Table of Content

10 September 2018, Volume 44 Issue 9

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RESEARCH PAPERS

Genotyping of SCN, SMV Resistance, Salinity Tolerance and Screening of Pyramiding Favorable Alleles in Introduced Soybean Accessions

Jun-Hua YE,Qi-Tai YANG,Zhang-Xiong LIU,Yong GUO,Ying-Hui LI,Rong-Xia GUAN,Li-Juan QIU

Acta Agronomica Sinica. 2018, 44(9):  1263-1273.  doi:10.3724/SP.J.1006.2018.01263

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China has introduced 3218 soybean accessions from 26 countries such as the United States, Russia and Japan, and some of them have been carried out soybean cyst nematode (SCN), soybean mosaic virus (SMV) and salinity tolerance resistance evaluation. However, the systematic genotyping of these accessions has not been reported yet. In this study, five robust functional markers have been developed for KASP assays, three SCN loci (rhg1, Rhg4, SCN3-11) and salinity tolerance gene (GmSALT3) included. A total of 1489 introduced soybean accessions were genotyped by these markers with high-throughput assay as well as a SCAR marker (SCN11) which is related to soybean mosaic virus resistance. The results showed that there were 1084 accessions detected with favorable alleles; where accessions detected with resistant alleles at three loci were as much as 19, including three pyramiding SCN genes (rhg1, Rhg4, SCN3-11) which were Peking type and seven pyramiding SCN and SMV , two pyramiding SCN and salinity favorable alleles, as well as seven pyramiding SCN, SMV and salinity favorable alleles; and accessions detected with four favorable alleles were as much as nine accessions, including six pyramiding SCN and SMV resistance alleles, one accession detected with SCN and salinity tolerance and two detected with SCN, SMV and salinity favorable alleles, eight detected with all the favorable alleles in this study. Among the elite accessions mentioned above, it has been proved that 44 accessions resistant to SCN, SMV-3 or tolerant to salinity. Among the 36 accessions with three or more favorable alleles, 52.78% had been reported of one or two characteristics. Among the accessions without resistance or tolerance alleles, it has been reported that 93 accessions were tolerant to salinity or resistant to SMV-3, where new resistance or tolerance genes could be found. Screening out the accessions with high-throughput SNP detection assays for resistance and tolerance alleles in soybean provides information for their further phenotyping, screening and breeding.

Characterization and Analytical Programs of the Restricted Two-stage Multi- locus Genome-wide Association Analysis

Jian-Bo HE,Fang-Dong LIU,Guang-Nan XING,Wu-Bin WANG,Tuan-Jie ZHAO,Rong-Zhan GUAN,Jun-Yi GAI

Acta Agronomica Sinica. 2018, 44(9):  1274-1289.  doi:10.3724/SP.J.1006.2018.01274

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Genome-wide association studies (GWAS) have been widely used for genetic dissection of quantitative trait loci (QTL), and the previous GWAS procedures were concentrated on finding a handful of major loci, while the plant breeders are more likely interested in exploring the whole QTL system for both forward selection and background control. We proposed the restricted two-stage multi-locus genome-wide association analysis (RTM-GWAS, https://github.com/njau-sri/rtm-gwas/) for a relatively thorough detection of QTL and their multiple alleles. Firstly, RTM-GWAS groups the tightly linked sequential SNPs into linkage disequilibrium blocks (SNPLDBs) to form genomic markers with multiple haplotypes as alleles. Secondly, it utilizes two-stage association analysis based on a multi-locus multi-allele model to save computer space for focusing on genome-wide QTL identification along with their multiple alleles. Compared with the previous GWAS methods, RTM-GWAS takes the trait heritability as the upper limit of detected genetic contribution, which can avoid a large amount of false positives for a precise detection of the QTL system of the trait. The QTL-allele matrix as a compact form of the population genetic constitution can be used to design optimal genotypes, to predict optimal crosses in plant breeding, and to study the genetic properties of the population as well as the novel and newly emerged alleles. In the present study, we first introduced the function and usage of the RTM-GWAS analytical programs, and then used the experimental data from a research program on soybean to illustrate the application details of the RTM-GWAS.

