Table of Content

12 November 2020, Volume 46 Issue 11

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Cloning and functional analysis of a drought tolerance-related gene IbNAC72 in sweet potato

ZHANG Huan, YANG Nai-Ke, SHANG Li-Li, GAO Xiao-Ru, LIU Qing-Chang, ZHAI Hong, GAO Shao-Pei, HE Shao-Zhen

Acta Agronomica Sinica. 2020, 46(11):  1649-1658.  doi:10.3724/SP.J.1006.2020.04051

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NAC (NAM/ATAF/CUC) is a plant-specific transcription factor family, which plays an important role in plant growth, development and stress responses. In this study, we cloned IbNAC72, a drought tolerance-related gene from sweet potato [Ipomoea batatas (L.) Lam.] variety Lizixiang by RACE method. The IbNAC72 cDNA of 1319 bp in length, had an open reading frame (ORF) of 1008 bp, and encoded a 335 amino acids polypeptide, with a molecular weight of 37.4 kD and an isoelectric point (pI) of 8.76. The genomic DNA of IbNAC72 gene was 1199 bp and was deduced to contain 3 exons and 2 introns. Sequence alignment and phylogenetic analysis revealed that IbNAC72 had a close relationship with the predicted protein products of Ipomoea nil. RT-qPCR analysis showed that IbNAC72 was expressed at the highest level in the leaves of sweet potato, and it was strongly induced by PEG-6000 and NaCl, respectively. IbNAC72 was transformed into tobacco via Agrobacterium-mediated transformation. Its overexpression significantly enhanced drought tolerance in the transgenic tobacco plants. Under drought stress, transgenic plants developed stronger root system; the SOD activity was significantly increased whereas the MDA content was significantly decreased in transgenic plants compared to those of wild type plants. This study showed that IbNAC72 gene was closely related to drought tolerance, providing a basis for in-depth study on the drought tolerance molecular mechanism of IbNAC72 in sweet potato.

Establishment of a high efficient method for chromosome doubling and exploration of cold-resistant resources in potato

DONG Jian-Ke, TU Wei, WANG Hai-Bo, YING Jing-Wen, DU Juan, ZHAO Xi-Juan, ZHAO Qing-Hao, HUANG Wei, CAI Xing-Kui, SONG Bo-Tao

Acta Agronomica Sinica. 2020, 46(11):  1659-1666.  doi:10.3724/SP.J.1006.2020.04073

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In this work, different treatment combinations including colchicine concentrations and treatment methods as well as different time points was used to investigate the survival rate and chromosome doubling efficiency of potato tissue culture plantlets. The potato chromosome doubling by using colchicine had been successfully optimized. The potato plantlet stems treated with 0.1% colchicine for three days shaking at 120 r min^-1 showed the highest doubling efficiency due to its better contact to the colchicine solution. Compared with other potato chromosome doubling techniques, this method has much higher chromosome doubling rate, shorter time treatment and easier to operate, so that it could provide a higher efficient method for potato ploidy operation. In the meantime, compared with the diploid, the tetraploid interspecific hybrids showed differences in the morphological characteristic, which had higher plants, thicker stem, bigger petals and pollen grain. In addition, no significant difference was found between diploid and tetraploid interspecific hybrids in terms of cold resistance, but both significantly enhanced cold resistance compared with the common potato cultivar. Taken together, the doubled interspecific hybrids could sever for improving cold resistance of potato cultivars.

Development of molecular markers and fine mapping of qBN-18 locus related to branch number in soybean (Glycine max L.)

WU Hai-Tao, ZHANG Yong, SU Bo-Hong, Lamlom F Sobhi, QIU Li-Juan

Acta Agronomica Sinica. 2020, 46(11):  1667-1677.  doi:10.3724/SP.J.1006.2020.04043

