Table of Content

12 May 2021, Volume 47 Issue 5

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Development and identification of transgenic rapeseed with a novel gene for glyphosate resistance

LI Jie-Hua, DUAN Qun, SHI Ming-Tao, WU Lu-Mei, LIU Han, LIN Yong-Jun, WU Gao-Bing, FAN Chu-Chuan, ZHOU Yong-Ming

Acta Agronomica Sinica. 2021, 47(5):  789-798.  doi:10.3724/SP.J.1006.2021.04169

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Glyphosate is the most widely used broad-spectrum herbicide in the world. However, at present there is no glyphosate-tolerant rapeseed variety with independent intellectual property rights in China. In the study, a novel glyphosate-resistant genes I. variabilis EPSPS was transferred to the Brassica napus pure line J9707 via the Agrobacterium tumefaciens-mediated hypocotyl method, and 126 T₀-positive transgenic plants with 97.0% positive rate were generated. The T-DNA insertion with a single copy (44.8%) is dominant. The insertion locations of T-DNA in the lines of EPS-2, EPS-6, and EPS-7 were identified by inverse PCR method. The stability of the T-DNA insertion in these lines were further confirmed by insertion-specific PCR in their T₀ to T₃ plants. The gene expression analysis revealed that the I. variabilis EPSPS gene and its protein was stably expressed in different generations of transgenic lines in RNA and protein levels. Treatments with different doses of glyphosate indicated that the lines of EPS-1, EPS-2, EPS-5, EPS-6, and EPS-7 could tolerate four times of the recommended dose of glyphosate in production. Thus, the novel glyphosate-tolerant rapeseed lines generated in the present study will lay the foundation for the herbicide- tolerance rapeseed breeding in China.

Regulation of ACC treatment on nitrogen supply response of maize seedlings with different genotypes

WU Bing-Hui, WANG Gui-Ping, WANG Yu-Bin, LI Zhao-Hu, ZHANG Ming-Cai

Acta Agronomica Sinica. 2021, 47(5):  799-806.  doi:10.3724/SP.J.1006.2021.03047

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Ethylene plays an important role in the growth and morphological formation of maize, while little research is involved in the regulatory effects of ethylene on the nitrogen absorption and accumulation in maize, which limits the application of ethylene in high yield and efficient cultivation of maize production. In this study, three maize varieties (Zhengdan 958, Ruifuer 1, and Demeiya 3) were used as experimental materials to study the response of maize varieties with different nitrogen absorption efficiency under different nitrogen levels condition. Combined with the addition of the precursor of ethylene synthesize 1-aminocyclopropane-1-carboxylic acid (ACC), the regulation effects of ethylene on nitrogen uptake of different genotypes were analyzed in maize. The results showed that nitrogen-sensitive varieties (Ruifuer 1 and Demeiya 3) had more obvious phenotype of nitrogen deficiency than Zhengdan 958 under low nitrogen condition, and were more sensitive to ACC treatment. Moreover, ACC treatment repressed the growth and dry matter accumulation in the shoot and root of maize plants. ACC treatment decreased the chlorophyll content of leaves under low nitrogen, reduced the accumulation of soluble protein in leaves, and promoted the premature aging of maize leaves. Among them, the contents of chlorophyll and soluble protein in Zhengdan 958 leaves with ACC treatment were significantly higher than those of Ruifuer 1 and Demeiya 3. Furthermore, low nitrogen treatment inhibited the expression of key enzymes (ZmACS7 and ZmACO15) in ethylene synthesis, while decreased the ethylene release rate. Thus, ACC treatment promoted the expression of ZmACS7 and ZmACO15 and enhanced ethylene release rate under low nitrogen treatments. Low nitrogen treatment inhibited the expression of ZmNRT2.1 in maize roots, but ACC treatment promoted the expression of ZmNRT2.1 in maize roots. In addition, the expression of ZmNRT2.1 in roots of Zhengdan 958 was significantly higher than those of Ruifuer 1 and Demeiya 3 under low nitrogen treatments. The results showed that ethylene regulated the uptake and distribution of nitrogen by regulating the key enzyme genes of ethylene synthesis and the expression of ZmNRT2.1 in maize which affected plants growth , and nitrogen-sensitive varieties were more sensitive to ethylene than green-holding variety.

