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.

Exploring the therapeutic potential of Qi Teng Mai Ning recipe in ischemic stroke and vascular cognitive impairment

Background:This study aims to explore the therapeutic effects of the Qi Teng Mai Ning recipe on ischemic stroke and vascular cognitive impairment through its potential to modulate cellular autophagy,with a focus on identifying its active ingredients and their target proteins.Methods:The study began with the identification of active ingredients in the Qi Teng Mai Ning recipe.It proceeded to screen the gene expression omnibus database for ischemic stroke and vascular cognitive impairment-associated differentially expressed mRNAs and to identify cellular autophagy-related proteins via the Human Autophagy Database.These proteins were annotated with Gene Ontology and Kyoto Encyclopedia of Genes and Genomes functions and subjected to molecular docking with the recipe’s core active ingredients.In vitro cell experiments were conducted on hypoxic HT22 cells,involving CCK8 assay,lentiviral transfection to silence autophagy related 9B(ATG9B),immunofluorescence staining,and qPCR validation to investigate the effects of the recipe on autophagy.Results:The analysis identified 104 active ingredients targeting 408 proteins and forming a complex ingredient-target network.Intersecting 55 ischemic stroke-related and 909 vascular cognitive impairment-related differentially expressed mRNAs revealed 14 co-expressed mRNAs.Molecular docking showed quercetin,kaempferol,myrcene,and conferone as key ingredients targeting autophagy-related proteins.Cellular experiments indicated that the recipe significantly enhanced cell viability under hypoxic conditions,reduced apoptosis,and modulated the expression of autophagy-related factors,thereby decreasing apoptosis rates in HT22 cells.Conclusion:The Qi Teng Mai Ning recipe offers protective effects against ischemic stroke and vascular cognitive impairment by modulating autophagy-related proteins.Its efficacy highlights the potential of traditional Chinese medicine in treating these conditions,though further research is needed to fully understand its mechanisms and clinical applications.

听力损失婴幼儿短纯音听性脑干反应与IT-MAIS评分的相关性

目的探究听力损失婴幼儿短纯音听性脑干反应(tb-ABR)与婴幼儿有意义听觉整合量表(infant-toddler meaningful auditory integration scale,IT-MAIS)评分的相关关系。方法选择2020年11月~2023年11月我院收治的120例听力损失婴幼儿作为研究组,同时选择在医院行听力检查的健听婴幼儿50例作为对照组,患者均行tb-ABR测定及IT-MAIS评估,比较两组tb-ABR阈值与IT-MAIS评分的差异,分析tb-ABR阈值与IT-MAIS评分相关性,分析以上两项指标对听力损失的评估价值,比较不同听力损失患儿tb-ABR阈值、IT-MAIS评分,分析以上两项指标与听力损失程度的相关性。结果研究组婴幼儿平均听阈在0.5、1、2、4 kHz情况下测定tb-ABR阈值均高于对照组,IT-MAIS评分低于对照组(P<0.05);Pearson相关性分析显示,在0.5、1、2、4 kHz情况下,tb-ABR阈值与IT-MAIS评分呈负相关关系(r=-0.511,-0.432,-0.309,-0.472;P<0.05);受试者工作特征曲线显示,在0.5、1、2、4 kHz情况下测定tb-ABR阈值与IT-MAIS评分在婴幼儿听力损失诊断曲线下面积(area under the curve,AUC)值依次为0.769、0.797、0.662、0.713、0.829;随着患者听力损失程度加重,平均听阈,0.5、1、2、4 kHz情况下测定tb-ABR阈值逐渐上升,而IT-MAIS评分逐渐降低(P<0.05);Spearman相关性分析显示,tb-ABR阈值与婴幼儿听力损失程度正相关(r=0.576,0.411,0.457,0.486;P<0.05),IT-MAIS评分与婴幼儿听力损失程度负相关关系(r=-0.418;P<0.05)。结论tb-ABR与IT-MAIS存在相关性,两者不仅可以用于听力损失婴幼儿诊断,还可用于评估患儿听力损失程度。

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.

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.

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.