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The branch number is one of the important factors influencing soybean yield, which is directly related to pod setting rate. At the same time, it is also an important component of soybean plant type, and further affects the yield by adjusting the population structure and planting density. At present, there is few report related to map-based cloning of genes related to branch number. Therefore, the discovery of genes/QTL involved in the regulation of soybean branching is of great significance for the basic research on the establishment of plant type and the applied research on the development of high-yielding varieties. In this study, based on the F₂ of crossing low-branched variety Kenfeng 19 (KF19) and high-branched variety Kennong 24 (KN24), we developed the F_7:8 recombinant inbred line (RIL) population, consisting of 606 lines, and two backcrossing populations consisting of 1486 individuals for KF19-BC₃F₂ and 1150 individuals for KN24-BC₂F₂. Within the localization interval of the new QTL of the branch number of chromosome 18 (qBN-18), 11 polymorphism SSR markers were screened out to identify the RIL population, and region of qBN-18 was reduced from 1.6 Mb to 113 kb. After developing two InDel markers BR69 and BR77 in the mapping region, the backcross population was used to screen the exchange individuals, the interval of qBN-18 was further reduced to 63.7 kb, including 9 genes. Those results provide the information for gene map-based cloning and molecular marker assisted breeding of branch number in soybean.

Regulatory mechanism of the seed coat color gene BrTT1 in Brassica rapa L.

WANG Yan-Hua, JIAN Hong-Jiu, QIU Xiao, LI Jia-Na

Acta Agronomica Sinica. 2020, 46(11):  1678-1689.  doi:10.3724/SP.J.1006.2020.04036

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Brassica rapa (B. rapa L., 2n = 20, AA) is a specie of Brassica genus, belonging to the basic species of cultivated rapeseed. China is the original center of Chinese cabbage and Brassica campestris. Compared with Brassica napus, it has a long history of origin and cultivation and rich genetic resources, which has natural and stable yellow seed resources. Dahuang has the natural yellow seed resource in B. rapa. Its seed coat color is bright yellow, the yellow seed trait can be stably inherited, and Dahuang has the advantages of large grain, high oil content and good self-adhesiveness. Sequence comparison showed that nucleotide polymorphisms were solely found in BrTT1 sequences from different seed color lines (yellow, red or brown, and black), which could be used to predict seed color phenotype. Yeast two-hybrid analysis indicated BrTT1 could interact with two other transcriptional factors R2R3-MYB (BrTT2) and WD40 (BrTTG1), and one catalytic enzyme (BrTT3). Quantitative RT-PCR analysis of transgenic B. rapa lines with the gene down-regulated by RNA interference and up-regulated by overexpression revealed that two contrasting groups of genes were regulated by BrTT1 in the biosynthesis and deposition of flavonoids pigments in the seed of B. rapa. These results further define the regulatory activity of BrTT1 in seed coat color formation in Brassica species.

Effects of SSIIa and SSIIIa alleles and their interaction on eating and cooking quality under Wx^mp background of rice

YAO Shu, ZHANG Ya-Dong, LIU Yan-Qing, ZHAO Chun-Fang, ZHOU Li-Hui, CHEN Tao, ZHAO Qing-Yong, ZHU Zhen, Balakrishna Pillay, WANG Cai-Lin

Acta Agronomica Sinica. 2020, 46(11):  1690-1702.  doi:10.3724/SP.J.1006.2020.02006

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In order to explain the variation of eating and cooking quality (ECQ) in different semi-waxy rice lines with Wx^mp allele, sixty-four semi-waxy lines with Wx^mp were developed by crossing from Wujing 13 and Kantou 194 (Milky Princess). The polymorphism of markers between the two parents was detected in soluble starch synthesis genes SSIIa and SSIIIa but not in other starch synthesis related genes. Genetic effects of SSIIa and SSIIIa on the amylose content (AC), gel consistency (GC), gelatinization temperature (GT) and rapid visco analyzer (RVA) profile characteristics were analyzed in Wx^mp rice lines. The results showed that SSIIa and SSIIIa had significant effects on the characteristic values of AC, GT, GC and RVA profile, and the interactive effects existed between the two genes. SSIIa² and SSIIIa² alleles (² indicated that allele was derived from Wujing 13, the same as in the below) had a tendency to increase AC by 1.87% and 1.23%, respectively. This result was consistent in two years. There was no significant effect on GT for SSIIa and SSIIIa allelic variation, whereas the GT of SSIIa¹SSIIIa¹(¹ indicated that the genes were derived from Kantou 194, the same as in the below) was significantly higher than that of SSIIa²SSIIIa² by 1.34 °C. This indicated that GT was not significantly affected by single gene of SSIIa and SSIIIa but was remarkably influenced by the interaction of the two genes. The GC was significant varied among rice lines with different genotypes. The SSIIa² and SSIIIa¹ alleles could increase GC of 8.74 mm and 9.62 mm respectively. From the interaction of the two genes, the GC of SSIIa²SSIIIa¹ genotype was 10.64 mm higher than the SSIIa¹SSIIIa² genotype, and was 16.95 mm higher than the SSIIa²SSIIIa² genotype. The allele SSIIa² increased the peak viscosity (PKV), hot paste viscosity (HPV), cool paste viscosity (CPV) and breakdown viscosity (BDV), but decreased the consistency viscosity (CSV) and setback viscosity (SBV). However, the effect of allele SSIIIa² was just the opposite, which decreased the PKV, HPV, CPV, BDV and increased CSV and SBV. For the combination of SSIIa and SSIIIa, SSIIa²SSIIIa¹ genotype showed the largest values in PKV, HPV and CPV, SSIIa²SSIIIa²genotype showed the largest values in BDV and CSV, and SSIIa²SSIIIa¹ genotype showed the least value in SBV. These results provide a theoretical basis for improving eating and cooking quality of semi-waxy japonica rice.

