The haplotype-resolved T2T genome of teinturier cultivar Yan73 reveals the genetic basis of anthocyanin biosynthesis in grapes

Teinturier grapes are characterized by the typical accumulation of anthocyanins in grape skin,flesh,and vegetative tissues,endowing them with high utility value in red wine blending and nutrient-enriched foods developing.However,due to the lack of genome information,the mechanism involved in regulating teinturier grape coloring has not yet been elucidated and their genetic utilization research is still insufficient.Here,the cultivar‘Yan73’was used for assembling the telomere-to-telomere(T2T)genome of teinturier grapes by combining the High Fidelity(HiFi),Hi-C and ultralong Oxford Nanopore Technologies(ONT)reads.Two haplotype genomes were assembled,at the sizes of 501.68 Mb and 493.38 Mb,respectively.In the haplotype 1 genome,the transposable elements(TEs)contained 32.77%of long terminal repeats(LTRs),while in the haplotype 2 genome,31.53%of LTRs were detected in TEs.Furthermore,obvious inversions were identified in chromosome 18 between the two haplotypes.Transcriptome profiling suggested that the gene expression patterns in‘Cabernet Sauvignon’and‘Yan73’were diverse depending on tissues,developmental stages,and varieties.The transcription program of genes in the anthocyanins biosynthesis pathway between the two cultivars exhibited high similarity in different tissues and developmental stages,whereas the expression levels of numerous genes showed significant differences.Compared with other genes,the expression levels of VvMYBA1 and VvUFGT4 in all samples,VvCHS2 except in young shoots and VvPAL9 except in the E-L23 stage of‘Yan73’were higher than those of‘Cabernet Sauvignon’.Further sequence alignments revealed potential variant gene loci and structure variations of anthocyanins biosynthesis related genes and a 816 bp sequence insertion was found in the promoter of VvMYBA1 of‘Yan73’haplotype 2 genome.The‘Yan73’T2T genome assembly and comparative analysis provided valuable foundations for further revealing the coloring mechanism of teinturier grapes and the genetic improvement of grape coloring traits.

Gene Expression and Activities of SOD in Cucumber Seedlings Were Related with Concentrations of Mn^(2+),Cu^(2+),or Zn^(2+) Under Low Temperature Stress

Effects of increasing Mn^2＋, Cu^2＋, or Zn^2＋ on SOD expressions were studied in cucumber seedlings under low temperature stress. Both gene expressions and activities of Cu/Zn-SOD and Mn-SOD in cucumber seedling leaves were induced by increasing Mn^2＋, Cu^2＋, or Zn^2＋ under low temperature stress, especially 48 h afterwards. The activities of Cu/Zn-SOD and Mn-SOD at 0 and 48 h after treatment were in accordance with their gene expression levels, which implied that the transcriptional regulation plays key roles in regulating their activities at the early stage of low temperature stress. Gene expressions of Cu/Zn-SOD and Mn-SOD declined at 96 h, but Cu/Zn-SOD and Mn-SOD activities still remain high, which suggested that Cu/Zn-SOD and Mn-SOD activities might be regulated by other factors after transcription at the later stage of low temperature stress. Therefore, we concluded that the increasing Mn^2＋, Cu^2＋, or Zn^2＋ could increase the capacity of scavenging ROS in cucumber seedlings under low temperature stress by inducing gene expressions of Cu/ Zn-SOD and Mn-SOD, elevating activities of Cu/Zn-SOD, Mn-SOD, or regulating other factors after transcription.

