Table of Content

12 December 2024, Volume 50 Issue 12

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REVIEW

Breeding objectives and strategies for maize in the Huang-Huai-Hai Region

CHEN Yong-Qiang, WANG Ya-Fei, XIE Hui-Ling, ZHANG Zhan-Hui, HEI Hong-Chao, PENG Qiang, YANG Xue-Li, HE Ge-Ming, TANG Ji-Hua

Acta Agronomica Sinica. 2024, 50(12):  2917-2924.  doi:10.3724/SP.J.1006.2024.43026

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The Huang-Huai-Hai region, the second largest maize-producing area in China, is situated in a transitional zone between the subtropical and north temperate climates. This region is characterized by a unique double cropping system of winter wheat-summer maize, which presents specific challenges for maize cultivation. The distinct ecological conditions and cropping system necessitate maize varieties with enhanced comprehensive resistance and adaptability. This paper provides a detailed analysis of the current production status and the primary issues facing maize cultivation in the Huang-Huai-Hai region. It identifies key breeding objectives, including “high yield, suitability for mechanized harvesting, early maturity, tolerance to high planting density, resilience to environmental stresses, and resistance to major diseases and pests.” Based on these objectives, the paper proposes several breeding strategies: “reducing heterosis to increase planting density, improving kernel bulk density and single-ear seed yield, incorporating multiple resistance genes to enhance disease resistance, strengthening lodging resistance by increasing the number of brace roots, and promoting earlier anther dehiscence and pollen release to avoid high temperatures.” Additionally, the paper emphasizes the importance of identifying and utilizing superior genes, advancing the development of new core germplasm resources, and establishing modern molecular breeding systems, such as genome editing and genome-wide selection. It also advocates for the creation of an innovative collaboration model among research institutes, universities, and seed enterprises to accelerate germplasm innovation, improve maize breeding efficiency, and enhance the breeding and promotion of the entire industry chain. The ultimate goal is to develop superior new maize varieties that will effectively support agricultural production in the Huang-Huai-Hai region.

CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Identification of the CLE gene family in Gossypium hirsutum and functional analysis of the drought resistance of GhCLE13

RONG Yu-Xuan, HUI Liu-Yang, WANG Pei-Qi, SUN Si-Min, ZHANG Xian-Long, YUAN Dao-Jun, YANG Xi-Yan

Acta Agronomica Sinica. 2024, 50(12):  2925-2939.  doi:10.3724/SP.J.1006.2024.44029

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The CLAVATA3/Embryo surrounding region-related (CLE) peptide family is the largest family of small peptide hormones in plants. It is widely present in various plant species and participates in multiple important life activities of plants. In this study, the CLE gene family was identified at the genome-wide level in Gossypium hirsutum, and their gene structures, cis-acting elements in the promoter, protein physicochemical properties, and phylogenetic analysis of GhCLE gene family members were analyzed. The expression profiles of GhCLE gene family members in various tissues were constructed using RNA-seq data. Finally, the drought resistance function of the screened GhCLE genes was validated by virus-induced gene silencing (VIGS) technology. The results showed that a total of 40 GhCLE genes were identified in the whole genome of Gossypium hirsutum. The structures of GhCLE genes were relatively simple, with 32 GhCLE genes having no introns, and their protein sequences all contained a 12 aa CLE domain. The GhCLE gene promoter region contains a variety of cis-acting elements related to light response, stress response, hormone response, and development. The gene expression profile showed that the GhCLE gene was expressed in multiple tissues of Gossypium hirsutum, with GhCLE13-D-2 being specifically expressed in root tissue and induced by drought. The function of the GhCLE13-D-2 gene in improving cotton drought resistance was validated through VIGS technology and the measurement and comparison of MDA content. This study provides a new theoretical basis for the in-depth study of small peptides, such as CLE, in plant drought resistance and cotton germplasm innovation.

Functional analysis of TaEMF2 in regulating wheat heading date

WU Li-Fen, XIA Chuan, ZHANG Li-Chao, KONG Xiu-Ying, CHEN Jing-Tang, LIU Xu

Acta Agronomica Sinica. 2024, 50(12):  2940-2949.  doi:10.3724/SP.J.1006.2024.41027

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A suitable heading date (flowering time) is a crucial breeding goal for achieving high and stable crop yields. EMF2 is an important gene involved in the regulation of heading date, but its function in wheat remains unclear. In this study, TaEMF2-2D, the orthologous gene of the rice heading date regulatory gene OsEMF2b, was cloned from wheat. Subcellular localization assays revealed that TaEMF2-2D is a nucleus and cytoplasm protein. To elucidate the role of TaEMF2 in regulating wheat heading date, we used the CRISPR/Cas9 gene editing system to knockout TaEMF2, which resulted in a delayed heading date in wheat. Conversely, overexpression of TaEMF2-2D caused an early heading date. Further analysis showed that the expression levels of the flowering-related genes VRN1 and VRN3 were significantly reduced in the knockout lines, while their expression levels were significantly increased in the overexpression plants, as determined by RT-qPCR. These results suggest that the TaEMF2 gene influences wheat heading date by regulating the expression levels of VRN1 and VRN3.