Function analysis of nitrogen-responsive transcription factor ZmNLP5 affecting root growth in maize

GE Min, WANG Yuan-Cong, NING Li-Hua, HU Meng-Mei, SHI Xi, ZHAO Han

Acta Agronomica Sinica. 2021, 47(5):  807-813.  doi:10.3724/SP.J.1006.2021.03039

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Improving nitrogen (N) use efficiency of crops is crucial for minimizing N loss and reducing environmental pollution, which is a requirement for the sustainable agriculture. Our previous study found that the transcription factor ZmNLP5 directly regulated the expression of ZmNIR1.1 and promoted nitrogen uptake and assimilation in maize, however, its underlying regulation mechanism is unclear. Here, we performed further phenotype analysis of zmnlp5 and wild type (W22) plants in hydroponic culture on sufficient nitrogen (SN) solution and deficient nitrogen (DN) solution. Compared with WT plants, the root length of zmnlp5 mutant plants was significantly decreased under DN condition. Compared with upper and middle regions of roots, ZmNLP5 was predominantly expressed in root tip regions. Then, we examined the relationship between root length and nitrite content in root tips under a series of nitrite concentrations. The results showed that there was no significant differences in root length between WT and zmnlp5 until the nitrite concentration reached 2 mmol L^-1 and higher; however, when the concentration of nitrite was higher than 2 mmol L^-1, the root length of zmnlp5 was significantly shorter than WT, and the accumulation of nitrite in the root tips of zmnlp5 was significantly higher than WT. Interestingly, zmnlp5 plants also accumulated significantly more nitrite in the root tips than WT under DN condition. The study showed that the transcription factor ZmNLP5 played an important role in the root growth of maize in response to deficient nitrogen condition, and provided the candidate genes for breeding of maize nitrogen use efficiency in the future.

GhMADS7 positively regulates petal development in cotton

MA Huan-Huan, FANG Qi-Di, DING Yuan-Hao, CHI Hua-Bin, ZHANG Xian-Long, MIN Ling

Acta Agronomica Sinica. 2021, 47(5):  814-826.  doi:10.3724/SP.J.1006.2021.04140

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The MADS-box gene family, as an important class of transcription factors, is mainly involved in plant floral organs growth and development. GhMADS7/98 has a conserved MADS-box and K domain, belonging to the AG subgroup of MIKC^C type MADS-box gene family. Through homology sequence alignment, GhMADS7/98 was 64% homologous to the Arabidopsis AGAMOUS (AG) gene. The GhMADS7 gene was expressed in petals, anthers, stigmas, and ovules, but with different temporal and spatial expression. To study the function of the gene, the RNA interference (RNAi) vector was constructed and transformed into cotton, and the transgenic lines with significantly reduced expression was obtained. These transgenic lines showed delayed petal development in the 5-6 mm and 7-8 mm buds. By observing the paraffin sections of the petals, it was found that vascular bundles in the petals of RNAi lines were shrived, compared with that in the wild type plants. To explore the reason, the expression of class A and B gene of ‘ABC’ model of floral development was detected in the petals by qRT-PCR, the result showed that the expression of most genes were upregulated in the RNAi plants, compared to WT. Therefore, it is speculated that GhMADS7 might cooperative with other petal development genes to regulate the cotton petal development.

Construction and identification of haploid induction gene OsMATL mutants in rice

WEN Qin, JIA Si-Si, WANG Jia-Feng, HUANG Cui-Hong, WANG Hui, CHEN Zhi-Qiang, GUO Tao

Acta Agronomica Sinica. 2021, 47(5):  827-836.  doi:10.3724/SP.J.1006.2021.02044

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MTL is the key gene for control haploid induction traits in maize, which is highly function conserved in crops. OsMATL is a homologous gene of MTL in rice. It has been confirmed that OsMATL mutation can induce haploid in rice, but the effect of OsMATL mutation in different genetic backgrounds remains to be determined. In this study, Nipponbare (Oryza sativa japonica) and Huahang 48 (Oryza sativa indica) were used as research materials. CRISPR/Cas9 technology was used to edit different sites in the promoter region and coding region of OsMATL, and a series of OsMATL mutations with different genetic backgrounds were successfully obtained. The effect of different mutation sites on seed setting rate was analyzed, and it was found that the seed setting rate was 2%-15% in the coding region of OsMATL. There were different types of abortion seeds, while large fragment deletion in the promoter region had no significant differences on seed setting rate. In addition, the background of indica rice mutants of seed setting rate was higher than japonica rice mutants. OsMATL mutants of different types created in this study provided basic materials for further research on the mechanism of parthenogenetic haploid induction in rice.

Integrated analysis between folate metabolites profiles and transcriptome of panicle in foxtail millet

MA Gui-Fang, MAN Xia-Xia, ZHANG Yi-Juan, GAO Hao, SUN Zhao-Xia, LI Hong-Ying, HAN Yuan-Huai, HOU Si-Yu