Changes of Aroma Components in Hongdeng Sweet Cherry During Fruit Development

To study the changes of aroma components in sweet cherry during fruit development, the aroma components in sweet cherry fruit from the green stage, the color stage, the commercial stage, and the ripe stage were collected using head-space solid phase microextraction （HS-SPME）, and were analyzed using a gas chromatograph-mass spectrophotometer （GC- MS）. A total of 37 compounds were identified from the sample extracts. Aldehydes, alcohols, and esters were the major constituents. The aroma components behaved differently during the fruit developmental period. C6 aldehydes and aromatic aldehydes were the main aldehydes in the sweet cherry fruit. The contents of C6 aldehydes increased quickly to 84.16% in the color stage, then decreased as ripening proceeded, and then, the contents decreased to 59.20 and 55.58% at the commercial stage and the ripe stage, respectively. The aromatic aldehydes （benzaldehyde） increased as ripening proceeded, and the maximum was found at the ripe stage. Alcohols of sweet cherry fruit included C6 alcohols and aromatic alcohols. The content of （E）-2-hexen-l-ol increased as ripening proceeded. The maximum was found at the commercial stage; alcohol was only found at the ripe stage. Ester components included ethyl acetate, butanoic acid ethyl ester, hexanoic acid ethyl ester, which increased as the fruit ripened. Hexanal, （E）-2-hexenal, benzaldehyde, （E）-2-hexen-l-ol, ethyl acetate, and hexanoic acid ethyl ester were the characteristic aroma components of sweet cherry fruit. These aroma components started to form drastically at the color stage, and the main aroma was formed at the commercial stage, which then turned bad at the ripe stage because of the presence of alcohol. So the optimal harvest time of sweet cherry was at the commercial stage.

Maize/peanut intercropping increases photosynthetic characteristics, 13C-photosynthate distribution, and grain yield of summer maize

Intercropping is used widely by smallholder farmers in developing countries to increase land productivity and profitability. We conducted a maize/peanut intercropping experiment in the 2015 and 2016 growing seasons in Shandong, China. Treatments included sole maize (SM), sole peanut (SP), and an intercrop consisting of four rows of maize and six rows of peanut (IM and IP). The results showed that the intercropping system had yield advantages based on the land equivalent ratio (LER) values of 1.15 and 1.16 in the two years, respectively. Averaged over the two years, the yield of maize in the intercropping was increased by 61.05% compared to that in SM, while the pod yield of peanut was decreased by 31.80% compared to SP. Maize was the superior competitor when intercropped with peanut, and its productivity dominated the yield of the intercropping system in our study. The increased yield was due to a higher kernel number per ear (KNE). Intercropping increased the light transmission ratio (LTR) of the ear layer in the maize canopy, the active photosynthetic duration (APD), and the harvest index (HI) compared to SM. In addition, intercropping promoted the ratio of dry matter accumulation after silking and the distribution of 13C-photosynthates to grain compared to SM. In conclusion, maize/peanut intercropping demonstrated the potential to improve the light condition of maize, achieving enhanced photosynthetic characteristics that improved female spike differentiation, reduced barrenness, and increased KNE. Moreover, dry matter accumulation and 13C-photosynthates distribution to grain of intercropped maize were improved, and a higher grain yield was ultimately obtained.

Risk assessment and ranking of pesticide residues in Chinese pears

The presence of pesticide residues in pears is a serious health concern. This study presents the results from a 2-year investigation （2013-2014） that used gas chromatography, GS/MS and UPLC/MS-MS to measure the levels of 104 pesti- cides in 310 pear samples. In 93.2% of the samples, 43 pesticides were detected, of which the maximum residue levels （MRLs） were exceeded in 2.6% of the samples. Multiple residues （two to eight compounds） were present in 69.7% of the samples; one sample contained nine pesticides and one sample contained 10. Only 6.8% of the samples did not contain residues. To assess the health risks, the pesticide residue data have been combined with daily pear consumption data for children and adult populations. A deterministic model was used to assess the chronic and acute exposures based on the Joint Meeting on Pesticide Residues （JMPR） method. A potential acute risk was demonstrated for children in the case of bifenthrin, which was found to be present at 105.36% of the acute reference dose （ARfD） value. The long- term exposure of the Chinese consumer to pesticide residues through the consumption of raw pears was far below the acceptable daily intake （ADI） criterion. Additionally, the matrix ranking scheme was used to classify risk subgroups of pesticides and pear samples. In general, 95.5% of samples were deemed to be safe and nine pesticides were classified as being of a relatively high risk. The findings indicated that the occurrence of pesticide residues in pears should not be considered a serious public health problem. Nevertheless, a more detailed study is required for vulnerable consumer groups, especially children. Continuous monitoring of pesticides in pears and tighter regulation of pesticide residue standards are recommended.