Metabolome and transcriptome analysis of flavonoids in peanut testa

JIN Xin-Xin, SU Qiao, SONG Ya-Hui, YANG Yong-Qing, LI Yu-Rong, WANG Jin

Acta Agronomica Sinica. 2024, 50(12):  2950-2961.  doi:10.3724/SP.J.1006.2024.44057

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To explore the regulatory mechanisms of flavonoid components and anthocyanin biosynthesis in the color formation of peanut testa, we conducted a study using five peanut cultivars with different testa colors: pink, red, white, black, and speckled (red and white). The key metabolites and genes related to anthocyanin biosynthesis were identified using flavonoid metabolomics and transcriptomics. Our results revealed the identification of 329 flavonoid metabolites in peanut testa, with flavonols being the most abundant in both relative content and variety. We detected 19 types of anthocyanidins, including cyanidin, delphinidin, and petunidin. Most anthocyanidins were modified with glucoside, morbuside, rutin, galactoside, and other glycosides. Notably, the anthocyanin content in black testa was 22.60-66.72 times higher than that in other testa colors, with cyanidin-3-O-sambutin being the most prevalent in black testa. Different metabolites were significantly enriched in anthocyanin biosynthesis, flavonoid biosynthesis, flavone and flavonol biosynthesis, and isoflavone biosynthesis pathways in colored testa compared to white testa. The high expression levels of structural genes in the flavonoid and anthocyanin biosynthesis pathways promoted anthocyanin accumulation in colored testa. Anthocyanin reductase (ANR) and glycosyltransferase (UGT) emerged as candidate genes involved in testa pigmentation, with the competition and activity of UGT and ANR against substrate anthocyanin determining the color pattern of peanut testa. These findings elucidate the regulatory mechanisms of flavonoid substances in peanut testa color, providing valuable references for the breeding of special peanut varieties and the utilization of their nutritional value based on color differences.

Overexpression of OsPIN2 increases tiller angle by reducing shoot gravitropic response in rice

WU Jia-Jun, TU Ran-Ran, ZHANG Qiu-Li, ZOU Qin-Wen, SUN Zhi-Hao, WANG Hong, HE Guang-Hua

Acta Agronomica Sinica. 2024, 50(12):  2962-2970.  doi:10.3724/SP.J.1006.2024.42021

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Shoot gravitropism is closely related to the formation of the tiller angle, and understanding its regulatory mechanism is crucial for rationally designing tiller angles to improve crop plant architecture. In the rice auxin efflux carrier gene OsPIN2 overexpression lines, two lines with significantly increased tiller angles, OE-OsPIN2-1 and OE-OsPIN2-2, were identified. Scanning electron microscopy revealed that the near-ground and far-ground parts of the tiller bases in OE-OsPIN2-1/2 grew nearly symmetrically. Shoot gravitropism assays indicated that the shoot gravitropic responses of OE-OsPIN2-1/2 seedlings were reduced, and the asymmetric expression of the auxin marker gene OsIAA20 and WUSCHEL RELATED HOMEOBOX6/11 (WOX6/11) was weakened upon gravistimulation. This suggests that overexpression of OsPIN2 attenuates the asymmetric distribution of auxin following gravistimulation. Furthermore, the expressions of positive regulators involved in the gravitropic response at the tiller base in OE-OsPIN2-1/2 lines were downregulated, while the expressions of negative regulators were upregulated. This further indicates that overexpression of OsPIN2 leads to a reduced shoot gravitropic response. This study elucidates the mechanism by which OsPIN2 controls rice tiller angle by regulating shoot gravitropism, providing a theoretical basis for in-depth studies of shoot gravitropic responses.