Transcription Abundances of CRY1b and CRY2 Genes in Response to Different Light Treatments in Maize

Hong-Dan LI,Lei YAN,Lei SUN,Xiao-Cong FAN,Shi-Zhan CHEN,Yan ZHANG,Lin GUO,Guang-Xia YOU,Zhuang LI,Zong-Ju YANG,Liang SU,Jian-Ping YANG

Acta Agronomica Sinica. 2018, 44(9):  1290-1300.  doi:10.3724/SP.J.1006.2018.01290

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Light is lightly related to the important agronomic traits in maize such as plant height, flowering time, yield and quality. Cryptochromes are blue and ultraviolet-A photoreceptors generally existing in animal, plant and microbial, which mainly regulate photomorphogenesis in plants and circadian rhythms in both of plant and animal. Therefore, the expression pattern analysis of cryptochrome in maize could lay a research foundation in the photomorphogenesis in maize. The ZmCRY1b and ZmCRY2 genes were cloned by RT-PCR. Their proteins’ function domains and the phylogenetic analysis of amino acid sequences were carried out through bioinformatics analysis. The transcription abundances of ZmCRY1b and ZmCRY2 genes in different tissues of inbred line B73 under different light treatments were analyzed by qRT-PCR. We found that the function domains of ZmCRY1b or ZmCRY2 protein was consistent with CRY1 or CRY2 in Arabidopsis, rice and wheat, which contains the PHR and CCE domains or the PHR domain, respectively. Phylogenetic analysis indicated that the three gramineous CRYs from maize, wheat, and rice belonged to the same branch, while showing low similarity to other CRY1 proteins from dicotyledons. ZmCRY1b and ZmCRY2 genes highly expressed in leaf. Meanwhile, they could respond to all treatments of different continuous light conditions, the transitions from the dark to light conditions, as well as long-day and short-day conditions. The transcription abundances of ZmCRY1b in all treatments were higher than those of ZmCRY2, indicating that ZmCRY1b was more important than ZmCRY2 in maize. In conclusion, both of ZmCRY1b and ZmCRY2 genes can greatly respond to different light conditions and light cycle treatments, and play an important role in maize photomorphogenesis. Our results also provide a research basis for functional exploration of ZmCRY1b and ZmCRY2 in crop improvement.

Phenotypic Analysis and Gene Mapping of the Rice Narrow-leaf Mutant nal20

Hai-Xin LONG,Hai-Yang QIU,UZAIR Muhammad,Jing-Jing FANG,Jin-Feng ZHAO,Xue-Yong LI

Acta Agronomica Sinica. 2018, 44(9):  1301-1310.  doi:10.3724/SP.J.1006.2018.01301

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Leaf is the major organ for photosynthesis in plant, and its area influences the light energy utilization efficiency and grain yield. To study the molecular mechanism of rice leaf morphology, we mutagenized the japonica cultivar Chunjiang 06 through ⁶⁰Co-γ radiation. A stable narrow leaf mutant named as narrow leaf20 (nal20) was obtained in the M₂ population. The nal20 mutant showed narrow leaf, reduced plant height, increased tiller number, shortened internodes, and earlier heading date. Here we mainly focused on the morphology of the flag leaf, the second top leaf and the third top leaf. We found that the blade width of the mutant reduced by 50%, compared with the wild type. Meanwhile, the variation on the blade length was relatively small. Cytological observation of leaf epidermal cells indicated that the reduced leaf width was mainly due to the decreased cell number, but not the cell size. Genetic analysis indicated that the narrow leaf phenotype was controlled by a recessive gene. Using the mutant plants from the F₂ mapping population derived from a cross between nal20 and Dular, the candidate mutation locus was mapped to 1.9 Mb within the centromere of chromosome 7 by using polymorphic InDel markers. The next-generation sequencing result showed that a deletion of 455 kb occurred in the predicted region. Our study lays a good foundation for the cloning and functional study of the NAL20 gene and provides gene resources and breeding materials for the improvement of rice plant architecture.