Genome-wide analysis and identification of cytokinin oxidase/dehydrogenase(CKX) gene family in foxtail millet(Setaria italica)

Cytokinin oxidase/dehydrogenase(CKX; EC.1.5.99.12) regulates cytokinin(CK) level in plants and plays an essential role in CK regulatory processes. CKX proteins are encoded by a small gene family with a varying number of members in different plants. In spite of their physiological importance, systematic analyses of SiCKX genes in foxtail millet have not yet been examined. In this paper, we report the genome wide isolation and characterization of SiCKXs using bioinformatic methods. A total of 11 members of the family were identified in the foxtail millet genome. SiCKX genes were distributed in seven chromosomes(chromosome 1, 3, 4, 5, 6, 7, and 11). The coding sequences of all the SiCKX genes were disrupted by introns, with numbers varying from one to four. These genes expanded in the genome mainly due to segmental duplication events. Multiple alignment and motif display results showed that all SiCKX proteins share FAD- and CK-binding domains. Putative cis-elements involved in Ca2+-response, abiotic stress response, light and circadian rhythm regulation, disease resistance and seed development were present in the promoters of SiCKX genes. Expression data mining suggested that SiCKX genes have diverse expression patterns. Real-time PCR analysis indicated that all 11 SiCKX genes were up-regulated in embryos under 6-BA treatment, and some were NaCl or PEG inducible. Collectively, these results provide molecular insights into CKX research in plants.

Assessing the concentration and potential health risk of heavy metals in China's main deciduous fruits

To assess levels of contamination and human health risk, we analyzed the concentrations of the heavy metals lead （Pb）, cadmium （Cd）, chromium （Cr）, and nickel （Ni） in China’s main deciduous fruits-apple, pear, peach, grape, and jujube. The concentration order of the heavy metals was Ni〉Cr〉Pb〉Cd. In 97.5% of the samples, heavy metal concentrations were within the maximum permissible limits. Among the fruits studied, the heavy metal concentrations in jujube and peach proved to be the highest, and those in grape proved to be the lowest. Only 2.2% of the samples were poluted by Ni, only 0.4% of the samples were poluted by Pb, and no samples were poluted by Cd or Cr. Compared with the other fruits, the combined heavy metal polution was signiifcantly higher （P〈0.05） in peach and signiifcantly lower （P〈0.05） in grape. For the combined heavy metal polution, 96.9% of the samples were at safe level, 2.32% at warning level, 0.65% at light level, and 0.13% at moderate level. In the fruits studied, the contribution of heavy metals to the daily intake rates （DIR） folowed the order of Ni〉Cr〉Pb〉Cd. The highest DIR came from apple, while the lowest DIR came from grape. For each of the heavy metals, the total DIR from ifve studied fruits corresponded to no more than 1.1% of the tolerable daily intake, indicating that no signiifcant adverse health effects are expected from the heavy metals and the fruits studied. The target hazard quotients and the total target hazard quotients demonstrated that none of the analyzed heavy metals may pose risk to consumers through the fruits studied. The highest risk was posed by apple, folowed in decreasing order by peach and pear, jujube, and grape. We suggest that the main deciduous fruits （apple, pear, peach, grape, and jujube） of China’s main producing areas are safe to eat.

Improvement of copper tolerance of Arabidopsis by transgenic expression of an allene oxide cyclase gene,GhA OC1, in upland cotton(Gossypium hirsutum L.)