Mechanism of reduced insecticidal protein expression in Bt cotton under low-iron stress based on transcriptome analysis

WANG Yong-Hui, HE Jiang, ZHANG Xiang-Xiang, LOU Xiang-Di, GAO Jing, SUN Yan-Ru, CAO Ting, SHI Yang

Acta Agronomica Sinica. 2024, 50(12):  2971-2983.  doi:10.3724/SP.J.1006.2024.44071

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To provide a theoretical basis for the safety of insecticidal efficiency in Bt cotton, this study investigated the effects of low iron on Bt insecticidal protein content and the physiological and molecular mechanisms in Bt cotton. Transgenic Bt cotton cultivar Zhongmian 50 was grown under low iron (LI, 0.1 μmol L^-1 Fe(II)-EDTA) and normal iron (CK, 20.0 μmol L^-1 Fe(II)-EDTA) conditions in hydroponic culture to assess the impact of low iron stress on Bt insecticidal protein content, activities of nitrogen metabolism-related enzymes, and substances in cotton seedlings. Differentially expressed genes (DEGs) were screened, and their relative expression patterns were analyzed by high-throughput sequencing, with results verified by qRT-PCR. The results showed that, compared with the control, the insecticidal protein contents significantly decreased under low iron conditions, with a more pronounced reduction in roots than in leaves. Iron deficiency decreased NH₄⁺-N and NO₃^--N levels in leaves and reduced soluble protein and nitrogen contents in both roots and leaves. Significant reductions in the activities of nitrate reductase (NR), nitrite reductase (NiR), and glutamine synthetase (GS) were observed when Bt insecticidal protein contents in roots and leaves were significantly reduced. High-throughput sequencing identified 11,661 DEGs in roots and 8972 in leaves, with 1652 genes down-regulated in both organs. GO annotation revealed that the functions of the differential genes in two organs were mainly concentrated in response to stimulus, cell wall, plasma membrane, binding, and catalytic activity. KEGG enrichment analysis demonstrated significant changes in phenylpropanoid biosynthesis, phenylalanine metabolism, cysteine and methionine metabolism, plant hormone signal transduction, zeatin biosynthesis, nitrogen metabolism, starch and sucrose metabolism, alanine, aspartate and glutamate metabolism, and tyrosine metabolism in both roots and leaves. Genes coding for NR, NiR1, and GLT1 related to the nitrogen reduction and assimilation pathway were significantly down-regulated under iron deficiency treatment. Therefore, low iron stress inhibits the transcription levels of genes related to nitrogen metabolism in Bt cotton, weakens the physiological activities of nitrogen metabolism, and subsequently reduces Bt insecticidal protein.

Genome-wide association analysis for plant height in foxtail millet (Setaria italica L.) germplasm resources in Shanxi, China

YANG Shi-Jie, WANG Hua-Zhi, PAN Yi-Min, HUANG Rui, HOU Sen, QIN Hui-Bin, MU Zhi-Xin, WANG Hai-Gang

Acta Agronomica Sinica. 2024, 50(12):  2984-2997.  doi:10.3724/SP.J.1006.2024.44070

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A suitable plant height can effectively enhance the nutrient utilization efficiency and lodging resistance of millet. This study utilized 313 local millet varieties from Shanxi as an association group. Plant height was investigated in five different environments, followed by whole-genome deep resequencing. After quality control of the data, 3,160,066 SNP markers uniformly distributed across the nine chromosomes of millet were obtained for genome-wide association analysis (GWAS) of plant height. Eight QTL loci significantly associated with plant height were identified, with each locus explaining 7.13% to 12.08% of the phenotypic variation. Within the 25 kb upstream and downstream confidence intervals of these eight stable QTL loci, forty candidate genes were discovered. Integrating gene annotation information, six candidate genes were identified to be primarily involved in hormone synthesis, cell division regulation, signal transduction, and carbohydrate metabolism. Haplotype analysis revealed that the superior haplotype Hap2 of the candidate gene Millet_GLEAN_10031852 can effectively reduce plant height.

Metabolome and transcriptome analysis reveal molecular response to drought stress in indica rice Fuxiangzhan

WANG Ying-Heng, CUI Li-Li, CAI Qiu-Hua, LIN Qiang, WU Fang-Xi, CHEN Fei-He, XIE Hong-Guang, ZHU Yong-Sheng, CHEN Li-Ping, XIE Hua-An, ZHANG Jian-Fu

Acta Agronomica Sinica. 2024, 50(12):  2998-3012.  doi:10.3724/SP.J.1006.2024.42023

