Genetic and Agronomic Parameter Estimates of Growth, Yield and Related Traits of Maize (Zea mays L.) under Different Rates of Nitrogen Fertilization

This study evaluated the genetic and agronomic parameter estimates of maize under different nitrogen rates. The trial was established at the Njala Agricultural Research Centre experimental site during 2021 and 2022 in a split block design with three maize varieties (IWCD2, 2009EVDT, and DMR-ESR-Yellow) and seven nitrogen (0, 30, 60, 90, 120, 150 and 180 kg∙N∙ha−1) rates. Findings showed that cob diameter and anthesis silking time (ASI) had intermediate heritability, ASI had high genetic advance, ASI and grain yield had high genotypic coefficient of variation (GCV), while traits with high phenotypic coefficient of variation (PCV) were plant height, ASI, grain yield, number of kernel per cob, number of kernel rows, ear length, and ear height. The PCV values were higher than GCV, indicating the influence of the environment in the studied traits. Nitrogen rates and variety significantly (p < 0.05) influenced grain yield production. Mean grain yields and economic parameter estimates increased with increasing nitrogen rates, with the 30 and 180 kg∙N∙ha−1 plots exhibiting the lowest and highest grain yields of 1238 kg∙ha−1 and 2098 kg∙ha−1, respectively. Variety and nitrogen effects on partial factor productivity (PFPN), agronomic efficiency (AEN), net returns (NR), value cost ratio (VCR) and marginal return (MR) indicated that these parameters were significantly affected (p < 0.05) by these factors. The highest PFPN (41.3 kg grain kg−1∙N) and AEN (29.4 kg grain kg−1∙N) were obtained in the 30 kg∙N∙ha−1 plots, while the highest VCR (2.8) and MR (SLL 1.8 SLL−1 spent on N) were obtained in the 180 kg∙N∙ha−1. The significant influence of variety and nitrogen on traits suggests that increasing yields and maximizing profits require use of appropriate nitrogen fertilization and improved farming practices that could be exploited for increased productivity of maize.

Cloning, Characterization and Transformation of Methyltransferase 2a Gene (Zmet2a) in Maize (Zea mays L.)

DNA methylation is an important epigenetic regulatory mechanism,it regulates gene expression by recruiting proteins involved in gene repression or by inhibiting the binding of transcription factor(s)to DNA.In this study,a novel methyltransferase 2a gene(Zmet2a)was cloned in maize and identified by polymerase chain reaction-base(PCR-base)using a bioinformatics strategy.The Zmet2a cDNA sequence is 2739 bp long and translates to 912 amino acid peptides.The Zmet2a protein revealed that it contains BAH and CHROMO structural domains,is a non-transmembrane protein that is hydrophilically unstable,and has no signal peptide structure.Meanwhile,we verified the biological roles of Zmet2a using transgenic Arabidopsis overexpressing Zmet2a and Zmet2a-knockout maize.Transgenic Zmet2a Arabidopsis thaliana showed highly significant advancement inflowering time,and Zmet2a-knockout maize showed advancement inflowering time,with significant changes in several traits.Altogether,these report the role of Zmet2a in the regulation offlowering time,which will lay a foundation for revealing the biological function and epigenetic regulation mechanism of Zmet2a in the growth,development andflowering of maize.

Determination and Quantification of Susceptibility of Heritance Resistance to Root Rot of Eight Commercial Genotypes of Maize (Zea mays L.)

Maize is susceptible to a number of diseases that can infect all plant organs and serve as a constraint on cereal production. The reduction in cereal production caused by disease is estimated at an average of 9.4%. Corn root rot contributes greatly to the reduction in grain production and quality. The main objective of this work was to review the research on root rot in maize to determine the susceptibility of genotypes to root rot and to quantify the inheritance of resistance to root rot in maize. The methodology used was a complete 8 × 8 diallel design planted during the year 1999/2000. Root discoloration, plant length, root volume, effective volume and yield were the evaluated parameters. To analyze the data and determine the combinatorial abilities, genetic correlations, heritability and correlated response, diallel analysis was used. Eight parental lines;P28, I137TN, MP706, E739, MO17, B37, B73, and B14 were planted. The lines were crossed into each other, all combinations according to the complete diallel model (Model 1). The F1 was harvested after maturation. For statistical analysis, the version of the Agrobase program (2016) was used. Results show that F1 hybrids showed significant differences in root rot discoloration, plant height, root volume, effective root volume and yield. The P28 line and the B73XE739 cross had, respectively, the highest general and specific combinations. Root discoloration had the highest genetic correlation (rA = 0.47) with plant length. Broad and narrow heritability for root rot discoloration were, respectively, h2 = 0.81 and h2 = 0.51. Root rot discoloration showed the highest correlated response (CR = 0.14) on plant length.