Increasing Fusarium verticillioides resistance in maize by genomicsassisted breeding:Methods,progress,and prospects

Maize(Zea mays L.)is an indispensable crop worldwide for food,feed,and bioenergy production.Fusarium verticillioides(F.verticillioides)is a widely distributed phytopathogen and incites multiple destructive diseases in maize:seedling blight,stalk rot,ear rot,and seed rot.As a soil-,seed-,and airborne pathogen,F.verticillioides can survive in soil or plant residue and systemically infect maize via roots,contaminated seed,silks,or external wounds,posing a severe threat to maize production and quality.Infection triggers complex immune responses:induction of defense-response genes,changes in reactive oxygen species,plant hormone levels and oxylipins,and alterations in secondary metabolites such as flavonoids,phenylpropanoids,phenolic compounds,and benzoxazinoid defense compounds.Breeding resistant maize cultivars is the preferred approach to reducing F.verticillioides infection and mycotoxin contamination.Reliable phenotyping systems are prerequisites for elucidating the genetic structure and molecular mechanism of maize resistance to F.verticillioides.Although many F.verticillioides resistance genes have been identified by genome-wide association study,linkage analysis,bulkedsegregant analysis,and various omics technologies,few have been functionally validated and applied in molecular breeding.This review summarizes research progress on the infection cycle of F.verticillioides in maize,phenotyping evaluation systems for F.verticillioides resistance,quantitative trait loci and genes associated with F.verticillioides resistance,and molecular mechanisms underlying maize defense against F.verticillioides,and discusses potential avenues for molecular design breeding to improve maize resistance to F.verticillioides.

Changes in grain-filling characteristics of single-cross maize hybrids released in China from 1964 to 2014

Grain filling is the physiological process for determining the obtainment of yield in cereal crops.The grain-filling characteristics of 50 maize brand hybrids released from 1964 to 2014 in China were assayed across multiple environments.We found that the grain-filling duration(54.46%)and rate(43.40%)at the effective grain-filling phase greatly contributed to the final performance parameter of 100-kernel weight(HKW).Meanwhile,along with the significant increase in HKW,the accumulated growing degree days(GDDs)for the actual grain-filling period duration(AFPD)among the selected brand hybrids released from the 1960s to the 2010s in China had a decadal increase of 23.41℃ d.However,there was a decadal increase of only 19.76℃ d for GDDs of the days from sowing to physiological maturity(DPM),which was also demonstrated by a continuous decrease in the ratio between the days from sowing to silking(DS)and DPM(i.e.,from 53.24%in the 1960s to 49.78%in the 2010s).In contrast,there were no significant changes in grain-filling rate along with the release years of the selected hybrids.Moreover,the stability of grain-filling characteristics across environments also significantly increased along with the hybrid release years.We also found that the exotic hybrids showed a longer grain-filling duration at the effective grain-filling phase and more stability of the grain-filling characteristics than those of the Chinese local hybrids.According to the results of this study,it is expected that the relatively longer grain-filling duration,shorter DS,higher grain-filling rate,and steady grain-filling characteristics would contribute to the yield improvement of maize hybrids in the future.

GA Associated Dwarf 5 encodes an ent-kaurenoic acid oxidase required for maize gibberellin biosynthesis and morphogenesis

Gibberellin(GA)functions in plant growth and development.However,genes involved in the biosynthesis and regulation of GA in crop plants are poorly understood.We isolated the mutant gad5-1(GAAssociated Dwarf 5),characterized by dwarfing,short internodes,and dark green and short leaves.Map-based gene cloning and allelic verification confirmed that ZmGAD5 encodes ent-kaurenoic acid oxidase(KAO),which catalyzes KA(ent-kaurenoic acid)to GA12 conversion during GA biosynthesis in maize.ZmGAD5 is localized to the endoplasmic reticulum and is present in multiple maize organs.In gad5-1,the expression of ZmGAD5 is severely reduced,and the levels of the direct substrate of KAO,KA,is increased,leading to a reduction in GA content.The abnormal phenotype of gad5-1 was restored by exogenous application of GA3.The biomass,plant height,and levels of GA12 and GA3 in transgenic Arabidopsis overexpressing ZmGAD5 were increased in comparison with the corresponding controls Col-0.These findings deepen our understanding of genes involved in GA biosynthesis,and could lead to the development of maize lines with improved architecture and higher planting-density tolerance.

Identification and Characterization of ZF-HD Genes in Response to Abscisic Acid and Abiotic Stresses in Maize

The zinc finger homeodomain(ZF-HD)genes belong to the homeobox gene family,playing critical roles in flower development and stress response.Despite their importance,however,to date there has been no genome-wide identification and characterization of the ZF-HD genes that are probably involved in stress responses in maize.In this study,24 ZF-HD genes were identified,and their chromosomal locations,protein properties,duplication patterns,structures,conserved motifs and expression patterns were investigated.The results revealed that the ZF-HD genes are unevenly distributed on nine chromosomes and that most of these genes lack introns.Six and two ZF-HD genes have undergone segmental and tandem duplication,respectively,during genome expansion.These 24 ZF-HD transcription factors were classified into six major groups on the basis of protein molecular evolutionary relationship.The expression profiles of these genes in different tissues were evaluated,resulting in producing two distinct clusters.ZF-HD genes are preferentially expressed in reproductive tissues.Furthermore,expression profiles of the 24 ZF-HD genes in response to different kinds of stresses revealed that ten genes were simultaneously up-regulated under ABA,salt and PEG treatments;meanwhile four genes were simultaneously down-regulated.These findings will pave the way for deciphering the function and mechanism of ZF-HD genes on how to implicate in abiotic stress.

