Identification of QTLs for grain size and characterization of the beneficial alleles of grain size genes in large grain rice variety BL129 免费阅读 下载全文
A genetic evidence of chromosomal fragment from bridge parent existing in substitution lines between two common wheat varieties 免费阅读 下载全文 Locating of important agronomic genes onto chromosome is helpful for efficient development of new wheat varieties. Wheat chromosome substitution lines between two varieties have been widely used for locating genes because of their distinctive advantages in genetic analysis, compared with the aneuploid genetic materials. Apart from the substituted chromosome, the other chromosomes between the substitution lines and their recipient parent should be identical, which eases the gene locating practice. In this study, a set of chromosome substitution lines with cv. Wichita(WI) as the recipient parent and cv. Cheyenne(CNN) as the donor parent were studied for the composition of high molecular weight glutenin subunits(HMW-GS) as well as a range of agronomic important traits. Results revealed that the substitution lines of WI(CNN5D), WI(CNN6A) and WI(CNN7B) had higher plant heights than the two parents of WI and CNN, and WI(CNN3D) had later maturity than the parents. By sodium dodecyl sulfate polyacrylamide gel electrophoresis(SDS-PAGE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry(MALDI-TOF-MS) analysis, a substitution line WI(CNN5B) was found to contain different HMW-GS patterns from its two parents, in which 1By9 was replaced by 1By8 on chromosome 1BL. Simple sequence repeat(SSR) analysis confirmed that the variation on 1BL in WI(CNN5B) was originated from Chinese Spring(CS). It is concluded that chromosomal fragments from bridge material and donor parent were quite often retained in intracultivaral chromosome substitution lines except the substituting chromosomes.
Mapping of QTL conferring leaf rust resistance in Chinese wheat lines W014204 and Fuyu 3 at adult plant stage 免费阅读 下载全文 Wheat leaf rust is a destructive foliar disease of common wheat(Triticum aestivum L.) worldwide. The most effective, economical s to control the disease is growing resistant cultivars with adult plant resistance(APR). The Chinese wheat lines W014204 and Fuyu 3 showed high leaf rust resistance in the field. To identify leaf rust APR genes in the two lines, two mapping populations with 215 and 163 F2:3 lines from the crosses W014204/Zhengzhou 5389 and Fuyu 3/Zhengzhou 5389, respectively, were phenotyped for leaf rust severities during the 2010–2011, 2011–2012 and 2012–2013 cropping seasons in the field at Baoding, Hebei Province, China. A total of 1 215 SSR markers were used to identify the quantitative trait loci(QTLs) for leaf rust APR in the two populations. In the W014204/Zhengzhou 5389 population, three QTLs were detected and designated as QLr.hbu-1BL.1, QLr.hbu-2BS.1 and QLr.hbu-7DS, and explained 2.9–8.4, 11.5–38.3 and 8.5–44.5% of the phenotypic variance, respectively; all the resistance alleles at these loci were derived from W014204. In the Fuyu 3/Zhengzhou 5389 population, three QTLs, QLr.hbu-1BL.2, QLr.hbu-2BS.2 and QLr.hbu-7BL, explained 12.0–19.2, 22.3–38.9 and 4.1–4.3% of the phenotypic variance, respectively, and all resistance alleles were contributed by Fuyu 3. Based on chromosome positions of closely linked markers, both QLr.hbu-1BL.1 and QLr.hbu-1BL.2 are Lr46, and QLr.hbu-7DS is Lr34. QLr.hbu-7BL was mapped on chromosome 7BL near to Lr68 and they are likely the same gene. Based on chromosome positions, pedigree and field reactions, the two 2BS QTLs are different from all the known APR genes and are likely to be new APR QTL for leaf rust. These QTLs and their closely linked markers are potentially useful for improving leaf rust resistance in wheat breeding.
Genome-wide identification, phylogeny and expression analysis of the SBP-box gene family in maize （Zea mays） 免费阅读 下载全文 The SQUAMOSA promoter binding protein(SBP)-box genes encode a kind of plant-specific transcription factors(TFs) and play important roles in the regulation of plant development. In this study, a genome-wide characterization of this family was conducted in maize(Zea mays). Thirty-one SBP-box genes were i dentified to be di stributed in nine chromosomes an d 16 of the m were complementary to the mature Zmmi R156 sequences. All the Z. mays SBP(Zm S BP) genes were classified into two clusters with eight subgroups according to the phylogenetic analysis of proteins, which were consistent with the pattern of exon-intron structures. The phylogenetic tree of the Zm SBP, Oryz a sativa SBP-like(Os SPL) and Arabidopsis thaliana SBP-like(AtSPL) genes were constructed and all the SBP-box genes were divided into eight groups, which was the same as the classification of Zm SBP genes. The comparision of the expression profiles of all SBP-box genes in these three species indicated that most orthologous genes had similar expression patterns. The results from this study provided a basic understanding of the Zm SBP genes and might facilitate future researches for elucidating the SBP-box genes function in maize.