Molecular characterization identification by genome sequencing of transgenic glyphosate-tolerant rice G2-7

MA Shuo, JIAO Yue, YANG Jiang-Tao, WANG Xu-Jing, WANG Zhi-Xing

Acta Agronomica Sinica. 2020, 46(11):  1703-1710.  doi:10.3724/SP.J.1006.2020.02002

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Molecular characterization, such as copy number and flanking sequence of foreign DNA fragment insertion site, is the important identity information, provided during safety assessment of genetic modified crop. In this study, the T-DNA insertion site, copy number and flanking sequences were identified in transgenic glyphosate-tolerant rice G2-7 based on whole genome sequencing in combination bioinformatics analysis method. 47.13 Gb clean sequence data for G2-7 was generated on Illumina NovaSeq 6000 platform. The junction reads mapped to boundaries of T-DNA and flanking sequences in G2-7 were identified by comparing with sequence of transformation vector and rice reference genome. The results showed that exogenous T-DNA fragments was integrated in the position of Chr. 1 36,189,491-36,189,507 with a single copy, 16 bp rice genome sequence was deleted at the insertion site and no insertion of vector backbone. 375 bp and 353 bp flanking host DNA sequence of 5′-end and 3′-end of the insertion DNA fragment were also obtained, respectively. The putative insertion location and flanking sequences were further confirmed by PCR amplification and Sanger sequencing. The results not only provided data support for safety assessment and event specific detection, but also demonstrated that WGS was an effective technique for identifying molecular characterization in rice.

Locus encryption for early flowering and QTL polymerization to create excellent early flowering resources of spring Brassica napus L.

LIU Hai-Dong, PAN Yun-Long, DU De-Zhi

Acta Agronomica Sinica. 2020, 46(11):  1711-1721.  doi:10.3724/SP.J.1006.2020.04012

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cqDTFA7a and cqDTFC8, two major effects of early flowering QTL, were identified in the NNDH population of spring Brassica napus, and closely linked markers SSR G1803, InDel IA7-4, and SSR S035 with cqDTFC8 developed in previous studies. In this study, a BC₂F₂ population for early flowering QTL locus cqDTFC8 was constructed, and a closely linked SNP marker was further developed. The early flowering genotypes of one natural resources contained 93 spring B. napus varieties were identified used four closely linked markers with two loci, and selected 3164 and 2216 resources with cqDTFA7a site, 3484 and 2857 resources with cqDTFC8 site. Two site resources were aggregated by site polymerization through reciprocal hybridization. The polymerized DH system was rapidly obtained by microspore culture and maker assisted selection. A hybrid combination was created between polymeric line with good traits and early flowers and the Polima CMS, and the utilization value of the polymeric line was further analyzed by the production test at multiple environments for two consecutive years. cqDTFC8 encryption results showed that this site was located in the SNP11 and SNP12 interval, and separated from SNP11 altogether. The identification results of early flowering genotypes of natural resources showed that there were 50 individuals containing cqDTFA7a locus, with an average initial flowering period of 58.1 days; 16 single plants containing cqDTFC8 locus, with an average flowering period of 58.3 days; and 16 single plants containing two loci, with an average flowering period of 55.2 days, indicating the more early flowering sites containing, the earlier flowering. The results of polymerization showed that the flowering time of the polymerized lines of cqDTFC8 and cqDTFA7a was 2-3 days earlier than that of the single locus parents, among which the polymerized DH18 from 3164 of cqDTFA7a and 3484 of cqDTFC8 was 3 days earlier than that of the parents, and the yield-related traits were better than those of other lines. The combination of DH18 and the Polima CMS 025A was further utilized, and the combination was named TZG18. Yield results of two years and nine environments showed that yield of TZG18 was above 17.5% higher than the Haoyou 11, a local B. rapa variety on the Qinghai-Tibet plateau. Those results indicated that the early flowering site polymeric lines had an obvious advantage over the single locus lines in flowering time, and had an effect on the increasement of rapeseed yield. This study is a preliminary exploration of MAS breeding for early flowering traits of Brassica napus, providing materials support for replacing B.rapa varieties using early maturity Brassica napus varieties in spring rapeseed region, and approaches for gene polymerization breeding technology.