Acta Agronomica Sinica. 2021, 47(5):  837-846.  doi:10.3724/SP.J.1006.2021.04173

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Folate (FA) is an important donor for energy metabolism, amino acid and nucleic acid synthesis, and participates in the intracellular carbon unit transfer reaction. In previous study, we found that folate content in panicle of foxtail millet was higher than other cereal crops, but the composition characteristics of folate metabolites are still unclear. In this study, in order to explore the expression patterns of folic acid components and folic acid metabolism pathway genes and their correlation with variable shear, and to predict the protein interaction network of folic acid synthesis pathway genes, folate metabolome was performed on three panicle development stages using the middle part of the ‘Jingu 21’ panicles as the experimental materials by RNA-seq. The results showed that the total folate content decreased with panicle development stage, and the contents of 5-methyl tetrahydrofolate (5-M-THF) and 10-formyl folate (10-F-FA) were the main components of panicle development. The expression pattern analysis of 17 key genes of folate synthesis can be divided into two groups during the panicle development in foxtail millet. The alternative splicing showed that the 16 key genes for folate synthesis produced transcription start site (TSS) and transcription terminal site (TTS) during the panicle development, the number of other types of alternative splicing was different at each stage, and this specific alternative splicing affects folate content. In addition, methylation pathway, hormone signaling pathway and immune pathway related genes showed a certain correlation with different folate metabolite content, and we preliminarily hypothesized that the expression of folate synthesis related and coupling pathway genes would influence the folate content during the panicle development. The different expression of ADCS, DHFR2, and GGH may be the main reason for the influence of folate content in panicle, and could be used as key target gen 837-846es for folate biofortification of foxtail millet by genetic engineering technology in the future.

Detecting QTL system of root hydraulic stress tolerance index at seedling stage in soybean

WANG Wu-Bin, TONG Fei, KHAN Mueen-Alam, ZHANG Ya-Xuan, HE Jian-Bo, HAO Xiao-Shuai, XING Guang-Nan, ZHAO Tuan-Jie, GAI Jun-Yi

Acta Agronomica Sinica. 2021, 47(5):  847-859.  doi:10.3724/SP.J.1006.2021.04176

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Soybean is an important source of plant protein and vegetable oil in the world. Drought is one of the important environmental stress factors affecting soybean yield. To explore the genetic base of drought tolerance in soybean, a nested association mapping population composed of two sets of recombinant inbred lines with a common parent in a total of 429 lines was investigated for leaf proline content under PEG simulated drought stress. The genetic system of root hydraulic stress tolerance index (RHSTI) was analyzed using the RTM-GWAS (restrictive two-stage multilocus genome-wide association study). The results showed that there were significant differences in RHSTI among the three parents under two different environments in spring and summer, and among the nested association mapping population with the variation range of 0.11-2.94 and 0.03-1.93, respectively. The heritability values of Line and Line×Environment were 37.9% and 60.1%, respectively, indicating that the variation of RHSTI was greatly affected by the environment. Using the RHSTI data and 6137 SNPLDB markers, a total of 45 main effect QTLs were detected on 18 chromosomes, which could explain a total of 37.58% phenotypic variation, including 7 large contribution QTLs with R ² more than 1%. Among them, 34 QTLs with QTL×Environment effect explained 12.50% of the phenotypic variation. Combined with the transcriptome data under PEG stress, totally 38 differentially expressed genes were identified within a QTL ± 500 kb, which can be grouped into different biological categories, including ABA responders, stress responders, transcription factors, development factors, protein metabolism factors, unknown functions and others, with stress responses, transcription factors and development factors as the major parts. In summary, the results indicated that the drought tolerance of soybean was a complex quantitative trait, with the complex genetic basis controlling by multiple loci, multiple genes and interaction with the environment. The present results can lay the foundation of molecular breeding for drought tolerance in soybean.

Genetic and cytological analysis of male sterile mutant msm2015-1 in mungbean

WU Ran-Ran, LIN Yun, CHEN Jing-Bin, XUE Chen-Chen, YUAN Xing-Xing, YAN Qiang, GAO Ying, LI Ling-Hui, ZHANG Qin-Xue, CHEN Xin

Acta Agronomica Sinica. 2021, 47(5):  860-868.  doi:10.3724/SP.J.1006.2021.04153

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In China, the low yield per unit has always been a problem in the mungbean industry. The heterosis of mungbean is an effective way to increase yield. The male sterile line is a valuable resource to realize the utilization of hybrid. In this study, ⁶⁰Co-γ radiation mutagenesis technology was used to induce male sterile mutants in mungbean, and we gained one mutant named male sterile mungbean 2015-1 (msm2015-1) for the first time. There was no significant phenotype difference between msm2015-1 and Sulyu 1 during the vegetative growth stage. The floral organ of msm2015-1 was normal, but the anthers of msm2015-1 were white and could not crack and disperse powder normally in the flowering stage. In the mature stage, hardly any normal pods grew up. Genetic analysis showed the separation ratio of fertility and sterility in the fertile segregation population was in line with 3:1, indicating that the sterility trait was controlled by a single recessive nuclear gene. Cytological analysis of pollen development revealed that there were few pollen grains of msm2015-1 attached to mature stigmas. The pollen grains of msm2015-1 did not germinate in vitro. The cytoplasm of msm2015-1’s pollen could not be stained by Alexander dye. Three abortion types showed up when stained by I₂-KI dye: typical abortion, spherical abortion and stained abortion. DAPI staining showed the nuclei of msm2015-1’s pollen developed abnormally. Magenta acetate staining indicated that abortion occurred in the early stage of pollen development, while the asymmetry and more anomalous fission of meiosis during the tetrad stage were the main causes of pollen abortion.