Allene oxide cyclase(AOC, E 5.3.99.6) is an essential enzyme in the jasmonic acid(JA)biosynthetic pathway and mediates a wide range of adaptive responses. In this report, five AOC genes(Gh AOC1–Gh AOC5) were cloned from upland cotton(Gossypium hirsutum L.),sequenced, and characterized. Real-time PCR analysis indicated that the transcripts of Gh AOCs were abundantly expressed in roots and less in fibers, and regulated in cotton plants under methyl jasmonate(Me JA) and Cu Cl2 stresses. To investigate the role of Gh AOC under copper stress, transgenic Arabidopsis plants overexpressing cotton Gh AOC1 under control of the Cauliflower mosaic virus 35S(Ca MV 35S) promoter were generated. Compared to untransformed plants, Gh AOC1-overexpressing Arabidopsis thaliana plants exhibited markedly higher survival rate, shoot fresh weight, shoot dry weight, and photosynthetic efficiency, and reduced cell membrane damage and lipid peroxidation under copper stress.This study provides the first evidence that Gh AOC1 plays an important role in copper stress tolerance.

Molecular, serological and biological characterization of a novel Apple stem pitting virus strain from a local pear variety grown in China

Apple stem pitting virus(ASPV)is an important causal agent of pear diseases.Nowadays,the infection status and molecular characteristics of the virus in old pear trees have never been investigated.In this study,we provide the first complete genome sequence of an ASPV isolate LYC from an over 300-year-old tree of a local Pyrus bretschneideri cultivar‘Chili’specifically grown at Laiyang area in China.ASPV-LYC possesses a chimeric genome consisting of 9273 nucleotides excluding a poly(A)tail at its 3′end and harboring a recombination region in its open reading frame(ORF1)with Aurora-1 and KL9 identified as the major and minor parents.Western blot analysis with antisera against recombinant coat proteins(CPs)of three ASPV isolates from pear indicates that ASPV-LYC is serologically related to these ASPV isolates,but with differential activities.Further biological tests on indicator plants of Pyronia veitchii show that ASPV-LYC can induce serious leaf and stem symptoms as other ASPV isolates.The results provide an important information for understanding molecular evolution of ASPV and suggest a need to prevent dissemination of the isolate among pear trees.

Site-directed mutagenesis identified the key active site residues of alcohol acyltransferase PpAAT1 responsible for aroma biosynthesis in peach fruits

The aroma of peach fruit is predominantly determined by the accumulation of γ-decalactone and ester compounds.A previous study showed that the biosynthesis of these aroma compounds in peach fruit is catalyzed by PpAAT1,an alcohol acyltransferase.In this work,we investigated the key active site residues responsible for γ-decalactone and ester biosynthesis.A total of 14 candidate amino acid residues possibly involved in internal esterification and 9 candidate amino acid residues possibly involved in esterification of PpAAT1 were assessed via site-directed mutagenesis.Analyses of the in vitro enzyme activities of PpAAT1 and its site-directed mutant proteins(PpAAT1-SMs)with different amino acid residue mutations as well as the contents of γ-decalactone in transgenic tobacco leaves and peach fruits transiently expressing PpAAT1 and PpAAT1-SMs revealed that site-directed mutation of H165 in the conserved HxxxD motif led to lost enzymatic activity of PpAAT1 in both internal esterification and its reactions,whereas mutation of the key amino acid residue D376 led to the total loss ofγ-decalactone biosynthesis activity of PpAAT1.Mutations of 9 and 7 other amino acid residues also dramatically affected the enzymatic activity of PpAAT1 in the internal esterification and esterification reactions,respectively.Our findings provide a biochemical foundation for the mechanical biosynthesis ofγ-decalactone and ester compounds catalyzed by PpAAT1 in peach fruits,which could be used to guide the molecular breeding of new peach species with more favorable aromas for consumers.

