Selection of reference genes for quantitative real-time RT-PCR on gene expression in Golden Pompano (Trachinotus ovatus).

Golden pompano (Trachinotus ovatus) is an important economically fish species. In this study, with an aim to identify reliable reference genes for quantitative real-time PCR (qRT-PCR) in golden pompano, we evaluated the expression stability of eight housekeeping genes in the presence and absence of poly I:C stimulation in eight tissues. The PCR data was analyzed by geNorm and NormFinder algorithms. The results showed that the expression of all the examined genes exhibited tissue-dependent variations. When under normal physiological condition, geNorm and NormFinder identified B2M and 18S as suitable genes. When studying gene expression under conditions of poly I:C stimulation, the selection of the internal controls should be selected on a tissue basis. At 12 h stimulation, geNorm ranked Actin/UBCE, Actin/B2M, UBCE/B2M, Actin/UBCE, RPL13/B2M, UBCE/GAPDH, B2M/RPL13, and UBCE/B2M, respectively, as the most stably expressed genes in liver, spleen, kidney, gill, intestine, heart, muscle, and brain. Comparable ranking orders were produced by NormFinder. Similar results were obtained at 48 h stimulation. Taken together, these results indicate that B2M and 18S are the most stable gene across tissue types under normal physiological conditions. However, during poly I:C stimulation, no single gene or single pair of genes in the examined set of housekeeping genes can serve as a universal reference across all tissue types. If one gene is preferred, B2M, B2M, UBCE, Actin, B2M/RPL13, B2M, B2M, and RPL13 may be used in spleen, kidney, liver, gill, intestine, brain, muscle, and heart of golden pompano, respectively.

Polymorphisms of AluI and Hin1I loci of the IGF-1R gene and their genetic effects on growth traits in Bian chickens.

Growth traits are important economic traits in broiler chicken production. AluI and Hin1I loci are two restriction sites, which are respectively located in exons 2 and 3 of the IGF-1R gene. These two loci are significantly related to the growth traits in Jinghai Yellow chickens. In this study, a correlation analysis was performed between these two loci and the growth traits of Bian chickens. The results showed a G376A mutation at the AluI site and a C919A mutation at the Hin1I site, which respectively resulted in three genotypes AA, AB, and BB in exon 2 and three genotypes CC, CD, and DD in exon 3. Correlation analysis showed that the female Bian chickens with the AA genotype of the AluI locus had higher body weights than those with the AB genotype (P < 0.05) at 8, 14, 16, and 18 weeks; individuals with CD genotype of Hin1I locus had higher body weights at 6, 8, 10, 12, and 14 weeks compared to the CC genotype (P < 0.05 or P < 0.01). Combined genotypes analysis showed that at the age of 8, 14, 16, and 18 weeks, the body weight of AACC genotype combination was higher than that of the ABCC genotype combination (P < 0.05); at the age of 6, 8, 12, 14, 16, and 18 weeks, the AACD genotype combination had higher (P < 0.05 or P < 0.01) body weight than that of the ABCC genotype.

Efficacy of minimally invasive tonsil surgery for treatment of obstructive sleep apnea-hypopnea syndrome in children.

This study aimed to investigate the efficacy of minimally invasive tonsil surgery for the treatment of obstructive sleep apnea-hypopnea syndrome (OSAHS) in children. Tonsil ablation or turbinate reduction was performed on 49 pediatric patients with OSAHS by minimally invasive tonsil surgery. In order to evaluate the efficacy of surgery, a comparison was conducted between pre-operation and post-operation data in terms of the symptoms, signs and polysomnography test. Total effectiveness rate of the surgery was 83.7%. Subgroup analysis was also performed based on the severity of their conditions: mild, moderate, and severe groups had an effectiveness rate of 90.0, 88.9, and 66.7%, respectively (Hc=6.665, P<0.05). Postoperatively, the apnea-hypopnea index, the minimum oxygen saturation (SaO2), and corresponding symptoms improved compared to pre-operation conditions (P<0.05). Minimally invasive tonsil surgery was a safe and effective method for treating OSAHS in children.

Detection of QTLs controlling fast kernel dehydration in maize (Zea mays L.).