Genetic analysis for yield related traits of wheat (Triticum aestivum L.) based on a recombinant inbred line population from Ningmai 9 and Yangmai 158

JIANG Peng, ZHANG Xu, WU Lei, HE Yi, ZHANG Ping-Ping, MA Hong-Xiang, KONG Ling-Rang

Acta Agronomica Sinica. 2021, 47(5):  869-881.  doi:10.3724/SP.J.1006.2021.01051

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Ningmai 9 and Yangmai 158 are the main commercial wheat varieties, as well as the backbone parents in wheat breeding programs in the middle and lower reaches of the Yangtze River in China. Both of them have high yield potential, while they showed significant difference in yield components. To understand the genetic mechanism of their high yield potential, 282 recombinant inbred lines (RILs) derived from the cross between Ningmai 9 and Yangmai 158 were genotyped with the Illumina iSelect 90K wheat single nucleotide polymorphism (SNP) assay to construct a high-density genetic map. Yield (YD) and yield-related traits including spike number (SN), kernel number per spike (KN), and 1000-kernel weight (TKW) were evaluated for three consecutive growing seasons. The results indicated that the KN of Ningmai 9 was higher than that of Yangmai 158, while TKW was lower than that of Yangmai 158. In total, 9, 8, 10, and 12 QTLs associated with SN, KN, TKW and YD were identified by QTL mapping, respectively. Among these traits, TKW possessed the highest heritability, and three QTL associated with TKW were identified repetitively. The markers related to such QTLs were then transferred to Kompetitive Allele Specific PCR (KASP) markers for high throughput selection in 139 wheat accessions. It was indicated that pyramiding 2 or 3 QTLs was more effective than single QTL for TKW improvement. The results in this study could provide more information for marker assisted selection in wheat yield breeding program.

Identification, localization and expression analysis of beta-carotene isomerase gene family in sugarcane

HUANG Ning, HUI Qian-Long, FANG Zhen-Ming, LI Shan-Shan, LING Hui, QUE You-Xiong, YUAN Zhao-Nian

Acta Agronomica Sinica. 2021, 47(5):  882-893.  doi:10.3724/SP.J.1006.2021.04128

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Strigolactones (SLs), a class of plant hormones, exists widely in plants and involves in the regulation of plant tillering and environmental adaptation. β-carotene isomerase (D27) is a key enzyme for SLs synthesis, but there are few reports about the identification and analysis of D27 gene family in sugarcane. In this study, five members of D27 gene family from one of the original parent of modern sugarcane cultivars, Saccharum spontaneum, were analyzed. Phylogenetic tree analysis showed that these D27s from S. spontaneum was clustered into 3 different branches and were highly homologous to sorghum D27s. Conserved domain prediction revealed that D27s contained a typical domain of β-carotene isomerase, Pfam: DUF4033. The results of cis-element analysis showed that D27s mainly involved in the regulation of hormone response, plant growth and development, and stress response. Based on the transcriptomic data of the modern cultivated varieties, the expression analysis of the homologous transcripts of Saccharum spontaneum D27s showed that Sspon.06G0012830-1A was regulated at tillering stage and under Sporisorium scitamineum infection. Besides, the cDNA sequence of Sspon.06G0012830-1A was cloned from sugarcane cultivar ROC22 and named as ScD27.1 (GenBank accession number: MT499895). Bioinformatics analysis indicated that ScD27.1 encoded an unstable protein of 266 amino acids with an isoelectric point of 8.91 and a molecular weight of 30.00 kD, and might be located in the chloroplast, containing chloroplast transit peptides, 4 ubiquitination sites and 18 phosphorylation sites. Its secondary structure mainly included alpha helix and random coils. qRT-PCR analysis demonstrated that ScD27.1 was significantly induced by ABA and H₂O₂ and did not respond to MeJA and SA. Subcellular localization revealed that ScD27.1 might be located in cell membrane and chloroplast and involved in the vesicle sorting or transported by sorting vesicle in plant cells. The results suggested that ScD27.1 may involve in the tillering induced by S. scitamineum and signaling pathway of ABA and H₂O₂. The present study provides a basic understanding of intracellular transport and tillering in sugarcane and the involvement of ScD27.1 during sugarcane-S. scitamineum interaction.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Response of endogenous brassinosteroids to nitrogen rates and its regulatory effect on spikelet degeneration in rice