Identification of additional QTLs for flowering time by removing the effect of the maturity gene E1 in soybean 免费阅读 下载全文 The adaptability of soybean to be grown at a wide range of latitudes is attributed to natural variation in the major genes and quantitative trait loci(QTLs) that control flowering time and maturity. Thus, the identification of genes controlling flowering time and maturity and the understanding of their molecular basis are critical for improving soybean productivity. However, due to the great effect of the major maturity gene E1 on flowering time, it is difficult to detect other small-effect QTLs. In this study, aiming to reduce the effect of the QTL, associated with the E1 gene, on the detection of other QTLs, we divided a population of 96 recombinant inbred lines(RILs) into two sub-populations: one with the E1 allele and another with the e1 nl allele. Compared with the results of using all 96 recombinant inbred lines, additional QTLs for flowering time were identified in the sub-populations, two(q FT-B1 and q FT-H) in RILs with the E1 allele and one(q FT-J-2) in the RILs with the e1 nl allele, respectively. The three QTLs, q FT-B1, q FT-H and q FT-J-2 were true QTLs and played an important role in the regulation of growth period. Our data provides valuable information for the genetic mapping and gene cloning of traits controlling flowering time and maturity and will help a better understanding of the mechanism of photoperiod-regulated flowering and molecular breeding in soybean.
Suitable growing zone and yield potential for late-maturity type of Yongyou japonica/indica hybrid rice in the lower reaches of Yangtze River, China 免费阅读 下载全文 Late-maturity type of Yongyou japonica/indica hybrids series(LMYS) have shown great yield potential, and are being widely planted in the lower reaches of Yangtze River, China. Knowledge about suitable growing zone and evaluation of yield advantage is of practical importance for LMYS in this region. Fifteen LMYS, two high-yielding inbred japonica check varieties(CK-J) and two high-yielding hybrid indica check varieties(CK-I) were grown at Xinghua(119.57°E, 33.05°N) of Lixiahe region, Yangzhou(119.25°E, 32.30°N) of Yanjiang region, Changshu(120.46°E, 31.41°N) of Taihu Lake region, and Ningbo(121.31°E, 29.45°N) of Ningshao Plain in 2013 and 2014. The results showed that maturity dates of the 15 were later than the secure maturity date at Xinghua and 6, 14 and 15 LMYS were mature before the secure maturity date at Yangzhou, Changshu and Ningbo, respectively. One variety was identified as high-yielding variety among LMYS(HYYS) at Yangzhou, 8 HYYS in 2013 and 9 HYYS in 2014 at Changshu, 9 HYYS at Ningbo. HYYS here referred to the variety among LMYS that was mature before the secure maturity date and had at least 8% higher grain yield than both CK-J and CK-I at each experimental site. Grain yield of HYYS at each experimental site was about 12.0 t ha–1 or higher, and was significantly higher than CK varieties. High yield of HYYS was mainly attributed to larger sink size due to more spikelets per panicle. Plant height of HYYS was about 140 cm, and was significantly higher than check varieties. Significant positive correlations were recorded between duration from heading to maturity stage and grain yield, and also between whole growth periods and grain yield. HYYS had obvious advantage over check varieties in biomass accumulation and leaf area duration from heading to maturity stage. Comprehensive consideration about safe maturity and yield performance of LMYS at each experimental site, Taihu Lake region(representative site Changshu) and Ningshao Plain(representative site ...Slight shading after anthesis increases photosynthetic productivity and grain yield of winter wheat （Triticum aestivum L,） due to the delaying of leaf senescence 免费阅读 下载全文 The solar radiation intensity and duration are continuously decreasing in the major wheat planting area of China. As a consequence, leaf senescence, photosynthesis, grain filling and thus wheat yield shall be affected by light deficiency. Therefore, two winter wheat(Triticum aestivum L.) cultivars, Tainong 18(a large-spike cultivar) and Ji’nan 17(a multiplespike cultivar), were subjected to shading during anthesis and maturity under field condition in 2010–2011 and 2011–2012. Under the slight shading treatment(S1, 88% of full sunshine), leaf senescence was delayed, net photosynthesis rate(Pn) and canopy apparent photosynthesis rate(CAP) were improved, and thus thousand-kernel weight(TKW) and grain yield were higher as compared with the control. However, mid and severe shading(S2 and S3, 67 and 35% of full sunshine, respectively) led to negative effects on these traits substantially. Moreover, superoxide dismutase(SOD), peroxidase(POD) and catalase(CAT) activities in flag leaf were significantly greater under slight shading than those in other treatments, while the malondialdehyde(MDA) content was less than that under other treatments. In addition, the multiple-spike cultivar is more tolerant to shading than large-spike cultivar. In conclusion, slight shading after anthesis delayed leaf senescence, enhanced photosynthesis and grain filling, and thus resulted in higher grain yield.