Genome-wide Association Study on Seed Oil Content in Rapeseed and Construction of Integration System for Oil Content Loci

Da-Yong WEI,Yi-Xin CUI,Jia-Qin MEI,Qing-Lin TANG,Jia-Na LI,Wei QIAN

Acta Agronomica Sinica. 2018, 44(9):  1311-1319.  doi:10.3724/SP.J.1006.2018.01311

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Genetic loci for oil content, one of the most important traits of rapeseed (Brassica napus L.), have been widely studied, however, comparisons were difficult to be carried out among studies due to different mapping populations and molecular marker systems. In the present study, a 60K Brassica SNP array was applied in the genome-wide association study (GWAS) using a natural rapeseed population which was comprised of 308 accessions and grown for four consecutive years to identify loci for seed oil content. An integration system was built by anchoring the present loci and previous loci that identified onto the rapeseed genome in other studies using ten segregation populations and two natural populations. A total of eight SNPs significantly associated with seed oil contents of rapeseed were detected in our study, explaining 3.22%-5.13% of the phenotypic variance each SNP. Combining the data from other 12 populations, 193 integrated loci were identified, spreading on all 19 chromosomes of B. napus with more loci distributed on A subgenome (13 loci/chromosome) than C subgenome (seven loci/chromosome). Seven integrated intervals from A subgenome (chromosome A01, A02, A03, A06, A08, A09, and A10) were identified in at least three populations, of which three were homologous to intervals on C subgenome, with 26 known genes associated with seed oil metabolism. The 193 loci were anchored to the reference genome of B. napus var. Darmor-Bzh, resulting in a visualized genome-wide integrated system for seed oil content loci. This study is helpful to determine the important seed oil content loci and to make the optimal breeding strategy to increase oil content in rapeseed.

QTL Mapping for Yield, Growth Period and Plant Height Traits Using MAGIC Population in Upland Cotton

Cong HUANG,Xiao-Fang LI,Ding-Guo LI,Zhong-Xu LIN

Acta Agronomica Sinica. 2018, 44(9):  1320-1333.  doi:10.3724/SP.J.1006.2018.01320

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The yield, growth period and plant height are important agronomic traits that decide the economic value and planting pattern of cotton (Gossypium spp.). In order to dissect the genetic basic of these traits, an 8-way upland cotton MAGIC (multi-parent advanced generation inter-cross) population and SSR markers were used for association mapping. Eight traits of this MAGIC population were phenotyped in five environments (three years and three locations), showing wider variations than these of the founder parents. The broad-sense heritability (H ²) of the eight traits ranged from 0.17 to 0.71. Association analysis based on mix linear model was performed using 284 polymorphic SSR markers. There were 51, 27, and 9 markers significantly associated with yield, growth period and plant height traits respectively. All identified loci had minor effect for controlling the phenotypic variations, showing a higher powerful ability of the MAGIC population in association mapping. Furthermore, 20 loci were found to be associated with multiple traits acting as pleiotropism. In addition, chromosome hot spots were found for effective boll number, lint weight, first fruit spur branch number and plant height, which provided references for deeply genetically studying these loci. The elite MAGIC lines and the valuable SSR loci lay a foundation for the genetic improvement of upland cotton.

