Table of Content

12 July 2021, Volume 47 Issue 7

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CROP GENETICS & BREEDING · GERMPLASM RESOURCES · MOLECULAR GENETICS

Genome-wide association study of β-glucan content in barley grains

GENG La, HUANG Ye-Chang, LI Meng-Di, XIE Shang-Geng, YE Ling-Zhen, ZHANG Guo-Ping

Acta Agronomica Sinica. 2021, 47(7):  1205-1214.  doi:10.3724/SP.J.1006.2021.01074

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β-glucan is an important trait in barley, as its content greatly affects the quality in the applications of malting, feeding, and food. Although the genes associated with β-glucan synthesis have been reported, genetic regulation of β-glucan accumulation in barley grains is still unclear. In this study, genome-wide association study (GWAS) with mixed linear model (MLM) and general linear model (GLM) was performed to analyze the grain β-glucan content of 119 barley germplasms collected from worldwide previously, which were planted at two plots with certain differences in soil and climate conditions. The results showed β-glucan content in barley grains was significantly different in genotypes and the heritability of β-glucan was 73.9% in two environments. There were eight and 40 loci for grain β-glucan content detected by MLM and GLM, respectively. A total of 44 loci were obtained by combining the same loci of the two models. HORVU5Hr1G022710 gene identified in both models and sites was considered as a putative candidate gene significantly associated with β-glucan content. Significantly positive correlation was detected between grain β-glucan content and the number of favorable alleles in both models. In addition, 10 enzymatic genes related to sugar synthesis, transport and decomposition were identified based on gene annotations. These genes may significantly relate to β-glucan synthesis, accumulation and hydrolysis. The results provided a new insight into the genetic regulation of β-glucan accumulation and laid a foundation for the genetic improvement breeding of barley seed β-glucan.

CROP GENETICS & BREEDING · GERMPLASM RESOURCES · MOLECULAR GENETICS

Genetic analysis of stigma traits with genic male sterile line by mixture model of major gene plus polygene in rice (Oryza sativa L.)

JIANG Jian-Hua, ZHANG Wu-Han, DANG Xiao-Jing, RONG Hui, YE Qin, HU Chang-Min, ZHANG Ying, HE Qiang, WANG De-Zheng

Acta Agronomica Sinica. 2021, 47(7):  1215-1227.  doi:10.3724/SP.J.1006.2021.02057

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Rice stigma traits are important traits that affects the yield of male sterile lines and hybrid rice seed production. To provide genetic information for the creation of thermo-sensitive genic male sterile lines with long stigmas and high exsertion rates in rice, we investigated the correlation among four stigma traits of 7001S (japonica photoperiod-thermo-sensitive genic male sterile line with short stigma length and low exsertion rate, P₁), Zitai S (indica thermo-sensitive genic male sterile line with long stigma length and high exsertion rate, P₂), and F₁, F₂ (350 lines), and F_2:3 (320 lines) from the cross P₁ × P₂. Coefficients of linear correlation in stigma traits were calculated, and genetic patterns were analyzed by mixed major-gene plus polygene inheritance models. The results showed that there were extremely significant linear positive correlations among four stigma traits. The correlation coefficients were between 0.262 and 0.895. Genetic analysis revealed that stigma length (STL), style length (SYL), the sum of stigma, and style length (TSSL) were controlled by two major genes plus polygenes. The two major genes expressed additive-dominant-epistatic effects, but they expressed equal additive effects and equal dominant effects of TSSL in F₂ population. The epistatic effect was dominant in STL, SYL, and TSSL in F₂ and F_2:3. Percentage of exserted stigma (PES) was controlled by two major genes plus polygenes with additive-dominant-epistatic effect in F₂. However, PES was controlled by one major gene with additive-dominant effect plus polygenes in F_2:3. The additive effect was dominant of PES in F₂ and F_2:3. Four stigma traits were mainly governed by major genes.

Genome-wide association study of ear cob diameter in maize

MA Juan, CAO Yan-Yong, LI Hui-Yong

Acta Agronomica Sinica. 2021, 47(7):  1228-1238.  doi:10.3724/SP.J.1006.2021.03048

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Maize ear cob diameter is an important trait impacting the yield of grain and cob, and the analysis of its genetic mechanism will provide a guidance for high-yield breeding. In this study, the genotypes of 309 inbred lines were identified by genotyping-by-sequencing technology. FarmCPU (fixed and random model circulating probability unification), MLMM (multiple loci mixed linear model), and CMLM (compressed mixed linear model) were used to identify significant single nucleotide polymorphisms (SNP) for ear cob diameter of Yuanyang of Henan province, Dancheng of Henan province, Yucheng of Henan province, Sanya of Hainan province in 2017 and 2019, and best linear unbiased estimate environment. A total of 12 significant SNP for ear cob diameter were detected at P < 8.60E-07. S4_29277313 was detected from Yuanyang in 2017 using FarmCPU and MLMM. The phenotypic variance explained of S1_29006330, S2_170889116, S2_2046026464, and S4_83821463 ranged from 10.23% to 14.17%, and were considered major-effect SNP. In addition, S1_29006330 was mapped in the interval of known QTL for ear cob diameter. A total of 17 candidate genes were identified. Among them, WAKL14 (wall-associated receptor kinase-like 14), transcription factor ZIM35 (zinc-finger protein expressed in inflorescence meristem 35), HMGA (HMG-Y-related protein A), histone-lysine N-methyltransferase ATX4 (Arabidopsis trithorax 4), and XTH32 (xyloglucan endotransglucosylase/hydrolase protein 32) might be important genes for ear cob diameter. The identification of four major-effect SNP and five candidate genes can provide an information for molecular marker-assisted breeding, fine mapping, and gene cloning.