Sugarcane PsbS subunit response to Sugarcane mosaic virus infection and its interaction with 6K2 protein

ZHANG Hai, LIU Shu-Xian, YANG Zong-Tao, WANG Tong, CHENG Guang-Yuan, SHANG He-Yang, XU Jing-Sheng

Acta Agronomica Sinica. 2020, 46(11):  1722-1733.  doi:10.3724/SP.J.1006.2020.04030

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Non-photochemical quenching (NPQ) is the main mechanism of photoprotective regulation in higher plants. The PsbS subunit of Photosystem II (PSII) plays a key role in NPQ. The involvement of PSII PsbS subunit in Sugarcane mosaic virus (SCMV) infection of sugarcane (Saccharum spp. hybrid) has not been reported. In the previous research, we cloned the coding sequence of the PsbS subunit from sugarcane and designated it as ScPsbS. ScPsbS had an open reading frame (ORF) length of 798 bp and encoded a protein of 265 aa. Bioinformatics analysis showed that ScPsbS was a stable hydrophobic protein with chloroplast localization signals and four transmembrane domains. The ScPsbS protein possesses a typical domain of PsbS protein. Phylogenetic tree analysis showed that ScPsbS was divergent between monocotyledons and dicotyledons, or C₃ plants and C₄ plants. Subcellular localization analysis showed that ScPsbS was located in chloroplasts and partially colocalized with SCMV-6k2 in chloroplasts. The interaction of ScPsbS with the SCMV-6K2 was further confirmed by bimolecular fluorescence complementation assays (BiFC). ScPsbS gene showed obvious tissue specificity in sugarcane tested by real-time quantitative PCR analysis. ScPsbS gene had highest expression in mature leaves, followed by immature leaves and leaves beginning to senesce, and hardly expressed in stems and roots. The expression of ScPsbS gene was significantly affected by SCMV infection, with significant upregulation in the early stage of SCMV infection, and no significant affection in the later stage of SCMV infection.

Genetic analysis and fine mapping of a sheathed panicle mutant sui2 in rice (Oryza sativa L.)

SUN Qi, ZHAO Zhi-Chao, ZHANG Jin-Hui, ZHANG Feng, CHENG Zhi-Jun, ZOU De-Tang

Acta Agronomica Sinica. 2020, 46(11):  1734-1742.  doi:10.3724/SP.J.1006.2020.02009

