Transcription activator-like effector nucleases （TALENs） and clustered regularly interspaced short palindromic repeats （CRISPR）/ CRISPR-associated （Cas） systems have emerged as powerful tools for genome editing ...Transcription activator-like effector nucleases （TALENs） and clustered regularly interspaced short palindromic repeats （CRISPR）/ CRISPR-associated （Cas） systems have emerged as powerful tools for genome editing in a variety of species. Here, we report, for the first time, targeted mutagenesis in Zea mays using TALENs and the CRISPR/Cas system. We designed five TALENs targeting 4 genes, namely ZmPDS, ZmlPKIA, ZmlPK, ZmMRP4, and obtained targeting efficiencies of up to 23.1% in protoplasts, and about 13.3% to 39.1% of the transgenic plants were somatic mutations. Also, we constructed two gRNAs targeting the ZmlPK gene in maize protoplasts, at frequencies of 16.4% and 19.1%, respectively. In addition, the CRISPR/Cas system induced targeted mutations in Z. mays protoplasts with efficiencies （13.1%） similar to those obtained with TALENs （9.1%）. Our results show that both TALENs and the CRISPR/Cas system can be used for genome modification in maize.展开更多
Genome-wide association study （GWAS） has become a widely accepted strategy for decoding genotype- phenotype associations in many species thanks to advances in next-generation sequencing （NGS） technol- ogies. Maize...Genome-wide association study （GWAS） has become a widely accepted strategy for decoding genotype- phenotype associations in many species thanks to advances in next-generation sequencing （NGS） technol- ogies. Maize is an ideal crop for GWAS and significant progress has been made in the last decade. This review summarizes current GWAS efforts in maize functional genomics research and discusses future prospects in the omics era. The general goal of GWAS is to link genotypic variations to corresponding dif- ferences in phenotype using the most appropriate statistical model in a given population. The current re- view also presents perspectives for optimizing GWAS design and analysis. GWAS analysis of data from RNA, protein, and metabolite-based omics studies is discussed, along with new models and new popula- tion designs that will identify causes of phenotypic variation that have been hidden to date. The joint and continuous efforts of the whole community will enhance our understanding of maize quantitative traits and boost crop molecular breeding designs.展开更多
Winter wheat-maize rotations are dominant cropping systems on the North China Plain, where recently the use of organic manure with grain crops has almost disappeared. This could reduce soil fertility and crop producti...Winter wheat-maize rotations are dominant cropping systems on the North China Plain, where recently the use of organic manure with grain crops has almost disappeared. This could reduce soil fertility and crop productivity in the long run. A 20-year field experiment was conducted to 1) assess the effect of inorganic and organic nutrient sources on yield and yield trends of both winter wheat and maize, 2) monitor the changes in soil organic matter content under continuous wheat-maize cropping with different soil fertility management schemes, and 3) identify reasons for yield trends observed in Xuzhou City, Jiangsu Province, over a 20-year period. There were eight treatments applied to both wheat and maize seasons: a control treatment (C); three inorganic fertilizers, that is, nitrogen (N), nitrogen and phosphorus (NP), and nitrogen, phosphorus and potassium (NPK); and addition of farmyard manure (FYM) to these four treatments, that is, M, MN, MNP, and MNPK. At the end of the experiment the MN, MNP, and MNPK treatments had the highest yields, about 7 t wheat ha-1 and 7.5 t maize ha-1, with each about 1 t ha-1 more than the NPK treatments. Over 20 years with FYM soil organic matter increased by 80% compared to only 10% with NPK, which explained yield increases. However, from an environmental and agronomic perspective, manure application was not a superior strategy to NPK fertilizers. If manure was to be applied, though, it would be best applied to the wheat crop, which showed a better response than maize.展开更多
To better understand the physiological and biochemical mechanisms of waterlogging tolerance, waterlogging effects on lipid peroxidation and the activity of antioxidative enzymes were investigated in leaves and roots o...To better understand the physiological and biochemical mechanisms of waterlogging tolerance, waterlogging effects on lipid peroxidation and the activity of antioxidative enzymes were investigated in leaves and roots of two maize genotypes, HZ32 （waterlogging-tolerant） and K12 （waterlogging-sensitive）. Potted maize plants were waterlogged at the second leaf stage under glasshouse conditions. Leaves and roots were harvested 1 d before and 2, 4, 6, 8 and 10 d after the start of waterlogging treatment. Through comparing the activities of superoxide dismutase （SOD）, ascorbate peroxidase （APX）, glutathione reductase （GR）, catalase （CAT） and guaiacol peroxidase （POD） between waterlogging-tolerant and waterloggingsensitive genotype, we deduced that CAT was the most important H2O2 scavenging enzyme in leaves, while APX seemed to play a key role in roots. POD, APX, GR and CAT activities in conjunction with SOD seem to play an essential protective role in the O2^- and H2O2 scavenging process. Lipid peroxidation was enhanced significantly only in K12 （P 〈 0.001） and there was no difference （P 〉 0.05） in HZ32 up to 6 d after waterlogging stress. These results indicated that oxidative stress may play an important role in waterlogging-stressed maize plants and that the greater protection of HZ32 leaves and roots from waterlogging-induced oxidative damage results, at least in part, through the maintenance of increased antioxidant enzyme activity.展开更多
One-dimensional electrophoresis （1-DE） of proteins, two-dimensional electrophoresis （2-DE） of proteins and cloning of cDNA sequence were used to study the virulence differentiation of Curvularia lunata （Wakker） ...One-dimensional electrophoresis （1-DE） of proteins, two-dimensional electrophoresis （2-DE） of proteins and cloning of cDNA sequence were used to study the virulence differentiation of Curvularia lunata （Wakker） Boed. isolated from maize （Zea maydis L.） in China. From 1-DE gel profiles of proteins, 110 reproducible bands were separated from six isolates of C. lunata CX-3, SD-6, C-152, C107-1, DD-60 and W-18. Sixty-eight bands （61.82%） were polymorphic, suggesting huge biodiversities among the isolates. All isolates for the experiment were clustered into three groups consisting of different virulent types by coefficient value of 0.605. Group 1, consisting of CX-3, SD-6 and C- 152 with high virulence displayed more protein bands than Groups 2 and 3, consisting of C107-1 and DD-60 with low virulence. Proteomics approaches based on 2-DE techniques were applied to identify specific proteins associated with the virulence differentiation in CX-3 and DD-60. A total of 423 protein spots were separated. Out of them 75 specific protein spots were displayed in 2-DE gels. Among them 28 protein spots were unique in CX-3 and eight in DD-60, and 39 protein spots were shown on both 2-DE gels but expressed differently in intensity. Twenty protein spots including three unique protein spots and 17 differentially expressed protein spots （more than two-fold DD- 60） in CX-3 were further identified with MALDI-TOF MS/MS. Results indicated that most of the identified proteins were found to be associated with virulence differentiation, metabolisms, stress response and signal transduction. One of them was identified as Brnl protein, which had been reported to be related to melanin biosynthesis and the virulence differentiation in fungi. Combined with our previous findings, we assumed that Brnl protein and its regulating products might be involved in the virulence differentiation of C. lunata. Consequently, we cloned a Brnl cDNA fragment and aligned it with the fragments in other fungi. Results indicated that the 633-b展开更多