Maize cryptochromes 1a1 and 1a2 promote seedling photomorphogenesis and shade resistance in Zea mays and Arabidopsis

Maize growth and development are regulated by light quality,intensity and photoperiod.Cryptochromes are blue/ultraviolet-A light receptors involved in stem elongation,shade avoidance,and photoperiodic flowering.To investigate the function of cryptochrome 1(CRY1) in maize,where it is encoded by Zm CRY1,we obtained two Zm CRY1a genes(Zm CRY1a1 and Zm CRY1a2),both of which share the highest similarity with other gramineous plants,in particular rice CRY1a by phylogenetic analysis.In Arabidopsis,overexpression of Zm CRY1a genes promoted seedling de-etiolation under blue and white light,resulting in dwarfing of mature plants.In seedlings of the maize inbred line Zong 31(Zm CRY1aOE),overexpression of Zm CRY1a genes caused a reduction in the mesocotyl and first leaf sheath lengths due to down-regulation of genes influencing cell elongation.In mature transgenic maize plants,plant height,ear height,and internode length decreased in response to overexpression of Zm CRY1a genes.Expression of Zm CRY1a were insensitive to low blue light(LBL)-induced shade avoidance syndrome(SAS) in Arabidopsis and maize.This prompted us to investigate the regulatory role of the gibberellin and auxin metabolic pathways in the response of Zm CRY1a genes to LBL treatment.We confirmed a link between Zm CRY1a expression and hormonal influence on the growth and development of maize under LBL-induced SAS.These results reveal that Zm CRY1a has a relatively conservative function in regulating maize photomorphogenesis and may guide new strategies for breeding high density-tolerant maize cultivars.

Use of the Biostimulant Based on the Mycorrhizae Consortium of the Glomeraceae Family in the Field to Improve the Production and Nutritional Status of Maize (Zea mays L.) Plants in Central Benin

Excessive use of mineral fertilizers in maize farming negatively affects farmers’ income and impacts long-term soil health. This study aims to appreciate the effectiveness of biostimulant based on native Glomeraceae arbuscular mycorrhizal fungi on the production and uptake of phosphorus, nitrogen and potassium of maize (Zea mays L.) plants in central Benin. The trials were set up in a farming environment with thirty-four producers. The experimental design was composed of three treatments installed at 34 producers. Three growth parameters were evaluated on 60 ème days after sowing. Grain yield, nutritional status of maize plants and mycorrhization parameters were determined at harvest. The results showed that the Glomeraceae + 50% NPK (NPK: azote-phosphore-potassium)_Urea treatment improved the height, the crown diameter and the leaf area by 17.85%, 21.79% and 28.32% compared to the absolute control and by 0.41%, 1.11% and 1.46% compared to the 100% NPK_Urea treatment, respectively. Similarly, grain yield improved by 45.87% with the use of Glomeraceae + 50% NPK_Urea compared to the absolute control and by 3.96% compared to the 100% NPK_Urea treatment. The Glomeraceae + 50% NPK_Urea significantly improved the phosphorus and potassium uptake of maize plants. With respect to nitrogen uptake, no statistical difference was observed between treatments. The mycorrhizae strains used improved root infection in the maize plants. We recorded 66% frequency and 40.5% intensity of mycorrhization. The biostimulant based on indigenous Glomeraceae combined with 50% NPK_Urea can be used as a strategy to restore soil health and improve maize productivity in Benin.