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The elongation and development of rice uppermost internode plays an important role in plant architecture development. In general, the sheathed panicle phenomenon in rice sterility line is caused by the elongation and development hindrance of the uppermost internode. The study on molecular mechanisms underlying sheathed panicle would be helpful for improving plant architecture in sterility line. At the present study, we reported the study on a sheathed panicle mutant, named sui2, originated from a tissue-culture progeny. Its uppermost internode severely shortened, resulted in its pancleen closed by flag leaf sheath, without significantly length alternation at other internodes. The cytological analysis demonstrated that the shorten of the uppermost internode is caused by insufficient elongation of the parenchyma cells. Genetic analysis of the progeny derived from the cross-combination of sui2 and IRAT129 revealed that sui2 is a single gene dominant mutant. Linkage analysis to 608 normal individuals from F₂ generation showed that SUI2 was located in a 110 kb region delimited by InDel marks S4-14.1 and S4-14.2 on the end of chromosome 4 long arm. The annotated genes on this region did not display any difference in genomic sequence, while the expression level of LOC_Os04g39430, encoding a cytochrome P450 protein and an allele of D11, increased by 264 times expression amount in mutant. Analysis of qRT-PCR for several crucial genes on BR (brasssinolide) signaling pathway showed that in mutant the expression level of all these genes increased, indicating that genes in BR signaling pathway may be involved in the regulation to the elongation and development of uppermost internode.

Analysis of the stripe rust resistance in a wheat line CB037 with high regeneration and transformation efficiency

ZHENG Yan-Yan, HUANG De-Hua, LI Ji-Long, ZHANG Hui-Fei, BAO Yin-Guang, NI Fei, WU Jia-Jie

Acta Agronomica Sinica. 2020, 46(11):  1743-1749.  doi:10.3724/SP.J.1006.2020.01016

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Genetic transformation is used for efficient gene cloning, gene editing and gene engineering, etc. Obtaining recipient lines amenable to transformation and with pure genetic background is critical for high efficiency transformations. For recent years, the wheat inbreed line CB037 had been widely used as a recipient for transgenes and obtain its high transformation potential. Despite having stable agronomic traits, the CB037 is genetically heterogeneous for resistance to wheat stripe rust (Puccinia striiformis f. sp. tritici, Pst). In this study, the Pst-resistant line CB037-PstR and Pst-susceptible line CB037-PstS were isolated, and their F₂ population was created. Genetic analysis showed that the CB037-PstR carried a single dominant resistance gene. The identified resistance gene was mapped on the short arm of chromosome 1B using BSR-seq and molecular marker analysis. GISH results further revealed that CB037-PstR is a 1BL/1RS translocation line and likely carried Yr9. This study segregated genetic heterogeneity in CB037 for stripe rust resistance and isolated its Pst-susceptible and resistant lines. These results will facilitate trait-oriented use of CB037 in genetic engineering of wheat.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Changes of endogenous hormones on storage root formation and its relationship with storage root number under different potassium application rates of sweet potato

JIANG Zhong-Yu, TANG Li-Xue, LIU Hong-Juan, SHI Chun-Yu

Acta Agronomica Sinica. 2020, 46(11):  1750-1759.  doi:10.3724/SP.J.1006.2020.04097

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In order to explore the changes of endogenous hormones on storage root formation and its relationship with storage root number under different potassium application rates of sweet potato root, sweet potato varieties ‘Yanshu 25’ and ‘Beijing 553’ with significant differences in storage root number were used as experimental materials, potassium oxide (K₂O) was used as fertilizer, and four potassium fertilizer gradients of 0 (K0), 120 (K2), 240 (K3), and 360 kg hm^-2 (K4) were set. The effects of different potassium application rates on the contents of endogenous hormones, the activity of related metabolic enzymes, the number of storage root and root evenness in swelling roots of sweet potato during root formation and harvest stage were studied. Compared with the treatment without potassium fertilizer (K0), the application of potassium fertilizer decreased the enzyme activities of indoleacetic acid oxidase (IAAO) and peroxidase (POD), increased the content of indole-3-acetic acid (IAA), increased the content of zeatin riboside (ZR) and decreased the content of gibberellins (GA₃). Potassium application enhanced the activity of primary cambium and promoted the differentiation from adventitious root to storage root by regulating the content of endogenous hormones in swelling roots of sweet potato. Compared with the control, the application of potash fertilizer significantly increased the number and weight of storage roots per plant and root yield of ‘Yanshu 25’ and ‘Beijing 553’. The number of storage roots per plant of ‘Yanshu 25’ and ‘Beijing 553’ increased by 3.16%-25.40% and 3.85%-33.11%, respectively, and the yield increased by 4.22%-17.31% and 3.94%-18.45%, respectively. Compared with the potassium application treatments of the two varieties, the K2 treatment had the highest storage roots number per plant, the highest weight and yield of storage roots, with the best root evenness.