Identification and Bioinformatics Analysis of the PIN Family Gene in Brassica napus

Kun GAO,Ying-Peng HUA,Hai-Xing SONG,Chun-Yun GUAN,Zhen-Hua ZHANG,Ting ZHOU

Acta Agronomica Sinica. 2018, 44(9):  1334-1346.  doi:10.3724/SP.J.1006.2018.01334

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The PIN family is a type of important carrier elements that regulate the polar transportation of auxin. The PIN genes encode auxin efflux carriers with multiple transmembrane domains that mediate auxin transport in plants. However, there is a lack of systematic research in the genome of complexity Brassica napus. In this study, the BnPIN genes were screened from the Brassica Database using bioinformatics, and study on molecular characteristics of BnPIN proteins, such as copy number variations, transmembrane domains, conserved motifs, chromosomal locations, phylogenetic relationships, secondary and three-dimensional structures, and high-throughput transcriptome sequencing was used to analyze the transcriptional level under low nitrate stress. The results showed that most of the BnPIN proteins which is belonged to the stable protein consisting of basic amino acids. The BnPIN family proteins contained secondary structures similar to those of Arabidopsis PINs accompanied by conserved N-terminal domains. The phylogenetic analysis showed that BnPIN genes were similar to the corresponding homologs of Brassica oleracea and Brassica rapa. High-throughput transcriptome analysis showed that the BnPIN1s, BnPIN2s, and BnPIN3s genes were mainly expressed in roots of Brassica napus under long-term (72 h) low nitrate (NO₃ ^-) stress. The BnPIN6s and BnPIN8s genes were mainly expressed in the shoot and limited NO₃ ^- repressed the BnPIN6s expression. This study is valuable for the research that the roles of the BnPIN family in the regulation of auxin transport. Our results also provide reference for the integrated genomic and transcriptomic studies of gene family in plant species with complex genomes.

Cloning and Salt Resistance Function Identification of GmHDL57 Gene from Glycine max

Dan-Xia KE,Kun-Peng PENG,Meng-Ke ZHANG,Yan JIA,Jing-Jing WANG

Acta Agronomica Sinica. 2018, 44(9):  1347-1356.  doi:10.3724/SP.J.1006.2018.01347

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The HD-Zip I class transcription factor plays an important role in plant resistance to abiotic stresses. An HD-Zip I class gene GmHDL57 (Glycine max homeodomain-leucine zipper protein 57) was cloned from soybean in this study. Sequence analysis showed that GmHDL57 gene contained a 1038 bp ORF, encoding 345 amino acids, and featured with HD-Zip family proteins’ typical conserved domain. GmHDL57 was expressed in different organs of soybean plants and the highest expression occurred in flowers. The effects of abiotic stresses (abscisic acid, NaCl, PEG, and cold) on GmHDL57 gene expression in soybean seedling stage were analyzed by real-time quantitative PCR. The expression level of GmHDL57 gene was obviously increased under high salinity stress and less affected by ABA and drought stress but decreased by cold stress. The expression level of GmHDL57 gene in roots was significantly higher than that in stems and leaves before and after salt stress, and reached the peak at 48 h, then decreased slowly at 72 h and 96 h after salt stress. The overexpression vector of GmHDL57 was constructed and transformed into Agrobacterium tumefaciens strain EHA105 to obtain the stable transgenic Lotus japonicus plants. After being treated with 200 mmol L ^-1 NaCl for 14 d, the shoot height, root length, chlorophyll content, root activity as well as K ⁺ and Ca ²⁺ content increased significantly in transgenic plants compared with the wild type. The malondialdehyde content, relative membrane permeability and Na ⁺content were obviously reduced in transgenic plants compared with the wild type. It is hypothesized that the GmHDL57 gene participates in the abiotic stress response of soybean, and over-expression of GmHDL57 gene could enhance resistance to saline in Lotus japonicus.

Fine Mapping and Genetic Effect Analysis of a Major QTL qPH3.2 Associated with Plant Height in Maize (Zea mays L.)

