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Table of Content

    12 May 2022, Volume 48 Issue 5
    • REVIEWS
      Contents and compositions of amino acids in rice grains and their regulation: a review
      YANG Jian-Chang, LI Chao-Qing, JIANG Yi
      Acta Agronomica Sinica. 2022, 48(5):  1037-1050.  doi:10.3724/SP.J.1006.2022.12062
      Abstract ( 377 )   HTML ( 51 )   PDF (658KB) ( 343 )   Save
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      Amino acids in cereal grains are important nutrients for both human and animals. Increasing the content of amino acids in the rice grain, especially lysine and other essential amino acids, plays a very important role in improving the nutritional standard of people in the countries with rice as staple food. This paper reviewed some research progresses in the contents and compositions of amino acids in the mature grain of rice and their distribution in the different parts of a grain, the synthesis and metabolism of amino acids in the grain, the role of plant hormones in regulating the synthesis and metabolism of on amino acids, and the effects of environmental factors and cultivation practices on the contents and compositions of amino acids in the grain, and discussed the existing problems and key points for future research. It merits further investigating the temporal (at different filling stages) and spatial (at different parts of a grain) distribution characteristics of the contents and compositions of amino acids in a grain during the filling, their physiological and biochemical mechanism, and cultivation regulation and its principle. Such a study is expected to gain new insight into the mechanism in the formation and distributions of amino acids in a rice grain, and explore a new way to increase the contents of amino acids, especially essential amino acids such as lysine, in milled rice.

      Mechanism and technology of stand establishment improvements through regulating the apical hook formation and hypocotyl growth during seed germination and emergence in cotton
      ZHOU Jing-Yuan, KONG Xiang-Qiang, ZHANG Yan-Jun, LI Xue-Yuan, ZHANG Dong-Mei, DONG He-Zhong
      Acta Agronomica Sinica. 2022, 48(5):  1051-1058.  doi:10.3724/SP.J.1006.2022.14116
      Abstract ( 173 )   HTML ( 20 )   PDF (839KB) ( 119 )   Save
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      Realizing full and strong stand establishment of seedlings is the basis for achieving high yields and bump harvests in cotton. However, cotton is a dicotyledonous plant whose cotyledons are successfully all unearthed for standing. Seedling emergence is susceptible to environmental conditions and seeding techniques. Therefore, it is generally more difficult for cotton to get full and strong stand establishment than other major crops. The apical hook formation and the hypocotyl growth at seed germination and emergence stages play key roles in seedling emergence and stand establishment. Here we systemically reviewed the regulation mechanism of cotton seedling growth for the first time and put forward the key agronomic cultivation techniques to promote cotton seedling growth, focusing on the physiological and molecular mechanism of hook formation and hypocotyl growth and their influencing factors. Precision monoseeding can improve timely and moderate expression of the key genes HLS1 and COP1 related to hypocotyl elongation and hook formation, which assures better stand establishment by timely formation and expansion of the hooks and timely shedding of seed shells. The hypocotyl can grow steadily and form strong seedings by regulating the expression of key genes HY5 and ARF2 related to hypocotyl growth under precision monoseeding. In this paper, the key cultivation techniques of cotton precision monoseedling, combined with fine soil preparation, improving seed quality, plastic mulching, and drip irrigation under mulching were summarized and reviewed. This review provides important reference and guidance for the improvement and development of cotton sowing and cultivation technology in cotton.

      CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS
      Development of genetically modified maize (Zea mays L.) NK603 matrix reference materials
      SHAN Lu-Ying, LI Jun, LI Liang, ZHANG Li, WANG Hao-Qian, GAO Jia-Qi, WU Gang, WU Yu-Hua, ZHANG Xiu-Jie
      Acta Agronomica Sinica. 2022, 48(5):  1059-1070.  doi:10.3724/SP.J.1006.2022.13025
      Abstract ( 146 )   HTML ( 17 )   PDF (1543KB) ( 143 )   Save
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      The implementation of genetically modified organisms (GMO) safety management and labeling system requires standardized testing methods and reference materials (RMs). Furthermore, the RMs are the guarantee of obtaining accurate, reliable and comparable testing results. At present, genetically modified (GM) maize (Zea mays L.) NK603 has been approved to be imported as processing raw material in China, and its safety supervision urgently needs to prepare RMs. In this study, the heterozygous seeds of GM maize NK603 and the non-GM maize counterpart after identification were well milled and then gravimetrically mixed to prepare three levels of powder RMs according to the mass fractions of 60.0, 100.0, and 1000 mg g-1. The homogeneity and stability test by duplex ddPCR method showed that the RMs of GM maize NK603 were homogenous and stable for not less than six months. The property values were collaboratively characterized by eight laboratories using duplex ddPCR method. The certified values together with their expanded uncertainties were (2.75±0.26)%, (4.68±0.39)%, and (51.8±3.7)%, respectively. The minimum sample intake was determined to be 100 mg. This batch of RMs can be used for the qualitative and quantitative detection of NK603 event in food and feed, as well as for the evaluation of GM maize NK603-specific assays and laboratory quality control.

      Analysis of blast resistance genes in Longliangyou and Jingliangyou hybrid rice varieties
      DENG Zhao, JIANG Nan, FU Chen-Jian, YAN Tian-Zhe, FU Xing-Xue, HU Xiao-Chun, QIN Peng, LIU Shan-Shan, WANG Kai, YANG Yuan-Zhu
      Acta Agronomica Sinica. 2022, 48(5):  1071-1080.  doi:10.3724/SP.J.1006.2022.12002
      Abstract ( 217 )   HTML ( 19 )   PDF (1601KB) ( 150 )   Save
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      Longke 638S and Jing 4155S, developed by Yuan Longping High-Tech Agriculture Co., Ltd. in 2014, were two thermo-sensitive genic male sterile (TGMS) lines with disease resistance, high grain quality and combining ability for producing mid-season indica hybrid rice. In this study, we analyzed the blast resistance evaluation data from the regional trials of the Longliangyou and Jingliangyou hybrid rice varieties approved by the state from 2015 to 2019. Meanwhile, to provide theoretical basis for distribution and further improvement of these hybrid rice varieties, a genotyping panel containing 16 rice blast resistance (R) genes based on KASP (Kompetitive Allele-Specific PCR) technology was developed and used for molecular detection of these hybrid rice varieties. The results showed that 43.92% of Longliangyou and Jingliangyou hybrid rice varieties conferred moderate resistance to high resistance to blast disease. The mean value of integrated disease index (IDI) and highest scale of panicle blast severity (HSPBS) was 3.3 and 4.7, respectively. These hybrid rice varieties carried different number of R genes, ranging from 3 to 7. The average number of R genes in each variety was 5.1. The distribution frequency of the five genes including Pia, Pita, Pi2, Pi5, and Piz were higher by more 50%, among which, it was 100% for Pia gene. In contrast, Pi9, Pi35, Pi36, and Pb1 genes were not detected in Longliangyou and Jingliangyou hybrid rice varieties. With the increase of the number of R genes in the varieties, the mean values of IDI and HSPBS were generally decreased. In conclusion, we suggested that introduction of Pi9 into Longke 638S and Jing 4155s might lead to the further improvement of blast resistance of Longliangyou and Jingliangyou hybrid rice varieties.