GhP4H2 encoding a prolyl-4-hydroxylase is involved in regulating cotton fiber development

GAO Lu, XU Wen-Liang

Acta Agronomica Sinica. 2021, 47(7):  1239-1247.  doi:10.3724/SP.J.1006.2021.04217

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Arabinogalactan proteins (AGPs) perform crucial roles during cotton fiber development, and they are composed of a hydroxyproline (Hyp)-rich core protein and large type-II arabinogalactan (AG) moieties. AGPs are highly glycosylated proteins which involve two most important post-translational processes. First, the proline residues were hydroxylated by prolyl- 4-hydroxylases (P4Hs), then the Hyps were substituted with large arabinogalactan polysaccharides or small arabino- oligosaccharides by glycosyltransferases (GTs). Our previous work had shown that fiber elongation was repressed when in vitro-cultured cotton ovules were treated with inhibitors of P4Hs, suggesting that P4Hs were involved in cotton fiber development. In this study, GhP4H2 was detected to be relatively highly expressed at fiber elongation stage. Overexpression and RNAi-silencing vectors of GhP4H2 were constructed and transformed into cotton. Phenotypic analysis showed that GhP4H2 overexpressing fibers were significantly shorter compared with the wild type from T₁ generation to T₃ generation. In addition, AGP content had increased in GhP4H2 overexpression fibers. Immuno dot-blot analysis also showed that carbohydrate moieties of AGP had changed. Moreover, RNA-seq revealed that expression levels of genes encoding hydroxyproline (Hyp)-rich glycoproteins including AGPs were enhanced. Overall, these results indicated that GhP4H2 may regulate fiber development primarily through affecting AGPs composition.

Differentially expressed protein analysis of different drought tolerance hulless barley leaves

LI Jie, FU Hui, YAO Xiao-Hua, WU Kun-Lun

Acta Agronomica Sinica. 2021, 47(7):  1248-1258.  doi:10.3724/SP.J.1006.2021.01062

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In order to reveal the differences in response to drought stress among different hulless barley varieties from the protein level and to analyze the protein molecular mechanism of drought tolerance, Handizi Barley (HDZ) resistant to drought stress and Dama Barley (DM) sensitive to drought stress were used as research materials in this study. Drought treatment were determined by potted-planting method with limited water supply, four physiological indexes of hulless barley leaves with different drought gradients, including chlorophyll, soluble protein, malondialdehyde content, and relative conductivity were investigated. iTRAQ technology was used to conduct differential protein analysis on the whole protein group of barley leaves under deep drought stress. The results showed that with the extension of the drought treatment, the chlorophyll and soluble protein content of two hulless barleys under drought stress gradually decreased, the electrical conductivity and malondialdehyde content gradually increased, and the decrease in chlorophyll and soluble protein content, the increase in electrical conductivity and the content of malondialdehyde in Dama were greater than that of Handizi; 4163 proteins (polypeptides) were quantified, among them, compared with normal culture in the Handizi comparison group, 68 up-regulated proteins and 63 down-regulated proteins were screened by iTRAQ; in the comparative group of Dama, 21 up-regulated proteins and 32 down-regulated proteins were screened. KEGG pathway showed that the top three enrichment pathways were metabolic, amino acid biosynthesis, and secondary metabolite biosynthesis. The first one mainly related to citric acid cycle, carbon cycle, and other metabolic pathways. The synthesis and degradation of amino acids were mainly involved arginine and alanine. The synthesis of secondary metabolites were about arachidonic acid and linolenic acid. This study screened the proteins related to the metabolic pathways and other related functions in response to drought stress on proteome level in hulless barley, providing a theoretical basis for revealing the molecular regulation mechanism in response to drought stress.