Zhong-Xiang LIU,Mei YANG,Peng-Cheng YIN,Yu-Qian ZHOU,Hai-Jun HE,Fa-Zhan QIU

Acta Agronomica Sinica. 2018, 44(9):  1357-1366.  doi:10.3724/SP.J.1006.2018.01357

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Plant height is one of the most important factors affecting maize yield, which is determined by the number and the length of internode in maize. In this research, two advanced-backcross recombinant inbred lines (W₁ and W₂) with significant difference in plant height were used. They have the same number of internodes. We found that the different cell lengths of the internode in upper spike were the main reason causing the difference in plant height. The results of exogenous GA test showed that the QTL/genes controlling plant height were not included in GA pathway. The F₂ and F_2:3 populations derived from W₁ and W₂ were used to map the QTLs associated with plant height, showing that one major named qPH3.2 was commonly identified under three different environments in two years which was located on chromosome 3 between markers C42 and P17 with 20 Mb and could explain 22.22% of phenotypic variation. On the basis of the primary mapping results, QTL qPH3.2 was divided into two major QTLs qPH3.2.1 and qPH3.2.2 via recombinant exchange individuals and its self-cross progeny. Furthermore, we did the fine mapping work for qPH3.2.1 and qPH3.2.2 using substitution lines. The qPH3.2.1 was fine-mapped to the region of about 2 Mb between markers YH305 and Y72, and qPH3.2.2 was fine-mapped to the region of about 1.6 Mb between markers YH112 and Y150, which all showed the positive additive effects. The results of this research provide reliable genetic loci for the genetic improvement of plant height in maize, and a good foundation for cloning QTLs for plant height in the future.

Cloning and Expression Characteristic Analysis of ScWRKY4 Gene in Sugarcane

Ling WANG,Feng LIU,Ming-Jian DAI,Ting-Ting SUN,Wei-Hua SU,Chun-Feng WANG,Xu ZHANG,Hua-Ying MAO,Ya-Chun SU,You-Xiong QUE

Acta Agronomica Sinica. 2018, 44(9):  1367-1379.  doi:10.3724/SP.J.1006.2018.01367

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WRKY is one of the specific transcriptional regulators in plants and widely involved in the response of plants to diverse biotic and abiotic stresses. In this study, based on our previous transcriptome data of sugarcane (Saccharum spp.), we successfully cloned a WRKY gene from sugarcane variety ROC22, named as ScWRKY4 (GenBank accession number MG852087). Sequence analysis showed that the full-length cDNA of ScWRKY4 gene was 1265 bp, containing a 741 bp complete open reading frame and encoding 246 amino acids residues. ScWRKY4 protein had a conservative WRKYGQK domain and a zinc finger motif C₂H₂, belonging to IIc subgroup of WRKY transcription factor family. Bioinformatics analysis indicated that ScWRKY4 was an alkaline unstable hydrophilic protein with no signal peptide and transmembrane structure. The secondary structural element of ScWRKY4 protein was lack of beta helix structure. ScWRKY4 was located in the nucleus after transient expression in Nicotiana benthamiana. The result of yeast hybridization experiment demonstrated that ScWRKY4 did not possess transcriptional activity. Real-time fluorescent quantitative PCR showed that the expression of ScWRKY4 gene had no significant difference in root, leaf, bud and stem epidermis, while had the highest expression level in stem pith, which was 18.38 times higher than that in root. During inoculation with smut pathogen (Sporisorium scitamineum) at 0-72 h, the gene expression level of ScWRKY4 was down-regulated in sugarcane smut-resistant cultivar Yacheng 05-179, while was more stable in the susceptible one ROC22. The transcript of ScWRKY4 was up-regulated by exogenous hormone stresses of abscisic acid, salicylic acid, and methyl jasmonate, as well as by the abiotic treatments of sodium chloride and polyethylene glycol. These results suggest that ScWRKY4 gene may not participate in sugarcane smut resistance, or only play a negative role in this defense reaction, but positively involve in the response mechanism of salt and drought resistance in sugarcane.