The integration QTL map for gray leaf spot resistance in maize was constructed by compiling a total of 57 QTLs available with genetic map IBM2 2005 neighbors as reference. Twenty-six ＂real QTLs＂ and seven consensus ...The integration QTL map for gray leaf spot resistance in maize was constructed by compiling a total of 57 QTLs available with genetic map IBM2 2005 neighbors as reference. Twenty-six ＂real QTLs＂ and seven consensus QTLs were identified by refining these 57 QTLs using overview and meta-analysis approaches. Seven consensus QTLs were found on chromosomes 1.06, 2.06, 3.04, 4.06, 4.08, 5.03, and 8.06, and the map coordinates were 552.53,425.72, 279.20, 368.97, 583.21, 308.68 and 446.14 cM, respectively. Using a synteny conservation approach based on comparative mapping between the maize genetic map and rice physical map, a total of 69 rice and maize resistance genes collected from websites Gramene and MaizeGDB were projected onto the maize genetic map IBM2 2005 neighbors, and 2 （Rgene32, htl）, 4 （RgeneS, rp3, scmv2, wsm2）, and 4 （ht2, Rgene6, Rgene8 and Rgene7） positional candidate genes were found in three consensus QTLs on chromosomes 2.06, 3.04, and 8.06, respectively. The results suggested that the combination of meta-analysis of gray leaf spot in maize and sequence homologous comparison between maize and rice could be an efficient strategy for identifying major QTLs and corresponding candidate genes for the gray leaf spot.展开更多
Drought is a major abiotic stress that causes the yearly yield loss of maize, a crop cultured worldwide. Breeding drought-tolerant maize cultivars is a priority requirement of world agriculture. Clade A PP2C phosphata...Drought is a major abiotic stress that causes the yearly yield loss of maize, a crop cultured worldwide. Breeding drought-tolerant maize cultivars is a priority requirement of world agriculture. Clade A PP2C phosphatases （PP2C-A）, which are conserved in most plant species, play important roles in abscisic acid （ABA） signaling and plant drought response. However, natural variations of PP2C-A genes that are directly associated with drought tolerance remain to be elucidated. Here, we conducted a candidate gene association analysis of the ZmPP2C-A gene family in a maize panel consisting of 368 varieties collected worldwide, and identified a drought responsive gene ZmPP2C-AIO that is tightly associated with drought tolerance. We found that the degree of drought tolerance of maize cultivars negatively corre- lates with the expression levels of ZmPP2C-AIO. ZmPP2C-A10, like its Arabidopsis orthologs, interacts with ZmPYL ABA receptors and ZmSnRK2 kinases, suggesting that ZmPP2C-A10 is involved in mediating ABA signaling in maize. Transgenic studies in maize and Arabidopsis confirmed that ZmPP2C-A10 functions as a negative regulator of drought tolerance. Further, a causal natural variation, deletion allele-338, which bears a deletion of ERSE （endoplasmic reticulum stress response element） in the 51-UTR region of ZmPP2C-AIO, was detected. This deletion causes the loss of endoplasmic reticulum （ER） stress-induced expression of ZmPP2C-AIO, leading to increased plant drought tolerance. Our study provides direct evidence linking ER stress signaling with drought tolerance and genetic resources that can be used directly in breeding drought-tolerant maize cultivars.展开更多
The objective of this study was to identify the response of grain yield to plant density and nitrogen rate in spring maize hybrids released from 1970 to 2010 and grown extensively in Northeast China.Twenty-one hybrids...The objective of this study was to identify the response of grain yield to plant density and nitrogen rate in spring maize hybrids released from 1970 to 2010 and grown extensively in Northeast China.Twenty-one hybrids were grown for 2 years in Northeast China at densities of 30,000,52,500,75,000,and 97,500 plants ha^(-1)and N application levels of 0,150,300,and 450 kg N ha^(-1).Irrespective of density or nitrogen application rate,grain yields both per plant and per unit area were significantly higher for newer than older hybrids.As plant density increased from 30,000 to 97,500 plant ha^(-1),yield per plant of 1970 s,1980 s,1990 s,and 2000 s hybrids decreased by 50%,45%,46%,and 52%,respectively.The response of grain yield per unit area to plant density was curvilinear.The estimated optimum plant densities were about 58,000,49,000,65,000,and 65,000 plants ha^(-1)for hybrids released in the 1970 s,1980s,1990 s,and 2000 s,respectively.The theoretical optimum densities for the hybrids released from the 1970 s to the 2000 s increased by 1750 plants ha^(-1)decade^(-1).Nitrogen fertilization significantly increased grain yields per plant and per unit area for all hybrids.The theoretical optimum N application rates for high yield for hybrids released in the 1970 s and 1980 s were about 280 and 360 kg ha^(-1),and the hybrids from the 1990 s and 2000 s showed highest yield at 330 kg ha^(-1)N.No significant difference in the grain yields of 2000 s hybrids between the N levels of 150 to 450 kg ha^(-1)was found.Significant yield gains per plant and per unit area were found,with average increases of 17.9 g plant^(-1)decade^(-1)and936 kg ha^(-1)decade^(-1)over the period 1970–2010,respectively.Yield gains were attributed mainly to increased yield per plant,contributed by increases in kernel number per ear and1000-kernel weight.The rates of lodging and barren plants of newer hybrids were significantly lower than those of older ones,especially at high plant density.展开更多
Better understanding of genotype-by-environment interaction （GEI） is expected to provide a solid foundation for genetic improvement of crop productivity especially under drought-prone environments. To elucidate the ...Better understanding of genotype-by-environment interaction （GEI） is expected to provide a solid foundation for genetic improvement of crop productivity especially under drought-prone environments. To elucidate the genetic basis of the plant and ear height, 2 F2：3 populations were derived from the crosses of Qi 319 × Huangzaosi （Q/H） and Ye 478 × Huangzaosi （Y/H） with 230 and 235 families, respectively, and their parents were evaluated under 3 diverse environments in Henan, Beijing, and Xinjiang, China during the year of 2007 and 2008, and all the lines were also evaluated under water stress environment. The mapping results showed that a total of 21 and 12 QTLs were identified for plant height in the Q/H and Y/H population, respectively, and 24 and 13 QTLs for ear height, respectively. About 56 and 73% of the QTLs for 2 traits did not present significant QTL-by-environment interaction （QE1） in the normal joint analyses for Q/H and Y/H population, respectively, and about 73% of the QTLs detected did not show significant QEI according to joint analyses for stress condition in Q/H. Most of the detected major QTLs exhibited high stability across different environments. Besides, several major QTLs were detected with large and consistent effect under normal condition （Chr. 6 and 7 in Q/H; Chr. 1, 3 and 9 in Y/H）, or across 2 water regimes （Chr. 1, 8 and 10 for in Q/H）. There were several constitutive QTLs （3 for Q/H and 1 for Y/H） with no or minor QTL-by-environment for the 2 populations. Finally, we found several genomic regions （Chr. 1, 10, etc.） to be co-located across the populations, which could provide useful reference for genetic improvement of these traits in maize breeding programs. Comparative genomic analysis revealed that 3 genes/genetic segments associated with plant height in rice were orthologous to these 3 identified genomic regions carrying the major QTLs for plant and ear height on Chr. 1, 6, and 8, respectively.展开更多