Construction of SSR fingerprint database and genetic diversity analysis of cigar germplasm resources

WANG Yan-Yan, WANG Jun, LIU Guo-Xiang, ZHONG Qiu, ZHANG Hua-Shu, LUO Zheng-Zhen, CHEN Zhi-Hua, DAI Pei-Gang, TONG Ying, LI Yuan, JIANG Xun, ZHANG Xing-Wei, YANG Ai-Guo

Acta Agronomica Sinica. 2021, 47(7):  1259-1274.  doi:10.3724/SP.J.1006.2021.04183

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In order to investigate the genetic diversity of Chinese cigar germplasm resources in molecular level and to establish the DNA fingerprint database of cigar varieties, 43 pairs of SSR primers with good polymorphic were used to analyze the genetic diversity of 220 cigar germplasms, and 14 pairs of core primers were screened from 43 pairs of SSR primers to construct the fingerprint database of 220 cigar germplasms in the study. Results showed that a total of 243 alleles were amplified by 43 pairs of SSR primers in 220 cigar germplasm materials, with an average of 5.65 per marker, ranging from 2 to 13. The polymorphic information content (PIC) of each locus varied from 0.2078 to 0.9087 with an average of 0.6360. The number of effective alleles (N_e) ranged from 1.3081 to 11.7876, and the average number of effective alleles was 3.9077. The observed heterozygosity (H_o) ranges from 0.0828 to 0.7639 with an average of 0.3191. The expected heterozygosity (H_e) ranged from 0.2361 to 0.9172 with an average of 0.6809. The average Shannon genetic diversity index (I) was 1.3756, the genetic distance was between 0.0233 and 0.9286, and the average genetic distance was 0.6816. Unweighted pair-group method with arithmetic means (UPGMA) cluster analysis showed that the tested cigar resources can be divided into three groups at the genetic distance of 0.74. All tested materials were divided into two groups by population genetic structure analysis and principal component analysis (PCA). Based on the primer analysis and phenotypic identification, it was determined that the ‘LZ’, ‘FS’ and ‘MED’, ‘SDDY’ and ‘MDJ 05-1’, ‘Florida 513’ and ‘CA0701’ were the same species with different names. One variety retained one germplasm, leaving 216 different germplasm. 14 pairs of SSR primers which could distinguish all the tested materials were screened to construct the fingerprint database of 216 cigar cultivars from 43 pairs of SSR primers as core primers. In conclusion, cigar germplasm resources in China had a high level of genetic diversity. In this study, the constructed SSR fingerprint database and genetic analysis of cigar germplasm resources provided the scientific basis for the screening and identification of high-quality cigar germplasms resources, the mining of important genes, and the broadening the basis of cigar genetic breeding.

Identification of thaumatin-like protein family in Saccharum spontaneum and functional analysis of its homologous gene in sugarcane cultivar

SU Ya-Chun, LI Cong-Na, SU Wei-Hua, YOU Chui-Huai, CEN Guang-Li, ZHANG Chang, REN Yong-Juan, QUE You-Xiong

Acta Agronomica Sinica. 2021, 47(7):  1275-1296.  doi:10.3724/SP.J.1006.2021.04192

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Thaumatin like protein (TLP) plays an important role in plant growth and development and resistance to environmental stress. In order to fully understand the structure and functional characteristics of sugarcane TLP gene family, 122 SsTLP family genes were screened and analyzed for their physicochemical properties, gene chromosomal distribution, gene structure, and phylogenetic evolution using the genomic database of Saccharum spontaneum and bioinformatics methods. In addition, one homologous gene of SsTLP87, ScTLP1, was cloned from a major sugarcane cultivar ROC22 in mainland China. Gene expression pattern, subcellular localization, transient expression, and transcriptional self-activation activity of ScTLP1 were identified. The results showed that 122 SsTLP family genes were distributed on 28 chromosomes, and there was a gene clustering with 1-13 SsTLP genes on each chromosome. Most SsTLP proteins were predicted to be acidic, hydrophobic, and unstable proteins which located in cytoplasm. There were many types and distributions of intron number (1-30), intron phase (0-2), and motif (1-5) in SsTLP family genes. Phylogenetic tree analysis indicated that the coding proteins of SsTLP genes were clustered in the I-X branches of TLP family, among which, the number of the class V SsTLPs with antibacterial potential was the most (36). ScTLP1 gene obtained from sugarcane cultivar ROC22 encoded 227 amino acid residues, belonging to the class V member. ScTLP1 was located in the cell membrane and had no transcriptional self-activation activity. The similarity of amino acid sequence between ScTLP1 and SsTLP87 was as high as 99.56%. qRT-PCR demonstrated that ScTLP1 gene was constitutively expressed in different tissues of sugarcane with the highest expression level in the bud. The expression level of ScTLP1 gene had no significant change under the treatments of abscisic acid (ABA) and salicylic acid (SA), but it was up-regulated by Sporisorium scitaminea, methyl jasmonate (MeJA), sodium chloride (NaCl), polyethylene glycol (PEG), and low temperature of 4℃. After transient overexpression of ScTLP1 gene, DAB staining in Nicotiana benthamiana leaves was deepened, and the expression level of NtEFE26 and NtPR3 was up-regulated. Furthermore, the incidence of transient overexpression of ScTLP1 gene in N. benthamiana leaves inoculated with Pseudomonas solanacearum and Fusarium solani var. coeruleum was lighter than that of the control, suggesting that ScTLP1 gene could induce an allergic reaction of N. benthamiana, participate in the ethylene and jasmonic acid signal transduction pathways, and enhance the defense effect of N. benthamiana against pathogens. These results laid a good foundation for further study on the structure and function of the TLP gene family in sugarcane.