      Root system architecture analysis and genome-wide association study of root system architecture related traits in cotton
      SUN Si-Min, HAN Bei, CHEN Lin, SUN Wei-Nan, ZHANG Xian-Long, YANG Xi-Yan
      Acta Agronomica Sinica. 2022, 48(5):  1081-1090.  doi:10.3724/SP.J.1006.2022.14067
      Abstract ( 198 )   HTML ( 29 )   PDF (4931KB) ( 258 )   Save
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      Root is the main organ of plants that absorbs water and nutrients. The growth of the root system will directly affect the absorption and utilization of nutrients, the resistance to abiotic stress and finally the yield of cotton. In this study, a natural population of 220 upland cotton accessions and a chromosomal segment substitution line (CSSL) population with 325 lines, derived from the crossing and backcrossing of Gossypium barbadense acc. 3-79 with G. hirsutum cv. ‘Emian 22’ were selected to collect the major root phenotypic traits. Four major traits, namely main root length (MRL), root fresh weight (RFW), root dry weight (RDW) and lateral root angle (LRA) were investigated, and genome-wide association analysis (GWAS) was performed for four root traits in natural populations in combination with genome resequencing. The results showed that the four root traits of the natural population are all in line with normal distribution, and the CSSL population were all in skewed distribution. The mean value of root index of CSSL population was higher than that of natural population. A total of 2,714,140 SNP was obtained from the resequencing data of the natural population. The principal component analysis (PCA) showed that the RFW and MRL could be used as two indexes for cotton root classification, through which the cotton root could be divided into nine types in each population. The analysis of population structure demonstrated that the natural population can be divided into five subgroups. Genome-wide association analysis rrevealed that two association sites were simultaneously associated by RFW and RDW in natural populations. The results of this study provide a theoretical basis for further research on root system architecture (RSA) and its genetic mechanism, and it is also of great significance to cotton breeding of abiotic stress resistance.

      Construction of a high density genetic map between cultivated and semi-wild soybeans and identification of QTLs for plant height
      YU Chun-Miao, ZHANG Yong, WANG Hao-Rang, YANG Xing-Yong, DONG Quan-Zhong, XUE Hong, ZHANG Ming-Ming, LI Wei-Wei, WANG Lei, HU Kai-Feng, GU Yong-Zhe, QIU Li-Juan
      Acta Agronomica Sinica. 2022, 48(5):  1091-1102.  doi:10.3724/SP.J.1006.2022.14063
      Abstract ( 152 )   HTML ( 16 )   PDF (3016KB) ( 80 )   Save
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      In this study, 252 plants and their parents of Fengshou 24 × Tongjiao 83-611 were genotyped by SNP160K DNA-chip. A high-density genetic linkage map with a total length of 3661.46 cM was constructed, composing of 5861 SNP markers. Seven QTLs of plant height were detected by inclusive composite interval mapping (ICIM), and each one explained 2.56%-10.41% of the variation in plant height. qPH-6-1 had the highest contribution rate of phenotypic variation and dominant effect, explaining 10.41% of plant height variation, and the additive and dominant effects are -1.72 and 18.94, respectively. The contribution rate of qPH-18-1 was the second, explaining 9.64% of plant height variation, but qPH-18-1 has the highest additive effect, reaching -12.42. 11 plants with qPH-6-1 and qPH-18-1 genotypes Q6Q6/Q18Q18 were screened in F2 population with an average plant height of 167.00 cm, and 16 plants with 2-locus genotypes q6q6/q18q18 were screened out with an average plant height of 91.25 cm. The addition of 23 SNP markers inside and outside the qPH-18-1 locus interval narrowed the locus interval from 766.97 kb to 66.03 kb, containing eight genes. Combined with gene annotation and relative expression difference analysis, it was hypothesized that Glyma.18G279800 and Glyma.18G280200 might be associated with plant height of soybean. This study provides a molecular reference base and genetic basis for the improvement of soybean plant architecture.

      Transcriptome analysis of leaves responses to elevated CO2 concentration, drought and interaction conditions in soybean [Glycine max (Linn.) Merr.]
      LI A-Li, FENG Ya-Nan, LI Ping, ZHANG Dong-Sheng, ZONG Yu-Zheng, LIN Wen, HAO Xing-Yu
      Acta Agronomica Sinica. 2022, 48(5):  1103-1118.  doi:10.3724/SP.J.1006.2022.14055
      Abstract ( 247 )   HTML ( 17 )   PDF (6292KB) ( 174 )   Save
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      Global consensus on climate warming and elevated atmospheric CO2 concentrations has increased the frequency and intensity of extreme weather events (droughts) and brought uncertainty about soybean production. In this study, the effects of elevated CO2 concentration, drought and their interaction on gene expression in soybean were elucidated by phenotypic and leaf transcriptome sequencing (RNA-seq) analysis. To provide theoretical reference for soybean breeding under the background of future climate change, we identified the regulatory pathway of CO2 affecting soybean drought tolerance. The phenotypic results showed that elevated CO2 concentration promoted the growth and alleviated the negative effects of drought stress on soybean. The results revealed that a total of 89 CO2-responsive genes were identified by transcriptome sequencing analysis. KEGG classification demonstrated that these genes were mainly involved in antioxidant metabolism (terpenoid, flavonoid, etc.), meanwhile, Functional of the specific differentially expressed gene mainly focused on cell components, growth, and development. Under drought condition, 1006 highly differentially expressed (16-fold) genes were screened out. These genes were mainly involved in various amino acid (proline, tryptophan, etc.) metabolic pathways, and almost all genes involved in protein synthesis and transport were up-regulated, indicating that there were a lot of material exchange processes in soybean leaves under drought stress. A total of 8566 differentially expressed genes, mainly involved in carbohydrate metabolism pathway, were detected under the interaction, and almost all genes related to the photosynthesis-antenna protein pathway were down-regulated, suggesting that the photosynthetic capacity of soybean was decreased under the interaction. 34 genes were found to be differentially expressed under all three conditions. These genes were mainly concentrated in antioxidant metabolism (flavonoids, glutathione, phenylpropanoids, etc.), and most of these genes were involved in the metabolism of various plant hormones and stimulus responses. The qRT-PCR results of six differentially expressed genes related to drought resistance in two soybean varieties with different genetic background showed that the RNA-seq data were accurate. In conclusion, elevated CO2 concentration could increase the relative expression levels of genes related to antioxidant metabolism, growth and development in soybean leaves. Drought stress induced the relative expression levels of genes related to amino acid metabolism and protein synthesis pathway. The photosynthetic capacity of soybean was inhibited under the interactive condition. Elevated CO2 concentration enhanced the tolerance of soybean to drought stress by regulating hormone metabolism, antioxidant (antioxidant enzyme, flavonoid, phenylpropanoid) metabolism and carbohydrate metabolism.