Identification and Expression Analysis of Multidrug and Toxic Compound Extrusion Protein Family Genes in Colored Cotton

Zuo-Min WANG,Jin LIU,Shi-Chao SUN,Xin-Yu ZHANG,Fei XUE,Yan-Jun LI,Jie SUN

Acta Agronomica Sinica. 2018, 44(9):  1380-1392.  doi:10.3724/SP.J.1006.2018.01380

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MATE (multidrug and toxic compound extrusion) is a transport proteins family that can transport toxins, glucosamine, antibiotics and drugs. In this study, the MATE family genes were identified from genome database of Gossypium hirsutum L. through bioinformatics analysis and phylogenetic relationship, chromosome distribution, gene structure and expression patterns of this family were comprehensively compared. A total of 91 GhMATE genes were found in the cotton genome and named as GhMATE1-GhMATE91. MATE genes of cotton were classified into seven groups namely A, B, C, D, E, F, and G with a classification is consistent with Arabidopsis. Multiple sequence alignment and conserved domain prediction indicated that 84 of the 91 GhMATE proteins contained 12 typical transmembrane domains. The chromosome mapping analysis showed that GhMATE genes were distributed with different densities over 25 chromosomes and clustered into five clusters. The qPCR showed that the GhMATE genes expressed in all tissues of cotton with different expression patterns. GhMATE13 and GhMATE23 were preferentially expressed in brown cotton fibers than in white cotton fibre, suggesting that they may play an important role in brown color formation of cotton fibre. This study provides valuable informations for dissecting functions and molecular mechanisms of MATEs in cotton.

Effect of Exogenous Nitric Oxide Donor on Carbon Assimilation and Antioxidant System in Leaves of Maize Seedlings under PEG-induced Water Deficit Stress

Qing-Hua YANG,Bo-Yuan ZHENG,Lei-Lei LI,Shuang-Jie JIA,Xin-Pei HAN,Jia-Meng GUO,Yong-Chao WANG,Rui-Xin SHAO

Acta Agronomica Sinica. 2018, 44(9):  1393-1399.  doi:10.3724/SP.J.1006.2018.01393

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The objective of this study was to explore the effect of exogenous nitric oxide (NO) donor (sodium nitroprusside, SNP) on key enzymes of carbon assimilation and antioxidant system of maize leaves under water deficit and its regulation mechanism. In this experiment, 20% PEG-6000 was used to stimulate water deficit stress, exogenous SNP was added into root rhizosphere of seedlings in maize variety Zhuyu 309. After three days of stresses, the changes of Rubisco and RCA activities and their gene level, antioxidase activity and their isoenzyme spectrum level were investigated. The expression levels of rbc L, rbc S, rca β were increased significantly, especially for rbc S that was increased the most by 1.86 fold, which resulted in up-regulation of Rubisco and RCA activities by 32.7% and 14.67% under exogenous SNP plus PEG stress. In addition, SNP enhanced the activity of SOD, POD, CAT, and the width in their isoenzyme spectrum, resulting in significant reduction of ROS accumulation. These results suggested that NO could increase photosynthetic carbon assimilation capacity and antioxidase activity, alleviate the damage of ROS burst on the cell membrane, which enhances PEG-simulated water deficit resistance of maize seedlings.

Development and Characterization of SSR Markers from the Whole Genome Sequences of Saccharum officinarum (LA-purple)

Heng-Bo WANG,Nai-Yan XIAO,Zhuan-Wei ZHU,Cui-Cui LIU,ALAM Intikhab,Ping-Hua CHEN,Yun-Hai LU

Acta Agronomica Sinica. 2018, 44(9):  1400-1410.  doi:10.3724/SP.J.1006.2018.01400