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Drought is one of the most significant factors affecting agricultural production. In this study, the physiological indexes, hormone metabolites, and gene expression regulation network of drought response were analyzed for the high grain quality fragrant rice Fuxiangzhan. After drought stress, Fuxiangzhan exhibited higher drought survival rates and antioxidant enzyme activity compared to restorer lines Minghui63, Minghui86, and the drought-sensitive line Lijiangxintuanheigu, while showing lower membrane iron leakage and less peroxide accumulation. Five hormone metabolites (IAA, ICA, ABA, cZ, and SA) increased, whereas 11 hormone metabolites, including tZ, DHZ, GA1, and JA, decreased. A total of 6118 differentially expressed genes (DEGs) were identified, including 2615 up-regulated and 3503 down-regulated genes, which are involved in biological processes such as photosynthesis, energy metabolism, transcriptional regulation, REDOX, and ion binding, as well as molecular functions related to amino acids, sugars, fatty acids, hormones, and other anabolic metabolism and plant hormone signal transduction. KEGG pathways involving plant hormone signal transduction, zein biosynthesis, carotenoid biosynthesis, and tryptophan metabolism were identified from hormone metabolites and transcriptome analysis. Differentially expressed gene regulatory networks of the four pathways were constructed. The expression levels of 28 drought response genes related to transcription factors, antioxidant enzymes, and osmotic regulation were all up-regulated after drought stress in Fuxiangzhan. Our conclusion is that the hormone levels in Fuxiangzhan change after drought stress. The expression of anti-stress genes, including transcription factors, antioxidant system genes, osmoregulation, and other drought tolerance genes, were up-regulated. These changes lead to alterations in the activity of antioxidant enzymes and other physiological indexes. These results are helpful for further exploration of drought-resistant genes and serve in rice drought resistance breeding.

Effect of allelic combinations of soybean maturity loci E1/E2/E3/E4 on latitude adaptation

FANG Ran, YUAN Li-Mei, WANG Yu-Lin, LU Si-Jia, KONG Fan-Jiang, LIU Bao-Hui, KONG Ling-Ping

Acta Agronomica Sinica. 2024, 50(12):  3013-3024.  doi:10.3724/SP.J.1006.2024.44060

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Soybean, as an important oil crop, is one of the main sources of high-quality protein and edible oil. Soybean yield and seed quality are closely related to growth-period traits, which are mainly controlled by a series of genes associated with the growth period. In this study, 16 near-isogenic lines (NILs) of E1-E4 were developed using Harosoy as the genetic background and were planted in experimental fields in Shijiazhuang and Hefei. The growth period, seed quality, and yield traits were investigated to understand the adaptability of different combinations of E1-E4 mutants to mid-latitude planting areas. The results showed that the 16 NILs had different photoperiod sensitivities and flowering times. WT and e4 NILs were unsuitable for planting in Shijiazhuang due to late flowering and low yield, while all NILs matured normally when planted in Hefei. Different allelic combinations of E1-E4 also affected plant height, node length, yield per plant, and seed quality. We found that e3 or e4 mutations could lead to early flowering under long-day conditions and simultaneously induce a shading response, resulting in taller plants and longer node lengths. We measured the protein, oil, and sucrose content of the seeds and found that the seeds of WT could not mature normally, exhibiting the lowest oil content and the highest sucrose content. Overall, seeds from the other NILs, when planted in Shijiazhuang, showed higher oil and sucrose content compared to those planted in Hefei but lower protein content. Therefore, to evaluate the latitude adaptability of soybean cultivars, it is necessary to comprehensively examine the effects of growth-period genes on photoperiod sensitivity, seed quality, and yield.

Development of functional markers of wheat grain size related gene TaCYP78A17

ZHANG Tian-Xing, LI Meng, WU Lin-Nan, ZHAO Hui-Xian, HU Sheng-Wu, MA Meng

Acta Agronomica Sinica. 2024, 50(12):  3025-3034.  doi:10.3724/SP.J.1006.2024.41009

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Grain size is a crucial factor influencing wheat yield. To develop functional markers related to wheat grain size, we cloned a potential grain size-related gene, TaCYP78A17, and conducted systematic evolution, expression pattern, allelic variation, and functional marker development studies. The results revealed that TaCYP78A17 belongs to the wheat cytochrome P450 CYP78A family and is highly expressed in wheat spikes and grains. Six SNPs and two InDels were identified in the TaCYP78A17-Ap among thirty common wheat varieties. A functional marker, InDel-A17, was developed based on InDel 4 and InDel 8, classifying the thirty wheat varieties into three haplotypes: TaCYP78A17-Ap-HapI, TaCYP78A17-Ap-HapII, and TaCYP78A17-Ap-HapIII. This functional marker was validated in 323 wheat varieties, demonstrating its ability to effectively distinguish the three haplotypes. Phenotypic investigations indicated that wheat with the TaCYP78A17-Ap-HapI haplotype exhibited significantly higher thousand-grain weight and larger seed size compared to those with TaCYP78A17-Ap-HapII or TaCYP78A17-Ap-HapIII. These findings hold promise for the application of molecular marker-assisted selection in wheat breeding.