Identification and expression analysis of cell wall invertase IbCWIN gene family members in sweet potato

SONG Tian-Xiao, LIU Yi, RAO Li-Ping, Soviguidi Deka Reine Judesse, ZHU Guo-Peng, YANG Xin-Sun

Acta Agronomica Sinica. 2021, 47(7):  1297-1308.  doi:10.3724/SP.J.1006.2021.04180

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Sweet potato is an important food, feed, industrial raw material crop and a new type of bioenergy crop. Cell wall sucrose invertase is a key enzyme for sucrose metabolism in plant sources and sink. However, the research of sweet potato cell wall sucrose gene invertase (IbCWIN) family members has not been reported. In this study, the content of sucrose starch in different tissues of the tested varieties was determined, and the physicochemical properties, conserved domains, phylogenetic relationships, promoter acting elements and tissue-specific expression patterns of IbCWIN gene family were analyzed by bioinformatics methods. The results showed that the sucrose content of sweet potato stems was the highest, followed by fibrous roots and leaves, and the lowest in tuber root; the starch content of tubers was the highest, which was significantly higher than other parts. There were 10 IbCWIN genes in sweet potato, encoding 442-1115 amino acids, protein molecular weight range 49.56-124.44 kD with isoelectric point of 5.0-9.1. Distributed on 8 chromosomes, they all contained the Glyco_32 conserved domain and the same or similar conserved motif, belonging to the glycosyl hydrolase gene family GH32. IbCWIN has a high homology relationship with cassava MeCWINV. The promoter region of the IbCWIN gene family contained many types of cis-acting elements. The results of qRT-PCR showed that the IbCWIN gene family was expressed in different tissues of sweet potato and had multiple expression patterns. Among them, the expression levels of IbCWIN2 and IbCWIN9 in tubers were significantly higher than those in other tissues. This study provides a theoretical guidance for the next step in exploring the functions of the sweet potato IbCWIN gene family and regulating the relationship between the source and sink of sweet potato.

Identification of resistance to wheat and molecular detection of resistance genes to wheat stripe rust of 78 wheat cultivars (lines) in Sichuan province

XI Ling, WANG Yu-Qi, ZHU Wei, WANG Yi, CHEN Guo-Yue, PU Zong-Jun, ZHOU Yong-Hong, KANG Hou-Yang

Acta Agronomica Sinica. 2021, 47(7):  1309-1323.  doi:10.3724/SP.J.1006.2021.01061

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Sichuan province is one of the main origins of new races of the wheat stripe rust pathogen. To understand the resistance level of wheat cultivars (lines) bred in Sichuan since 2016 to the current predominant races of the pathogen and pathotypes and to clarify the distribution of resistance genes can provide a theoretical basis for the management of wheat stripe rust by breeding resistance wheat cultivars and wheat variety deployment in Sichuan. In this study, 78 Sichuan wheat cultivars (lines) were identified at seedling stage by two races CYR32 and CYR34. At adult plant stage in wheat, the mixture of the current predominant races of CYR32, CYR33, CYR34, G22-14, and G22 pathogenic groups virulent to wheat cultivar Guinong 22 were artificially inoculated to assess the resistance of the tested wheat. Nineteen resistance genes and QTLs, including QYr.nwafu-4BL, Yr5, Yr10, Yr15, Yr17, Yr18, Yr26, Yr28, Yr29, Yr30, Yr36, Yr39, Yr41, Yr48, Yr65, Yr67, Yr78, Yr80, and Yr81, were detected the presence of the resistance genes in all tested materials. The results showed that 60 (76.92%) of the 78 tested materials were resistant to CYR32, 40 (51.28%) resistant to CYR34, and 36 (46.15%) resistant to both races at seedling stage. Seventy-eight wheat materials were resistant to wheat stripe rust at adult stage, 4 out of which, including Mianmai 835, Shumai 1743, Shumai 1829, and Shumai 1868, were immune to the disease. Disease resistance identification showed that 42 (53.85%) exhibited adult plant resistance and 36 (46.15%) were all stage resistant to wheat stripe rust. Molecular detection indicated that 5, 5, 45, 2, 30, 5, 30, 39, 3, 2, 22, 8, 23, 6, and 24 carried the resistance gene QYr.nwafu-4BL, Yr15, Yr17, Yr18, Yr26, Yr28, Yr29, Yr30, Yr39, Yr41, Yr65, Yr67, Yr78, Yr80, and Yr81, respectively. Two to six resistance genes were detected in 24, 22, 11, 14, and 3 of the tested wheat materials, accounting for 94.87%. Yr5, Yr10, Yr36, and Yr48 were not detected in all wheat cultivars (lines), and only Xikemai 18, not detected any of the 19 resistance genes mentioned above, presumably, may carried other known or new resistance genes to wheat stripe rust. In summary, that resistance level of 78 wheat cultivars (lines) to wheat stripe rust was identified, and the resistance genes of these cultivars were identified. These results provide scientific basis for breeding durable resistant wheat cultivar.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Effects of irrigating at different growth stages on kernel number of spring maize in the North China Plain