      Functional studies of rice blast resistance related gene OsSAMS1
      YANG De-Wei, WANG Xun, ZHENG Xing-Xing, XIANG Xin-Quan, CUI Hai-Tao, LI Sheng-Ping, TANG Ding-Zhong
      Acta Agronomica Sinica. 2022, 48(5):  1119-1128.  doi:10.3724/SP.J.1006.2022.12022
      Abstract ( 176 )   HTML ( 21 )   PDF (6096KB) ( 126 )   Save
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      Rice blast is one of the most devastating diseases in rice, which causes great economic losses to agricultural production. It has been reported that S-Adenosyl-l-Mmethionine Synthetase 1 (OsSAMS1) is involved in the process of senescence in rice. Transcriptome sequencing analysis showed that the relative expression level of OsSAMS1 was significantly increased after inoculation with Magnaporthe oryzae (M. oryzae). However, it remains unclear whether OsSAMS1 is involved in rice immunity. To verify this, we constructed the knock-out mutants of OsSAMS1 in the wild type variety ZH11. The results showed that OsSAMS1 was mainly expressed in rice leaves, and its expression was significantly induced by M. oryzae inoculation. Subcellular localization revealed that OsSAMS1 was distributed in the plasma membrane, cytoplasm, and nucleus. Compared to the wild type, the two knockout mutants, ossams1-1 and ossams1-2, displayed enhanced susceptibility upon M. oryzae infection, and the expression of pathogenesis-related (PR) genes was significantly inhibited. In addition, ethylene synthesis-related genes were also dramatically decreased in both two mutants. These results suggested that OsSAMS1 was involved in rice immune response and positively regulated rice blast resistance, which lays a foundation for further revealing the molecular mechanism of OsSAMS1 in plant immunity and provides genetic resources for rice breeding of blast resistance.

      Rice transcription factor WRKY68 plays a positive role in Xa21-mediated resistance to Xanthomonas oryzae pv. oryzae
      ZHU Zheng, WANG Tian-Xing-Zi, CHEN Yue, LIU Yu-Qing, YAN Gao-Wei, XU Shan, MA Jin-Jiao, DOU Shi-Juan, LI Li-Yun, LIU Guo-Zhen
      Acta Agronomica Sinica. 2022, 48(5):  1129-1140.  doi:10.3724/SP.J.1006.2022.12010
      Abstract ( 133 )   HTML ( 16 )   PDF (3133KB) ( 88 )   Save
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      Leaf blight is a bacterial disease of rice which leads to heavy yield losses. Xa21 which harbors broad spectrum resistance to leaf blight is the first resistant gene cloned in rice and is widely used in rice breeding program. The identification of transcription factor involved in Xa21-mediated resistance to bacterial leaf blight is of great significance. In this study, transgenic WRKY68-RNAi lines with reduced expression level of WRKY68 protein in the background of Xa21 were generated. The WRKY68-RNAi transgenic lines showed reduced resistance to Xanthomonas oryzae pv. oryzae (Xoo), indicating that WRKY68 played a positive role in Xa21-mediated resistance in rice. No detectable changes of WRKY68 protein abundance in leaves at different stages and positions after inoculation were identified by Western blot, indicating that the expression of WRKY68 protein were independent of Xa21 and Xoo, and thus WRKY68 gene may function as a transcription factor to regulate downstream genes. It was further found that the abundance of a number of pathogenesis-related proteins, including PR1A, PR5, PR10A, PR-pha, and PAL1 were dramatically changed in WRKY68-RNAi transgenic lines when inoculated with Xoo, suggested that these pathogenesis-related proteins were regulated by WRKY68 and the corresponding genes were involved in the downstream defenses responses.

      QTL mapping for plant architecture in rice based on chromosome segment substitution lines
      WANG Xiao-Lei, LI Wei-Xing, OU-YANG Lin-Juan, XU Jie, CHEN Xiao-Rong, BIAN Jian-Min, HU Li-Fang, PENG Xiao-Song, HE Xiao-Peng, FU Jun-Ru, ZHOU Da-Hu, HE Hao-Hua, SUN Xiao-Tang, ZHU Chang-Lan
      Acta Agronomica Sinica. 2022, 48(5):  1141-1151.  doi:10.3724/SP.J.1006.2022.12024
      Abstract ( 144 )   HTML ( 7 )   PDF (1367KB) ( 95 )   Save
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      Plant architecture is a compound trait integrated with multiple morphological and physiological traits, and it is closely related to rice yield. Deciphering excellent plant architecture alleles or QTLs is of great significance for high-yield rice breeding. In this study, we constructed a set of Changhui 121/Koshihikari chromosome segment substitution lines (CSSLs) with the size of 208 in our laboratory. QTLs controlling plant height, flag leaf morphology, and tiller numbers were detected under three environments. A total of 35 QTLs for rice architecture were identified on 11 chromosomes except chromosome 9, and the range of the phenotypic variation explaining was 2.00%-22.86%. It was worth noting that qPH-1-1, qFLW-6, and qFLA-3 could be detected in three environments, among which qFLW-6 was a newly identified QTL of the flag leaf width. Phenotypic identification verified that the additive effects and environmental stability of the two locus alleles by the replacement lines carrying qPH-1-1 and sites. The results of this study laid the foundation for further fine mapping and cloning of QTLs for rice plant architecture and the molecular marker-assisted selection (MAS) in rice breeding.