YAO Jia-Yu, YU Ji-Xiang, WANG Zhi-Qin, LIU Li-Jun, ZHOU Juan, ZHANG Wei-Yang, YANG Jian-Chang

Acta Agronomica Sinica. 2021, 47(5):  894-903.  doi:10.3724/SP.J.1006.2021.02048

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In order to investigate whether and how brassinosteroids (BRs) mediate the effect of nitrogen (N) rates on spikelet degeneration of rice, rice cultivars Yangdao 6 and Yongyong 2640 were grown in pots subjected to three N rates in the whole growth periods. The contents of N, BRs, hydrogen peroxide (H₂O₂) and total antioxidant capacity (T-AOC) in young rice panicles at meiosis stage and their relationship with spikelet degeneration rate were observed. The results showed that the decreased spikelet degeneration rate was closely associated with enhanced 24-epicastasterone (24-epiCS) and 28-homobrassinolide (28-homBL) contents in young panicles. When N content of rice panicle was 1.25%, the BRs (24-epiCS and 28-homBL) content in young panicle increased significantly, and the spikelet degeneration rate decreased. The variation trend of T-AOC level was very consistent with BRs, and T-AOC was significantly negatively correlated with spikelet degeneration rate, whereas the variation trend of H₂O₂ content was opposite to that of T-AOC and BRs contents in the young panicles. Application of exogenous BRs (24-epiCS or 28-homBL) to young panicles could significantly increase the T-AOC level and contents of endogenous 24-epiCS and 28-homBL, but significantly reduce the H₂O₂ content and spikelet degeneration rate, while application of BRs synthesis inhibitor had the opposite effect. In summary, BRs mediated the effects of N application rates on spikelet degeneration, and elevated BRs contents in young panicles could inhibit spikelet degeneration by elevating antioxidant capacity under a proper panicle N content (1.25%) at meiosis stage in rice.

Relationships among grain yield, rice quality and nitrogen uptake of inbred middle-ripe japonica rice in the middle and lower reaches of Yangtze River

LIU Qiu-Yuan, ZHOU Lei, TIAN Jin-Yu, CHENG Shuang, TAO Yu, XING Zhi-Peng, LIU Guo-Dong, WEI Hai-Yan, ZHANG Hong-Cheng

Acta Agronomica Sinica. 2021, 47(5):  904-914.  doi:10.3724/SP.J.1006.2021.02050

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In 2017 and 2018, 90 and 105 inbred middle-ripe japonica rice varieties (lines) in the middle and lower reaches of Yangtze River were collected and planted in a unified way, and grain yield, rice quality and nitrogen uptake of each variety were measured at mature stage. The relationships among grain yield, rice quality and nitrogen uptake were analyzed, so as to clarify the coordinated improvement path of grain yield, rice quality and nitrogen uptake of inbred middle-ripe japonica rice in the middle and lower reaches of Yangtze River. The results indicated that grain yield was significantly positive correlated with spikelet per panicle and 1000-grain weight, and negatively correlated with percentage of filled grains. There was no significant correlation between grain yield and the number of effective panicles. Spikelet per panicle had the greatest direct path coefficient to grain yield, the number of effective panicles had the greatest limiting effect on yield formation through other yield components, and 1000-grain weight had the least limiting effect on yield formation through other yield components. The total nitrogen uptake was significantly positive correlated with the dry matter weight of stem, leaf and panicle. Path analysis showed that increasing biomass had a positive effect on increasing nitrogen uptake. Amylose and protein were significantly correlated with rice milling quality, appearance quality and taste value. Reducing amylose and protein content was beneficial to improve eating quality, but not conducive to the improvement of milling and appearance quality. The results of correlation analysis showed that there was a significant positive correlation between 1000-grain weight, spikelet per panicle, dry weight of stem, leaf and panicle. There was no significant correlation between dry weight of stem, leaf and panicle, 1000-grain weight, spikelet per panicle and amylose content, but they were significantly negatively correlated with protein content. To sum up, the selection of varieties with low amylose content among those with large biomass, suitable population spikelet and higher 1000-grain weight would be an effective way to realize the coordinated improvement of grain yield, nitrogen uptake and eating quality of inbred middle-ripe japonica rice in the middle and lower reaches of Yangtze River. However, this may not be conducive to the improvement of milling and appearance quality and it needs to be further studied.