Phenotypic Characterization and QTL/Gene Identification for Internode Number and Length Related Traits in Maize

Internode number and length are the foundation to constitute plant height, ear height and the above-ground spatial structure of maize plant. In this study, segregating populations were constructed between EHel with extremely low ear height and B73. Through the SNP-based genotyping and phenotypic characterization, 13 QTL distributed on the chromosomes (Chrs) of Chr1, Chr2, Chr5-Chr8 were detected for four traits of internode no. above ear (INa), average internode length above ear (ILaa), internode no. below ear (INb), and average internode length below ear (ILab). Phenotypic variation explained (PVE) by a single QTL ranged from 6.82% (qILab2-2) to 12.99% (qILaa5). Zm00001d016823 within the physical region of qILaa5, the major QTL for ILaa with the largest PVE was determined as the candidate through the genomic annotation and sequence alignment between EHel and B73. Product of Zm00001d016823 was annotated as a WEB family protein homogenous to At1g75720. qRT-PCR assay showed that Zm00001d016823 highly expressed within the tissue of internode, exhibiting statistically higher expression levels among internodes of IN4 to IN7 in EHel than those in B73 (P Zm00001d016823 might provide novel insight into molecular mechanism beyond phytohormones controlling internode development in maize.

Elite,transformable haploid inducers in maize

The introduction of alleles into commercial crop breeding pipelines is both time consuming and costly.Two technologies that are disrupting traditional breeding processes are doubled haploid(DH)breeding and genome editing(GE).Recently,these techniques were combined into a GE trait delivery system called HI-Edit(Haploid Inducer-Edit).In HI-Edit,the pollen of a haploid inducer line is reprogrammed to deliver GE traits to any variety,obviating recurrent selection.For HI-Edit to operate at scale,an efficient transformable HI line is needed,but most maize varieties are recalcitrant to transformation,and haploid inducers are especially difficult to transform given their aberrant reproductive behaviors.Leveraging marker assisted selection and a three-tiered testing scheme,we report the development of new Iodent and Stiff Stalk maize germplasm that are transformable,have high haploid induction rates,and exhibit a robust,genetically-dominant anthocyanin native trait that may be used for rapid haploid identification.We show that transformation of these elite‘‘HI-Edit”lines is enhanced using the BABYBOOM and WUSCHEL morphogenetic factors.Finally,we evaluate the HI-Edit performance of one of the lines against both Stiff Stalk and non-Stiff Stalk testers.The strategy and results of this study should facilitate the development of commercially scalable HI-Edit systems in diverse crops.

Regulatory mechanisms of iron homeostasis in maize mediated by ZmFIT

Regulation of iron homeostasis in maize remains unclear,despite the known roles of FER-Like Fe deficiency-induced transcription factor(FIT)in Arabidopsis and rice.ZmFIT,like At FIT and Os FIT,interacts with iron-related transcription factors 2(ZmIRO2).Here,we investigate the involvement of ZmFIT in iron homeostasis.Mutant ZmFIT lines exhibiting symptoms of Fe deficiency had reduced shoot iron content.Transcriptome analysis revealed downregulation of Fe deficiency-responsive genes in the roots of a Zmfit mutant.ZmFIT facilitates the nuclear translocation of ZmIRO2 to activate transcription of downstream genes under Fe-deficient conditions.Our findings suggest that ZmFIT,by interaction with ZmIRO2,mediates iron homeostasis in maize.Notably,the binding and activation mechanisms of ZmFIT resemble those in Arabidopsis but differ from those in rice,whereas downstream genes regulated by ZmFIT show similarities to rice but differences from Arabidopsis.In brief,ZmFIT,orthgologs of Os FIT and At FIT in rice and maize,respectively,regulates iron uptake and homeostasis in maize,but with variations.