Identification and comprehensive evaluation of salt-alkali tolerance throughout the growth period of 155 faba bean germplasms

FAN Hui-Ling, BAI Sheng-Wen, LU Yan, PENG Xiao-Xing, ZHOU Xian-Li, ZHANG Hong-Yan, TENG Chang-Cai, WU Xue-Xia, LIU Yu-Jiao

Acta Agronomica Sinica. 2024, 50(12):  3035-3045.  doi:10.3724/SP.J.1006.2024.44067

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Soil salinization has become one of the critical abiotic stresses affecting the growth of faba bean. Identifying salt-alkali tolerant germplasm in faba bean lays the foundation for exploring salt-alkali tolerant genes and selecting and breeding salt-alkali tolerant varieties, which is of great significance for the utilization of salinized land. In this study, 155 faba bean germplasm resources from domestic and international collections were subjected to stress treatment with a matrix + mixed salt-alkali (9 g L^-1, NaCl+Na₂CO₃+Na₂SO₄, pH 10.5) throughout their entire growth period. Seven indicators were measured, including the seedling rate, salt damage index (SDI), plant height, fresh weight, dry weight, chlorophyll content, and nitrogen content. Correlation analysis, principal component analysis, membership function analysis, and systematic cluster analysis were used to comprehensively evaluate and classify the salt-alkali tolerance of various germplasms. A predictive regression equation for salt-alkali tolerance was established using stepwise regression analysis. The results showed as follows: (1) Three faba bean germplasms with salt-alkali tolerance (20 ≤ salt damage index < 40) were identified, constituting 1.94% of the total, while eight germplasms displayed moderate salt-alkali tolerance (40 ≤ salt damage index < 60), comprising 5.16% of the tested germplasms. No highly salt-alkali tolerant (salt damage index < 20) faba bean germplasms were detected. (2) The salt damage index was negatively correlated with plant height, fresh weight, dry weight, chlorophyll content, and nitrogen content (P < 0.01). (3) Five indicators—fresh weight, plant height, salt damage index, chlorophyll content, and seedling rate—can be used as evaluation criteria for assessing salt-alkali tolerance throughout the entire growth period of faba beans. (4) The 155 faba bean germplasms were divided into two major groups, with the salt-alkali tolerant germplasm group exhibiting higher seedling rates, biomass, nitrogen content, and chlorophyll content. These research findings provide reliable materials for studying the mechanisms of salt-alkali tolerance in faba beans, exploring salt-alkali tolerant genes, and selecting and breeding salt-alkali tolerant varieties.

Genetic dissection of the albino hull mutations in barley (Hordeum vulgare L.)

SUN Man, AN Chao-Dan, GAO Guang-Qi, GUO Jie, YANG Ping, JIANG Cong-Cong

Acta Agronomica Sinica. 2024, 50(12):  3046-3054.  doi:10.3724/SP.J.1006.2024.41014

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Lemma and palea are the outermost organs on each floret of barley (Hordeum vulgare L.), where the majority of spike photosynthesis occurs, supplying carbohydrates to the developing grains. The barley albino hull (alh) mutants, obtained from EMS mutagenesis, showed albinistic lemma and palea, as well as albinistic pulvini, stem nodes, and stem bases, while the leaves and awns remain green. In this study, multiple allelic alh mutants were identified, and segregating populations were generated accordingly. Genetic analysis indicated that a single recessive gene is responsible for the alh phenotype. Through re-sequencing of the candidate gene in multiple alh mutants, and co-segregation tests using competitive allele-specific PCR (KASP) markers, loss-of-function mutations in the gene HvGLK2 were shown to account for the alh phenotype. Each of the three independent mutations identified in this study is distinct from previously reported albino lemma variants such as alm1 or ebu-a. HvGLK2 encodes a Golden 2-like (GLK2) transcription factor, belonging to the GARP subfamily of MYB transcription factors, and has a paralog designated GLK1 in most monocot and dicot species. The temporal and spatial expression patterns showed that HvGLK2 is abundantly transcribed in senescent leaves, lemmas, and rachises. This study highlights the importance of HvGLK2 in chlorophyll synthesis in various organs, including lemma, palea, and stem nodes of barley plants. Moreover, it provides valuable materials for further studies aimed at evaluating the contribution of spike photosynthesis to the eventual grain yield.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Effect of low-temperature stress on glucose and water status in rice germ and its relationship with seedling emergence