Effects of drought treatments at different growth stages on growth and the activity of osmotic adjustment in sweet potato [Ipomoea batatas (L.) Lam.]

ZHANG Hai-Yan, WANG Bao-Qing, FENG Xiang-Yang, LI Guang-Liang, XIE Bei-Tao, DONG Shun-Xu, DUAN Wen-Xue, ZHANG Li-Ming

Acta Agronomica Sinica. 2020, 46(11):  1760-1770.  doi:10.3724/SP.J.1006.2020.04079

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Field experiments were conducted using two sweet potato cultivars (Jishu 21, a drought-tolerant cultivar, and Jizishu 1, a drought-sensitive cultivar) with four water treatments to investigate the effects of drought treatments at different growth stages on growth and the activity of osmotic adjustment in sweet potato [Ipomoea batatas (L.) Lam.], including well-watered treatment during the whole growth period (WW, control), drought stress during the establishment stage (DS1), drought stress during the storage root initial stage (DS2), and drought stress during the storage root bulking stage (DS3). Drought stress resulted in significant decrease of fresh weight of storage roots in sweet potato. Compared with drought stress in different periods, drought stress during the establishment stage (DS1) decreased the fresh weight most. Compared between cultivars, drought-sensitive cultivar decreased the fresh weight most. The average in three years, compared with the control, the fresh weight of drought-tolerant cultivar (Jishu 21) and drought-sensitive cultivar (Jizishu 1) decreased 28.59% and 38.77% in DS1 treatment, respectively, while 25.20% and 33.50% in DS2 treatment, respectively and 14.55% and 19.56% in DS3 treatment, respectively. Drought stress resulted in significant decrease of biomass of storage roots in sweet potato. One hundred days after planting, compared with the control, the biomass of aboveground part of Jishu 21 in DS1, DS2, and DS3 decreased 32.68%, 20.79%, and 11.72%, respectively, while Jizishu 1 decreased 46.45%, 31.89%, and 18.43%, respectively. The biomass of underground part of Jishu 21 in DS1, DS2, and DS3 decreased 37.69%, 25.86%, and 10.67%, respectively, while Jizishu 1 decreased 54.34%, 33.48%, and 14.20%, respectively. Under drought stress, the relative water content of functional leaves decreased, and the content of soluble sugar, soluble protein, free amino acid and proline in functional leaves, fibrous roots and storage roots increased. The earlier the application of drought stress, the greater the decrease or increase. The effects of drought stress applied at early stages on osmotic adjustment could not be effectively recovered after re-watering, while the osmotic adjustment could be recovered to the control level after re-watering when drought stress was applied at later stage.

Classification of soybean pods using deep learning

YAN Zhuang-Zhuang, YAN Xue-Hui, SHI Jia, SUN Kai, YU Jiang-Lin, ZHANG Zhan-Guo, HU Zhen-Bang, JIANG Hong-Wei, XIN Da-Wei, LI Yang, QI Zhao-Ming, LIU Chun-Yan, WU Xiao-Xia, CHEN Qing-Shan, ZHU Rong-Sheng

Acta Agronomica Sinica. 2020, 46(11):  1771-1779.  doi:10.3724/SP.J.1006.2020.94187

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Crop phenotype investigation is a key task in the selection and breeding of crop varieties. The traditional phenotypic survey mainly relies on human labors, which makes the results of the phenotypic survey difficult to meet the requirements of automation, high precision and high reliability. In the investigation of soybean phenotypes, the correct identification of pod types is the key and premise for the accurate extraction of phenotypes such as the number, length and width of pods. This study focused on the pictures of mature soybean pods by using deep learning to migrate five different network models [AlexNet, VggNet (Vgg16, Vgg19), GoogleNet, ResNet-50], to identify one-pod, two-pod, three-pod, and four-pod. In order to improve training speed and accuracy, this experiment fine-tuning the model and selected different optimizers (SGD, Adam) to optimize the network model. Adam’s performance was better than SGD in the problem of pod identification. With the Vgg16 network model and the Adam optimizer, the test accuracy of the pod category reached 98.41%, which reflected the best performance in the selected network model. In the 10-fold cross-validation test, the Vgg16 network model had good stability. Therefore, this study indicates that the Vgg16 network model can be applied to the actual identification of pods, and provide an important solution for further automatic extraction of pod phenotypes.