Seed Priming with Potassium Nitrate Can Enhance Salt Stress Tolerance in Maize

Salinity is a major abiotic stress that hinders plant development and productivity and influences agricultural yield.Seed priming is a technique used to boost germination and seedling growth under abiotic stress.A pot experiment was conducted to evaluate the impact of seed priming with potassium nitrate(KNO_(3))at various levels(0%,0.50%,1.00%and 1.50%)under salt stress(0,75,100 mM NaCl)on two maize verities(MNH360 and 30T60)for the growth,development and metabolic attributes results revealed that in maize variety MNH360,KNO_(3)priming’s significantly enhanced growth parameters than in maize variety 30T60 under control and salt-stressed conditions.Priming with KNO_(3)enhanced carotenoids and total chlorophyll in the 30T60 variety that protected the maize plants from salt stress.Nevertheless,it was shown that priming with 1.00%KNO_(3)acts as safeguarded to protect them from oxidative damage by salt stress minimizing reactive oxygen species(ROS)formation through increased levels of malondialdehyde(MDA),catalase(CAT),peroxidase(POD),ascorbate peroxidase(APX),and total soluble protein.The findings of the present study confirm that the use of the KNO_(3)seed priming technique is a lowcost,environmentally friendly technique for mitigating adverse impacts of salt stress in maize crops by activating the antioxidant defense system and improving chlorophyll and osmolyte contents.

The ZmHSF08-ZmUGT92A1 module regulates heat tolerance by altering reactive oxygen species levels in maize

GTs(Glycosyltransferases)are important in plant growth and abiotic stresses.However,its role in maize heat response is far from clear.Here,we describe the constitutively expressed UDP-glycosyltransferase ZmUGT92A1,which has a highly conserved PSPG box and is localized in chloroplasts,is induced under heat stress.Functional disruption of ZmUGT92A1 leads to heat sensitivity and reactive oxygen species accumulation in maize.Metabolomics analysis revealed that ZmUGT92A1 affected multiple metabolic pathways and altered the metabolic homeostasis of flavonoids under heat stress.In vitro assay showed ZmUGT92A1 exhibits glycosyltransferase activity on flavonoids and hormones.Additionally,we identified a rapidly heat-induced transcription factor,ZmHSF08,which can directly bind and repress the promoter region of ZmUGT92A1.The ZmHSF08 overexpression line exhibits heat sensitivity and reactive oxygen species accumulation.These findings reveal that the ZmHSF08-ZmUGT92A1 module plays a role in heat tolerance in maize and provide candidate strategies for the development of heat-tolerant varieties.

Seasonal Dynamic of the Fall Armyworm, Spodoptera frugiperda (J.E Smith, 1797) (Lepidoptera: Noctuidae) on Maize Crop in the Sub-Sudanese Zone of Côte d’Ivoire

In Côte d’Ivoire, maize (Zea mays L) is the second most cultivated cereal after rice. Since the first report of Spodoptera frugiperda in Côte d’Ivoire, maize production in the northern regions has been affected resulting in maize production losses. This study aims to study the seasonal dynamic of Spodoptera frugiperda in maize fields in the sub-Sudanese zone, main zone of maize cultivation in Côte d’Ivoire. The study was done using pheromone trap lures. The results revealed a variation in the moth population at various growth stages during rainy and dry seasons. Notably, the highest numbers of moths were consistently trapped during the whorl stage with counts ranging from 131 ± 35.7 during the rainy season to 70.6 ± 15.01 in the dry season. The lowest numbers of moths were observed during pod maturation, with counts ranging from 30.3 ± 13.05 during the rainy season to 11.7 ± 3.05 in the dry season. Between the 7th and 21st days after sowing, the count of moths displayed a consistent upward trajectory, reaching 188 moths during the rainy season. The damages were particularly observed at whorl stage. The relationship between the numbers of moths and some climatic variables revealed a negative correlation between moths numbers and rainfall (r= −0.44) and relative humidity (r= −0.684). In contrast, there were positive relationships with temperature (r = 0.16), highlighting the significant impact of temperature changes on moth population dynamics. The research highlights the need for integrated pest management strategies that consider climatic factors and growth stages of maize to mitigate the impact of this insect pest on maize.

Cloning and Identification of A New Na^+/H^+ Antiporter Gene ZmSOS1 in Maize(Zea mays L.)

[ Objective] The study aimed to clone and identify Na^＋/H^＋ antiporter genes in maize, and provided the information for characterizing the function of such genes in abiotic stress tolerance of maize. Method The in silico cloning, RT-PCR, and bioinformatics analysis were used in this study. Result By in sifico cloning, a plasma membrane Na^＋/H^＋ antiporter gene, named as ZmSOS1 （EMBL accession No. BN001309）, was cloned from maize （ Zea mays L. ）. ZmSOS1 has an open reading frame （ORF） of 3 411 bp which encoded a protein of 1 136 amino acids. By multiple sequence alignment analysis, it showed the predicated peptide of ZmSOS1 were 61% and 82% identities in amino acids to the plasma membrane Na^＋/H^＋ antiporter AtSOS1 and OsSOS1, respectively. The RT-PCR analysis revealed that ZmSOS1 could be significantly up-regulated by salt stress, which indicated ZmSOS1 might play a role in salt tolerance of maize. Conclusion ZmSOS1 is a putative plasma membrane Na^＋/H^＋ antiporter gene and may play a role in abiotic stress tolerance of maize.