Characterization and Expression of Ammonium Transporter in Peach (Prunus persica) and Regulation Analysis in Response to External Ammonium Supply

As the preferred nitrogen(N)source,ammonium(NH_(4)^(+))contributes to plant growth and development and fruit quality.In plants,NH 4+uptake is facilitated by a family of NH_(4)^(+) transporters(AMT).However,the molecular mechanisms and functional characteristics of the AMT genes in peach have not been mentioned yet.In this present study,excess NH_(4)^(+) stress severely hindered shoot growth and root elongation,accompanied with reduced mineral accumulation,decreased leaf chlorophyll concentration,and stunned photosynthetic performance.In addition,we identified 14 putative AMT genes in peach(PpeAMT).Expression analysis showed that PpeAMT genes were differently expressed in peach leaves,stems and roots,and were distinctly regulated by external NH_(4)^(+) supplies.Putative cis-elements involved in abiotic stress adaption,Ca^(2+) response,light and circadian rhythms regulation,and seed development were observed in the promoters of the PpeAMT family genes.Phosphorylation analysis of residues within the C-terminal of PpeAMT proteins revealed many conserved phosphorylation residues in both the AMT1 and AMT2 subfamily members,which could potentially play roles in controlling the NH 4+transport activities.This study provides gene resources to study the biological function of AMT proteins in peach,and reveals molecular basis for NH_(4)^(+) uptake and N nutrition mechanisms of fruit trees.

Expression profiles of Cry1Ab protein and its insecticidal efficacy against the invasive fall armyworm for Chinese domestic GM maize DBN9936

The fall armyworm(FAW)Spodoptera frugiperda,which originated in the Americas,is advancing across China and threatening the nation’s maize crops.Currently,one widely used tool for its control is genetically modified(GM)Bacillus thuringiensis(Bt)maize.Sufficient content of Bt protein in appropriate plant parts is crucial for enhancing resistance against insect pests.In this study,we conducted a systematic investigation of Cry1 Ab levels in Chinese domestic GM maize DBN9936,which has recently obtained a biosafety certificate,and evaluated its efficacy against FAW.Quantification of expression levels of Cry1 Ab,via ELISA,indicated a spatio-temporal dynamic,with significant variation of mean Cry1 Ab,ranging from 0.76 to 8.48μg g-1 FW with the Cry1 Ab protein level ranked as:V6-V8 leaf>R1 leaf>R4 leaf>R1 silk>VT tassel>R4 kernel.Among the nine locations,the Cry1 Ab levels in DBN9936 of the Xinxiang,Langfang,and Harbin fields were significantly lower than those from Wuhan and Shenyang,and were slightly,but not significantly lower than those from the other four fields.Furthermore,the artificial diet-Cry1 Ab mixture and plant tissue feeding bioassays revealed that DBN9936 has high efficacy against FAW.The insecticidal efficacy of different tissues against FAW larvae reached 34-100%with a descending order of lethality as follows:VT leaf>R4 leaf>R1 husk>R1 silk>VT tassel>R4 kernel.Taken together,our results showed that Bt-Cry1 Ab maize DBN9936 has potential as a promising strategy to manage FAW.

Functional identification of MdSMXL8.2,the homologous gene of strigolactones pathway repressor protein gene in Malus×domestica