ZHENG Guang-Jie, YE Chang, XU Chun-Mei, CHEN Song, CHU Guang, CHEN Li-Peng, ZHANG Xiu-Fu, WANG Dan-Ying

Acta Agronomica Sinica. 2024, 50(12):  3055-3068.  doi:10.3724/SP.J.1006.2024.42014

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To investigate varietal differences in rice germ survival and seedling emergence under low-temperature stress and to analyze the mechanisms of low-temperature tolerance during seedling emergence, germinated seeds of four rice varieties with different cold tolerance were used as experimental material and exposed to low temperature and ambient temperature (control) conditions. Carbohydrate and moisture content of seed and germ, seed α-amylase activity, sucrose synthase, antioxidant enzyme activity, hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) content of germ during seedling emergence were analyzed over time, along with their correlation with germ survival. The study found that the glucose content and antioxidant enzyme activity (SOD, POD, and CAT) in the germ of the cold-sensitive varieties Zhongjia 8 (S1) and Zhongjiazao 17 (S2) decreased significantly after 4 days of cold treatment, while H₂O₂ and MDA contents increased gradually, leading to phenotypical stagnation of germ growth and symptoms of death under low-temperature stress. In contrast, the glucose content in the germ of cold-tolerant varieties Nipponbare (T1) and Yunliangyoujiu 48 (T2) remained relatively high, and the enzyme activity of SOD, POD, and CAT, as well as H₂O₂ and MDA contents, remained stable after 8 days of cold treatment, allowing the germ to maintain upright growth. Analysis revealed that cold inhibited seed α-amylase activity but promoted germ sucrose synthase activity. Cold also delayed root development in cold-tolerant varieties T1 and T2 but inhibited root development in cold-sensitive varieties S1 and S2. Additionally, the root vigor of cold-sensitive varieties was significantly lower than that of cold-tolerant varieties, and the water content of seeds and germs in cold-sensitive varieties S1 and S2 decreased continuously, while that of cold-tolerant varieties T1 and T2 remained stable. Correlation analysis demonstrated that germ survival rate was significantly positively correlated with germ and seed glucose content, germ water content, CAT activity, root length, volume, and root vigor, but significantly negatively correlated with seed starch and germ sucrose content. Moreover, increasing water supply to S1 and S2 exogenously significantly improved their survival rate under low temperature. In conclusion, low-temperature stress not only inhibited seed α-amylase activity but also suppressed root growth and development, reducing the ability to transport water to seeds and germs. This, led to a decrease in the ability to degrade seed starch and germ sucrose during the seedling emergence process, resulting in inadequate glucose supply to germs, an imbalance in germ antioxidant metabolism, and reduced survival rate. However, exogenous increase in water supply could improve germ survival rate to some extent under low temperature.

Effects of cropping practices and nitrogen application on nutrient uptake characteristics and root vigor of hybrid indica rice

WANG Cheng, MA Yang-Ming, WANG Chun-Yu, LI Zhi-Xin, LUO Jian-Sheng, PENG Zheng-Lan, LIU Ru-Hong-Ji, HUANG Xing-Hai, CAO Yun, PENG Zheng-Bo, MA Jun

Acta Agronomica Sinica. 2024, 50(12):  3069-3082.  doi:10.3724/SP.J.1006.2024.42012

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To explore the effects of different planting methods and nitrogen application rates on nutrient absorption characteristics, root activity, and yield of hybrid indica rice, F You 498 was used as the experimental material in a two-factor split-plot design. The main plot consisted of carpet seedling machine transplanting, wet precision hole direct seeding, and manual transplanting, while the sub-plot included four nitrogen application rates (0 kg hm^-2, 90 kg hm^-2, 135 kg hm^-2, and 180 kg hm^-2). The effects on nitrogen, phosphorus, and potassium accumulation, root activity, yield, and yield components of hybrid indica rice under different treatments were studied. The results showed that the total nitrogen accumulation at the heading and maturity stages was highest in manually transplanted rice, followed by mechanical transplanting, and then direct seeding. The total phosphorus accumulation at the jointing stage and potassium accumulation at the heading stage were also highest in manually transplanted rice. The nutrient accumulation rate of nitrogen, phosphorus, and potassium before jointing was highest in direct-seeded rice, being 40.68%-63.64% and 19.42%-71.43% higher than in mechanical and manual transplanting, respectively. The nutrient accumulation rate peaked from jointing to heading stage under different planting methods. There was no significant difference in rice yield between manual and mechanical transplanting. However, compared to manual transplanting, direct seeding reduced rice yield by 8.09%-15.00%. The 1000-grain weight, grain number per panicle, and seed setting rate of manually transplanted rice were higher than those of mechanical transplanting and direct seeding, but the effective panicle number was significantly reduced, being 15.99%-41.77% and 23.19%-29.60% lower than those of mechanical transplanting and direct seeding, respectively. The dry matter accumulation of shoots and roots reached its maximum at the maturity and heading stages, respectively. Under manual transplanting conditions, the dry weight of shoots and roots at maturity was greater than that of mechanical transplanting and direct seeding. As the growth process advanced, the bleeding intensity of single stems and populations after heading gradually decreased, and the root activity of single stems and populations in mechanical transplanting was significantly higher than in manual transplanting and direct seeding. The optimal nitrogen application rate for machine-transplanted rice was in the middle to low range (90-135 kg hm^-2), while for direct-seeded and manually transplanted rice, it was in the middle to high range (135-180 kg hm^-2).

