(consistent)directions of favorable allele effects for GYP and grain quality were identified,indicating the presence of partial genetic overlaps between GYP and grain quality.Three strategies are proposed to develop hybrid rice with high yield and good grain quality:1)pyramiding favorable alleles with consistent directions of gene effects for GYP and grain quality at the M-QTL on different chromosomes;2)introgressing favorable alleles for GYP and grain quality into the parents and then pyramiding and fixing these additive effects in hybrids;and 3)pyramiding overdominant and dominant loci and minimizing or eliminating underdominant loci from the parents.
基金the National Key Research and Development Program of China[2016YFD0101705]the Earmarked Fund for Modern Agro–industry Technology Research System[CARS–25]the Key Laboratory of Biology and Genetic Improvement of Horticultural Crops,Ministry of Agriculture,China.
文摘Heterosis has historically been exploited in plants;however,its underlying genetic mechanisms and molecular basis remain elusive.In recent years,due to advances in molecular biotechnology at the genome,transcriptome,proteome,and epigenome levels,the study of heterosis in vegetables has made significant progress.Here,we present an extensive literature review on the genetic and epigenetic regulation of heterosis in vegetables.We summarize six hypotheses to explain the mechanism by which genes regulate heterosis,improve upon a possible model of heterosis that is triggered by epigenetics,and analyze previous studies on quantitative trait locus effects and gene actions related to heterosis based on analyses of differential gene expression in vegetables.We also discuss the contributions of yield-related traits,including flower,fruit,and plant architecture traits,during heterosis development in vegetables(e.g.,cabbage,cucumber,and tomato).More importantly,we propose a comprehensive breeding strategy based on heterosis studies in vegetables and crop plants.The description of the strategy details how to obtain F_(1) hybrids that exhibit heterosis based on heterosis prediction,how to obtain elite lines based on molecular biotechnology,and how to maintain heterosis by diploid seed breeding and the selection of hybrid simulation lines that are suitable for heterosis research and utilization in vegetables.Finally,we briefly provide suggestions and perspectives on the role of heterosis in the future of vegetable breeding.
文摘The experiment was conducted at the experimental field of Olericulture Division, Horticulture Research Centre (HRC), Bangladesh Agricultural Research Institute (BARI), Gazipur, Bangladesh during the winter season of 2018-2019 to study the genetic architecture of yield in a seven parent half diallel cross of bottle gourd. The values of mean square for GCA (general combining ability) and SCA (specific combining ability) were highly significant which suggested the presence of both additive and non-additive genetic variance in the population. But the higher magnitude of GCA compared to SCA indicated predominance of additive genetic variance. In most of the cases, the cross between poor and poor parents showed positive SCA effect for fruit yield, which indicated the higher yield. The estimates of significant positive better parent heterosis ranged from 6.27 to 49.72 percent. Analysis of genetic components of variation suggested that additive components were more important in the inheritance of fruit yield. This character was observed being controlled by two to three pairs of genes or groups of genes. Narrow sense heritability was 23 percent indicating probability of selection in generations. The graphical analysis also indicated wide genetic diversity among the parents.
文摘Hybrid millet Zhang and its parental cultivars were studied for their potassium (K) uptake and accumulation characteristics and related physiological mechanisms. Hydroponic culture was performed with two K levels (i.e., high and low) set up. At high K level, hybrid millet showed heterobeltiosis in K accumulation and leaf K content, and it also had higher H+-ATPase activity, respiration rate, root oxidant activity and root K+ influx rate than its parental cultivars. All these lay the physiological foundation of heterosis for potassium uptake of hybrid millet. At low K level, the hybrid millet had a lower H+-ATPase activity and a higher K efflux rate than its parental cultivars, thus heterobeltiosis in K accumulation or leaf K content was not observed. Therefore, high level K fertilizer application is recommended for hybrid millet cultivation as it is favorable for hybrid millet to display heterosis in K uptake and K accumulation.
文摘13 normal maize inbred lines with quite different quantitative traits were used as experimental materials in this paper. The results showed that there was significantly positive correlation between genetic distance and plot yield,mid-parent heterosis,super heterosis,or SCA of yield. In a certain range,the longer the genetic distance between parental inbred lines,the stronger the heterosis. Therefore,in genetic practice,it was necessary to take the molecular genetic distance between inbred lines as an important reference.
文摘Although heterosis is widely utilized in crop production, its genetic and molecular basis is still elusive. It is arguably that heterosis arises in crosses between genetically and/or epigenetically distinct individuals. Various genetic models have been proposed to explain heterosis, such as dominance and overdominance hypothesis. With the recent advancements in functional genomics, epigenetics, transcriptomics, proteomics, and metabolomics-related technologies, systems-level approaches have been adopted to understand the molecular basis of heterosis. In this review, we gather a brief account of findings from various studies in order to better understand the genetic and molecular basis of heterosis.