GAO Zhen, LIANG Xiao-Gui, ZHANG Li, ZHAO Xue, DU Xiong, CUI Yan-Hong, ZHOU Shun-Li

Acta Agronomica Sinica. 2021, 47(7):  1324-1331.  doi:10.3724/SP.J.1006.2021.03045

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Drought stress is the main limiting factor for kernel setting of spring maize in the North China plain (NCP). It is important to investigate the effects of irrigation at different growth stages on kernel number, which contributes much to improve grain yield and water use efficiency of spring maize in the NCP. A three-year field experiment was conducted from 2014 to 2016. Irrigating at V6, V12, tasseling, 15 days after silking stage, and rain-fed treatments were set to evaluate the soil water change, ear leaf photosynthesis rate, kernel number per ear and their relationships. The results indicated that irrigating could increase kernel number in dry years, and irrigating at tasseling stage increased kernel number by 1.4%-97.0% compared with other treatments in 2015 and 2016. However, there were no significant differences among each treatment in kernel number in the rainy year of 2016. Irrigating at V6 and V12 stage increased vegetative growth of spring maize, including leaf area and biomass, whereas drought stress occurring at flowering stage still reduced kernel number. In irrigating treatment at tasseling stage, vegetative growth would be inhibited by drought, thus lowing leaf area index and biomass, but ensuring water availability during silking-pollination-kernel growth stage. Moreover, irrigating at tasseling stage increased photosynthesis rate (P_n) by 5.2%-32.8% than other treatments. Regression analysis suggested that high water availability could significantly increase P_n (P = 0.0034) and kernel number (P = 0.0137), but excess rainfall (low solar radiation) had adverse effect on kernel setting. Overall, irrigating at tasseling stage in dry years was a critical management to ensure kernel number of spring maize.

Preliminary study of the peptide aptamer R18 promotes grain filling of rice inferior spikelets

ZHANG Zhi-Xing, CHEN Hua, MIN Xiu-Mei, XU Hai-Long, SONG Guo, LIN Wen-Xiong

Acta Agronomica Sinica. 2021, 47(7):  1332-1341.  doi:10.3724/SP.J.1006.2021.02049

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14-3-3 protein plays an important role in plant growth and development. The high expression abundant of 14-3-3 isoform (GF14f) was an important reason for the poor grain-filling of rice inferior spikelets. In the present study, firstly we used molecular docking to study the most possible binding sites between GF14f protein and peptide aptamer R18. Furthermore, in vitro competitive experiment showed that the R18 could block GF14f binding to its interaction proteins, in turn, lead to a weakened interaction of GF14f with the SuS2, SS, and AGPS. Meanwhile, in vitro enzymatic assays showed that exogenous added R18 significantly increased the activity of sucrose synthase (SuSase), adenosine diphosphate-glucose pyrophosphorylase (AGPase), and starch synthase (StSase). Coimmunoprecipitation (Co-IP) experiments revealed that, in addition to GF14f, R18 could interacted with the other 14-3-3 isoforms, such as GF14b, GF14c, GF14d, and GF14e, which were further confirmed by Bimolecular Fluorescent Complimentary (BiFC) assay. These results also showed that the exogenous application (60 mg L ^-1) of R18 at grain-filling stage could significantly increase the activity of StSase, SuSase, and AGPase, resulting in the improvement of 1000-grain weight and seed-setting rate of rice inferior spikelets. In the present study, R18 had been investigated to competitively interfere with the interaction of rice 14-3-3 protein with multiple client proteins, weak the binding force, which increased the activity of sucrose conversion and starch synthesis related enzyme, resulting in the improvement of grain filling of rice inferior spikelets.

Deep learning models for estimation of paddy rice leaf nitrogen concentration based on canopy hyperspectral data

LI Jin-Min, CHEN Xiu-Qing, YANG Qi, SHI Liang-Sheng

Acta Agronomica Sinica. 2021, 47(7):  1342-1350.  doi:10.3724/SP.J.1006.2021.02060