Programmed cell death, antioxidant response and oxidative stress in wheat flag leaves induced by chemical hybridization agent SQ-1 免费阅读 下载全文 Male sterility induced by a chemical hybridization agent（CHA） is an important tool for utilizing crop heterosis. Leaves, especially the flag leaves, as CHA initial recipients play a decisive role in inducing male sterility. To investigate effects of different treatment times of CHA-SQ-1 used, morphological, biochemical and physiological responses of wheat flag leaves were detected in this study. CHA induced programmed cell death（PCD） as shown in terminal deoxynucleotidyl transferase-mediated d UTP nick end-labelling（TUNEL） and DNA laddering analysis. In the early phase, CHA-SQ-1 triggered organelle changes and PCD in wheat leaves accompanied by excess production of reactive oxygen species（ O-.2and H2O2） and down-regulation of the activities of superoxide dismutase（SOD）, catalase（CAT） and guaiacol peroxidase（POD）. Meanwhile, leaf cell DNAs showed ladder-like patterns on agarose gel, indicating that CHA-SQ-1 led to the activation of the responsible endonuclease. The oxidative stress assays showed that lipid peroxidation was strongly activated and photosynthesis was obviously inhibited in SQ-1-induced leaves. However, CHA contents in wheat leaves gradually reduced along with the time CHA-SQ-1 applied. Young flags returned to an oxidative/antioxidative balance and ultimately developed into mature green leaves. These results provide explanation of the relations between PCD and anther abortion and practical application of CHA for hybrid breeding.
Blue light is more essential than red light for maintaining the activities of photosystem II and I and photosynthetic electron transport capacity in cucumber leaves 免费阅读 下载全文 Blue and red lights differently regulate leaf photosynthesis. Previous studies indicated that plants under blue light generally exhibit better photosynthetic characteristics than those under red light. However, the regulation mechanism of related photosynthesis characteristics remains largely unclear. Here, four light qualities treatments(300 μmol m–2 s–1) including white fluorescent light(FL), blue monochromatic light(B, 440 nm), red monochromatic light(R, 660 nm), and a combination of red and blue light(RB, R:B=8:1) were carried out to investigate their effects on the activity of photosystem II(PSII) and photosystem I(PSI), and photosynthetic electron transport capacity in the leaves of cucumber(Cucumis sativus L.) seedlings. The results showed that compared to the FL treatment, the R treatment significantly limited electron transport rate in PSII(ETRII) and in PSI(ETRI) by 79.4 and 66.3%, respectively, increased non-light induced non-photochemical quenching in PSII(ΦNO) and limitation of donor side in PSI(ΦND) and reduced most JIP-test parameters, suggesting that the R treatment induced suboptimal activity of photosystems and inhibited electron transport from PSII donor side up to PSI. However, these suppressions were effectively alleviated by blue light addition(RB). Compared with the R treatment, the RB treatment significantly increased ETRII and ETRI by 176.9 and 127.0%, respectively, promoted photosystems activity and enhanced linear electron transport by elevating electron transport from QA to PSI. The B treatment plants exhibited normal photosystems activity and photosynthetic electron transport capacity similar to that of the FL treatment. It was concluded that blue light is more essential than red light for normal photosynthesis by mediating photosystems activity and photosynthetic electron transport capacity.