A field experiment was conducted to investigate the effects of soil amendments(lime,nano-Si foliar solution and used diatomite) on the growth and metal uptake of three maize(Zea mays L.) cultivars grown in a Cd and Zn...A field experiment was conducted to investigate the effects of soil amendments(lime,nano-Si foliar solution and used diatomite) on the growth and metal uptake of three maize(Zea mays L.) cultivars grown in a Cd and Zn-contaminated acidic soil.The addition of lime significantly increased the maize grain yields and decreased the concentrations of Zn and Cd in the grains and shoots of maize when compared with the control.Among the three maize cultivars,Yunshi-5 accumulated the lowest amounts of Cd and Zn in the grain.The concentrations of Zn and Cd in the grain of Yunshi-5 conformed to the Chinese feed standards.These data revealed that a combination of low metal-accumulating maize and chemical fixation could effectively provide a barrier to prevent metals from entering the human food chain.展开更多
A detailed understanding of genetic architecture of mRNA expression by millions of genetic variants is important for studying quantitative trait variation. In this study, we identified 1.25M SNPs with a minor allele f...A detailed understanding of genetic architecture of mRNA expression by millions of genetic variants is important for studying quantitative trait variation. In this study, we identified 1.25M SNPs with a minor allele frequency greater than 0.05 by combining reduced genome sequencing （GBS）, high- density array technologies （600K）, and previous deep RNA-sequencing data from 368 diverse inbred lines of maize. The balanced allelic frequencies and distributions in a relatively large and diverse natural panel helped to identify expression quantitative trait loci （eQTLs） associated with more than 18 000 genes （63.4% of tested genes）. We found that distant eQTLs were more frequent （~75% of all eQTLs） across the whole genome. Thirteen novel associated loci affecting maize kernel oil concentration were identified using the new dataset, among which one intergenic locus affected the kernel oil variation by controlling expression of three other known oil-related genes. Altogether, this study provides resources for expanding our understanding of cellular regulatory mechanisms of transcriptome variation and the landscape of functional variants within the maize genome, thereby enhancing the understanding of quantitative variations.展开更多
Waterlogging strongly affects agronomic performance of maize （Zea mays L.）. In order to investigate the suitable selection criteria of waterflooding tolerant genotypes, and identify the most susceptible stage and th...Waterlogging strongly affects agronomic performance of maize （Zea mays L.）. In order to investigate the suitable selection criteria of waterflooding tolerant genotypes, and identify the most susceptible stage and the best continuous treatment time to waterlogging, 20 common maize inbred lines were subjected to successive artificial waterflooding at seedling stage, and waterlogging tolerance coefficient （WTC） was used to screen waterflooding tolerant genotypes. In addition, peroxidase （POD） activities and malondialdehyde （MDA） contents were measured for 6 of 20 lines. The results showed that the second leaf stage （V2） was the most susceptible stage, and 6 d after waterflooding was the best continuous treatment time. Dry weight （DW） of both shoots and roots of all lines were significantly reduced at 6 d time-point of waterlogging, compared to control. POD activities and MDA contents were negatively and significantly correlated, and the correlation coefficient was -0.9686 （P 〈 0.0001）. According to the results, WTC of shoot DW can be used for practical screening as a suitable index, which is significantly different from control and waterlogged plants happened 6 d earlier. Furthermore, leaf chlorosis, MDA content and POD activities could also be used as reference index for material screening. The implications of the results for waterlogging-tolerant material screening and waterlogging-tolerant breeding have been discussed in maize.展开更多
Nitric oxide （NO） is a bioactive molecule involved in many biological events, and has been reported as pro-oxidant as well as anti-oxidant in plants. In the present study, the sources of NO production under water st...Nitric oxide （NO） is a bioactive molecule involved in many biological events, and has been reported as pro-oxidant as well as anti-oxidant in plants. In the present study, the sources of NO production under water stress, the role of NO in water stress-induced hydrogen peroxide （H2O2） accumulation and subcellular activities of anti-oxidant enzymes in leaves of maize （Zea mays L.） plants were investigated. Water stress induced defense increases in the generation of NO in maize mesphyll cells and the activity of nitric oxide synthase （NOS） in the cytosolic and microsomal fractions of maize leaves. Water stress-induced defense increases in the production of NO were blocked by pretreatments with inhibitors of NOS and nitrate reductase （NR）, suggesting that NO is produced from NOS and NR in leaves of maize plants exposed to water stress. Water stress also induced increases in the activities of the chloroplastic and cytosolic anti-oxidant enzymes superoxide dismutase （SOD）, ascorbate peroxidase （APX）, and glutathione reductase （GR）, and the increases in the activities of anti-oxidant enzymes were reduced by pretreatments with inhibitors of NOS and NR. Exogenous NO increases the activities of water stress-induced subcellular anti-oxidant enzymes, which decreases accumulation of H2O2. Our results suggest that NOS and NR are involved in water stress-induced NO production and NOS is the major source of NO. The potential ability of NO to scavenge H2O2 is, at least in part, due to the induction of a subcellular anti-oxidant defense.展开更多
It is known that salt stress and exogenously applied abscisic acid （ABA） can enhance the polyamine content in plants and that salt stress itself can lead to an increase in endogenous ABA production. In the present s...It is known that salt stress and exogenously applied abscisic acid （ABA） can enhance the polyamine content in plants and that salt stress itself can lead to an increase in endogenous ABA production. In the present study, the relationships between salt-induced ABA and polyamine accumulation were inves- tigated using ABA-deficient mutant （vp5/vp5） maize （Zea mays L.） seedlings and ABA and polyamine biosynthesis inhibitors. The results show that reduced endogenous ABA levels, as a result of either the mutation or by using a chemical inhibitor （sodium tungstate）, also reduced the accumulation of polyamines in salt-stressed leaves of maize seedlings. The polyamine synthesis inhibitors D-arginine and α- difluoromethylornithine also reduced the polyamine content of the leaves of maize seedling under salt stress. Both ABA and polyamine enhanced the dry weight accumulation of salt-stressed seedlings and also increased the activities of the two dominant tonoplast membrane enzymes, H^＋-ATPase and H^＋-PPase, when plants were under salt stress. The results suggest that salt stress induces an increase in endogenous ABA levels, which then enhances polyamine synthesis. Such responses may increase a plant＇s tolerance to salt.展开更多