      Codon usage bias analysis of S-locus genes SRK, SLG, and SP11/SCR in Brassica oleracea
      ZHANG Yi-Zhong, ZENG Wen-Yi, DENG Lin-Qiong, ZHANG He-Cui, LIU Qian-Ying, ZUO Tong-Hong, XIE Qin-Qin, HU Deng-Ke, YUAN Chong-Mo, LIAN Xiao-Ping, ZHU Li-Quan
      Acta Agronomica Sinica. 2022, 48(5):  1152-1168.  doi:10.3724/SP.J.1006.2022.14003
      Abstract ( 84 )   HTML ( 9 )   PDF (738KB) ( 59 )   Save
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      S-locus is the key locus in Brassica that controls the recognition and initiation of the self-incompatibility response. To clarify the codon usage characteristics of the S domain of S-locus genes SRK and SLG as well as of SP11/SCR coding sequence in Brassica oleracea, the codon usage bias of 41, 36, and 11 alleles of SRK, SLG, and SP11/SCR were analyzed by Codon W, SPSS, Python, and EMBOSS online tools, respectively. Neutrality, ENC-GC3, and Parity Rule 2 (PR2) plotting together with multivariate statistical analysis were also used for the exploration of possible factors that might affect the formation of the codon usage bias of these genes. The cluster analysis performed using various methods showed that S domains of SRK, SLG, and SP11/SCR genes of Brassica oleracea were rich in AT base pairs, the codon preference ended with A/T base and had a lower codon usage bias, which were affected by the natural selection (a main factor) and the mutational pressure (a secondary factor) as well as dinucleotide abundance. Based on the RSCU values, 4 over-expressed codons of SRK and SLG, and 11 over-expressed codons of SP11/SCR were identified. Cluster analysis based on RSCU could accurately reflect the relationship among SRK, SLG, and SP11/SCR alleles in Brassica oleracea, which was consistent and reliable with CDS sequence clustering. According to codon usage bias and cluster relationship, the S domain of SRK and the SP11/SCR coding sequence might be coevolutionary in the codon usage bias. This study enhances our understanding of the mechanism of distribution of codons and the evolution of SRK, SLG, and SP11/SCR genes in Brasscia oleracea.

      Regulation of flavonoid synthesis by BjA09.TT8 and BjB08.TT8 genes in Brassica juncea
      HUANG Wei, GAO Guo-Ying, WU Jin-Feng, LIU Li-Li, ZHANG Da-Wei, ZHOU Ding-Gang, CHENG Hong-Tao, ZHANG Kai-Xuan, ZHOU Mei-Liang, LI Mei, YAN Ming-Li
      Acta Agronomica Sinica. 2022, 48(5):  1169-1180.  doi:10.3724/SP.J.1006.2022.14058
      Abstract ( 126 )   HTML ( 9 )   PDF (8553KB) ( 76 )   Save
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      bHLH transcription factors TT8 can effectively regulate the biosynthesis of plant flavonoids. In this study, two copies of TT8 were obtained in Brassica juncea by homologous cloning method, and named BjA09.TT8 and BjB08.TT8, which encoded 521 and 517 amino acids, respectively. Interestedly, qRT-PCR showed that the relative expression levels of the two copies in leaves were significantly higher than those in stems and roots, both responded to jasmonic acid (JA) signal, and the relative expression levels of Bju.TT8 reached maximum after 50 µmol L-1methyl jasmonate treatment for 0.5 hour. Furthermore, we found that both Bj.TT8 can increase the contents of total flavonoids in hairy roots of purple leaf mustard and green leaf mustard cultiver Sichuan Yellow Seed by hairy root system overexpression assay. It promoted the expression of flavonoid synthesis Bj.CHS, indicating they acted as redundant function. Over expression of BjA09.TT8 and BjB08.TT8 of wild-type Arabidopsis and Arabidopsis tt8 mutant revealed that the leaf colour of overexpressed Arabidopsis plant turned purple. Moreover, the contents of total flavonoid and proanthocyanidins increased significantly. In summary, BjA09.TT8 and BjB08.TT8 genes could promote the synthesis of flavonoids in Brassica juncea, which provided a reference for further analysis of the regulatory mechanism of proanthocyanidin synthesis in Brassica.

      Isolation and expression of a new gene HvMEL1 AGO in Tibetan hulless barley under leaf stripe stress
      YAO Xiao-Hua, WANG Yue, YAO You-Hua, AN Li-Kun, WANG Yan, WU Kun-Lun
      Acta Agronomica Sinica. 2022, 48(5):  1181-1190.  doi:10.3724/SP.J.1006.2022.11042
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      To explore AGO genes related to leaf stripe in Tibetan hulless barley (BLS), we obtained a differentially expressed HvMEL1 AGO gene from the transcriptional sequencing in normal and diseased leaves from resistant Tibetan hulless barley variety Kunlun 14 and the susceptible variety 1141. The HvMEL1 AGO gene was 3462 bp in length, of which the CDS (coding domain sequence) was 100% consistent in Kunlun 14 and 1141 varieties. The length of HvMEL1 AGO gene was 3161 bp without intron, contained a 3129 bp open reading frame, encoded 1043 amino acids, had a theoretical isoelectric point of 9.33, and has a predicted molecular weight of 115,865.58 Da. Protein sequence analysis showed that HvMEL1 AGO was a hydrophilic unstable acidic protein with highly conserved structural domains of DUF1785, PAZ and PIWI, belonging to AGO gene family. Phylogenetic tree analysis showed that HvMEL1 AGO belonged to the AGO1 class in Arabidopsis AGO family phylogenetic tree with HvAGO12, HvAGO18, HvAGO1D and HvAGO1B in barley AGO family, and were closely related to HvAGO12. The predicted protein interactions showed that the known proteins that acted closely with MEL1 in rice were the DCL classes, DCL1, DCL2A, DCL3A, DCL3B and DCL4, respectively. Semi-quantitative and quantitative PCR results indicated that the relative expression levels of HvMEL1 AGO gene were significantly down-regulated in 1141 and Kunlun 14 under BLS. We hypothesized that HvMEL1 AGO gene played an important role in the streak resistance mechanism of barley. This study lays the foundation for exploring the role and regulatory mechanism of HvMEL1 AGO in the process of BLS resistance.