Biochemical and microbial properties of rhizospheres under maize/ peanut intercropping 免费阅读 下载全文 Maize/peanut intercropping system shows the significant yield advantage. Soil microbes play major roles in soil nutrient cycling and were affected by intercropping plants. This experiment was carried out to evaluate the changing of rhizosphere microbial community composition, and the relationship between microbial community and soil enzymatic activities, soil nutrients in maize/peanut intercropping system under the following three treatments: maize(Zea mays L.) and peanut(Arachis hypogaea L.) were intercropped without any separation(NS), by half separation(HS) using a nylon net(50 μm) and complete separation(CS) by using a plastic sheet, respectively. The soil microbial communities were assessed by phospholipid fatty acid(PLFA). We found that soil available nutrients(available nitrogen(Avail N) and available phosphorus(Avail P)) and enzymatic activities(soil urase and phosphomonoesterase) in both crops were improved in NS and HS treatments as compared to CS. Both bacterial and fungal biomasses in both crops were increased in NS followed by HS. Furthermore, Gram-positive bacteria( G+) in maize soils were significant higher in NS and HS than CS, while the Gram-negative(G–) was significant higher in peanut soil. The ratio of normal saturated to monounsaturated PLFAs was significantly higher in rhizosphere of peanut under CS treatment than in any other treatments, which is an indicator of nutrient stress. Redundancy analysis and cluster analysis of PLFA showed rhizospheric microbial community of NS and HS of both plants tended to be consistent. The urase and Avail N were higher in NS and HS of both plants and positively correlated with bacteria, fungi(F) and total PLFAs, while negatively correlated with G+/G– and NS/MS. The findings suggest that belowground interactions in maize/peanut intercropping system play important roles in changing the soil microbial composition and the dominant microbial species, which was closely related with the improving of soil available ...Evaluation of thermotherapy against Huanglongbing （citrus greening） in the greenhouse 免费阅读 下载全文 Huanglongbing(HLB, or citrus greening) is the most destructive disease of citrus, which is associated with Candidatus Liberibacter asiaticus(Las). Few management options are available, aside from preventive measures such as removing infected plants, planting disease-free seedlings, and managing the insect vector. In this study, we assessed the efficacy of thermotherapy against HLB under controlled greenhouse conditions. A total of 60 two-year-old, graft-infected Citrus reticulata Blanco plants were used. The plants were randomly divided into three groups(45°C, 48° C, and untreated control), with five plants/replicate(rep) and four reps/treatment. The treated plants were placed in phytotrons for a 4-h treatment session, repeated once per week for three consecutive weeks. Disease remission was observed eight weeks post-treatment. Real-time PCR assays revealed that Las titers in HLB-affected seedlings were significantly reduced in both 45 and 48°C treatments four weeks after treatment, with the exception of eight plants. In contrast, Las titers in the untreated control plants increased significantly during the same period, with a maximum increase of 28-fold. Except for seven plants, Las titers in the new flushes of treated plants decreased more than 90% eight weeks after treatment. Las titers in mature leaves of treated plants decreased 56 and 60% in average at 45 and 48°C, respectively, eight weeks after treatment. The HLB symptoms and Las titer of seedings were markedly alleviated eight weeks after treatment in both 45 and 48°C treatments. Our results laid a good foundation for the further development of citrus free-disease seedling cultivation and Huanglongbing control in the field. The whole plants were replaced for scion or branch in previous as the research object in this study, and the expression of Huanglongbing symptoms combined with real-time polymerase chain reaction(PCR) were used to evaluate the effect of heat treatment in the greenhouse.
Parasitism and pathogenicity of Radopholus similis to Ipomoea aquatica, Basella rubra and Cucurbita moschata and genetic diversity of different populations 免费阅读 下载全文 Ten populations of Radopholus similis from different ornamental hosts were tested for their parasitism and pathogenicity to water spinach(Ipomoea aquatic), malabar spinach(Basella rubra), and squash(Cucurbita moschata) in pots. The results showed all three plants were new hosts of R. similis. Growth parameters of plants inoculated with nematodes were significantly lower than those of healthy control plants. All R. similis populations were pathogenic to the three plants, but pathogenicity differed among populations from different hosts. The same R. similis populations also showed different pathogenic effects in the three different plants. Rad N5 population from Anthurium andraeanum had the highest pathogenicity to the three studied plants. Rad N1 from A. andraeanum had the lowest pathogenicity to squash and Rad N7 from Chrysalidocarpus lutesens had the lowest pathogenicity to water spinach and malabar spinach. R. similis is usually associated with root tissues, but here we report that it could be found to move and feed in the stem bases of all three studied plants. Sequence and phylogenetic analyses of DNA markers of the 18 S r RNA, 28 S r RNA, ITS r RNA, and mitochondrial DNA gene sequences of ten R. similis populations revealed significant genetic diversity. Rad N5 and Rad N6 populations from anthurium showed a close genetic relationship and could be distinguished from other populations by PCR-RFLP. At the same time, Rad N5 and Rad N6 populations were the most pathogenic to three studied plants. These results confirm the e xistence of large biological variability and molecular diversity among R. similis populations from the same or different hosts, and these characteristics are related to pathogenic variability.