Drought or water stress is a serious agronomic problem resulting in maize （Zea mays L.） yield loss throughout the world. Breeding hybrids with drought tolerance is one important approach for solving this problem. Ho...Drought or water stress is a serious agronomic problem resulting in maize （Zea mays L.） yield loss throughout the world. Breeding hybrids with drought tolerance is one important approach for solving this problem. However, lower efficiency and a longer period of breeding hybrids are disadvantages of traditional breeding programs. It is generally recognized that applying molecular marker techniques to traditional breeding programs could improve the efficiency of the breeding of drought-tolerant maize. To provide useful information for use in studies of maize drought tolerance, the mapping and tagging of quantitative trait loci （QTL） for yield and its components were performed in the present study on the basis of the principle of a mixed linear model. Two hundred and twenty-one recombinant inbred lines （RIL） of Yuyu 22 were grown under both well-watered and water-stressed conditions. In the former treatment group, plants were well irrigated, whereas those in the latter treatment group were stressed at flowering time. Ten plants of each genotype were grown in a row that was 3.00 m × 0.67 m （length × width）. The results show that a few of the QTL were the same （one additive QTL for ear length, two additive QTL and one pair of epistatic QTL for kernel number per row, one additive QTL for kernel weight per plant）, whereas most of other QTL were different between the two different water treatment groups. It may be that genetic expression differs under the two different water conditions. Furthermore, differences in the additive and epistatic QTL among the traits under water-stressed conditions indicate that genetic expression also differs from trait to trait. Major and minor QTL were detected for the traits, except for kernel number per row, under water-stressed conditions. Thus, the genetic mechanism of drought tolerance in maize is complex because the additive and epistatic QTL exist at the same time and the major and minor QTL all contribute to phenotype under water-stressed conditions. In particu展开更多
Using F2 population derived from the cross of tall inbred 7922 by dwarf inbred 5003, an RFLP linkage map of maize has been constructed, on which 85 markers are distributed among 10 linkage groups and span maize genome...Using F2 population derived from the cross of tall inbred 7922 by dwarf inbred 5003, an RFLP linkage map of maize has been constructed, on which 85 markers are distributed among 10 linkage groups and span maize genome about 1827.8 cM with an average distance (24.4 cM) between markers. 106 F2:3 lines of the population were grown in a 10×11 simple rectangular lattice design of one-raw plots with two replications and evaluated for plant height (PH). With interval mapping procedure, 5 QTLs controlling plant height have been identified and their genetic effects and gene action determined. 2 major OTLs with opposite effect have been discovered. One for increasing plant height is ph 1 which is located at chromosome 2 and accounts for 51.8% of the total phenotypic variation; the other for decreasing plant height is ph3 which is located at chromosome 5 and accounts for 38.6% of the total phenotypic variation. The chromosomal location of ph3 might be the same as or close to the position of bv1, a dwarf mutant展开更多
Genetic similarities of 13 inbred lines of maize (Zea mays L.) were analyzed by restriction fragment length polymorphisms (RFLPs). The objectives of the study were to detect genetic similarities among 13 inbreds and t...Genetic similarities of 13 inbred lines of maize (Zea mays L.) were analyzed by restriction fragment length polymorphisms (RFLPs). The objectives of the study were to detect genetic similarities among 13 inbreds and to assign them to heterotic groups. By means of 24 probe_enzyme combinations (PECs) selected for locus specificity, clear patterns and reproducibility, 85 alleles were found with an average of 3.3 alleles per locus. The allelic frequency data were used to estimate genetic similarities among lines, and as a result the diversity index of 0.499 was obtained. Genetic similarities between the pairs of 13 lines ranged from 0.523 up to 0.802 with an average of 0.649. The UPGMA clustering algorithm analysis classified the 13 lines into five groups, which generally corresponded to known maize heterotic groups based on pedigree information. The authors concluded that RFLP_based markers could be used for investigating genetic relationships between maize inbred lines and assigning them to heterotic groups, but it seemed that a large number of PECs were needed to obtain reliable estimates of genetic similarity.展开更多
Maize genotypes vary significantly in their nitrogen use efficiencies（NUEs）.Better understanding of early grain filling characteristics of maize is important,especially for maize with different NUEs.The objectives o...Maize genotypes vary significantly in their nitrogen use efficiencies（NUEs）.Better understanding of early grain filling characteristics of maize is important,especially for maize with different NUEs.The objectives of this research were（i）to investigate the difference in apical kernel development of maize with different NUEs,（ii）to determine the reaction of apical kernel development to N application levels,and（iii）to evaluate the relationship between apical kernel development and grain yield（GY）for different genotypes of maize.Three maize hybrid varieties with different NUEs were cultivated in a field with different levels of N fertilizer arranged during two growing seasons.Kernel fresh weight（KFW）,volume（KV）and dry weight（KDW）of apical kernel were evaluated at an early grain filling stage.Ear characteristics,GY and its components were determined at maturity stage.Apical kernel of the high N and high efficiency（HN-HE）type（under low N,the yield is lower,and under higher N,the yield is higher）developed better under high N（N210 and N240,pure N of 210 and 240 kg ha^–1）than at low N（N120 and N140,pure N of 120 and 140 kg ha^–1）.The low N and high efficiency（LN-HE）type（under low N,the yield is higher,while under higher N,the yield is not significantly higher）developed better under low N than at high N.The double high efficiency（D-HE）type（for both low and high N,the yield is higher）performed well under both high and low N.Apical kernel reacted differently to the N supply.Apical kernel developed well at an early grain filling stage and resulted in a higher kernel number（KN）,kernel weight（KW）and GY with better ear characteristics at maturity.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 31271795 and 31200273)
文摘Transcription activator-like effector nucleases （TALENs） and clustered regularly interspaced short palindromic repeats （CRISPR）/ CRISPR-associated （Cas） systems have emerged as powerful tools for genome editing in a variety of species. Here, we report, for the first time, targeted mutagenesis in Zea mays using TALENs and the CRISPR/Cas system. We designed five TALENs targeting 4 genes, namely ZmPDS, ZmlPKIA, ZmlPK, ZmMRP4, and obtained targeting efficiencies of up to 23.1% in protoplasts, and about 13.3% to 39.1% of the transgenic plants were somatic mutations. Also, we constructed two gRNAs targeting the ZmlPK gene in maize protoplasts, at frequencies of 16.4% and 19.1%, respectively. In addition, the CRISPR/Cas system induced targeted mutations in Z. mays protoplasts with efficiencies （13.1%） similar to those obtained with TALENs （9.1%）. Our results show that both TALENs and the CRISPR/Cas system can be used for genome modification in maize.