A homologous gene of strigolactones repressor protein gene SMXL7/D53,MdSMXL8.2(GenBank accession No.:MD07G1222400),was cloned from‘Royal Gala’apple(Malus×domestica Borkh.)in this study.The sequence analysis revealed that the length of this gene was 3243 bp,which encoded 1080 amino acids,and had a protein molecular mass of∼110 kD.The phylogenetic tree analysis indicated that the MdSMXL8.2 exhibited the highest sequence similarity with Arabidopsis AtSMXL7.The protein conserved domain analysis revealed that the MdSMXL8.2 contained two ClpA domains.The prediction of the secondary and tertiary structures of the MdSMXL8.2 indicated that it contained 34.54%αhelix,3.43%β-sheet,and 11.76%extended chain.The in-silico analysis suggested that the promoter sequence of MdSMXL8.2 contained several typical cisacting elements,including abscisic acid(ABA),gibberellin(GA),ethylene,auxin,jasmonic acid(JA),salicylic acid(SA),drought,and heat stressresponsive elements.Quantitative real-time(qRT)-PCR analyses revealed that MdSMXL8.2 was expressed in different apple tissues,with the highest transcript level found in the stem.The expression of MdSMXL8.2 was significantly induced by exogenous ABA,PEG and mannitol,while exogenous NaCl significantly inhibited MdSMXL8.2 expression.The growing status of MdSMXL8.2-overexpressed Orin apple callus was worse than the wild type(WT)after NaCl treatment and had a higher malondialdehyde(MDA)content and relative conductance(REC).Additionally,MdSMXL8.2-overexpressed Arabidopsis exhibited shorter root length and a reduction in fresh weight under salt stress,indicating that MdSMXL8.2 negatively regulated salt tolerance in apples.

The comparative analysis and identification of secondary metabolites between Tibet wild and cultivated pomegranates(Punica granatum L.)in China

Secondary metabolites are closely related to the nutritional quality and health functions of plants.We investigated the secondary metabolites of both wild(n=23)and cultivated(n=27)pomegranate plants(Punica granatum L.)growing in China.The total flavonoid(TF)and tannin(TT)contents from the peel and juice were determined and the secondary metabolites in the peel(ZLP)and juice(ZLZ)of‘Zela 4’were identified using liquid chromatography–electrospray ionization tandem mass spectrometry(LC–ESI-MS/MS).Analysis of variance(P<0.05)showed that there were significant differences in the TF content of peel(TF(P))and juice(TF(J)),and the TT content of peel(TT(P))and juice(TT(J))among different pomegranate accessions.Pearson correlation analysis showed that latitude and altitude might be the main environmental factors affecting TF and TT contents in pomegranates.In this study,279 secondary metabolites were identified in the ZLP and ZLZ.In addition,we report for the first time 227 secondary metabolites in pomegranates.Using orthogonal partial least squares discriminant analysis,90 differential metabolites were identified in ZLP and ZLZ.In addition,we screened eight specific germplasms(high-TF(P),‘Junyong 3’;low-TF(P),‘Yanzhihong’;high-TF(J),‘Zela 4’;low-TF(J),‘Yudazi’,high-TT(P),‘Junyong 4’;low-TT(P),‘Anba 1’;high-TT(J),‘Yeba 1’;and low-TT(J),‘Baihuayushizi’).The results of our study provide a reference for the development and utilization of wild pomegranate resources and pomegranate breeding in China.

Preference of Adult Bradysia odoriphaga Yang et Zhang to Different Colors and Trapping Effect of Yellow Sticky Trap

The trapping effects of yellow, blue, green, cyan and white sticky traps on adult Bradysia odoriphaga Yang et Zhang were studied in the field during its peak occurrence period. The results showed that yellow sticky trap received the best trapping effect on adult B. odoriphaga, follow by blue and green sticky traps, while cyan and white sticky traps received worse effects. The yellow sticky trap settled at south position was most attractive to adult B. odoriphaga, which had significant differences with tho^e placed at east and north positions （P 〈 0.05 ） ; the yellow sticky trap at hanging height of 0 cm showed significantly higher attractive- ness than those at heights of 20 and 40 cm.

Effects of Exogenous Manganese (Mn) on Mineral Elements, Polyamines and Antioxidants in Apple Rootstock Malus robusta Rehd.