In order to understand the effect of grain moisture of inbred lines at the silking and physiological maturity stages on kernel dehydration rate, 59 maize inbred lines from six subgroups were selected. Grain moisture was measured and QTLs associated with kernel dehydration were mapped. A rapid dehydration evaluation and association analysis revealed eight inbred lines with faster dehydration rate, including Yuanwu 02, K36, Zhonger/O2, Lo1125, Han 49, Qi 319, Hua 160, and PH4CV. A single sequence repeat analysis using 85 pairs detected five QTLs with phenotypic variation contribution ≥10% in the permanent F2 generation populations Zheng 58 x S1776 and Chang 7-2 x K1131, which had LOD threshold values ≥ 3 in both 2013 and 2014. The chromosome region of qFkdr7b had not previously been reported and is preliminarily identified as a new major QTL. A false positive field verification of grain dehydration rate of 53 inbred lines indicated that the screening result of the rapid dehydration inbred lines by specific amplification with marker Phi114 was most similar to the field assessment result, followed by markers Phi127 and Phi029. The rapid dehydration lines selected based on primer Phi114 amplification were also similar to the field dehydration rate and can thus be used for molecular marker-assisted selection. A significant effort is needed to improve stress resistance and shorten the growth period via fast kernel dehydration in intermediate materials of the inbred lines K36, Zhonger/ O2, Lo1125, Han 49, Hua 160, and PH4CV, and further using the selected lines for new combinations.

Genetic effect of an A/G polymorphism in the HSP70 gene on thermotolerance in chicken.

Studying thermotolerance is important for the prevention of thermostress in chickens. This study aimed to analyze the effect of mutations in the heat shock protein 70 (HSP70) gene on chicken thermotolerance. The C.-69A>G SNP in the 5'-flanking region of the HSP70 gene was genotyped in Lingshan and White Recessive Rock (WRR) chickens. Association of this SNP with thermotolerance traits revealed it to be significantly associated with CD4+/CD8+, and potentially associated with heterophil-to-lymphocyte ratio in WRR chickens exposed to thermoneutral temperature (15°C). Online prediction detected a putative myeloid zinc finger protein 1 binding factor in the C.-69A>G mutation. Under acute thermostress, mRNA levels of HSP70 in individuals with different C.-69A>G genotypes varied in the heart, leg muscle, and liver tissues. The HSP70 protein was expressed at higher levels in individuals with the GG genotype than in those with the AA genotype. In heart and liver, protein expression of HSP70 in individuals with the GG genotype was significantly higher than in those with the AA genotype. In leg muscle, protein expression was higher in birds with the GG genotype than in those with the AA and AG genotypes. Luciferase activity of the GG genotype was significantly higher than that of the AA genotype, suggesting that the C.-69A>G SNP regulates HSP70 gene expression. These results indicate that the C.-69A>G SNP in the 5'-flanking region of the HSP70 gene might affect chicken thermotolerance and that the GG genotype might be advantageous for the prevention of thermostress.

Interactions of allele E of the MC1R gene with FM and mutations in the MLPH gene cause the five-gray phenotype in the Anyi tile-like gray chicken.

The Anyi tile-like gray chicken is a Chinese indigenous breed with a gray dilution phenotype, having gray feathers, comb, skin, shanks, and beak, which is valuable for genetic research on pigmentation. However, the genetic basis of the gray dilution phenotype remains unknown. The objective of this study was to investigate the genetic basis of the gray dilution phenotype in the Anyi tile-like gray chicken. We found that all Anyi tile-like gray chickens tested in this study carried at least one E allele, which is responsible for the appearance of black feathers, and some of them carried the FM allele, which is responsible for the black skin phenotype. A single nucleotide polymorphism (C.1909A>G) was identified within the melanophilin (MLPH) gene and was significantly associated with the gray dilution phenotype. Our findings suggest that the E and FM alleles act together to cause the development of the "five-black" phenotype (black feather, comb, skin, shank, and beak), whereas the MLPH mutation results in defective melanosome transport, leading to the development of the "five-gray" phenotype.

Single nucleotide polymorphisms associated with growth traits in Jinghai yellow chickens.

Body weight is one of the most important economic traits in the poultry industry. In the present study, a custom SNP Beadchip was used to analyze the association between those 15 SNPs and 12 growth traits of Jinghai yellow chickens, and other important genetic parameters were also calculated and analyzed. The results indicated that nine of the 15 SNPs were associated with growth traits in Jinghai yellow chickens (P < 0.05), and the identified SNPs were also in linkage disequilibrium. Five of the nine identified SNPs were mainly associated with all of the growth traits, which indicated that those five SNPs might have significant influence on Jinghai yellow chicken growth traits. Polymorphism information content (PIC) analyses indicated that five of the nine SNPs exhibited moderate polymorphism (0.25 < PIC < 0.5), which reflected intermediate genetic diversity. Six candidate genes surrounding the significant SNPs were obtained and subjected to Gene Ontology annotation analyses and pathway analyses. The functions of six important candidate genes (SETDB2, ATP7B, INTS6, KPNA3, DLEU7, and FOXO1A) were discussed. The present study provided basic data for marker-assisted selection in Jinghai yellow chickens.