Characteristics of post-anthesis carbon and nitrogen accumulation and translocation in maize cultivars with different low nitrogen tolerance

WU Ya-Wei, PU Wei, ZHAO Bo, WEI Gui, KONG Fan-Lei, YUAN Ji-Chao

Acta Agronomica Sinica. 2021, 47(5):  915-928.  doi:10.3724/SP.J.1006.2021.03033

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To understand the suitable amount of nitrogen (N) application and the potential of increasing yield and improve efficiency for the maize cultivars with different low N tolerance. The experiment was setting from 2017 to 2019, the low-N tolerant cultivar ‘Zhenghong 311 (ZH311)’ and the low-N sensitive cultivar ‘Xianyu 508 (XY508)’ were selected and four N application rates (0 kg hm^-2, 150 kg hm^-2, 300 kg hm^-2, and 450 kg hm^-2) were set to investigate the effects of N level on carbon (C) and N accumulation and translocation in the later growth stage of different maize cultivars. The results showed that in low N environment, maize increased the C and N translocations of pre-silking to the grain to ensure the yield. Increasing the N fertilizer applications could improve the contribution rates of dry matter and carbohydrate to grain yield. Compared with XY508, ZH311 had higher accumulations of plant dry matter, N and non-structural carbohydrate (NSC) of pre- and post-silking, and higher contribution rates of dry matter, N and accumulations to grain yield of post-silking, so it had higher grain yield. There was no significant difference between cultivars in the rate of dry matter, N and NSC translocation of pre-silking. In the face of low N stress, ZH 311 not only ensured the sufficient C and N translocations of pre-silking to the grain, but also maintained a higher capacity of assimilate accumulation to affect the yield formation.

Response of photosynthetic performance of intercropped wheat to interaction intensity between above- and below-ground

WANG Yi-Fan, YIN Wen, HU Fa-Long, FAN Hong, FAN Zhi-Long, ZHAO Cai, YU Ai-Zhong, CHAI Qiang

Acta Agronomica Sinica. 2021, 47(5):  929-941.  doi:10.3724/SP.J.1006.2021.01047

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The purpose of this study is to explore the effects of above-ground and underground interaction intensity of intercropped population on the photosynthetic performance of intercropped wheat and to provide a basis for further revealing the photosynthetic mechanism of crop yield advantage in intercropping system. From 2015 to 2017 wheat intercropping with maize was taken as the research object. Three root separation methods were designed: no root separation (complete below-ground interaction treatment, W/M), 300 mesh nylon net separation (partial below-ground interaction treatment, NW/M), 0.12 mm plastic cloth separation (no below-ground interaction treatment, PW/M), and tow level maize densities. Meanwhile, the corresponding monocluture was carried out. The results showed that the P_n of intercropped wheat was significantly increased by the complete below-ground interaction treatment during per-symbiotic period and late symbiotic period of wheat/maize intercropping, with the increase of maize density the P_n of wheat increased during late symbiotic period. During per-symbiotic period, mid-symbiotic period and late symbiotic period of wheat/maize intercropping, the complete below-ground interaction treatment can significantly improve the G_s, C_i of intercropped wheat. The increase of maize density can promote the increase of G_s in the complete below-ground interaction treatment and partial below-ground interaction treatment during per-symbiotic period. The T_r of leaves was higher during mid-symbiotic period and late symbiotic period of wheat/maize intercropping without below-ground interaction treatment, while the T_r of leaves remained lower in both stages of complete below-ground interaction and partial below-ground interaction. Complete below-ground interaction treatment was helpful to increase the daily leaf area (LAD) in wheat, with the development of growth process, the increase ratio was larger. Complete belowground interaction treatment significantly increased the SPAD of leaves during mid-symbiotic period, which was beneficial to increase photosynthetic intensity. Intercropped wheat had significant yield-increasing effect. The grain yield of wheat under complete below-ground interaction treatment reached 76.8% of the corresponding single-cropped, which had the advantage of significantly increasing the grain yield of intercropping population. Moreover, the enhancement of above-ground interaction intensity was conducive to the positive effect of complete below-ground interaction treatment. The intensity of above- and below-ground interaction was one of the important factors affecting the photosynthetic characteristics of intercropped wheat.

Evaluation of orderly mechanical seedling-broadcasting on yield formation and growth characteristics of rice

WANG Wei-Qin, TANG Qi-Yuan, CHEN Yuan-Wei, JIA Wei, LUO You-Yi, WANG Xiao-Hui, ZHENG Hua-Bin, XIONG Jiao-Jun

Acta Agronomica Sinica. 2021, 47(5):  942-951.  doi:10.3724/SP.J.1006.2021.02032

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Orderly mechanical seedling-broadcasting refers to the rice establishment methods that throw-transplanted the rice seedlings to the field in rows and lines by seedling broadcasting machine. Which are suggested to prominently increase the uniformity and efficiency of rice crops compared with manual seedling broadcasting. The present study was carried out to compare the differences between orderly mechanical seedling-broadcasting, manual transplanting and manual seedling broadcasting regarding yield formation and growth characteristics of rice. The results suggested that the grain yield of rice under orderly mechanical seedling-broadcasting was increased compared with manual transplanting and manual seedling broadcasting by 22.4%-28.3% and 2.8%-8.9%, respectively. On the aspect of growth traits, the orderly mechanical seedling-broadcasting was characterized as good ventilation, better assimilation ability of dry matter at late growth stages, delayed leaf senescence and high grain filling percentage, which increased the panicle numbers per square meter by 20.9%-64.2% compared with that of manual transplanting and increased the seed setting rate as compared with manual seedling-broadcasting. However, in order to further develop the potential of high yield, the techniques and planting machines of orderly mechanical seedling-broadcasting still need to be improved. In addition, the process of seedling recovery, tiller development and root growth traits of rice under orderly mechanical seedling-broadcasting should be explored in future studies.