      Effects of drought hardening on contemporary expression of drought stress memory genes and DNA methylation in promoter of B73 inbred progeny
      WANG Xia, YIN Xiao-Yu, Yu Xiao-Ming, LIU Xiao-Dan
      Acta Agronomica Sinica. 2022, 48(5):  1191-1198.  doi:10.3724/SP.J.1006.2022.13027
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      Plants may remember the existing stresses, and this memory can be passed down across generations. To study the effects of drought hardening in G0 generation on the contemporary drought stress memory genes’ expression and DNA methylation in promoter region in G1 generation, 20% PEG-6000 was used to simulate drought condition, qRT-PCR was used to analyze the expression level changes of six genes with drought-stressed memory function in maize and Arabidopsis. The changes of DNA methylation rates in the promoter regions of the most differentially expressed gene was analyzed by bisulfite sequencing technology. The results showed that the expression of six genes were up-regulated under drought stress in a +/+ mode, and the expression level of G1 generation was significantly higher than that of G0 generation. Drought stress reduced the DNA methylation’ level in the promoter region of GRMZM2G088396 gene. The reduction of methylation in the detection region 1 of two generations was mainly caused by the reduction of CHG and CHH methylation level, the decrease of methylation in the detection region 2 was mainly caused by the decrease of CG and CHH methylation level. The total cytosine methylation rate of G1 generation was significantly lower than that of G0 generation, suggesting that drought exercise in G0 generation resulted in heritable variation of DNA methylation in the promoter region of GRMZM2G088396 gene in G1 generation, which may be directly involved in the expression of GRMZM2G088396 gene.

      TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY
      Effects of reduced nitrogen application on soil aeration and root nodule growth of relay strip intercropping soybean
      PENG Xi-Hong, CHEN Ping, DU Qing, YANG Xue-Li, REN Jun-Bo, ZHENG Ben-Chuan, LUO Kai, XIE Chen, LEI Lu, YONG Tai-Wen, YANG Wen-Yu
      Acta Agronomica Sinica. 2022, 48(5):  1199-1209.  doi:10.3724/SP.J.1006.2022.14069
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      To study the effects of planting system and nitrogen application rate on soybean soil aeration environment and nodulation and nitrogen fixation, we adopted a two-factor split area experiment design, with the main area of planting pattern [soybean monoculture (SS), maize/soybean relay strip intercropping (MS)], and the sub-regions of different nitrogen application rates [no nitrogen application (NN: 0 kg hm-2), reduced nitrogen application (RN: 45 kg hm-2), and constant nitrogen application (CN: 60 kg hm-2)]. The dynamic changes of soil O2 content and soil respiration rate during soybean growth period was monitored, the differences of soil water-stable aggregates, bulk density, and porosity of each treatment were analyzed, and the variation characteristics of nodulation amount and nitrogen fixation capacity during soybean growth period were discussed. Two years’ data showed that, compared with monoculture soybean, relay strip intercropping soybeans increased soil O2 content, the percentage of aggregates with a particle size > 2 mm, significantly increased soil porosity and soil respiration rate during the late growth period in soybean; reduced the percentage of aggregates with a particle size of < 1 mm and soil porosity. There was no significant difference in the dry weight of nodules at R5 stage, but the number of nodules was significantly increased by 39.9%. Nitrogenase activity and nitrogen fixation potential were also significantly higher than those of monocrops. Among the various nitrogen application rates, the soil O2 content, the percentage content of 0.25-1.00 mm particle size, and the soil respiration rate of relay strip intercropping soybean were the highest in RN treatment. Nitrogen application decreased the percentage content of water-stable aggregates with particle size < 0.25 mm and soil bulk density; nitrogen application significantly inhibited the nodulation amount, nitrogenase activity and nitrogen fixation potential of monoculture soybean in the early stage, but the inhibitory effect of nitrogen fertilizer was alleviated at R5 stage. Reduced nitrogen application increased nodulation at the late stage of relay strip intercropping soybean, and it could significantly enhance the nitrogenase activity and nitrogen fixation potential of soybeans during the growth period. Relay strip intercropping soybean combined with reduced nitrogen application promoted the formation of large aggregates, increased soil porosity, improved soybean soil aeration environment, maintained higher soil O2 content, promoted soil respiration, and facilitated the nodulation and nitrogen fixation of soybean at later stages.

      Effects of soaking seeds with MT and EBR on germination and seedling growth in buckwheat under salt stress
      LEI Xin-Hui, WAN Chen-Xi, TAO Jin-Cai, LENG Jia-Jun, WU Yi-Xin, WANG Jia-Le, WANG Peng-Ke, YANG Qing-Hua, FENG Bai-Li, GAO Jin-Feng
      Acta Agronomica Sinica. 2022, 48(5):  1210-1221.  doi:10.3724/SP.J.1006.2022.11040
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      Soil salinization is an important limiting factor affecting seed germination, emergence, and growth of crop seeds. It is of great significance to explore the relieving effect of exogenous hormones on buckwheat seed germination and seedling growth under salt stress. This experiment was conducted to study the effects of melatonin (MT) and 2,4-epbrassinolide (EBR) on seed germination, seedling growth, antioxidant enzyme activity, and osmotic regulation substances of buckwheat varieties Xinong 9976 under different salt concentration stress using petri dish germination and pot germination. The results showed that salt stress increased the malondialdehyde (MDA) content, soluble sugar content, and antioxidant enzyme (SOD, POD, CAT) activities of buckwheat seeds and seedling leaves, decreased the germination potential, germination rate, and seedling rate of buckwheat seeds, and significantly decreased the germ length, radicle length, and seedling height of buckwheat seeds. MT and EBR soaking buckwheat seeds could effectively alleviate the harm of salt stress. Compared with the control, the germination potential, germination rate, and seedling formation rate of buckwheat seeds were increased by 14.9%-33.3%, 11.5%-27.3%, and 20.0%-46.2%, respectively. It significantly increased the radicle length, embryo length, embryo fresh weight, dry weight, seedling height, seedling fresh weight, and dry weight of buckwheat seeds, and significantly increased the soluble sugar content and the activities of SOD, POD, and CAT in buckwheat seeds and seedling leaves, and decreased MDA content. In conclusion, MT and EBR soaking can promote the germination and seedling growth of buckwheat seeds under salt stress, and improve the salt resistance of buckwheat by improving the protective enzyme activity of buckwheat seeds, reducing the accumulation of reactive oxygen species, and increasing the content of osmotic regulation substances.