Screening Methods for Waterlogging Tolerance at Maize (Zea mays L.) Seedling Stage

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.

Top-grain filling characteristics at an early stage of maize(Zea mays L.) with different nitrogen use efficiencies

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.

Establishment and Optimization of the Regeneration System of Mature Embryos of Maize (Zea mays L.)

A reliable system was developed for regeneration from mature embryos derived from callus of four maize inbred lines （Liao 7980, Dan 9818, Dan 340, and Dan 5026）. The protocol was mainly based on a series of experiments involving the composition of culture medium. We found that 9 pM 2,4-dichlorophenoxyacetic acid in MS medium was optimum for the induction of callus. The induction frequency of primary calli was over 85% for four inbred lines tested. The addition of L- proline （12 mM） in subculture medium significantly promoted the formation of embryogenic callus but it did not significantly enhance growth rate of callus. Efficient shoot regeneration was obtained on regeneration medium containing 2.22 μM 6- benzylaminopurine in combinations with 4.64 μM Kinetin. Regenerated shoots were rooted on half-strength MS medium containing 2.85 μM indole-3-butyric acid. This plant regeneration system provides a foundation for genetic transformation of maize.

Genome-wide identification,phylogeny and expression analysis of the SBP-box gene family in maize(Zea mays)

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 identified to be distributed in nine chromosomes and 16 of them were complementary to the mature ZmmiR156 sequences. All the Z. mays SBP （ZmSBP） 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 ZmSBP, Oryza sativa SBP-like （OsSPL） 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 ZmSBP 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 ZmSBP genes and might facilitate future researches for elucidating the SBP-box genes function in maize.

Activity of Acetolactate Synthase from Maize (Zea mays L.) as Influenced by Chlorsulfuron and Tribenuron-methyl

Study on relative sensitivity of maize (Zea mays L.) Nongda108 and Nongda3138 to sulfony-lurea herbicide chlorsulfuron and tribenuron-methyl using maize taproot length by sand bioassy indicated that, Nongda3138 had higher tolerance to chlorsulfuron and tribenuron-methyl than Nongda108 did. Chlorsulfuron had stronger growth inhibition to maize Nongda108 and Nongda3138 than tribenuron-methyl did. Study on target enzyme of sulfonylurea herbicide acetolactate synthase (ALS) showed that, chlorsulfuron and tribenuron-methyl inhibited ALS in vitro strongly, and non-competitively. In the same concentration of inhibitors, chlorsulfuron had stronger ALS activity inhibition than tribenuron-methyl did. Lower level of chlorsulfuron and tribenuron-methyl has no ALS activity inhibition in vivo, the ALS inhibition only occurred in the condition of high concentration of chlorsulfuron and tribenuron-methyl in vivo.

Influence of Zinc Nutrition on Growth and Yield Behaviour of Maize (<i>Zea mays</i>L.) Hybrids

A field experiment was conducted during spring 2011 at Agronomic Research Area, University of Agriculture, Faisalabad, Pakistan to evaluate the comparative efficacy of Zn uptake and grain yield in three maize hybrids namely Pioneer-32F 10, Monsanto-6525 and Hycorn-8288 through the application of Zn in the form of ZnSO4. The ZnSO4 treatments comprised;soil application at the time of sowing @ 12 kg&middotha-1 (Zn1), foliar application at vegetative stage (9 leaf stage) @ 1% ZnSO4 solution (Zn2) and foliar application at reproductive stage (anthesis) @ 1% ZnSO4 solution (Zn3) and one treatment was kept as a control, where zinc was not applied (Zn0). The experimental results showed substantial difference in all physiological and yield parameters except plant height and stem diameter. Statistically maximum grain yield (8.76 t&middotha-1) was obtained with foliar spray of ZnSO4 at 9 leaf stage (Zn2) in case of Monsanto-6525. As regard to quality parameters, Pioneer-32F 10 and Hycorn-8288 accumulated more zinc contents in grains but Monsanto-6525 attained more zinc concentration in straw. Foliar spray of ZnSO4 at 9 leaf stage produced 19.42% more zinc contents in grains as compared to other ZnSO4 treatments. Foliar spray of ZnSO4 at 9 leaf stage in Monsanto-6525 hybrid produced higher grain yield.