Growth visualized prediction method of multi-variety rice based on improved Pix2Pix-HD network

DUAN Ling-Feng, WANG Xin-Yi, WANG Zhi-Hao, GENG Ze-Dong, LU Yun-Rui, YANG Wan-Neng

Acta Agronomica Sinica. 2024, 50(12):  3083-3095.  doi:10.3724/SP.J.1006.2024.42016

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With the advancement of information technology and agricultural digitization, the visualized prediction of digital plant growth holds significant development potential. As an important food crop, achieving visualized growth prediction for rice is of great significance for analyzing its growth and development. However, due to the large size and complex morphology of rice, attaining high-precision and high-resolution visualized growth prediction has been challenging. This study proposes a growth prediction method for rice based on an improved Pix2Pix-HD network, achieving high-precision visualized growth prediction from the heading stage to the filling stage of rice. Comparative experiments were designed to verify the effectiveness of the model improvement scheme. The results showed that the FID, PSNR, and SSIM values between the predicted and real filling stage rice images in the test set were 24.75, 13.58, and 0.78, respectively. The average correlation coefficient between the predicted and actual phenotypes was 0.762, demonstrating good accuracy at different scales. The proposed data-driven rice growth prediction method can achieve high-resolution and high visual realism in rice growth visualization predictions, providing new solutions for rice growth forecasting.

Effects of side-deep fertilization on yield formation and nitrogen absorption of high-quality early indica rice under precision sowing in line and machine planting

JIANG Da-Ren, XIONG Ruo-Yu, WU Jia-Qing, MAO Fu-Qin, FENG Jun-Jie, TAO Lei, XIE Xiao-Bing, PAN Xiao-Hua, ZENG Yong-Jun, WANG Ya-Liang, ZENG Yan-Hua

Acta Agronomica Sinica. 2024, 50(12):  3096-3106.  doi:10.3724/SP.J.1006.2024.42017

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As a major grain crop in China, the efficient cultivation of rice is essential to ensure national food security. Side-deep fertilization and precision drill sowing technology are key measures to improve the efficiency of mechanized rice cultivation. This study aims to elucidate the effects of side-deep fertilization on rice yield formation, rice quality, and nitrogen absorption under precision drill sowing and machine planting, providing a theoretical basis for mechanized high-quality rice cultivation in the southern rice region. In 2022-2023, field experiments were conducted using the Wufengyou 286 rice cultivar. The experiments included two factors: mechanical seeding and raising (precision drill sowing (PS) and broadcast sowing (BS)), and fertilization method (side-deep fertilization (SF) and conventional surface fertilization (CK)). The effects of different treatments on seedling quality, machine transplanting quality, yield formation, nitrogen absorption, and rice quality of high-quality early indica rice were investigated. (1) The yield of precision drill sowing with side-deep fertilization was significantly the highest. Compared with conventional surface fertilization, side-deep fertilization increased rice grain yield by 9.97%-19.62%. Compared with broadcast sowing, precision drill sowing increased rice grain yield by 4.32%-6.29%, primarily due to improvements in the effective panicle number and uniformity of the machine-transplanted population. (2) Precision drill sowing significantly improved the quality of seedlings, reducing the missing hill percentage of machine transplanting by 5.6%-6.0%, and improving the uniformity of seedling number transplanted per hill by 22.0%-33.0%. (3) Both side-deep fertilization and precision drill sowing improved the number of tillers at the tillering peak stage. These methods also increased dry matter accumulation and leaf area index during the rice growing period.Side-deep fertilization, compared with conventional fertilization, increased dry matter accumulation at maturity by 15.71%-18.08% and leaf area index by 19.15%-20.78%. Precision drill sowing, compared with broadcast sowing, increased dry matter accumulation at maturity by 4.56%-7.42% and leaf area index by 8.08%-9.88%. (4) During the middle and late rice growth stages (panicle initiation to maturity), precision drill sowing with side-deep fertilization increased nitrogen accumulation. Side-deep fertilization, compared with conventional fertilization, increased nitrogen accumulation at maturity by 22.66%-28.24%. Precision drill sowing, compared with broadcast sowing, increased nitrogen accumulation at maturity by 7.97%-11.76%. (5) Compared with conventional fertilization, side-deep fertilization significantly reduced the chalky grain rate by 10.63%-20.41%, chalkiness by 13.63%-19.62%, and amylose content by 8.08%-10.42%, but increased protein content by 10.98%-11.25%. In conclusion, side-deep fertilization under precision drill sowing and machine planting can improve seedling quality, machine transplanting quality, rice tillering and panicle formation, growth and development, and nitrogen absorption, thereby increasing the yield of high-quality early indica rice. Additionally, while the appearance quality of rice was improved, the protein content of rice was also increased.