Genetic mechanism associated with congenital cytomegalovirus infection and analysis of effects of the infection on pregnancy outcome.

We aimed to compare the diagnostic value of various detection methods for cytomegalovirus (CMV) infection, to investigate the genetic mechanism associated with CMV infection in pregnant women, and to analyze the risk of sequelae development in fetuses with CMV infection. A total of 300 participants who had the same immunosuppressive regimen and received preemptive therapy for CMV infection were prospectively enrolled in this study; they included 289 vaccine trial participants. The gB-absorbed CMV IgG assay was performed for each vaccine trial participant. The healthy women were divided into 2 groups, and amniotic fluids were collected from them at 15-18 weeks of gestation to test for CMV seropositivity before conception by using IgM specific antibodies, CMV-DNA, and IgG analysis. In 104 cases, cord blood sera and urine specimens were also collected from the infants and examined. The sensitivity and specificity of immediate-early messenger RNA and pp67 (late) messenger RNA detection by the nucleic acid sequence-based amplification technique was comparable to those of virus isolation and PCR. Furthermore, an association between single nucleotide polymorphisms in the TLR-2 gene and congenital CMV infection was observed and confirmed. Moreover, CMV infection during early pregnancy has been shown to have a much more severe effect on the pregnancy outcome compared to infection during later stages of pregnancy.

Characterization of HSP70 and its expression in tissue: correlation with physiological and immune indices in goose (Anser cygnoides) serum.

We cloned the goose heat shock protein 70 gene (HSP70), to determine its sequence variation and elucidate its mRNA expression. We designed primers to amplify the entire goose HSP70 sequence. We used 10 commercial Wuzong goslings in a heat-stress experiment. We collected tissue samples for RNA extraction and quantitative real-time polymerase chain reaction (qRT-PCR). We analyzed the variation in expression of goose HSP70 before and after heat stress. We constructed a DNA pool from six different species, for single nucleotide polymorphism (SNP) screening. We detected 18 SNPs and selected three of these SNPs for correlation analysis with biological and immune traits in 200 Wuzong geese. We showed that T+237C was significantly correlated with the serum corticosterone level, whereas T+1122C was significantly correlated with the heterophil to lymphocyte ratio. Goose HSP70 contained no introns. The results of qRT-PCR analysis revealed significant gender differences in the expression of goose HSP70 at 40°C but not at 25°C; moreover, in general, expression was significantly higher at 40°C than at 25°C. With the exception of the leg muscle and cerebellum, HSP70 expression was significantly higher in male geese than in female geese. Our results indicate that goose HSP70 plays an important role in response to severe heat stress.

Effect of bone marrow mesenchymal stem cells on the TGF-ß1/Smad signaling pathway of hepatic stellate.

This study investigated the effect of bone marrow mesenchymal stem cells (BMCs) on the transforming growth factor-ß1 (TGF-ß1)-induced activation of the Smad signaling pathway in rat hepatic stellate cells (HSCs). There were four experimental groups: 1) a blank control group, 2) a TGF-ß1 treatment group, 3) an MSC-combined group, and 4) an induced MSC-combined group. Isolation and culture of rat liver HSCs in vitro and the proliferation of HSCs in each group were detected by MTT method. The expression of α-SMA and the TGF receptors (TbRI and II) were determined by immunohistochemical staining of HSCs in all groups, while Smad2/3, Smad4, and Smad7 mRNA expressions were detected by RT-PCR for HSCs in each group. TGF-ß1 treatment significantly promoted the proliferation of HSCs (P < 0.01); it has different inhibition effects on the proliferation of HSCs in the MSC-combined group and in the induced MSC-combined group (P < 0.05). TGF-ß1 treatment also enhanced the expression of α-SMA as compared to the control group (P < 0.01). Alternatively, when compared with the pure TGF-ß1 group, the MSC-combined group and the induced MSC-combined group showed lower α-SMA expression (P < 0.05). Activation of HSCs induced by TGF-ß1, TßRI and TßRII fluorescence was (+ + +); the fluorescences of TßRI and TßRII in MSC-combined group and in induced MSC-combined group were (+ +) and (± ~ +), respectively. The expressions of TßRI and TßRII in activated HSCs induced by TGF-ß1 were significantly decreased in the MSC-combined group (P < 0.05) and in the induced MSC-combined group (P < 0.01). The expression of HSC Smad2/3 and Smad4 was reduced in the MSC-combined group (P < 0.05) and in the induced MSC-combined group (P < 0.01), as compared to the TGF-ß1 group. However, the expression of Smad7 in HSCs was upregulated in the MSC-combined group (P < 0.05) and in the induced MSC-combined group (P < 0.01). These results indicate that BMCs can inhibit the activation and proliferation of HSCs by downregulating the expression of TßRI and TßRII in the cell membrane of HSCs. Moreover, BMCs can upregulate the expression of Smad7 and downregulate the expression of Smad2/3 and Smad4 in the HSCs induced by TGF-ß1, which resulted in an inhibition of HSC activation.