Insecticide induction of O-demethylase activity and expression of cytochrome P450 genes in the red imported fire ant （Solenopsis invicta Buren） 免费阅读 下载全文 The red imported fire ant( Solenopsis invicta) is a global major invasive pest, and has caused significant economic, social and environmental impacts since its invasion to mainland of China in 2004. To date, chemical control has been the most effective measure. However, the long-term use of chemicals would lead to an unexpected rebound. To understand the risks and explore the mechanisms of detoxification or induction to insecticides in S. invicta, the O-demethylase activity and expression of cytochrome P450 genes of workers and queens, and the effects of chlorpyrifos and fipronil exposure in workers were investigated. Biochemical assays showed the O-demethylase activity of cytochrome P450 was significantly higher in workers than in queens(1.66-fold), and was significantly induced in workers exposed to chlorpyrifos and fipronil, reaching a maximum(3.00- and 1.95-fold) at 48 h and then decreasing dramatically compared to controls(exposed to acetone counterpart). The relative expression levels of 12 cytochrome P450 expressed sequence tags(ESTs) in workers were significantly higher than in queens(from 2.3- to 36.4-fold). Multiple cytochrome P450 genes(except 9E4) were co-up-regulated(from 1.5- to 2.86-fold) in workers exposed to fipronil. These results indicated that the increased O-demethylase activity may result from the increased transcription levels of cytochrome P450 related to detoxification of insecticides in S. invicta. It appears that cytochrome P450 plays an important role in enhanced metabolic detoxification of insecticides. At the same time, it also provides the theoretical basis for resistance management and rational usage of in secticides to control S. invicta.
Application of the combination of 1,3-dichloropropene and dimethyl disulfide by soil injection or chemigation： effects against soilborne pests in cucumber in China 免费阅读 下载全文 The combination of 1,3-dichloropropene+dimethyl disulfide(1,3-D+DMDS), which forms a pre-plant soil fumigant, can provide a substitute for the environmentally unfriendly methyl bromide(MB). Three greenhouse trials were performed to evaluate the root-knot nematode and soilborne fungi control efficacy in the suburbs of Beijing in China in 2010-2014. Randomized blocks with three replicates were designed in each trial. The combination of 1,3-D+DMDS(10+30 g m-2) significantly controlled Meloidogyne incognita, effectively suppressed the infestation of Fusarium oxysporum and Phytophthora spp., and successfully provided high commercial fruit yields(equal to MB but higher than 1,3-D or DMDS). The fumigant soil treatments were significantly better than the untreated controls. These results indicate that 1,3-D+DMDS soil treatments can be applied by soil injection or chemigation as a promising MB alternative against soilborne pests in cucumber in China.
SFRP2 affects prenatal muscle development and is regulated by microRNA-1/206 in pigs 免费阅读 下载全文 Secreted frizzled-related protein 2(SFRP2), a member of the SFRPs family, is associated with cell growth and differentiation in myogenesis. Our previous study suggested that SFRP2 was a potential target of micro RNA(mi RNA)-1/206, which was considered as myomiR s. To further explore the biological function and regulation mechanisms of the SFRP2 gene in porcine skeletal muscle development, we first analyzed the sequence structure of the porcine SFRP2 gene. Subsequently, we detected its tissue distribution in adult Tongcheng pigs(a Chinese indigenous breed) and investigated its dynamic expression in developmental skeletal muscle(13 prenatal and 7 postnatal time points) in Tongcheng pigs. An interaction analysis between SFRP2 and myomi Rs was also performed. The results showed that the expression pattern of the SFRP2 varied greatly across diverse tissues. It exhibited abundant expression in prenatal skeletal muscle and peaked at 55 days post coitus(E55), and had a lower expression in postnatal skeletal muscle, indicating that the SFRP2 gene might affect porcine embryonic skeletal muscle development. Co-expression analysis revealed that the expression levels of SFRP2 correlated negatively with mi RNA-1(r=–0.570, P-value=0.009) and mi RNA-206(r=–0.546, P-value=0.013), but positively with SFRP1(r=0.613, P-value=0.004). The bioinformatics analysis and dual luciferase assay verified that the SFRP2 was a putative target of mi RNA-1/206 in pigs. Therefore, this study is helpful for understanding the biological function and molecular regulation of the SFRP2 gene during porcine skeletal muscle development.