Manganese(Mn)is one of the essential microelements in all organisms.However,high level of Mn is deleterious to plants.In this study,the effects of exogenous manganese application on mineral element,polyamine(PA)and antioxidant accumulation,as well as polyamine metabolic and antioxidant enzyme activities,were investigated in Malus robusta Rehd.,a widely grown apple rootstock.High level of Mn treatments decreased endogenous Mg,Na,K and Ca contents,but increased Zn content,in a Mn-concentration-dependent manner.Polyamine metabolic assays revealed that,except the content of perchloric acid insoluble bound(PIS-bound)spermine,which increased significantly,the contents of putrescine(Put),spermidine(Spd)and spermine(Spm)all decreased progressively,accompanied with the decreased activities of arginine decarboxylase(ADC,EC 4.1.1.19)and ornithine decarboxylase(ODC,EC 4.1.1.17),and the increased activities of diamine oxidase(DAO,EC 1.4.3.6)and polyamine oxidase(PAO,EC 1.5.3.3).Further antioxidant capacity analyses demonstrated that contents of anthocyanin,non-protein thiols(NPT)and soluble sugar,and the activities of guaiacol peroxidase(POD,EC 1.11.1.7),catalase(CAT,EC 1.11.1.6)and superoxide dismutase(SOD,EC 1.15.1.1),also increased upon different concentrations of Mn treatments.Our results suggest that endogenous ion homeostasis is affected by high level of Mn application,and polyamine and antioxidant metabolism is involved in the responses of M.robusta Rehd.plants to high level of Mn stress.

Application of Synergist Beichuang in Dose-reduced Chemical Control of Bradysia odoriphaga Yang et Zhang

[ Objective] The paper aimed to explore the dose-reduced pesticide control technique of Bradysia odoriphaga Yang et Zhang. [ Method] The field trids were carried out by routine spraying method, and the control effects of mixtures of Beichuang （ Liangfenbao and Jianweikang） and less dose of phoxim than conrentional against B. odoriphaga larvae were examined. [Result] The results indicated that the control effects of mixtures （containing 14% of Liandeibao or Jian- veikang and 30% -40% less phoxim than conventional dosage） against B. odoriphaga larvae were 84.01% -2.46% and 81.07% -86.12%, respectively. The mntrol effects were equivalent to the conventional dose of phoxim （89.42%）. [ Conclusion] When Beichuang is mixed with phoxim in controlling B. odor/phaga arvae, the suitable reduction level of phoxim is 30% -40%.

Physiological Characteristics of Nitrogen Nutrition in Peanut and Efficient Nitrogen Application Technology

Nitrogen plays a very important role in peanut nutrition and fertilization.For peanuts,the nitrogen nutrition comes from root nodules,soil and fertilizer,which are separately referred to as root nodule nitrogen,soil nitrogen and fertilizer nitrogen.The research obtained following findings.(ⅰ)The nitrogen supply ratio of the three nitrogen sources for peanut is about 5∶3∶2.There are significant differences in the nitrogen supply capacity of the three nitrogen sources.The root nodules have the largest variation in nitrogen fixation and have a high potential for development.Nitrogen fixation in root nodules is closely related to carbon metabolism indicators such as photosynthesis in peanut leaves.Phosphorus application could increase the accumulation of three nitrogen sources,and the increase in nodule nitrogen accumulation is greater than that of soil nitrogen and fertilizer nitrogen.(ⅱ)Nitrogen fertilizer has a significant effect on nitrogen nutrition of peanuts.Different forms of nitrogen fertilizers,such as amide nitrogen,ammonium nitrogen,nitrate nitrogen and mixed ammonium nitrate nitrogen,have significant effects on nitrogen metabolism and nitrogen accumulation in peanuts.Amide nitrogen fertilizer is beneficial to improving the activity of enzymes related to nitrogen metabolism and nitrogen accumulation.Controlled-release fertilizer can significantly increase the content of soluble protein and improve the activities of NRase,GDH,GS,GPT,etc.in roots and leaves at the pod setting and mature stages of peanuts,which is favorable for delaying the plant senescence and increasing the yield of peanuts.Mixed application of common nitrogen fertilizer and slow-release fertilizer can increase the soil nitrate nitrogen level at the later growth stage,which is beneficial to the development of the root system at the later stage of growth,increasing the distribution ratio of nitrogen in the pods,and also favorable for increasing the yield and nitrogen utilization rate.(ⅲ)Increasing the ploughing depth,improving fertilization methods,selecting nitrogen-efficient varieties,paying attention to foliar topdressing,and adopting fertilizer-water integrated cultivation are conducive to increasing the nitrogen utilization rate of peanuts,reducing the amount of nitrogen fertilizers,accordingly saving costs,increasing efficiency and realizing sustainable development of agricultural production.