Association analysis between SNPs in the 5'-flanking region of the chicken GRP78 gene, thermotolerance parameters, and tissue mRNA expression.

Glucose-regulated protein 78 (GRP78) is a molecular chaperone in the endoplasmic reticulum and can be induced by different kinds of environmental and physiological stress. Thus far, the role of the GRP78 gene in thermotolerance in chickens has not been investigated. In the present study, we detected sequence variations in the 5ꞌ-flanking region of the GRP78 gene and evaluated several thermotolerance parameters, such as T3, corticosterone, H/L ratio, and levels of CD3(+), CD4(+), and CD8(+) T cells, to further determine its associations at 35° and 15°C. The sequencing results revealed 10 SNPs in the 5'-flanking region of the GRP78 gene, and seven mutations were chosen for further genotyping in a White Recessive Rock (WRR) chicken population. The SNP C.-744C>G in WRR chickens was significantly correlated with heat tolerance parameters under both conditions; it may therefore exert a potential hereditary effect on heat tolerance, and the genotype GG may be advantageous for thermotolerance. The heart, liver, brain, and leg muscle tissues of 8-day-old WRR chickens were sampled from heat stress groups, which were defined by exposure to 1, 2, 3, and 6 h of persistent thermal stress, and a control group, which was not exposed to thermal stress. Quantitative real-time polymerase chain reaction assay indicated that the mRNA expression level of the GRP78 gene increased gradually under heat stress, peaked at 3 h, and then decreased. We conclude that the mRNA expression of the GRP78 gene is time- and tissue-dependent.

Analysis of genetic diversity of the heat shock protein 70 gene on the basis of abundant sequence polymorphisms in chicken breeds.

This study was designed to detect the sequence variation of the chicken heat shock protein 70 (HSP70) gene. A total of 102 individuals from 8 native Chinese breeds together with Dwarf White Chicken and Red Junglefowl were used to detect sequence variations. The coding regions of the chicken HSP70 gene from 102 individuals were cloned and sequenced. Thirty-six variations were identified, which included 34 single nucleotide polymorphisms and 2 indel mutations. Fifty-seven haplotypes were observed, of which, 43 were breed-specific and 14 were shared. There were 7 Red Junglefowl-specific haplotypes, while Haidong and Silkie only had 2 specific haplotypes. Eleven and 3 haplotypes were shared between and within species, respectively. The variation in nucleotide diversity (Pi) and average number of nucleotide differences (K) among species were consistent. The total Pi of HSP70 was 0.0016, and the total K was 4.1998. The Pi value of Red Junglefowl was the highest (0.0018) and K was 4.8000, while the Pi of Silkie was the lowest (0.0010) and K was 2.5000. These results demonstrated that variation in chicken HSP70 was abundant between and within species.

Assessment of genetic diversity of bermudagrass germplasm from southwest China and Africa by using AFLP markers.

Cynodon dactylon (L.) Pers. var. dactylon (common bermudagrass) is widely distributed geographically between approximately 45°N and 45°S latitude, penetrating to approximately 53°N latitude in Europe. The extensive variation of morphological and adaptive characteristics of the taxon has been substantially documented, but information is lacking on DNA molecular variation in geographically disparate forms. The genetic diversity of 51 wild accessions of bermudagrass from southwest China (Sichuan, Chongqing, Yunnan, Guizhou, and Tibet) and 8 African bermudagrass was analyzed using amplified fragment length polymorphism molecular markers. A total of 670 polymorphic bands were detected with 11 primer combinations, of which 663 (98.74%) bands were found to be polymorphic. The genetic similarity among the accessions ranged from 0.64-0.96 with an average of 0.78. All 59 wild accessions were clustered into 5 eco-geographic groups, and nearly all accessions from the same area were classified into the same group and were found to be associated with their geographical distributions. Therefore, complex geographical and ecological environments are important factors for the genetic structure and geographical distribution of C. dactylon.