Nitrogen demand characteristics with different grain yield levels for wheat after rice

DU Yu-Xiao, LI Xin-Ge, WANG Xue, LIU Xiao-Jun, TIAN Yong-Chao, ZHU Yan, CAO Wei-Xing, CAO Qiang

Acta Agronomica Sinica. 2020, 46(11):  1780-1789.  doi:10.3724/SP.J.1006.2020.01027

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It is necessary to clarify the nitrogen (N) demand characteristics with yield levels for wheat after rice in the middle and down reaches of the Yangtze River, which could provide theoretical basis for N fertilizer management. Based-on the multi-years and multi-sites wheat experiments in Jiangsu province, this study constructed the datasets of different yield levels derived from different varieties, N rates, densities, and sowing date experiments. N indicators including N requirement per ton grain (N_req), dry matter accumulation (DMA), plant N accumulation (PNA), plant N concentration (PNC), straw N concentration (SNC), grain N concentration (GNC), harvest index (HI), N harvest index (NHI) and N nutrition index (NNI) were analyzed. The results showed that there were not significant differences in N_req among the different yield levels, and the highest N_req was middle-low yield with 27.8 kg t^-1, while the lowest value was 24.8 kg t^-1for low yield level. With the increase of yield levels, DMA, PNA and PNC all showed a gradually increasing trend during maturity stage, and there were significant differences among the different yield levels. There was a significant positive correlation between grain yield and PNA, the DMA and PNA increased with the increase of yield in the sowing-jointing stage, jointing-flowering stage and flowering-maturing stage, but the DMA and PNA proportion in different growth stages showed different trends. The SNC and GNC increased with the increase of yield levels. For SNC, there was no significant difference between the high yield and middle yield level, but it was significantly higher than the low-middle and low yield level. For GNC, there were significant differences among different yield levels except for the middle and low-middle yield level. The HI increased gradually with the increase of the yield levels, and its range was 0.39-0.49. The HI for low-middle and low yields were significantly lower than that of middle and high yield levels, while there were not significant differences in NHI among different yield levels. Its variation range was 0.60-0.96. The NNI gradually increased with the increase of the yield levels, and there was significant difference between different yield levels. The NNI of the high-yield level was higher, and some of the values were greater than 1 which indicating that some experiments had excessive nitrogen fertilizer supply. With the increase of the yield level, the N_req increased first and then decreased, while the DMA, PNA, PNC, SNC, and GNC were gradual increased. The increase of SNC was higher than the GNC, therefore, the extravagant absorption of N by wheat should be avoided in field management. The variation ranges of the HI and NHI were consistent with previous studies. The higher DMA and PNA in the late growth stages were the main reasons for the high yield of wheat. The NNI could be a promising indictor in the field N management of wheat.

Effects of sowing and fertilizing methods on yield and fertilizer use efficiency in red-soil dryland rapeseed (Brassica napus L.)

LYU Wei-Sheng, XIAO Fu-Liang, ZHANG Shao-Wen, ZHENG Wei, HUANG Tian-Bao, XIAO Xiao-Jun, LI Ya-Zhen, WU Yan, HAN De-Peng, XIAO Guo-Bin, ZHANG Xue-Kun

Acta Agronomica Sinica. 2020, 46(11):  1790-1800.  doi:10.3724/SP.J.1006.2020.94203

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In order to explicit proper sowing and fertilizing methods of rapeseed production in red-soil dryland, a two-year field experiment covering two rapeseed seasons (2017-2018 and 2018-2019) was conducted with four treatments of sowing and fertilizing methods to analyze the impact on yield formation and fertilizer use efficiency of rapeseed, including conventional sowing and fertilizing method (T1), sowing in row with surface broadcast fertilizing (T2), synchronous sowing in uniform row with side deep fertilizing (T3) and synchronous sowing in wide-narrow row with side deep fertilizing (T4). The results were as follows: The yield and fertilizer use efficiency of rapeseed in red-soil dryland were significantly affected by sowing and fertilizing methods. Besides, these differences were more significant in poor soil condition and drought season (2017-2018) than those in nutrient-rich soil condition and rainy season (2018-2019). Compared with T1 and T2, T3 and T4 promoted the yield formation and increased its fertilizer use efficiency significantly, whereas there was no significant difference between T3 and T4. Specifically, the technique of synchronous drilling sowing with side deep fertilizing could improve dry matter production during the whole growth period of rapeseed, especially from anthesis to maturity, with a corresponding rise of dry matter accumulation of both underground and aboveground after anthesis. Meanwhile, compared with the conventional cultivation, the technique of synchronous drilling sowing with side deep fertilizing increased the uptake of nutrients (N, P and K), effective plant density and maintained sufficient pod number, and thus improved the yield and fertilizer use efficiency of rapeseed. This study indicated that the technique of synchronous drilling sowing with side deep fertilizing had the potential of improving rapeseed productivity in red-soil dryland of southern China. Therefore, it should be suggested to promote the application according to local condition.