QTL analysis of the developmental changes in cell wall components and forage digestibility in maize(Zea mays L.)

Cell wall architecture plays a key role in stalk strength and forage digestibility.Lignin,cellulose,and hemicellulose are the three main components of plant cell walls,and they can impact stalk quality by affecting the structure and strength of the cell wall.To explore cell wall development during secondary cell wall lignification in maize stalks,conventional and conditional genetic mapping were used to identify the dynamic quantitative trait loci(QTLs)of the cell wall components and digestibility traits during five growth stages after silking.Acid detergent lignin(ADL),cellulose(CEL),acid detergent fiber(ADF),neutral detergent fiber(NDF),and in vitro dry matter digestibility(IVDMD)were evaluated in a maize recombinant inbred line(RIL)population.ADL,CEL,ADF,and NDF gradually increased from 10 to 40 days after silking(DAS),and then they decreased.IVDMD initially decreased until 40 DAS,and then it increased slightly.Seventytwo QTLs were identified for the five traits,and each accounted for 3.48–24.04%of the phenotypic variation.Six QTL hotspots were found,and they were localized in the 1.08,2.04,2.07,7.03,8.05,and 9.03 bins of the maize genome.Within the interval of the pleiotropic QTL identified in bin 1.08 of the maize genome,six genes associated with cell wall component biosynthesis were identified as potential candidate genes for stalk strength as well as cell wall-related traits.In addition,26 conditional QTLs were detected in the five stages for all of the investigated traits.Twenty-two of the 26 conditional QTLs were found at 30 DAS conditioned using the values of 20 DAS,and at 50 DAS conditioned using the values of 40 DAS.These results indicated that cell wall-related traits are regulated by many genes,which are specifically expressed at different stages after silking.Simultaneous improvements in both forage digestibility and lodging resistance could be achieved by pyramiding multiple beneficial QTL alleles identified in this study.

Genomic and transcriptomic insights into cytochrome P450 monooxygenase genes involved in nicosulfuron tolerance in maize(Zea mays L.)

Postemergence application of nicosulfuron for weed control in maize fields can cause great damage to certain maize inbred lines and hybrids. Two maize genotypes, tolerant inbred(HBR) and sensitive inbred(HBS), were found to significantly differ in their phenotypic responses to nicosulfuron, with the EC50(50% effective concentration) values differed statistically(763.6 and 5.9 g a.i. ha–1, respectively). Pre-treatment with malathion, a known cytochrome P450 inhibitor, increased nicosulfuron injury in both HBR and HBS. Our results support the hypothesis that nicosulfuron selectivity in maize is associated with cytochrome P450 metabolism. Further analysis of the maize genome resulted in the identification of 314 full length cytochrome P450 monooxygenase(CYP) genes. These genes were classified into 2 types, 10 clans and 44 families. The CYP71 clan was represented by all A-type genes(168) belonging to 17 families. Nine clans possessed 27 families containing 146 non-A-type genes. The consensus sequences of the heme-binding regions of A-type and non-A-type CYP proteins are ‘PFGXGRRXCPG’ and ‘FXXGPRXCXG’, respectively. Illumina transcriptome sequence results showed that there were 53 differentially expressed CYP genes on the basis of high variation in expression between HBS and HBR, nicosulfuron-treated and untreated samples. These genes may contribute to nicosulfuron tolerance in maize. A hierarchical clustering analysis obtained four main clusters named C1 to C4 in which 4, 15, 21, and 13 CYP genes were found in each respective cluster. The expression patterns of some CYP genes were confirmed by RT-q PCR analysis. The research will improve our understanding of the function of maize cytochrome P450 in herbicide metabolism.