Alteration of HSF3 and HSP70 mRNA expression in the tissues of two chicken breeds during acute heat stress.

This study aimed to estimate changes in HSF3 and HSP70 mRNA expression in stress-sensitive tissues of 2 chicken breeds during acute heat stress. Lingshan chickens (LSC) and White Recessive Rock (WRR) (24 chickens of each breed) were randomly divided into 4 groups (0, 2, 3, and 6 h of heat treatment). With increasing heat treatment time, both HSF3 and HSP70 expression first declined and then showed a significant increase in both breeds. However, HSP70 expression decreased in the heart following 6 h of heat treatment, whereas HSF3 expression continued to increase. After 2 h of heat treatment, HSF3 expression was significantly higher in the brain and leg muscle of LSC compared to WRR (P < 0.05, P < 0.01). In comparison, HSP70 expression was significantly higher in the liver and leg muscle of WRR compared to LSC (P < 0.01, P < 0.05). After 3 h of heat treatment, HSF3 expression was significantly higher in the brain and leg muscle of LSC compared to WRR (P < 0.01). In comparison, HSP70 expression was significantly higher in the liver and heart of LSC compared to WRR (P < 0.01). These results indicate that the expression of HSF3 and HSP70 mRNA in LSC and WRR exhibit species-specific and tissue-specific differences during heat treatment.

Genetic diversity and relationships in cultivars of Lolium multiflorum Lam. using sequence-related amplified polymorphism markers.

Sequence-related amplified polymorphism (SRAP) markers were used to analyze and estimate the genetic variability, level of diversity, and relationships among 20 cultivars and strains of annual ryegrass (Lolium multiflorum Lam.). Eighteen SRAP primer combinations generated 334 amplification bands, of which 298 were polymorphic. The polymorphism information content ranged from 0.4715 (me10 + em1) to 0.5000 (me5 + em7), with an average of 0.4921. The genetic similarity coefficient ranged from 0.4304 to 0.8529, and coefficients between 0.65 and 0.90 accounted for 90.00%. The cluster analysis separated the accessions into five groups partly according to their germplasm resource origins.

Isolation of the P5CS gene from reed canary grass and its expression under salt stress.

Reed canary grass (RCG) is a perennial grass traditionally cultivated for forage. It is also used as fuel to produce energy in Finland and Sweden, and other countries have expressed interest in the cultivation of RCG. In China, arable land is limited. Salinity is considered to be a major factor limiting plant crop development and productivity. To boost biofuel production of RCG and extend its range in saline soil, we seek to improve its salt tolerance. Proline acts as an osmolyte that accumulates when plants are subjected to abiotic stress. P5CS plays a crucial role in proline biosynthesis. We isolated a P5CS gene from RCG, designated B231P5CS (GenBank accession No. JQ622685). B231P5CS is a fragment (971 bp) that encodes a 323-amino acid polypeptide. We also cloned an actin gene fragment from RCG as a reference gene in expression analysis of B231P5CS gene. Expression analysis revealed that B231P5CS transcripts were upregulated in leaves after treatment with salt (200 mM NaCl) and that transcript levels of B231P5CS reached a maximum 12 h after exposure, which was 14.69 times the level in control plants. The trends of expression were exactly opposite in roots; transcripts were downregulated after salt treatment. Proline concentration increased in leaves after stress. In contrast, proline content of roots decreased up to 3.6-fold relative to controls. Changes in proline concentration after stress were correlated with B231P5CS expression. Our results suggest that B231P5CS is a stress-inducible gene and plays a non-redundant role in plant development. This gene may be used to improve stress tolerance of RGC and other bioenergy feedstock.

Genetic diversity and relationship of chicory (Cichorium intybus L.) using sequence-related amplified polymorphism markers.