      Characteristics of endophytic bacterial community structure in roots of sugarcane under different fertilizer applications
      XIAO Jian, CHEN Si-Yu, SUN Yan, YANG Shang-Dong, TAN Hong-Wei
      Acta Agronomica Sinica. 2022, 48(5):  1222-1234.  doi:10.3724/SP.J.1006.2022.14060
      Abstract ( 159 )   HTML ( 9 )   PDF (673KB) ( 116 )   Save
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      To explore the beneficial endophytic bacteria in sugarcanes and their functions, we analyzed the characteristics of endophytic bacterial community structure in roots of sugarcane under different fertilizer applications. At the phylum level, the proportion of Actinobacteria in roots of sugarcanes under different fertilization levels were lower than that in the control. However, the proportion of Chloroflexi in roots of sugarcanes under different fertilization levels applications were higher than that in CK. At the genus level, Haliangium, Acidicapsa, unclassified_f__Ktedonobacteraceae, and unclassified_f__Acidobacteriaceae_ Subgroup_1 were the specific dominant endophytic bacterial genera in root of sugarcanes under conventional fertilization level (3000 kg hm-2, H treatment); while Sphingomonas was the specific dominant endophytic bacterial genus in roots of sugarcanes under fertilization level (1500 kg hm-2, M treatment); Mesorhizobium, norank_f__BIrii41, Glycomyces, norank_f__67-14, Reyranella, unclassified_f__Steroidobacteraceae, unclassified_f__Xanthobacteraceae, norank_f__Roseiflexaceae, and Dongia were the specific dominant endophytic bacterial genus in roots of sugarcanes under the fertilization level (300 kg hm-2, L treatment). On the contrary, Caulobacter, Pseudonocardia, Nocardia, Kitasatospora, norank_f__norank_o__norank_c__Actinobacteria, Oceanibaculum, and Amycolatopsis were the unique dominant endophytic bacterial genera in root of sugarcane without fertilization application (control). And Actinospica, Catenulispora, Acidothermus, Dyella, and norank_f__Xanthobacteraceae were lost in root of sugarcanes under low nitrogen applications. Gene function prediction also revealed that, compared to no-fertilization treatment, both the endophytic bacterial community structure and the metabolic functions of endophytic bacteria in roots of sugarcanes were affected by different fertilizer applications. However, the structures of endophytic bacterial community in roots of sugarcane were significant differences among different fertilization treatments depending on the amounts of fertilizer applications. Compared to conventional fertilization, the yields of sugarcanes, and the structure, metabolic function of endophytic bacteria in roots of sugarcanes were not significantly changed by fertilizer application under 1500 kg hm-2 treatment. In conclusion, the conventional fertilization at the present stage can be substituted by reducing fertilizer application from 3000 kg hm-2 to 1500 kg hm-2 level in sugarcane.

      Effects of cotton stubble return and subsoiling on dry matter accumulation, nutrient uptake, and yield of cotton in coastal saline-alkali soil
      YAN Xiao-Yu, GUO Wen-Jun, QIN Du-Lin, WANG Shuang-Lei, NIE Jun-Jun, ZHAO Na, QI Jie, SONG Xian-Liang, MAO Li-Li, SUN Xue-Zhen
      Acta Agronomica Sinica. 2022, 48(5):  1235-1247.  doi:10.3724/SP.J.1006.2022.14064
      Abstract ( 148 )   HTML ( 13 )   PDF (541KB) ( 105 )   Save
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      To study the effects of cotton straw returning and deep loosening on cotton yield, salt content in 0-40 cm soil layer, dry matter accumulation dynamics, nitrogen (N), phosphorus (P), and potassium (K) accumulation, and distribution characteristics, four treatments including conventional tillage (CT), subsoiling tillage (ST), cotton stubble return (SR), and cotton stubble return + subsoiling tillage (SRT) were conducted using Lumianyan 36 as experimental material. The results showed that cotton stubble return increased cotton yield across two years. Lint yield of SR was 33.9% higher than CT, and SRT 32.1% higher than SR. Subsoiling increased cotton yield in 2017 and had no effect on it in 2018. Cotton stubble return reduced the salt content of 0-40 cm soil layer. The salt content of SR was 22.4% lower than that of CT, and the soil salt content of SRT was 20.7% lower than that of ST at the late growth stage in cotton. However, the effect of subsoiling on the salt content of 20-40 cm soil layer was inconsistent during the two-year experiment. The soil salt content of ST was 16.5% lower than of CT at late growth stage in 2017, but subsoiling had no effect on soil salt content in 2018. The accumulation dynamic of dry matter and N, P, K in cotton were consistent with the Logistic growth curve. Cotton stubble return increased maximal accumulation of dry matter and N, P, K in two years. The maximum accumulation of dry matter, N, P, and K in SR was 35.5%, 38.3%, 53.4%, and 55.0% higher than that in CT, and the accumulation of SRT was 27.0%, 30.7%, 21.2%, and 42.4% higher than that in ST. Compared with CT, the dry matter, N, P, and K accumulation of ST increased by 17.8%, 22.2%, 51.3%, and 40.6% in 2017, respectively, but had no effect in 2018. The dynamic of dry matter and nutrient accumulation were mainly affected by the maximum accumulation rate and rapid accumulation duration. Stubble return increased the amount and proportion of dry matter and N, P, K allocated to reproductive organs of cotton in the two-year experiment. Compared with CT, ST increased the allocation amount of dry matter and N, P, K to reproductive organs in 2017, but had no effect in 2018. In summary, the results revealed that cotton stubble return (SR) or cotton stubble return + subsoiling tillage (SRT) could be recommended tillage measures for soil improvement and high cotton yield in coastal saline-alkali cotton area.