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Rapid and nondestructive detection of crop nitrogen status is crucial to precision agriculture management. Hyperspectral remote sensing has been proposed to be a powerful tool for expediently monitoring crop nitrogen status. However, conventional regression methods and machine learning (ML) are difficult to utilize the full information of hyperspectral data, and deep neural networks (DNN) usually require a huge number of training data. Therefore, we attempt to construct deep learning models with a small amount of data and achieve accurate estimation of leaf nitrogen concentration (LNC). A two-year field experiment of paddy rice with four nitrogen levels were conducted at Jianli, Hubei province, China. A total of 216 samples containing canopy hyperspectral data and rice LNC were measured during two growing seasons. Based on the first derivative of hyperspectral data, a new deep learning model (deep forest, DF) was constructed for LNC estimation and compared with two traditional machine learning models (random forest, RF and support vector machine, SVM) and one deep neural network model (multi-layer perceptron, MLP). The results showed that, based on a small number of hyperspectral data, deep forest acquired higher accuracy than MLP. And the optimal estimation (R² = 0.919, RMSE = 0.327) was obtained by the deep forest model based on full-wave band spectrum (350-2500 nm). Between two classical machine learning models, random forest achieved better results than SVM, but both methods were unstable. In conclusion, deep forest improved the prediction accuracy and model robustness for all band situations, and alleviated the degree of overfitting by multi-grained scanning. These results can provide a deep insight to detect crop nitrogen status rapidly when confronted with limited data.

Differences in photosynthetic performance of leaves at post-flowering stage in different cultivation modes of summer maize (Zea mays L.)

LI Jing, WANG Hong-Zhang, LIU Peng, ZHANG Ji-Wang, ZHAO Bin, REN Bai-Zhao

Acta Agronomica Sinica. 2021, 47(7):  1351-1359.  doi:10.3724/SP.J.1006.2021.03051

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Photosynthesis plays an important role in crop growth and yield formation. Different cultivation patterns can significantly affect the photosynthetic performance of leaves at post-flowering stage in summer maize. In order to explore the effects of different cultivation modes on the photosynthetic performance of summer maize leaves at post-flowering stage, field experiments were carried out with Denghai 605 maize hybrid variety as experimental material from 2018 to 2019 in Tai’an, Shandong, China. With the local farmer management mode (FP) as the control, the super-high-yield cultivation mode (SH) and high-yield and high-efficiency cultivation mode (HH) by comprehensively optimizing the planting density, fertilizer planting and management mode were set in this study. Leaf area index, chlorophyll content, gas exchange parameters, rapid chlorophyll fluorescence induction kinetic curve (OJIP) were evaluated, which indicated significant differences in biomass of different cultivation modes at maturity stage. Compared with FP, the biomass of SH and HH increased by 27.77% and 7.43%, respectively, and the population biomass at post-flowering stage of HH increased significantly as well. Besides, the photosynthetic rate all declined in different cultivation modes, reaching the highest degree of decline on the 30th day at post-flowering stage (R₁+30 d). In contrast with FP, the net photosynthetic rate (P_n) of SH and HH increased at post-flowering stage stage (R₁) by 21.63% and 12.96%, respectively, and on the 30th day (R₁+30 d) at post-flowering stage by 35.37% and 12.37%, respectively, which could maintain a higher level of photosynthetic capacity. In addition, these results revealed that the differences of net photosynthetic rate among the different cultivation modes were caused by non-stomatal factors. The stomatal conductance (G_s) of SH and HH was increased at the silking stage by 18.36%, 16.66%, 26.16%, and 10.74%, respectively, and while on the 30th day at post-flowering stage intercellular carbon dioxide (C_i) declined by 12.85%, 7.34%, 14.08%, and 9.75%, respectively. Compared with FP, W_k and V_j of SH and HH significantly decreased, indicating that SH and HH apparently improved the performances of both electron donor and acceptor sides of electron transport chain in PSII reaction center, the quantum yield of electron transfer (φ_E0), the electron transfer ability as well as the reaction center activities of PSII and the coordination between PSI and PSII. In conclusion, SH and HH effectively improved the photosystems performance, increased the net photosynthetic rate, and prolonged duration of high photosynthesis rate, resulting in the increase of the population biomass and high yield.

Effects of sowing date on eating quality of indica hybrid rice in Sichuan Basin

LI Bo, ZHANG Chi, ZENG Yu-Ling, LI Qiu-Ping, REN Hong-Chao, LU Hui, YANG Fan, CEHN Hong, WANG Li, CHEN Yong, REN Wan-Jun, DENG Fei

Acta Agronomica Sinica. 2021, 47(7):  1360-1371.  doi:10.3724/SP.J.1006.2021.02053

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In order to clarify the effects of sowing date on the eating quality of indica hybrid rice, field experiments were conducted in Dayi, Nanbu, and Shehong, Sichuan province, using indica hybrid rice Yixiangyou 2115, F you 498, and Chuanyou 6203 as experimental materials. The effects of sowing dates in different locations on the appearance, taste, comprehensive score, hardness and viscosity of indica hybrid rice were investigated using the rice taste analyzer and the hardness and viscosity analyzer. The results showed as follows: (1) Location, variety, sowing date, and their interaction had significant influences on eating quality of indica hybrid rice. (2) The appearance, taste, and comprehensive score of rice were ranked as Yixiangyou 2115 > Chuanyou 6203 > F you 498 at each sowing date, while F you 498 possessed the highest hardness value, which indicated that the eating quality of Yixiangyou 2115 was obviously greater than others. The appearance, taste and comprehensive score of rice could be improved with appropriate delaying of sowing date at different locations, and then the quality of rice can be improved. (3) The correlation analysis showed that the comprehensive score was significantly and positively associated with the accumulated temperature, but negatively related to the rainfall from sowing stage to heading stage. Comprehensive score also significantly and negatively correlated to the accumulated temperature, sunshine hours from heading stage to maturity stage, as well as the rainfall during the whole growth period. (4) According to GGE model, a higher comprehensive score and stability was observed in Dayi by ten days postponing at sowing date; Whereas, 10 to 20 days delay at sowing date could improve both comprehensive score and stability in Nanbu and Shehong. In conclusion, the delayed sowing date of 10-20 days leaded to a more reasonable temperature and light condition during the grain filling stage of rice in Sichuan basin, thus contributed to the improvement in eating quality of indica hybrid rice by increasing both comprehensive score and stability.