A genome scan of recent positive selection signatures in three sheep populations 免费阅读 下载全文 Domesticated sheep have been exposed to artificial selection for the production of fiber, meat, and milk as well as to natural selection. Such selections are likely to have imposed distinctive selection signatures on the sheep genome. Therefore, detecting selection signatures across the genome may help elucidate mechanisms of selection and pinpoint candidate genes of interest for further investigation. Here, detection of selection signatures was conducted in three sheep breeds, Sunite(n=66), German Mutton(n=159), and Dorper(n=93), using the Illumina Ovine SNP50 Genotyping Bead Chip array. Each animal provided genotype information for 43 273 autosomal single nucleotide polymorphisms(SNPs). We adopted two complementary haplotype-based statistics of relative extended haplotype homozygosity(REHH) and the cross-population extended haplotype homozygosity(XP-EHH) tests. In total, 707, 755, and 438 genomic regions subjected to positive selection were identified in Sunite, German Mutton, and Dorper sheep, respectively, and 42 of these regions were detected using both REHH and XP-EHH analyses. These genomic regions harbored many important genes, which were enriched in gene ontology terms involved in muscle development, growth, and fat metabolism. Fourteen of these genomic regions overlapped with those identified in our previous genome-wide association studies, further indicating that these genes under positive selection may underlie growth developmental traits. These findings contribute to the identification of candidate genes of interest and aid in understanding the evolutionary and biological mechanisms for controlling complex traits in Chinese and western sheep.
Chemical composition and in vitro fermentation characteristics of high sugar forage sorghum as an alternative to forage maize for silage making in Tarim Basin, China 免费阅读 下载全文 The chemical composition, mineral profile and in vitro fermentation characteristics of maize(MZ), high sugar forage sorghum(HS) and forage sorghum(FS), and silages made from each forage type were measured. The MZ and MZ silage(MZS) had higher crude protein, starch and ether extract contents than both sorghum forages and sorghum silages. HS had higher ash and water-soluble carbohydrate concentrations than FS and MZ. MZ, MZS, HS and HS silage(HSS) had lower neutral detergent fibre, acid detergent fibre and acid detergent lignin than FS and FS silage(FSS). FSS had higher dry matter(DM) and p H than MZS and HSS. HSS contained higher concentrations of P and K than FSS and MZS. MZS and HSS had higher in vitro dry matter and organic matter digestibility, CH4 production, total volatile fatty acids, acetate and propionate than FSS. p H was higher for FSS than for HSS, and ammonia was lower for HSS than for MZS and FSS. HSS had higher gas production than MZS and FSS after 2, 4, 6 and 8 h incubation. MZS had higher gas production than HSS and FSS after 26 and 28 h of incubation. The results indicate that HS may substitute for MZ to make good quality silage. However, animal studies are needed to assess the acceptability and feeding values of HSS vs. MZS for ruminant production.
Effects of low ambient temperatures and dietary vitamin C supplementation on pulmonary vascular remodeling and hypoxic gene expression of 21-d-old broilers 免费阅读 下载全文 The objective of this study was to evaluate the effects of low ambient temperature（LAT） and dietary vitamin C（VC）supplementation on pulmonary vascular remodeling（PVR） and the relative expression of hypoxia inducible factor-1α（HIF-1α）,vascular endothelial growth factor（VEGF） and its receptor 2（VEGFR-2） mRNA of lungs in 21-d-old broilers.4001-d-old male Cobb broilers were assigned randomly to 4 treatments as follows for 21 d:1) LAT and a basal diet;2) LAT and a basal diet supplemented with 1 000 mg kg-1 VC（LAT+VC）;3) normal ambient temperature（NAT） and a basal diet;4) NAT and a basal diet supplemented with 1 000 mg kg-1 VC（NAT+VC）.Each treatment was composed of 10 replicates of 10 birds per replicate.Samples of lung were collected after the broilers were killed at d 21.LAT increased the ratio of vessel wall area to vessel total area（WA/TA,%） and mean media thickness in pulmonary arterioles（mMTPA,%）（P<0.05）.Dietary VC supplementation decreased mMTPA（P<0.05）,but had no effect on the WA/TA.LAT increased（P<0.05） the relative mRNA expression of HIF-1α,VEGF and VEGFR-2,while adding VC to the diet could decrease（P<0.05） their relative mRNA expression.A significant positive correlation existed between the level of VEGF mRNA expression and the value of WA/WT（P<0.05） or mMTPA（P<0.05）.These results suggested LAT resulted in pulmonary vascular remodeling,and the increase of HIF-1a,VEGF and VEGFR-2 mRNA expression,and dietary VC supplementation can alleviate pulmonary vascular remodeling in broiler by affecting these gene expression.