      Estimation and evaluation of paddy rice canopy characteristics based on images from UAV and ground camera
      WANG Ze, ZHOU Qin-Yang, LIU Cong, MU Yue, GUO Wei, DING Yan-Feng, NINOMIYA Seishi
      Acta Agronomica Sinica. 2022, 48(5):  1248-1261.  doi:10.3724/SP.J.1006.2022.02065
      Abstract ( 193 )   HTML ( 10 )   PDF (12317KB) ( 127 )   Save
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      Phenotypic monitoring of rice in the field can be used to analyze traits related to rice yield, which is of great significance to guide rice cultivation management and yield prediction. In this study, to explore the applicability of image analysis methods to evaluate rice growth in different fields under multiple cultivars and cultivation environments, we estimated and evaluated the main phenotypic parameters of rice canopy in paddy fields with six different cultivars under three nitrogen treatments. Based on UAV and field fixed camera images, this study used image processing, three-dimensional modeling and machine learning to automatically estimate rice canopy coverage, plant height, and panicle number in the field, and evaluated the accuracy combining with the actual measurement results. The results showed that the rice canopy segmentation based on the decision tree classification model using UAV images were consistent with the manually segmented results (mean value and variance of Qseg was 0.75 and 0.08), and the rice canopy coverage calculated by this method had a relatively high correlation with that calculated by manually segmentation (R2= 0.83, RMSE = 5.36%). The average rice plant height estimated by the canopy height model in each plot had a high correlation with the mean plant height measured in the field (R2= 0.81, RMSE = 9.81 cm), but it was underestimated as a whole. Based on the ground image, the panicle count results obtained by decision tree classification and morphological parameter filter had a relatively high correlation with the measured panicle number (R2= 0.83, RMSE = 10.99). Overall, combined with image analysis algorithm, using low-altitude UAV remote sensing technology to high-throughput and automatically estimate rice canopy coverage and plant height can achieve relatively high accuracy; using image from ground camera to accurately count the rice panicle number is of significant potentiality. The proposed pipeline in this research could be used to analyze nitrogen effect on rice growth status and evaluate nitrogen response of different rice cultivars, and it is of great significance for mining rice field phenotypic information and yield prediction.

      Response of winter wheat yield, nitrogen use efficiency and soil nitrogen balance to rainfall types and nitrogen application rate in dryland
      GUO Xing-Yu, LIU Peng-Zhao, WANG Rui, WANG Xiao-Li, LI Jun
      Acta Agronomica Sinica. 2022, 48(5):  1262-1272.  doi:10.3724/SP.J.1006.2022.11034
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      To study the effects of nitrogen application rate on grain yield, nitrogen utilization, and soil nitrogen balance of dryland winter wheat fields under different rainfall types, we explored the optimal nitrogen input levels for stable yield and high efficiency of winter wheat in the Weibei highland of North China, which could provide a theoretical basis for efficient fertilization. Five nitrogen treatments including 0, 60, 120, 180, and 240 kg hm-2 (designated as N0, N60, N120, N180, and N240, respectively) were arranged in Heyang County, Shaanxi Province from 2017 to 2020. The three-year in situ experiment were as follows: (1) Different rainfall types had significant impact on yield and economic profits of winter wheat. Compared with the normal and dry year, the yield of the humid year was increased by 33.6% and 113.3% and economic profits were increased by two to three times or more. Nitrogen fertilizer recycling and agronomic efficiency of winter wheat had similar change patterns with yield, and the nitrogen fertilizer recycling, and agronomic efficiency were increased by 4.7%, 0.6 kg kg-1 (normal year), and 11.9%, 2.5 kg kg-1 (dry year) in the humid year compared with the normal and dry year. (2) Regardless of the rainfall type, the yield and nitrogen fertilizer recycling and agronomic efficiency of winter wheat increase first and then decrease with the increase of N application. The highest values were found under N180 treatment in both humid and normal years, and the NO3--N accumulation in 0-100 cm layer after wheat harvest were 108.9 and 113.6 kg hm-2, respectively. In dry year, the NO3--N accumulation under N120 treatment in 0-100 cm layer after wheat harvest was 100.8 kg hm-2 reaching the highest value. (3) The threshold of nitrogen input was determined by the best economic benefit and the highest yield, the nitrogen application rates in humid year, dry year, and normal year were 158.9-166.5, 121.2-130.0, and 148.1-155.7 kg hm-2, respectively; The threshold of nitrogen input was determined by the balance of soil nitrogen pool and the maximum nitrogen uptake, the nitrogen application rates in humid year, dry year, and normal year were 166.5-190.3, 109.6-147.7, and 153.5-198.9 kg hm-2, respectively. Considering the high yield and high efficiency of winter wheat and low soil nitrogen loss, we concluded that when the nitrogen application rates in humid year, dry year, and normal year were 158.9-190.3, 109.6-147.7, and 148.1-198.9 kg hm-2, respectively. It was the suitable nitrogen application rate for both high yield and good environmental benefits, which could be benefit for reference in the production of this region.

      RESEARCH NOTES
      Identification of chromosome loss and rearrangement in potato and eggplant somatic hybrids by rDNA and telomere repeats
      WANG Hai-Bo, YING Jing-Wen, HE Li, YE Wen-Xuan, TU Wei, CAI Xing-Kui, SONG Bo-Tao, LIU Jun
      Acta Agronomica Sinica. 2022, 48(5):  1273-1278.  doi:10.3724/SP.J.1006.2022.14070
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      Somatic hybridization is an important way to create new germplasm. Somatic hybrids produced plenty of genetic variation during protoplast regeneration. In this study, to analyze the chromosome composition and variation of potato and eggplant somatic hybrids, rDNAs and telomeric repeats were used as probes for FISH (fluorescence in situ hybridization), combined with GISH (Genomic in situ hybridization). The results showed that rearranged chromosomes and dicentric chromosomes existed in somatic hybrids, and the parts of the rearranged chromosomes was derived from the end-to-end fusion of potato and eggplant chromosomes 2. One centromere of the rearranged dicentric chromosomes was derived from potato and the other was from eggplant. Eggplant 5S rDNA sites were lost in somatic hybrids to homogenize the rDNA of somatic hybrids. The results of this study indicated that the chromosomes were unstable during the somatic hybridization of potato and eggplant, which can easily cause dicentric and chromosomal rearrangements in somatic hybrids. The chromosomes of somatic hybrids tended to be stable through various ways such as chromosome rearrangement, dicentric and rDNA homogenization.