Effects of different application methods of controlled-release nitrogen fertilizer on grain yield and nitrogen utilization of indica-japonica hybrid rice in pot-seedling mechanically transplanted

KE Jian, CHEN Ting-Ting, XU Hao-Cong, ZHU Tie-Zhong, WU Han, HE Hai-Bing, YOU Cui-Cui, ZHU De-Quan, WU Li-Quan

Acta Agronomica Sinica. 2021, 47(7):  1372-1382.  doi:10.3724/SP.J.1006.2021.02055

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To investigate the optimal application of controlled-release nitrogen fertilizer (CRNF) under the super-high-yield cultivation of indica-japonica hybrid rice in pot-seedling mechanically transplanted, the field experiments were carried out to investigate the effects of three application methods of CRNF [one-time basal application of polymer-coated urea (BC), basal application of polymer-coated urea combined with urea top-dressing at the tillering stage (BC+TU, 8:2), and basal application of polymer-coated urea combined with urea top-dressing at panicle initiation (BC+PU, 7:3)] on grain yield, nitrogen utilization (NRE), and agronomic traits of Yongyou 1540, a high-yield indica-japonica hybrid rice variety, with the pot-seedling mechanically transplanted in 2016 and 2017. Conventional high-yield fertilization of urea at 280 kg hm ^-2 (SU) and 0 N treatments were set as the controls. The cumulative release ratio of basal tiller fertilizer to panicle fertilizer for CRNF was 7:3, which was higher than that of SCU (6:4), leading to N redundancy at tillering stage and deficit during the following growth stages. Therefore, BC and BC+TU presented lower rice yields and NRE compared with SU. In comparison with BC and BC+TU, BC+PU was applied in combination with CRNF basal fertilizer reduction and urea fertilizer application at panicle initiation stage, and increased N uptake and photosynthetic capacity from panicle initiation stage to maturity stage ensured the basic N supply during the vegetative growth period in rice, leading to significantly higher spikelets per panicle, grain filling percentage, and grain yield while an equal panicles per m ² and 1000-grain weight. Meanwhile, N application rates can be well matched with rice N uptake patterns during the whole growth period. The grain yield of BC+PU was 12.2-13.1 t hm ^-2 in 2016 and 2017, which were 7.4%-9.2% and 8.0%-11.9% higher than those of BC and BC+TU, respectively. Moreover, the NRE of BC+PU were 43.8%-44.1% in 2016-2017, which were 48.5%-59.9% and 63.9%-74.5% higher than those of BC and BC+TU, respectively. In addition, compared with SU, there was not significant differences of grain yield and NRE in BC+PU, and net income was higher by 6.5%-12.3% due to the significant reduction of labor cost of N application. In conclusion, the basal application of CRNF combined with urea top-dressing at panicle initiation stage at ratios of 7:3 was the simplified fertilization method that could effectively replace conventional simplified fractional fertilization, and exhibit no significant differences in rice yield, NRE, and higher economic benefits.

RESEARCH NOTES

Effects of combined application of bio-bacterial fertilizer and inorganic fertilizer on agronomic characters, yield, and quality in quinoa

DENG Yan, WANG Juan-Ling, WANG Chuang-Yun, ZHAO Li, ZHANG Li-Guang, GUO Hong-Xia, GUO Hong-Xia, QIN Li-Xia, WANG Mei-Xia

Acta Agronomica Sinica. 2021, 47(7):  1383-1390.  doi:10.3724/SP.J.1006.2021.04171