Response of yield of different growth types of japonica rice varieties to climatic factors at different sowing dates in Taihu region of Jiangsu province

DONG Ming-Hui, CHEN Pei-Feng, JIANG Yi, CAO Peng-Hui, SONG Yun-Sheng, GU Jun-Rong, XIE Yu-Lin, QIAO Zhong-Ying, ZHANG Wen-Di, HUANG Li-Fen

Acta Agronomica Sinica. 2021, 47(5):  952-963.  doi:10.3724/SP.J.1006.2021.02031

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Light, temperature, water are important factors affecting the formation of rice yield. In order to investigate the response of different growth types of rice to climate factors under different sowing dates in Taihu region of Jiangsu province and to provide the basis for reasonable sowing date arrangement of different growth type varieties in the region, two different growth types with high-quality early maturing line Su 1785 and late maturing variety Suxiangjing 100 were planted at different sowing dates from 2018 to 2019 in the experimental farm of Suzhou Academy of Agricultural Sciences. The results showed that the yield of varieties with different growth stages decreased with the delay of sowing date. The yield variation of late maturing varieties was larger than that of early maturing varieties during sowing dates and years, and the stability of yield was poor. The effective panicles and the total grains per panicle of two varieties at different growth stages decreased with the delay of sowing date, while the differences of sowing dates of seed-setting rate and 1000-grain weight varied with different growth types. Early sowing dates significantly reduced the seed setting rate of early maturing varieties, while late sowing dates significantly decreased 1000-grain weight of late maturing varieties. The effects of sowing dates on photosynthetic production before heading stage of early maturing varieties were significantly higher than that of late maturing varieties, while the effects on dry matter accumulation and population productivity after heading stage were opposite. Under the condition of late sowing dates, the stem sheath matter export rate and translocation rate of late maturing varieties decreased rapidly, which was not conducive to the transport of stem sheath materials and accumulation of filling materials. The correlation analysis showed that sunshine hours were the first most important climatic factors affecting rice yield. The effects of daily average temperature and effective accumulated temperature on rice yield varied with different growth types. Daily average temperature and effective accumulated temperature were significantly positively correlated with the yield of early maturing varieties, but not with late maturing varieties. The effects of climate factors on yield were as follows: sunshine hours > average daily temperature, and effective cumulative temperature > precipitation.

RESEARCH NOTES

Effects of nitrogen reduction on stem vascular bundles, panicle and yield characters of RIL populations in Liaojing 5/Akitakaomaqi and their correlation

CHENG Yan-Shuang, HU Mei-Yan, DU Zhi-Min, YAN Bing-Chun, LI Li, WANG Yi-Wei, JU Xiao-Tang, SUN Li-Li, XU Hai

Acta Agronomica Sinica. 2021, 47(5):  964-973.  doi:10.3724/SP.J.1006.2021.02040

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The recombinant inbred lines (RILs) population constructed by crossing between Liaojing 5 (a typical erect panicle type rice variety in Liaoning) and Akitakaomaqi (a good quality rice variety in Japan) were used as experimental materials and planted under high nitrogen and low nitrogen fertilization mode. In order to explore the possible ways to maintain stable yield while reducing the amount of nitrogen application, we investigated the stem vascular, panicle and yield traits of the RIL population and analyzed the effects of nitrogen reduction on them and their correlation. The results showed that the traits of stem vascular bundle, spike and yield of RIL population showed continuous variation under two different fertilization models, which was consistent with the genetic characteristics of quantitative traits controlled by multiple genes. The number of vascular bundles of panicle neck and penultimate internode in a stem, the area of vascular bundles of panicle neck and penultimate internode in a plant were decreased, the number of primary branches decreased, the seed setting rate of primary and secondary branches, the total seed setting rate and 1000-grain weight increased, the weight of single panicle increased, the number of panicle decreased, and the yield was decreased after nitrogen fertilizer reduction. The traits of vascular bundle in stem were closely related to the traits of panicle and yield. The traits of vascular bundle in single stem were positively correlated with the thickness of panicle neck, number of primary branches, number of secondary branches, number of panicle grains, kernel density, 1000-seed weight, and the number of panicles. The area of vascular bundle per plant was positively correlated with the number of panicles and yield. After nitrogen decrease treatment, the main characteristics of no reduction yield type in RIL populations were as follows: under the condition of low nitrogen, there was a stable differentiation of tiller and stem vascular bundle, ensuring the stable number of panicles and neck diameter; there was not significant differences in the number of big and small vascular bundles of panicle necks and penultimate internodes in a stem, the area of big vascular bundles of penultimate internodes in a stem and in a plant, and number of stems and branches. Under the condition of reducing nitrogen fertilizer, it is possible to achieve the goal of reducing nitrogen without reducing yield by selecting rice varieties with developed vascular bundles in stems and stable panicle numbers and panicle necks.