      Drought resistance identification and drought resistance indexes screening of Tibetan hulless barley resources at adult stage
      WANG Xing-Rong, LI Yue, ZHANG Yan-Jun, LI Yong-Sheng, WANG Jun-Cheng, XU Yin-Ping, QI Xu-Sheng
      Acta Agronomica Sinica. 2022, 48(5):  1279-1287.  doi:10.3724/SP.J.1006.2022.11048
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      Drought is one of the main factors affecting the production of hulless barley in the Qinghai-Tibet Plateau. Identification of drought resistance of hulless barley germplasm resources at adult stage and screening of reliable drought resistance indexes can provide basis for breeding drought resistant varieties. In the present study, a total of 238 hulless barley germplasms were used as materials, and two treatments of normal irrigation and drought stress in the field conditions were conducted in Zhangye of Gansu Province in 2019 and 2020, respectively. Seven indexes, such as the plant height, spike number per plant, biomass per plant, grain weight per spike, spike length, 1000-grain weight, and yield were determined. The drought resistance comprehensive evaluation value (D-value), comprehensive drought resistance coefficient (CDC-value), and weight drought resistance coefficient (WDC-value) were used to identify drought resistance at adult stage of hulless barley germplasms. The results showed that the effects of drought stress on all indexes were extremely significant, and the correlation analysis showed that the yield was significantly positively correlated with plant height and 1000-grain weight at P < 0.01, and significantly positively correlated with the grain weight per panicle at P<0.05. Frequency analysis showed that the sensitivity of seven indexes to drought stress was plant height, yield, biomass per plant, grain weight per ear, number of ears per plant, ear length and 1000-grain weight, respectively. The ranks of drought resistance of germplasms based on the D-value, CDC-value, and WDC-value were similar. Grey correlation degree analysis showed that the correlation degree between DC-value and D-value was in the order of yield, biomass per plant, grain weight per spike, plant height, number of spikelets per plant, ear length and 1000-grain weight, which was basically consistent with the close degree between DC-value and WDC-value of each index. Stepwise regression analysis showed that yield, plant height, panicle number per plant, 1000-grain weight and biomass per plant could be used as reliable indexes for drought resistance identification of hulless barley in adult stage. D-value was determined as the appropriate method for drought resistance identification. Based on D-value, the tested hulless barley germplasms were divided into five drought resistance grades, and 38 germplasms were classified in grade I, such as Ziyanwoqingke, Liulengqingke, Ziqingke, ZDM8125, Tuhuluqingke, etc. These results provided important basic materials and theoretical reference for the breeding of drought-resistant varieties and the study of drought-resistant mechanism of hulless barley.

      Effects of ridge tillage with film mulching in furrow on photosynthetic characteristics of potato and yield formation in dryland farming
      SHI Yan-Yan, MA Zhi-Hua, WU Chun-Hua, ZHOU Yong-Jin, LI Rong
      Acta Agronomica Sinica. 2022, 48(5):  1288-1297.  doi:10.3724/SP.J.1006.2022.14050
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      To investigate the effects of ridge tillage with film mulching in furrow on photosynthetic characteristics and yield formation of potato in dry land, field experiment was conducted from 2018 to 2019 in mountain area of south Ningxia. Ridges were covered with common plastic film in all treatments, while different furrow treatments were mulched with common plastic film (DD), degradable permeable mulch film (DS), and bast fiber film (DM), and no mulching furrows was used as the control check (CK). The effects of ridge tillage with film mulching in furrow on soil moisture, photosynthetic characteristics of potato functional leaves and yield formation during the key growth period (60-120 days after sowing) were investigated and compared. The results showed that the different mulching treatments could significantly increase soil water storage in 0-100 cm layer during potato squaring stage (60 days after sowing). DD treatment was the highest in 2018 and DM treatment was the highest in 2019, which significantly increased by 11.2% and 21.6% than CK, respectively. In the key growth periods of potato, leaf area index of DS treatment was significantly higher than that of CK in 2019, but there was no significant difference among the other treatments. Different mulching treatments could increase the net photosynthetic rate and transpiration rate, while DM treatment significantly increased the net photosynthetic rate and transpiration rate by 30.0% and 23.2% in the tuber swelling stage (120 days after sowing), compared with CK, respectively. The average tuber dry matter accumulation with DD, DM and DS treatments in the 2-year tuber swelling stage was significantly increased by 54.9%, 50.0%, and 22.6%. During the 2-year experiments, the average potato yield with DD, DM and DS treatments was increased by 13.2%, 14.1%, and 5.2%, the average net income was increased by 16.3%, 14.6% and 4.0%, respectively, compared with CK, while the differences in potato yield and net income were not significant between DS and CK. Correlation analysis showed that soil moisture and net photosynthetic rate were the main factors affecting potato yield formation. The treatments of ridge tillage with common plastic film mulching in furrow (DD) and ridge tillage with bast fiber film mulching in furrow (DM) could improve soil moisture at squaring stage, thus promoting the increase of potato photosynthesis and yield. Therefore, ridge tillage with bast fiber film mulching in furrow had the same effect of increasing yield and income as ridge tillage with common plastic film mulching in furrow, and it had the advantage of partially replacing common plastic mulching.

Co-sponsored:
the Crop Science Society of China
the Institute of Crop Science, CAAS
China Science Publishing & Media Ltd.
Published: Science Press
Editor-in-chief: Wan Jian-min
Associate Editors-in-Chief:
Chen Xiao-ya Yang Jian-chang Zhang Xian-long Wang Jian-kang Xu Ming-liang Liu Chun-ming Wang Dao-wen Sun Chuan-qing Ding Yan-feng Jin Wei-wei Chu Cheng-cai Cheng Wei-hong
Director of the editorial department:
Cheng Wei-hong
CN 11-1809/S
ISSN 0496-3490
Post subscription code: 82-336

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  • Started in 2013
  • Covered by SCIE
  • Open access in ScienceDirect

Editor in chief: Wan Jian-min
CN 10-1112/S
ISSN 2095-5421, 2214-5141(online)
Online published:
https://www.sciencedirect.com/journal/the-crop-journal
Submission: https://www.editorialmanager.com/cj/
E-mail: cropjournal@caas.cn
Tel: 8610-82108548

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