Hepatitis associated with hepatitis B virus in broilers 免费阅读 下载全文 Infection by hepatitis B virus(HBV) results in acute and chronic liver damages in humans. Liver products of broilers as a primary food consumed in our daily life have a close connection with public health. The prevalence of the virus in livers and serum of broilers is of great significance, owning to the potential transmission between chickens and humans. Liver tissues and serum samples were tested to investigate the prevalence of hepatitis B virus infection in slaughtered broilers, for expression of HBV antigens and antibodies. The distribution and positive rate of hepatitis B surface antigen(HBs Ag), hepatitis B core antigen(HBc Ag) and hepatitis B e antigen(HBe Ag) in liver samples were examined using immunohistochemistry. HBs Ag was mainly located in the cytoplasm of hepatocytes with a positivity of 81.61% whereas HBe Ag and HBc Ag were primarily located in the nucleus of hepatocytes with a positivity of 40.13 and 49.10%, respectively. Enzyme-linked immunosorbent assay(ELISA) analysis of serum for HBV serological markers demonstrated a high prevalence of hepatiits B surface antibody(HBsA b, 54.91%) and hepatitis B core antibody(HBcA b, 27.68%), whereas HBeA b, HBsA g and HBeA g were rarely detectable. Classic hepatitis pathological changes, including swollen hepatocytes, focal parenchymal necrosis, lymphocytic infiltration and hyperplasia of fibrous connective tissues were observed using histopathological analysis. Some of the liver samples were found positive for HBV DNA using nested PCR. Sequence comparison confirmed that all sequences shared 97.5–99.3% identity with human HBV strains. These results demonstrated the existence of HBV in livers and serums of broilers. Animals or animal products contaminated with HBV could raise an important public health concern over food safety and zoonotic risk.
Long-term phosphorus accumulation and agronomic and environmtal critical phosphorus levels in Haplic Luvisol soil, northern China 免费阅读 下载全文 Sufficient soil phosphorus（P） content is essential for achieving optimal crop yields,but accumulation of P in the soil due to excessive P applications can cause a risk of P loss and contribute to eutrophication of surface waters.Determination of a critical soil P value is fundamental for making appropriate P fertilization recommendations to ensure safety of both environment and crop production.In this study,agronomic and environmental critical P levels were determined by using linear-linear and linear-plateau models,and two segment linear model,for a maize（Zea mays L.）-winter wheat（Triticum aestivum L.） rotation system based on a 22-yr field experiment on a Haplic Luvisol soil in northern China.This study included six treatments:control（unfertilized）,no P（NoP）,application of mineral P fertilizer（MinP）,MinP plus return of maize straw（MinP+StrP）,MinP plus low rate of farmyard swine manure（MinP+L.Man） and MinP plus high rate of manure（MinP+H.Man）.Based on the two models,the mean agronomic critical levels of soil Olsen-P for optimal maize and wheat yields were 12.3 and 12.8 mg kg-1,respectively.The environmental critical P value as an indicator for P leaching was 30.6 mg Olsen-P kg-1,which was 2.4 times higher than the agronomic critical P value(on average 12.5 mg P kg-1).It was calculated that soil Olsen-P content would reach the environmental critical P value in 41 years in the MinP treatment,but in only 5-6years in the two manure treatments.Application of manure could significantly raise soil Olsen-P content and cause an obvious risk of P leaching.In conclusion,the threshold range of soil Olsen-P is from 12.5 to 30.6 mg P kg-1 to optimize crop yields and meanwhile maintain relatively low risk of P leaching in Haplic Luvisol soil,northern China.