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Modern sugarcane cultivars (2n = 100-130) are derived from interspecific hybridization and backcross breeding between Saccharum officinarum (2n = 80) and Saccharum spontaneum (2n = 40-128), forming polyploid and aneuploid crops. The main components (80%-90%) of the sugarcane cultivars’ genome are originated from S. officinarum. The development and mining of genomic SSR molecular marker of S. officinarum, will benefit sugarcane genetic diversity analysis, molecular marker assisted selection, and construction of genetic maps. In this study, we explored the SSR loci from 255 398 predicted gene sequences (with a cumulative length of 1 029 222 285 bp) derived from the whole genome sequencing project of a S. officinarum clone LA-purple, by combining Perl program with bioinformatics software. A total of 153 150 SSR loci, with an average of 1.67 genes per SSR locus, were identified, of which 39 556 (25.8%) were dinucleotide repeat motifs and 50 072 (32.7%) were tri-nucleotide repeat motifs. Among the dinucleotide repeat motifs, TA/AT had the highest proportion, accounting for 41.4%, while CG/GC had the lowest proportion, accounting for only 4.6%. Among the trinucleotide repeat motifs, TGT/ACA had the highest proportion, accounting for 15.6%. One hundred SSR loci with 60-90 repeats of TA/AT motifs were selected and analyzed by PCR amplification in 12 representative Saccharum clones, of which 52 were polymorphic among the 12 clones and 27 were polymorphic between the tested two modern sugarcane cultivars. The genome-wide development of these gene-based SSR markers will not only facilitate the DNA fingerprinting analysis of sugarcane cultivars, but also help to construct the genetic maps, analyze the genetic diversity, study the genetic mechanism of important traits in Saccharum species, and provide important support to the molecular breeding in sugarcane.

RESEARCH NOTE

Relationship between Grain Moisture and Maize Mechanical Harvesting Qualities in Dry Highland of Loess Plateau

Ting-Lu FAN,Shu-Ying WANG,Chuang-Ye XU,Shang-Zhong LI,Jia-Xi WANG,Ke-Ru WANG,Gang ZHAO,Wan-Li CHENG,Jian-Jun ZHANG,Lei WANG,Yi DANG

Acta Agronomica Sinica. 2018, 44(9):  1411-1429.  doi:10.3724/SP.J.1006.2018.01411

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Grain harvesting is a key process in whole mechanization of maize, and grain breakage and ear and kenenal losses have attracted more and more attention, therefore studying on maize mechanical harvesting qualities and its related factors has very important practical significance for promoting maize grain harvesting techniques in dryland. From 2016 to 2017, 33 maize varieties were used under full film mulched ridge-furrow planting system at Pingliang, Jingchuan county to harvest grain with Futian leiwo Ceres harvester for determining relationship between grain harvesting qualities and grain moisture. Grain harvesting qualities highly depended on maize genotypes, the average values were 26.05% in grain moisture content, 7.47% in grain broken rate, 2.58% in ear loss rate, 1.04% in impurity rate, and 3.25% in total grain loss rate. Grain broken rate (Y₁) and total grain yield loss rate (Y₂) were significantly and positively correlated with grain moisture content (X), expressing as Y₁ = 0.027X ²-0.987X+14.06 (R ² = 0.373 ^**, n = 51) and Y₂ = 0.052X ²-2.223X+24.86 (R ² = 0.418 ^**, n = 51). When grain moisture content declined to 18.3% in Y₁ and 21.4% in Y₂, grain breakage rate and grain loss reduced to minimum value of 5.1% and 1.1%, respectively. When the suitable grain moisture for mechanical harvesting was 18%-22% in the broken rate was in a range of 5.0%-5.5%. In a certain range of grain moisture content, grain broken rate and grain loss rate increased with the increase of grain moisture content. Effect of grain moisture on ear loss rate was higher than that on kernel loss rate, and the increasing extent of ear loss rate along with grain moisture was much higher than that of kernel loss rate. The effect of problem factors in maize mechanical harvesting on total grain loss was era loss rate > grain moisture > broken rate, showing that high grain moisture content and high ear loss are main factors affecting maize mechanical harvesting qualities in dryland.