文摘Genome-wide association study （GWAS） has become a widely accepted strategy for decoding genotype- phenotype associations in many species thanks to advances in next-generation sequencing （NGS） technol- ogies. Maize is an ideal crop for GWAS and significant progress has been made in the last decade. This review summarizes current GWAS efforts in maize functional genomics research and discusses future prospects in the omics era. The general goal of GWAS is to link genotypic variations to corresponding dif- ferences in phenotype using the most appropriate statistical model in a given population. The current re- view also presents perspectives for optimizing GWAS design and analysis. GWAS analysis of data from RNA, protein, and metabolite-based omics studies is discussed, along with new models and new popula- tion designs that will identify causes of phenotypic variation that have been hidden to date. The joint and continuous efforts of the whole community will enhance our understanding of maize quantitative traits and boost crop molecular breeding designs.
基金Project supported by the National Natural Science Foundation of China (No. 30030090)the National High-Tech Research and Development Program of China (863 Program) (No. 2003AA209030).
文摘Winter wheat-maize rotations are dominant cropping systems on the North China Plain, where recently the use of organic manure with grain crops has almost disappeared. This could reduce soil fertility and crop productivity in the long run. A 20-year field experiment was conducted to 1) assess the effect of inorganic and organic nutrient sources on yield and yield trends of both winter wheat and maize, 2) monitor the changes in soil organic matter content under continuous wheat-maize cropping with different soil fertility management schemes, and 3) identify reasons for yield trends observed in Xuzhou City, Jiangsu Province, over a 20-year period. There were eight treatments applied to both wheat and maize seasons: a control treatment (C); three inorganic fertilizers, that is, nitrogen (N), nitrogen and phosphorus (NP), and nitrogen, phosphorus and potassium (NPK); and addition of farmyard manure (FYM) to these four treatments, that is, M, MN, MNP, and MNPK. At the end of the experiment the MN, MNP, and MNPK treatments had the highest yields, about 7 t wheat ha-1 and 7.5 t maize ha-1, with each about 1 t ha-1 more than the NPK treatments. Over 20 years with FYM soil organic matter increased by 80% compared to only 10% with NPK, which explained yield increases. However, from an environmental and agronomic perspective, manure application was not a superior strategy to NPK fertilizers. If manure was to be applied, though, it would be best applied to the wheat crop, which showed a better response than maize.
基金supported by the Natural Science Foundation of Hubei Province, China (2008CDB079)the National High Technology Research and Development Program of China (863 Program, 2006AA100103)
文摘To better understand the physiological and biochemical mechanisms of waterlogging tolerance, waterlogging effects on lipid peroxidation and the activity of antioxidative enzymes were investigated in leaves and roots of two maize genotypes, HZ32 （waterlogging-tolerant） and K12 （waterlogging-sensitive）. Potted maize plants were waterlogged at the second leaf stage under glasshouse conditions. Leaves and roots were harvested 1 d before and 2, 4, 6, 8 and 10 d after the start of waterlogging treatment. Through comparing the activities of superoxide dismutase （SOD）, ascorbate peroxidase （APX）, glutathione reductase （GR）, catalase （CAT） and guaiacol peroxidase （POD） between waterlogging-tolerant and waterloggingsensitive genotype, we deduced that CAT was the most important H2O2 scavenging enzyme in leaves, while APX seemed to play a key role in roots. POD, APX, GR and CAT activities in conjunction with SOD seem to play an essential protective role in the O2^- and H2O2 scavenging process. Lipid peroxidation was enhanced significantly only in K12 （P 〈 0.001） and there was no difference （P 〉 0.05） in HZ32 up to 6 d after waterlogging stress. These results indicated that oxidative stress may play an important role in waterlogging-stressed maize plants and that the greater protection of HZ32 leaves and roots from waterlogging-induced oxidative damage results, at least in part, through the maintenance of increased antioxidant enzyme activity.
基金Supported by the National Natural Science Foundation of China （30471057 and 30370917）, the State Key Basic Research and Development Plan of China （2006CB101901）, the National Science ＆ Technology Supporting Programme （2006BAD08A06）, the Postdoctoral Foundation of China （20060390638） and the Postdoctoral Foundation of Shanghai （06R214135）.