Identification of wheat dwarf mutants and analysis on association between the mutant traits of the dwarf plants

HE Jun-Yu, YIN Shun-Qiong, CHEN Yun-Qiong, XIONG Jing-Lei, WANG Wei-Bin, ZHOU Hong-Bin, CHEN Mei, WANG Meng-Yue, CHEN Sheng-Wei

Acta Agronomica Sinica. 2021, 47(5):  974-982.  doi:10.3724/SP.J.1006.2021.01066

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Dwarf mutant is an important gene resource in wheat breeding and plant height genetic research. In this paper, EMS (ethyl methyl sulfonate) was used to mutate the mature seeds of ‘Yunmai 53’, and 33 candidate dwarf mutants of M₃ generation were finally obtained by self-bred. Twenty-six dwarf mutants were selected by analyzing differences between the mutant parent in two years and that of M₂ and M₃ generation candidate plants, and the variation range of their plant height was from (13.61 ± 0.11) cm to (44.08 ± 1.73) cm. Twenty-six dwarf mutants with at least 2 mutant sites were verified based on 12 specific markers of 8 dwarf genes. In addition to plant height, 26 dwarf mutants also carried four mutational traits, spike length, spikelet density, internode number, and average internode length. The 26 dwarf mutants could be clustered into 5 subgroups. Among them, the first subgroup was the least in spikelets and florets, the second subgroup was the shortest in plant height, spike length and average internode length, and the highest spikelet density, while the third subgroup was the least in internode number. Plant height was significantly correlated with average internode length and internode number with partial correlation coefficients of 0.94 and 0.58, respectively, but not correlated with spike length, spikelet number and spikelet density. The plant height was genetically associated with internode length and internode number in 26 dwarf mutants. The mutants carried different combinations of the mutant gene, and can be useful in wheat dwarf breeding and the studies on genetic mechanism of the traits, such as plant height, spike length and spikelet density.

Morphological characteristics and cytological study of anther abortion of temperature-sensitive nuclear male sterile line 160S in Brassica napus

TANG Xin, LI Yuan-Yuan, LU Jun-Xing, ZHANG Tao

Acta Agronomica Sinica. 2021, 47(5):  983-990.  doi:10.3724/SP.J.1006.2021.04207

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The main purpose of this study was to explore the flower morphologies, anther abortion times and cytological characteristics of the thermo sensitive genic male sterile line 160S in Brassica napus. The results will provide a theoretical basis for further study on the molecular regulation mechanism and guide significance for its practical application in two-line hybrid breeding of rape. The 160S were grown at 15℃ and 28℃. The flower morphology, microspore, anther structure and tapetum at different stages of fertile plants (Male Fertile/160S-MF) and sterile plants (Male Sterile/160S-MS) were observed by stereomicroscope with carmine acetate staining, paraffin section, hematoxylin eosin staining and TUNEL staining. The anther was yellow, plump and dehiscent with high pollen viability at 15℃. At 28℃, there was no differences in pistil and potato chips between 160S-MS and 160S-MF flowers, but the petals and the filaments of 160S-MS were smaller and shorter. The stamens of 160S-MS degenerated obviously and its anthers were shriveled in yellowish brown without pollen grains, indicating completely male sterility. But interestingly, the 160S-MF developed normally with higher pollen viability. However, microspore and pollen grains were not observed in 160S-MS due to complete abortion of stamens. Paraffin section results showed that there was no significant difference between 160S-MS and 160S-MF in sporulation and pollen mother cell stages. The morphology and structure of tapetum of 160S-MS appeared some abnormal appearances, such as irregularly cell arrangement, vacuolization, and premature disintegration at meiosis stage. Meanwhile, the development of pollen mother cells were hindered and no tetrads structure were formed leading to the empty pollen sac before the completion of meiosis. TUNEL assay showed that the tapetum of 160-MS began to apoptosis at meiosis stage. In summary, these results showed that 160S belongs to pollen mother cell abortion type male sterile line, whose abortion stage occured during meiosis stage and the tapetum cells degraded prematurely and failed to be transformed to the glandular type, so that the nutrients needed for pollen mother cell development were not provided. The tetrad structures and microspores can not be formed, which leaded to the formation of empty anther sac and resulted in male sterility.