The PcHY5 methylation is associated with anthocyanin biosynthesis and transport in ‘Max Red Bartlett' and ‘Bartlett' pears

The red coloring of pear fruits is mainly caused by anthocyanin accumulation. Red sport, represented by the green pear cultivar ‘Bartlett’(BL) and the red-skinned derivative ‘Max Red Bartlett’(MRB), is an ideal material for studying the molecular mechanism of anthocyanin accumulation in pear. Genetic analysis has previously revealed a quantitative trait locus(QTL) associated with red skin color in MRB. However, the key gene in the QTL and the associated regulatory mechanism remain unknown. In the present study, transcriptomic and methylomic analyses were performed using pear skin for comparisons between BL and MRB. These analyses revealed differential PcHY5 DNA methylation levels between the two cultivars;MRB had lower PcHY5 methylation than BL during fruit development, and PcHY5 was more highly expressed in MRB than in BL. These results indicated that PcHY5 is involved in the variations in skin color between BL and MRB. We further used dual luciferase assays to verify that PcHY5 activates the promoters of the anthocyanin biosynthesis and transport genes PcUFGT, PcGST, PcMYB10 and PcMYB114, confirming that PcHY5 not only regulates anthocyanin biosynthesis but also anthocyanin transport. Furthermore, we analyzed a key differentially methylated site between MRB and BL, and found that it was located in an intronic region of PcHY5. The lower methylation levels in this PcHY5 intron in MRB were associated with red fruit color during development, whereas the higher methylation levels at the same site in BL were associated with green fruit color. Based on the differential expression and methylation patterns in PcHY5 and gene functional verification, we hypothesize that PcHY5, which is regulated by methylation levels, affects anthocyanin biosynthesis and transport to cause the variations in skin color between BL and MRB.

Effects of Epigeic Earthworms on Decomposition of Wheat Straw and Nutrient Cycling in Agricultural Soils in a Reclaimed Salinity Area:A Microcosm Study

Earthworms, one of the most important macroinvertebrates in terrestrial ecosystems of temperate zones, exert important influ- ences on soil functions. A laboratory microcosm study was conducted to evaluate the influence of the earthworm Eisenia fetida on wheat straw decomposition and nutrient cycling in an agricultural soil in a reclaimed salinity area of the North China Plain. Each microcosm was simulated by thoroughly mixing wheat straw into the soil and incubated for 120 d with earthworms added at 3 different densities as treatments： control with no earthworms, regular density （RD） with two earthworms, and increased density （ID） with six earthworms. The results showed that there was no depletion of carbon and nitrogen pools in the presence of the earthworms. Basal soil respiration rates and metabolic quotient increased with the increase in earthworm density during the initial and middle part of the incubation period. In contrast, concentrations of microbial biomass carbon and microbial biomass quotient decreased in the presence of earthworms. Earthworm activity stimulated the transfer of microbial biomass carbon to dissolved organic carbon and could lead to a smaller, but more metabolically active microbial biomass. Concentrations of inorganic nitrogen and NO^-N increased significantly with the increase in earthworm density at the end of the incubation （P ~ 0.05）, resulting in a large pool of inorganic nitrogen available for plant uptake. Cumulative net nitrogen mineralization rates were three times higher in the ID treatment than the RD treatment.