文摘One-dimensional electrophoresis （1-DE） of proteins, two-dimensional electrophoresis （2-DE） of proteins and cloning of cDNA sequence were used to study the virulence differentiation of Curvularia lunata （Wakker） Boed. isolated from maize （Zea maydis L.） in China. From 1-DE gel profiles of proteins, 110 reproducible bands were separated from six isolates of C. lunata CX-3, SD-6, C-152, C107-1, DD-60 and W-18. Sixty-eight bands （61.82%） were polymorphic, suggesting huge biodiversities among the isolates. All isolates for the experiment were clustered into three groups consisting of different virulent types by coefficient value of 0.605. Group 1, consisting of CX-3, SD-6 and C- 152 with high virulence displayed more protein bands than Groups 2 and 3, consisting of C107-1 and DD-60 with low virulence. Proteomics approaches based on 2-DE techniques were applied to identify specific proteins associated with the virulence differentiation in CX-3 and DD-60. A total of 423 protein spots were separated. Out of them 75 specific protein spots were displayed in 2-DE gels. Among them 28 protein spots were unique in CX-3 and eight in DD-60, and 39 protein spots were shown on both 2-DE gels but expressed differently in intensity. Twenty protein spots including three unique protein spots and 17 differentially expressed protein spots （more than two-fold DD- 60） in CX-3 were further identified with MALDI-TOF MS/MS. Results indicated that most of the identified proteins were found to be associated with virulence differentiation, metabolisms, stress response and signal transduction. One of them was identified as Brnl protein, which had been reported to be related to melanin biosynthesis and the virulence differentiation in fungi. Combined with our previous findings, we assumed that Brnl protein and its regulating products might be involved in the virulence differentiation of C. lunata. Consequently, we cloned a Brnl cDNA fragment and aligned it with the fragments in other fungi. Results indicated that the 633-b
文摘The integration QTL map for gray leaf spot resistance in maize was constructed by compiling a total of 57 QTLs available with genetic map IBM2 2005 neighbors as reference. Twenty-six ＂real QTLs＂ and seven consensus QTLs were identified by refining these 57 QTLs using overview and meta-analysis approaches. Seven consensus QTLs were found on chromosomes 1.06, 2.06, 3.04, 4.06, 4.08, 5.03, and 8.06, and the map coordinates were 552.53,425.72, 279.20, 368.97, 583.21, 308.68 and 446.14 cM, respectively. Using a synteny conservation approach based on comparative mapping between the maize genetic map and rice physical map, a total of 69 rice and maize resistance genes collected from websites Gramene and MaizeGDB were projected onto the maize genetic map IBM2 2005 neighbors, and 2 （Rgene32, htl）, 4 （RgeneS, rp3, scmv2, wsm2）, and 4 （ht2, Rgene6, Rgene8 and Rgene7） positional candidate genes were found in three consensus QTLs on chromosomes 2.06, 3.04, and 8.06, respectively. The results suggested that the combination of meta-analysis of gray leaf spot in maize and sequence homologous comparison between maize and rice could be an efficient strategy for identifying major QTLs and corresponding candidate genes for the gray leaf spot.
文摘Drought is a major abiotic stress that causes the yearly yield loss of maize, a crop cultured worldwide. Breeding drought-tolerant maize cultivars is a priority requirement of world agriculture. Clade A PP2C phosphatases （PP2C-A）, which are conserved in most plant species, play important roles in abscisic acid （ABA） signaling and plant drought response. However, natural variations of PP2C-A genes that are directly associated with drought tolerance remain to be elucidated. Here, we conducted a candidate gene association analysis of the ZmPP2C-A gene family in a maize panel consisting of 368 varieties collected worldwide, and identified a drought responsive gene ZmPP2C-AIO that is tightly associated with drought tolerance. We found that the degree of drought tolerance of maize cultivars negatively corre- lates with the expression levels of ZmPP2C-AIO. ZmPP2C-A10, like its Arabidopsis orthologs, interacts with ZmPYL ABA receptors and ZmSnRK2 kinases, suggesting that ZmPP2C-A10 is involved in mediating ABA signaling in maize. Transgenic studies in maize and Arabidopsis confirmed that ZmPP2C-A10 functions as a negative regulator of drought tolerance. Further, a causal natural variation, deletion allele-338, which bears a deletion of ERSE （endoplasmic reticulum stress response element） in the 51-UTR region of ZmPP2C-AIO, was detected. This deletion causes the loss of endoplasmic reticulum （ER） stress-induced expression of ZmPP2C-AIO, leading to increased plant drought tolerance. Our study provides direct evidence linking ER stress signaling with drought tolerance and genetic resources that can be used directly in breeding drought-tolerant maize cultivars.
基金supported by grants from the National Natural Science Foundation of China(No.31301279)National Basic Research Program of China(No.2015CB150404)+1 种基金the National Key Technology R&D Program of China(No.2011BAD16B14)the Innovation Program of Heilongjiang Academy of Agricultural Sciences
文摘The objective of this study was to identify the response of grain yield to plant density and nitrogen rate in spring maize hybrids released from 1970 to 2010 and grown extensively in Northeast China.Twenty-one hybrids were grown for 2 years in Northeast China at densities of 30,000,52,500,75,000,and 97,500 plants ha^(-1)and N application levels of 0,150,300,and 450 kg N ha^(-1).Irrespective of density or nitrogen application rate,grain yields both per plant and per unit area were significantly higher for newer than older hybrids.As plant density increased from 30,000 to 97,500 plant ha^(-1),yield per plant of 1970 s,1980 s,1990 s,and 2000 s hybrids decreased by 50%,45%,46%,and 52%,respectively.The response of grain yield per unit area to plant density was curvilinear.The estimated optimum plant densities were about 58,000,49,000,65,000,and 65,000 plants ha^(-1)for hybrids released in the 1970 s,1980s,1990 s,and 2000 s,respectively.The theoretical optimum densities for the hybrids released from the 1970 s to the 2000 s increased by 1750 plants ha^(-1)decade^(-1).Nitrogen fertilization significantly increased grain yields per plant and per unit area for all hybrids.The theoretical optimum N application rates for high yield for hybrids released in the 1970 s and 1980 s were about 280 and 360 kg ha^(-1),and the hybrids from the 1990 s and 2000 s showed highest yield at 330 kg ha^(-1)N.No significant difference in the grain yields of 2000 s hybrids between the N levels of 150 to 450 kg ha^(-1)was found.Significant yield gains per plant and per unit area were found,with average increases of 17.9 g plant^(-1)decade^(-1)and936 kg ha^(-1)decade^(-1)over the period 1970–2010,respectively.Yield gains were attributed mainly to increased yield per plant,contributed by increases in kernel number per ear and1000-kernel weight.The rates of lodging and barren plants of newer hybrids were significantly lower than those of older ones,especially at high plant density.