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.

Responses of photosynthetic characteristics and leaf senescence in summer maize to simultaneous stresses of waterlogging and shading

A field experiment was performed to investigate the physiological mechanism of the simultaneous stresses of waterlogging and shading on leaf photosynthetic and senescence during three growth stages of summer maize.The responses of leaf gas exchange parameters and antioxidant enzyme activities of the summer maize hybrids Denghai 605(DH605)to waterlogging(W),shading(S),and their combination(W+S)for 6 days at the third leaf stage(V3),the sixth leaf stage(V6),and the tasseling stage(VT)were recorded.Shading,waterlogging,and their combination disturbed the activities of protective enzymes and increased the contents of H2O2and O-2,accelerating leaf senescence and disordering photosynthetic characteristics.Under waterlogging,shading and their combination,leaf Pn,the photo-assimilates and grain yield was decreased.The greatest reduction for waterlogging and the combined stresses occurred at V3 and that for shading stress occurred at VT.The individual and combined stresses reduced the activities of protective enzymes and inhibited photosynthesis,reducing the accumulation of photosynthetic compounds and thereby yield.Waterlogging and the combined stresses at the V3 stage showed the greatest effect on leaf photosynthetic and senescence,followed by the V6 and VT stages.The greatest effect for shading stress occurred at VT,followed by the V6 and V3 stages,and the combined influence of shading and waterlogging was greater than that of either single stress.

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.

A peptide chain release factor 2a gene regulates maize kernel development by modulating mitochondrial function

Mitochondrial protein translation that is essential for aerobic energy production includes four essential steps of the mitochondrial ribosome cycle,namely,initiation,elongation,termination of the polypeptide,and ribosome recycling.Translation termination initiates when a stop codon enters the A site of the mitochondrial ribosome where it is recognized by a dedicated peptide release factor(RF).However,RFs and mechanisms involved in translation in plant mitochondria,especially in monocotyledons,remain largely unknown.Here,we identified a crumpled kernel(crk5 allele)mutant,with significantly decreased kernel size,100-kernel weight,and an embryo-lethal phenotype.The Crk5 allele was isolated using map-based cloning and found to encode a mitochondrial localization RF2a.As it is an ortholog of Arabidopsis mitochondrial RF2a,we named the gene ZmmtRF2a.ZmmtRF2a is missing the 5th–7th exons in the crk5 resulting in deletion of domains containing motifs GGQ and SPF that are essential for release activity of RF,mitochondrial ribosome binding,and stop codon recognition.Western blot and qRT-PCR analyses indicate that the crk5 mutation results in abnormal mitochondrion structure and function.Intriguingly,we observed a feedback loop in the crk5 with up-regulated transcript levels detected for several mitochondrial ribosome and mitochondrial-related components,in particular mitochondrial complexes CI,CIV,and a ribosome assembly related PPR.Together,our data support a crucial role for ZmmtRF2a in regulation of mitochondrial structure and function in maize.

Dry Matter Accumulation,Moisture Content in Maize Kernel and Their Influences on Mechanical Harvesting

[Objective] The aim of this study was to investigate the dry matter accumulation,moisture content in maize kernel and their influences on mechanical harvesting.[Methods] Using Zhengdan 958,Xianyu 335,Hongda 8 and Liyu 16 as experimental materials,we preliminarily measured the dynamic changes of dry matter accumulation and moisture content with the days after pollination lasted,and investigated the effect of moisture content in kernels on mechanical harvesting of Zhengdan 958 and Liyu 16.[Results] During summer growing season,Zhengdan 958 and Liyu 16 became physiologically mature and suitable for harvesting at about 51 days after pollination,Xianyu 335 and Hongda 8 required 58 days to become physiologically mature and suitable for harvesting after pollination.At physiologically mature stage,the moisture contents in kernels of Zhengdan 958,Xianyu 335,Hongda 8 and Liyu 16 were respectively 33.74%,28.86%,32.05% and 35.24%,respectively.Adopting mechanical harvesting at physiologically mature stage,the kernel loss rate of Zhengdan 958 and Liyu 16 was consistent with the range of mechanical operation index（kernel loss rate of 0.84%≤2%）,while the percentage of broken kernels did not accord with the range of mechanical operation index（kernel crashing rate of 10.12%≧1%）.The results indicate that Zhengdan 958 and Liyu 16 are not suitable for mechanical harvesting using full feeding combine havester.[Conclusion] This study provided theoretical basis for improving the maize harvest index under delayed harvesting.

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.