Soil N transformation and microbial community structure as affected by adding biochar to a paddy soil of subtropical China 免费阅读 下载全文 We have had little understanding on the effects of different types and quantities of biochar amendment on soil N transformation process and the microbial properties. In this study, various biochars were produced from straw residues and wood chips, and then added separately to a paddy soil at rates of 0.5, 1 and 2%(w/w). The effects of biochar application on soil net N mineralization and nitrification processes, chemical and microbial properties were examined in the laboratory experiment. After 135 d of incubation, addition of straw biochars increased soil p H to larger extent than wood biochars. The biochar-amended soils had 37.7, 7.3 and 227.6% more soil organic carbon(SOC), available P and K contents, respectively, than the control soil. The rates of net N mineralization and nitrification increased significantly as biochars quantity rose, and straw biochars had greater effect on N transformation rate than wood biochars. Soil microbial biomass carbon increased by 14.8, 45.5 and 62.5% relative to the control when 0.5, 1 and 2% biochars(both straw- and wood-derived biochars), respectively, were added. Moreover, biochars amendments significantly enhanced the concentrations of phospholipid fatty acids(PLFAs), as the general bacteria abundance increased by 161.0% on average. Multivariate analysis suggested that the three rice straw biochar(RB) application levels induced different changes in soil microbial community structure, but there was no significant difference between RB and masson pine biochar(MB) until the application rate reached 2%. Our results showed that biochars amendment can increase soil nutrient content, affect the N transformation process, and alter soil microbial properties, all of which are biochar type and quantity dependent. Therefore, addition of biochars to soil may be an appropriate way to disposal waste and improve soil quality, while the biochar type and addition rate should be taken into consideration before its large-scale application in ag...Using side-dressing technique to reduce nitrogen leaching and improve nitrogen recovery efficiency under an irrigated rice system in the upper reaches of Yellow River Basin, Northwest China 免费阅读 下载全文 The excessive nitrogen（N） fertilizer input coupled with flood irrigation might result in higher N leaching and lower nitrogen recovery efficiency（NRE）.Under an intensive rice system in the Ningxia irrigation region,China,environmental friendly N management practices are heavily needed to balance the amount of N input for optimum crop production while minimize the nitrogen loss.The objective of this study was to determine the influences of side-dressing（SD） technique in mechanical transplanting systems on the NRE,N leaching losses and rice yield in anthropogenic-alluvial soil during two rice growing seasons（2010-2011）.Four fertilizer N treatments were established,including conventional urea rate(CU,300 kg ha-1yr-1);higher SD of controlled-release N fertilizer rate(SD1,176 kg ha-1yr-1);lower SD of controlled-release N fertilizer rate(SD2,125 kg ha-1yr-1);and control（CK,no N fertilizer）.Field lysimeters were used to quantify drainage from undisturbed soil during six rice growing stages.Meanwhile,the temporal variations of total nitrigen（TN）,NO3--N,and NH4+-N concentrations in percolation water were examined.The results showed that SD1 substantially improved NRE and reduced N leaching losses while maintaining rice yields.Across two years,the averaged NRE under SD1 treatment increased by 25.5%as relative to CU,but yet the rice yield was similar between two treatments.On average,the nitrogen loss defined as TN,NH4+-N,and NO3--N underthe SD1 treatment reduced by 27.4,37.2 and 24.1%,respectively,when compared with CU during the study periods.Although the SD2 treatment could further reduce N leaching loss to some extent,this technique would sharply decline rice yield,with the magnitude of as high as 21.0%relative to CU treatment.Additionally,the average NRE under SD2 was 11.2% lower than that under SD1 treatment.Overall,the present study concluded that the SD technique is an effective strategy to reduce N leaching and increase NRE,thus potentially mitigate local environme...Effect of four crop straws on transformation of organic matter during sewage sludge composting 免费阅读 下载全文 A 45-d laboratory experiment was conducted to compare the effect of four crop straws on the transformations of organic matter（OM） during composting of sewage sludge. The four crop straws included rape straw, wheat straw, maize straw and rice straw. The following parameters such as temperature, OM, humic-like substances（HS）, fulvic-like acids（FA） and humic-like acids（HA） were determined. The degradation of OM and the formation of HS and HA could be described well by the first-order kinetic model, while the FA content fluctuated during composting. T he maximal degradation rates of OM in the compost piles added with rape straw, wheat straw, maize straw and rice straw were 34.7, 46.9, 54.7 and 52.8%, respectively, and the final contents of HS were 118, 128, 141 and 134 g kg–1, respectively, while the humification indices were higher in the compost piles added with maize straw and wheat straw than in those with rice straw and rape straw. The results indicate that a higher hemicellulose content and a lower C/N ratio in crop straw can result in a higher rate of OM degradation and higher contents of HS, while a higher content of lignin can lead to a higher polymerization degree of humic substances in compost piles. The final compost piles added with maize straw has the highest contents of OM, total nitrogen and humus substance as well as the highest values of polymerization degree, while compost piles with rape straw have the highest potassium content and those with rice straw have the highest pH values.
Journal of Integrative Agriculture 免费阅读 下载全文