基金supported by grants provided by the Ministry of Science and Technology of China(2006CB101700,2009CB118401,2006BAD13B03)National Natural Science Foundation of China(30730063)
文摘Better understanding of genotype-by-environment interaction （GEI） is expected to provide a solid foundation for genetic improvement of crop productivity especially under drought-prone environments. To elucidate the genetic basis of the plant and ear height, 2 F2：3 populations were derived from the crosses of Qi 319 × Huangzaosi （Q/H） and Ye 478 × Huangzaosi （Y/H） with 230 and 235 families, respectively, and their parents were evaluated under 3 diverse environments in Henan, Beijing, and Xinjiang, China during the year of 2007 and 2008, and all the lines were also evaluated under water stress environment. The mapping results showed that a total of 21 and 12 QTLs were identified for plant height in the Q/H and Y/H population, respectively, and 24 and 13 QTLs for ear height, respectively. About 56 and 73% of the QTLs for 2 traits did not present significant QTL-by-environment interaction （QE1） in the normal joint analyses for Q/H and Y/H population, respectively, and about 73% of the QTLs detected did not show significant QEI according to joint analyses for stress condition in Q/H. Most of the detected major QTLs exhibited high stability across different environments. Besides, several major QTLs were detected with large and consistent effect under normal condition （Chr. 6 and 7 in Q/H; Chr. 1, 3 and 9 in Y/H）, or across 2 water regimes （Chr. 1, 8 and 10 for in Q/H）. There were several constitutive QTLs （3 for Q/H and 1 for Y/H） with no or minor QTL-by-environment for the 2 populations. Finally, we found several genomic regions （Chr. 1, 10, etc.） to be co-located across the populations, which could provide useful reference for genetic improvement of these traits in maize breeding programs. Comparative genomic analysis revealed that 3 genes/genetic segments associated with plant height in rice were orthologous to these 3 identified genomic regions carrying the major QTLs for plant and ear height on Chr. 1, 6, and 8, respectively.
基金Supported by the National Natural Science Foundation of China (Nos.40801115 and 41071306)the Science and Technology Planning Project of Guangdong Province,China (Nos.2007A032303001,2009B030802016 and 2010B031800006)
文摘A field experiment was conducted to investigate the effects of soil amendments(lime,nano-Si foliar solution and used diatomite) on the growth and metal uptake of three maize(Zea mays L.) cultivars grown in a Cd and Zn-contaminated acidic soil.The addition of lime significantly increased the maize grain yields and decreased the concentrations of Zn and Cd in the grains and shoots of maize when compared with the control.Among the three maize cultivars,Yunshi-5 accumulated the lowest amounts of Cd and Zn in the grain.The concentrations of Zn and Cd in the grain of Yunshi-5 conformed to the Chinese feed standards.These data revealed that a combination of low metal-accumulating maize and chemical fixation could effectively provide a barrier to prevent metals from entering the human food chain.
文摘A detailed understanding of genetic architecture of mRNA expression by millions of genetic variants is important for studying quantitative trait variation. In this study, we identified 1.25M SNPs with a minor allele frequency greater than 0.05 by combining reduced genome sequencing （GBS）, high- density array technologies （600K）, and previous deep RNA-sequencing data from 368 diverse inbred lines of maize. The balanced allelic frequencies and distributions in a relatively large and diverse natural panel helped to identify expression quantitative trait loci （eQTLs） associated with more than 18 000 genes （63.4% of tested genes）. We found that distant eQTLs were more frequent （~75% of all eQTLs） across the whole genome. Thirteen novel associated loci affecting maize kernel oil concentration were identified using the new dataset, among which one intergenic locus affected the kernel oil variation by controlling expression of three other known oil-related genes. Altogether, this study provides resources for expanding our understanding of cellular regulatory mechanisms of transcriptome variation and the landscape of functional variants within the maize genome, thereby enhancing the understanding of quantitative variations.
基金supported by the Natural Science Foundation of Hubei Province, China (2008CDB079)the National High Technology Research and Development Program of China (863 Program,2006AA100103)
文摘Waterlogging strongly affects agronomic performance of maize （Zea mays L.）. In order to investigate the suitable selection criteria of waterflooding tolerant genotypes, and identify the most susceptible stage and the best continuous treatment time to waterlogging, 20 common maize inbred lines were subjected to successive artificial waterflooding at seedling stage, and waterlogging tolerance coefficient （WTC） was used to screen waterflooding tolerant genotypes. In addition, peroxidase （POD） activities and malondialdehyde （MDA） contents were measured for 6 of 20 lines. The results showed that the second leaf stage （V2） was the most susceptible stage, and 6 d after waterflooding was the best continuous treatment time. Dry weight （DW） of both shoots and roots of all lines were significantly reduced at 6 d time-point of waterlogging, compared to control. POD activities and MDA contents were negatively and significantly correlated, and the correlation coefficient was -0.9686 （P 〈 0.0001）. According to the results, WTC of shoot DW can be used for practical screening as a suitable index, which is significantly different from control and waterlogged plants happened 6 d earlier. Furthermore, leaf chlorosis, MDA content and POD activities could also be used as reference index for material screening. The implications of the results for waterlogging-tolerant material screening and waterlogging-tolerant breeding have been discussed in maize.
文摘Nitric oxide （NO） is a bioactive molecule involved in many biological events, and has been reported as pro-oxidant as well as anti-oxidant in plants. In the present study, the sources of NO production under water stress, the role of NO in water stress-induced hydrogen peroxide （H2O2） accumulation and subcellular activities of anti-oxidant enzymes in leaves of maize （Zea mays L.） plants were investigated. Water stress induced defense increases in the generation of NO in maize mesphyll cells and the activity of nitric oxide synthase （NOS） in the cytosolic and microsomal fractions of maize leaves. Water stress-induced defense increases in the production of NO were blocked by pretreatments with inhibitors of NOS and nitrate reductase （NR）, suggesting that NO is produced from NOS and NR in leaves of maize plants exposed to water stress. Water stress also induced increases in the activities of the chloroplastic and cytosolic anti-oxidant enzymes superoxide dismutase （SOD）, ascorbate peroxidase （APX）, and glutathione reductase （GR）, and the increases in the activities of anti-oxidant enzymes were reduced by pretreatments with inhibitors of NOS and NR. Exogenous NO increases the activities of water stress-induced subcellular anti-oxidant enzymes, which decreases accumulation of H2O2. Our results suggest that NOS and NR are involved in water stress-induced NO production and NOS is the major source of NO. The potential ability of NO to scavenge H2O2 is, at least in part, due to the induction of a subcellular anti-oxidant defense.