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To explore the suitable cultivation and management model of quinoa in northern Shanxi province, and therefore improve the yield and quality of quinoa, an experiment was conducted with cultivar Huaqing 1 as plant material. The effects of varied proportion of organic and inorganic fertilizer on the growth process of quinoa, agronomic traits, yield, and quality were studied using single factor completely random design. There were three treatments including T1 (1500 kg hm ^-2 organic fertilizer, 225 kg hm ^-2 each for urea and diamine phosphate), T2 (2250 kg hm ^-2 organic fertilizer, 225 kg hm ^-2 each for urea and diamine phosphate), and T3 (3000 kg hm ^-2 organic fertilizer, 225 kg hm ^-2 each for urea and diamine phosphate), conventional fertilization (0 kg hm ^-2 organic fertilizer, 450 kg hm ^-2 each for urea and diamine phosphate) was the control. The results showed that the combined biological bacterial fertilizer and inorganic fertilizer could increase the content of organic matter, available nitrogen, phosphorus, and potassium in soil, and decrease the pH of soil. Compared with CK, the combined biological fertilizer could effectively shorten the growth period, and increase plant height, stem diameter and stem strength at mature stage, thus reduce lodging rate. Also, combined biological fertilizer treatment promoted the branches and 1000-grain weight of quinoa, and improved quinoa yield, protein content and fat content, and the above favorite effects were obviously showed in T2 treatment. Starch content was the lowest in T2 treatment, but there was no significant differences among the three treatments. With the increase application of bacterial fertilizer, nitrogen use efficiency, phosphorus fertilizer use efficiency and partial productivity of nitrogen and phosphorus fertilizer was firstly increased and then decreased. Among three groups, the above index was the highest in T2 treatment. Correlation analysis showed that the relationship between the yield and 1000-grain weight was the most correlated, and protein content in grains was positively correlated with yield, 1000-grain weight, branch number, and stem strength, but negatively correlated with lodging rate. In conclusion, under the condition of current experiment, the suitable nitrogen application rate for quinoa was the combination of urea (225 kg hm ^-2), diamine phosphate (225 kg hm ^-2) and inorganic fertilizer (2250 kg hm ^-2).

Mapping QTLs for yield-related traits using chromosome segment substitution lines of Dongxiang common wild rice (Oryza rufipogon Griff.) and Nipponbare (Oryza sativa L.)

LUO Lan, LEI Li-Xia, LIU Jin, ZHANG Rui-Hua, JIN Gui-Xiu, CUI Di, LI Mao-Mao, MA Xiao-Ding, ZHAO Zheng-Wu, HAN Long-Zhi

Acta Agronomica Sinica. 2021, 47(7):  1391-1401.  doi:10.3724/SP.J.1006.2021.02054

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In former study, we constructed a chromosome segment substitution lines (CSSLs) of Dongxiang common wild rice (Oryza rufipogon Griff.) in the background of Nipponbare (Oryza sativa L.). In this study, in order to investigate 11 yield-related traits, such as tillering number, grains per panicle and grain shapes, the CSSLs were planted in Beijing, Linyi and Nanchang. The results of quantitative trait loci (QTLs) for yield-related traits showed that a total of 68 QTLs were detected, including 4 QTLs for plant height, 5 QTLs for panicle length, 2 QTLs for tillering number, 7 QTLs for primary branch grain number, 8 QTLs for primary branch grain number, 8 QTLs for secondary branch grain number, 10 QTLs for secondary branch grain number, 6 QTLs for grains per panicle, 7 QTLs for 1000-grain weight, 8 QTLs for grain length and 3 QTLs for grain width. LOD score of the detected QTLs ranged from 2.50 to 12.66. The phenotypic variation explained by these QTLs ranged from 4.67% to 27.79%. There were 15 QTLs with a contribution rate more than 15%, 24 QTLs overlapped with the reported loci or gene position, 44 QTLs newly detected loci. In addition, 6 QTLs were stably detected at two sites, and 1 QTL (qTGW2) as a novel QTL was detected at three sites. Finally, the reliability of the three QTLs of qPH7, qPBPP8-2 and qGW10 was verified by BSA. Our results will be helpful for the subsequent cloning of yield-related trait genes and further analysis of their genetic basis and molecular regulation mechanism.

Creation of disomic addition, substitution and translocation lines of durum wheat-Thinopyrum elongatum

DUAN Ya-Mei, LUO Xian-Lei, CHEN Shi-Qiang, GAO Yong, CHEN Jian-Min, DAI Yi

Acta Agronomica Sinica. 2021, 47(7):  1402-1414.  doi:10.3724/SP.J.1006.2021.01072

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The establishment of chromosome addition, substitution and translocation lines through distant hybridization between wheat and Thinopyrum elongatum is an important approach to utilize useful genes of Th. elongatum in wheat improvement. Based on chromosome-specific molecular markers, chromosome counting, genome in situ hybridization (GISH), and non-denaturing fluorescence in situ hybridization (ND-FISH), several stable addition, substitution or translocation lines were identified from a cross between Triticum turgidum ssp. durum Langdon (AABB) and Trititrigia 8801 (AABBEE). Two 3E and 6E disomic addition lines Du-DA3E and Du-DA6E of durum wheat-Th. elongatum, a 1E (1B) disomic substitution line Du-DS1E (1B), and a 1AS-1EL disomic translocation line Du-T1AS·1EL were created in this study. The chromosome-segments of Th. elongatum could be inherited stably in these new lines, which not only increased the types of addition and substitution lines of durum wheat-Th. elongatum, but also provided special germplasm resources for the follow-up use of excellent genes of Th. elongatum in wheat improvement.