RESEARCH NOTES

Low concentration of vomitoxin as elicitor induced resistance of dry rot disease of potato and its mechanism

ZHAO Xiao-Can, XU Yong-Qing, HE Fu-Meng, SUN Mei-Li, YUAN Qiang, WANG Xue, KONG De-Xing, LIU Dan, FENG Yan-Zhong, CHEN He-Shu, TIAN Ming, LIU Di, LI Feng-Lan

Acta Agronomica Sinica. 2020, 46(11):  1801-1809.  doi:10.3724/SP.J.1006.2020.04049

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Dry rot disease is a fungal disease caused by Fusarium sp. infection in the process of potato cellar storage, which seriously affects the commercial value. Vomitoxin (DON), also known as deoxynivalenol, is a secondary metabolite produced by fusarium sp. in the process of infecting potato lump. Biological control is an effective method of disease control. Using biological factors as elicitors to induce plant system produce disease resistance has become a hot research topic. In this study, in order to provide theoretical basis for biological control of dry rot disease, potato tubers were treated with low concentration of DON as elicitor to determine its role in the resistance to dry rot disease and the mechanism of inducing systemic acquired resistance (SAR) of potato. DON treatment had a certain effect on the development of dry rot disease, and affected by the concentration. The treatment of potato tubers with 5 ng mL^-1 DON for four hours could effectively reduce the diameter expansion of dry rot disease lesions induced by Fusarium sambucinum. Low concentration of DON increased the activities of SOD, POD, chitinase and β-1, 3-glucanase in tuber tissue, and decreased the accumulation of MDA. DON treatment increased the activities of PAL and 4CL, the key enzymes of phenylpropane metabolism, and promoted the accumulation of total phenols, flavonoids, lignin and anthocyanins. Meanwhile, the content of endogenous signal molecules SA, JA, and ET in potato tubers could be increased by using DON as elicitor, and the expression of NPR1 (regulatory gene of plant systemic resistance) was increased.

Salicylic acid improved salinity tolerance of Glycyrrhiza uralensis Fisch during seed germination and seedling growth stages

LI Run-Zhi, JIN Qing, LI Zhao-Hu, WANG Ye, PENG Zhen, DUAN Liu-Sheng

Acta Agronomica Sinica. 2020, 46(11):  1810-1816.  doi:10.3724/SP.J.1006.2020.04080

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The present study investigated the effects of salicylic acid treatments on morphology, physiological and biochemical parameters and their relationship to salt stress of G. uralensis Fisch seeds and seedlings. Under the salt stress of 200 mmol L^-1 NaCl, the application of 0.5 mmol L^-1 salicylic acid on G. uralensis Fisch seeds could significantly promote the elongation of radicle, increase fresh weight of seedlings, reduce the content of malondialdehyde (MDA) and proline in the radicle, and improve the activity of peroxidase (POD). Under the salt stress (i.e. 100 mmol L ^-1 and 200 mmol L^-1 NaCl), the application of 0.5 mmol L^-1 salicylic acid on G. uralensis Fisch seedling could reduce MDA and proline content, and increase the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in different degrees. Under salt stress condition, the application of salicylic acid could increase the root glycyrrhizinic acid content. In summary, the application of salicylic acid could improve the tolerance to salt stress by alleviating the inhibition of salt stress on the germination of seeds, increasing the activity of antioxidant enzymes, and reducing the degree of membrane lipid peroxidation.