Chicory is a crop with economically important roles and is cultivated worldwide. The genetic diversity and relationship of 80 accessions of chicories and endives were evaluated by sequence-related amplified polymorphism (SRAP) markers to provide a theoretical basis for future breeding programs in China. The polymorphic rate was 96.83%, and the average polymorphic information content was 0.323, suggesting the rich genetic diversity of chicory. The genetic diversity degree of chicory was higher (GS = 0.677) than that of endive (GS = 0.701). The accessions with the highest genetic diversity (effective number of alleles, NE = 1.609; Nei's genetic diversity, H = 0.372; Shannon information index, I = 0.556) were from Italy. The richest genetic diversity was revealed in a chicory line (NE = 1.478, H = 0.289, I = 0.443) among the 3 types (line, wild, and cultivar). The chicory genetic structure of 8 geographical groups showed that the genetic differentiation coefficient (GST) was 14.20% and the number of immigrants per generation (Nm) was 3.020. A GST of 6.80% and an Nm of 6.853 were obtained from different types. This observation suggests that these chicory lines, especially those from the Mediterranean region, have potential for providing rich genetic resources for further breeding programs, that the chicory genetic structure among different countries obviously differs with a certain amount of gene flow, and that SRAP markers could be applied to analyze genetic relationships and classifications of Cichorium intybus and C. endivia.

Inhibitory effect of survivin-targeting small interfering RNA on gastric cancer cells.

A pair of inverted repeated sequences of the gene survivin was designed for stable double-stranded RNA establishment. After stable transfection, the biological behaviors of gastric cancer cells were observed. The interference rates of survivin-targeting siRNA (siRNA-survivin) in BGC823, MKN45, SGC7901, and cisplatin-resistant SGC7901 groups were 55.363 ± 3.974, 71.433 ± 3.774, 69.433 ± 7.336, and 76.767 ± 3.541%, respectively, compared with those in the control group. After siRNA-survivin interference, survivin protein expression noticeably decreased, apoptotic rates markedly increased, and cell proliferation was inhibited to varying degrees. Mitochondrial cytochrome C protein expression decreased and the levels of cytoplasmic cytochrome C and caspase-3 increased, which showed significant differences compared with values before transfection. pRNA-shSU eukaryotic expression vectors were constructed. After plasmid transfection, green fluorescent protein expression increased and survivin protein expression noticeably increased in BGC823 and SGC7901. siRNA-survivin promotes GC cell apoptosis and inhibits cell proliferation by downregulating survivin mRNA and protein expression. The underlying mechanisms are correlated with a decrease in mitochondrial cytochrome C and cytoplasmic cytochrome C and caspase-3.

Analysis of diversity and relationships among orchardgrass (Dactylis glomerata L.) accessions using start codon-targeted markers.

Orchardgrass, or cocksfoot, is an important perennial forage grass worldwide. The comprehensive understanding of orchardgrass accessions will benefit germplasm collection and breeding progress, and it will enhance efforts to improve forage yield and quality. Therefore, 24 novel, simple, polymorphic, and reliable start codon-targeted (SCoT) markers were used to analyze the diversity and genetic relationships among 95 orchardgrass accessions. In total, 273 polymorphic bands were detected with an average of 11.4 bands per primer. The average polymorphic rate for the species was 83.4%, suggesting a high discriminating ability of the SCoT technique for orchardgrass. The molecular variance analysis revealed that 69.13 and 30.87% of variation resided within and among groups, respectively, demonstrating that the orchardgrass germplasms had a higher level of genetic diversity within groups than among geographical regions and distributions. The distinct geographical divergence of orchardgrass was revealed between North America and Oceania. The unweighted pair-group method with arithmetic mean dendrogram revealed a separation of 7 main clusters between 95 accessions according to the geographical origin. Furthermore, each cluster was divided into subgroups mainly according to the origin of its state. The genetic divergence of orchardgrass might be influenced by the ecogeographical conditions, climatic types, breeding systems and gene flow with variations in cultures, bird migration, and breeder selection. These results could facilitate orchardgrass germplasm collection, management, and breeding worldwide.

Morphological and genetic characteristics of hybrid combinations of Dactylis glomerata.

Six F1 populations derived from crosses among 4 orchardgrass (Dactylis glomerata L.) cultivars were studied by morphological and simple sequence repeat molecular markers to test for hybrid vigor and a correlation between genetic distance and heterosis. Heterosis was observed for days to length of culm, leaf traits, tiller numbers, etc. Significant differences between obverse and inverse crosses were found for eleven traits. A cytoplasmic effect existed for the agronomic traits considered in this study. The correlations between genetic distance and heterosis were investigated by analyzing the performance of 3 crosses. The results showed that genetic distance was significantly correlated with tiller number (r = 0.834) and negatively correlated with length of culm (r = -0.889). However, there was no significant correlation with heterosis for the other traits, including yield; the correlation coefficient were too small to allow prediction of orchardgrass heterosis from the parental genetics.