基金国家自然科学基金，Research Foundation for Doctoral Programs at the Chinese University
文摘It is known that salt stress and exogenously applied abscisic acid （ABA） can enhance the polyamine content in plants and that salt stress itself can lead to an increase in endogenous ABA production. In the present study, the relationships between salt-induced ABA and polyamine accumulation were inves- tigated using ABA-deficient mutant （vp5/vp5） maize （Zea mays L.） seedlings and ABA and polyamine biosynthesis inhibitors. The results show that reduced endogenous ABA levels, as a result of either the mutation or by using a chemical inhibitor （sodium tungstate）, also reduced the accumulation of polyamines in salt-stressed leaves of maize seedlings. The polyamine synthesis inhibitors D-arginine and α- difluoromethylornithine also reduced the polyamine content of the leaves of maize seedling under salt stress. Both ABA and polyamine enhanced the dry weight accumulation of salt-stressed seedlings and also increased the activities of the two dominant tonoplast membrane enzymes, H^＋-ATPase and H^＋-PPase, when plants were under salt stress. The results suggest that salt stress induces an increase in endogenous ABA levels, which then enhances polyamine synthesis. Such responses may increase a plant＇s tolerance to salt.
文摘Drought or water stress is a serious agronomic problem resulting in maize （Zea mays L.） yield loss throughout the world. Breeding hybrids with drought tolerance is one important approach for solving this problem. However, lower efficiency and a longer period of breeding hybrids are disadvantages of traditional breeding programs. It is generally recognized that applying molecular marker techniques to traditional breeding programs could improve the efficiency of the breeding of drought-tolerant maize. To provide useful information for use in studies of maize drought tolerance, the mapping and tagging of quantitative trait loci （QTL） for yield and its components were performed in the present study on the basis of the principle of a mixed linear model. Two hundred and twenty-one recombinant inbred lines （RIL） of Yuyu 22 were grown under both well-watered and water-stressed conditions. In the former treatment group, plants were well irrigated, whereas those in the latter treatment group were stressed at flowering time. Ten plants of each genotype were grown in a row that was 3.00 m × 0.67 m （length × width）. The results show that a few of the QTL were the same （one additive QTL for ear length, two additive QTL and one pair of epistatic QTL for kernel number per row, one additive QTL for kernel weight per plant）, whereas most of other QTL were different between the two different water treatment groups. It may be that genetic expression differs under the two different water conditions. Furthermore, differences in the additive and epistatic QTL among the traits under water-stressed conditions indicate that genetic expression also differs from trait to trait. Major and minor QTL were detected for the traits, except for kernel number per row, under water-stressed conditions. Thus, the genetic mechanism of drought tolerance in maize is complex because the additive and epistatic QTL exist at the same time and the major and minor QTL all contribute to phenotype under water-stressed conditions. In particu
文摘Using F2 population derived from the cross of tall inbred 7922 by dwarf inbred 5003, an RFLP linkage map of maize has been constructed, on which 85 markers are distributed among 10 linkage groups and span maize genome about 1827.8 cM with an average distance (24.4 cM) between markers. 106 F2:3 lines of the population were grown in a 10×11 simple rectangular lattice design of one-raw plots with two replications and evaluated for plant height (PH). With interval mapping procedure, 5 QTLs controlling plant height have been identified and their genetic effects and gene action determined. 2 major OTLs with opposite effect have been discovered. One for increasing plant height is ph 1 which is located at chromosome 2 and accounts for 51.8% of the total phenotypic variation; the other for decreasing plant height is ph3 which is located at chromosome 5 and accounts for 38.6% of the total phenotypic variation. The chromosomal location of ph3 might be the same as or close to the position of bv1, a dwarf mutant
文摘Genetic similarities of 13 inbred lines of maize (Zea mays L.) were analyzed by restriction fragment length polymorphisms (RFLPs). The objectives of the study were to detect genetic similarities among 13 inbreds and to assign them to heterotic groups. By means of 24 probe_enzyme combinations (PECs) selected for locus specificity, clear patterns and reproducibility, 85 alleles were found with an average of 3.3 alleles per locus. The allelic frequency data were used to estimate genetic similarities among lines, and as a result the diversity index of 0.499 was obtained. Genetic similarities between the pairs of 13 lines ranged from 0.523 up to 0.802 with an average of 0.649. The UPGMA clustering algorithm analysis classified the 13 lines into five groups, which generally corresponded to known maize heterotic groups based on pedigree information. The authors concluded that RFLP_based markers could be used for investigating genetic relationships between maize inbred lines and assigning them to heterotic groups, but it seemed that a large number of PECs were needed to obtain reliable estimates of genetic similarity.
基金supported by the National Natural Science Foundation of China (31271645)the Agricultural Science and Technology Project of Shanxi Province, China (20140311007-4)
文摘Maize genotypes vary significantly in their nitrogen use efficiencies（NUEs）.Better understanding of early grain filling characteristics of maize is important,especially for maize with different NUEs.The objectives of this research were（i）to investigate the difference in apical kernel development of maize with different NUEs,（ii）to determine the reaction of apical kernel development to N application levels,and（iii）to evaluate the relationship between apical kernel development and grain yield（GY）for different genotypes of maize.Three maize hybrid varieties with different NUEs were cultivated in a field with different levels of N fertilizer arranged during two growing seasons.Kernel fresh weight（KFW）,volume（KV）and dry weight（KDW）of apical kernel were evaluated at an early grain filling stage.Ear characteristics,GY and its components were determined at maturity stage.Apical kernel of the high N and high efficiency（HN-HE）type（under low N,the yield is lower,and under higher N,the yield is higher）developed better under high N（N210 and N240,pure N of 210 and 240 kg ha^–1）than at low N（N120 and N140,pure N of 120 and 140 kg ha^–1）.The low N and high efficiency（LN-HE）type（under low N,the yield is higher,while under higher N,the yield is not significantly higher）developed better under low N than at high N.The double high efficiency（D-HE）type（for both low and high N,the yield is higher）performed well under both high and low N.Apical kernel reacted differently to the N supply.Apical kernel developed well at an early grain filling stage and resulted in a higher kernel number（KN）,kernel weight（KW）and GY with better ear characteristics at maturity.