Effects of micro-sprinkling limited irrigation on winter wheat yield, water and nitrogen use efficiency

KANG Xiu-Li, MA Ai-Ping, JING Hua, ZHAO Yu-Kun, CUI Huan-Hu, XI Ji-Long, HUANG Xue-Fang

Acta Agronomica Sinica. 2024, 50(12):  3107-3117.  doi:10.3724/SP.J.1006.2024.41010

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To clarify the influence of micro-sprinkling limited irrigation on winter wheat yield, water, and nitrogen use efficiency, we conducted an experiment with four treatments in irrigated wheat fields in southern Shanxi: normal micro-sprinkling irrigation (S₀), micro-sprinkling limited irrigation (S₁), excessive micro-sprinkling irrigation (S₂), and flood irrigation (F₀). We analyzed the different performance rules in farmland soil water storage and consumption, yield component factors, plant nitrogen distribution, and water and nitrogen utilization under these different irrigation levels. The results showed that soil pondage in the 0-200 cm layer under excessive irrigation (F₀ and S₂) was significantly higher than under normal micro-sprinkling irrigation (S₀) and micro-sprinkling limited irrigation (S₁), with no significant difference between S₀ and S₁. Soil pondage increased with increasing irrigation amounts in all treatments, with the 0-100 cm soil pondage being lower than the 100-200 cm pondage. The percentage of 0-200 cm soil water consumption relative to total water consumption during the winter wheat growth period ranged from 8.95% to 48.48% under the four irrigation treatments, decreasing with increasing irrigation amounts. The peak of 0-200 cm soil water consumption was observed in the S₁ treatment, while the peak of irrigation water consumption was in the F₀ treatment. The deeper 100-200 cm soil water consumption in the F₀ and S₂ treatments was significantly lower than in S₀ and S₁. The spike number of the yield components under excessive irrigation treatments (F₀ and S₂) were significantly lower than those in S₀ and S₁, while the 1000-grain weight was higher in F₀ and S₂. The ranks of winter wheat grain yield in different irrigation treatments were S₀, S₁, S₂, and F₀. There was no significant difference between S₀ and S₁; however, the yields of both treatments were significantly higher than those of F₀ and S₂. Water use efficiency (WUE) in winter wheat decreased with increasing irrigation amounts, with the WUE in the micro-sprinkling limited irrigation (S₁) treatment being 1.39 to 7.36 kg hm^-2 mm^-1 higher than in the other treatments. The nitrogen uptake efficiency and nitrogen harvest index of the S₁ treatment were 1.64% and 1.91% higher than those of the normal micro-sprinkling irrigation (S₀) treatment, while nitrogen fertilizer partial productivity was slightly lower. The nitrogen fertilizer partial productivity in the S₀ and S₁ treatments was significantly higher than in F₀ and S₂. The nitrogen apparent surplus amount in the S₁ treatment was 2.46% to 21.01% lower than in the other treatments, while the nitrogen accumulation in the seeds of the S₁ treatment was 3.64% to 31.39% higher. In summary, micro-sprinkling limited irrigation can promote water uptake in deeper soil layers and grain nitrogen accumulation in winter wheat, optimize irrigation patterns, and improve water use and nitrogen uptake efficiency. This irrigation pattern is characterized by stable production and high efficiency, significantly reducing soil nitrogen surplus and the risk of inorganic nitrogen downward leaching. Thus, it promotes the sustainable and healthy development of water-saving agriculture.

Effects of straw return on soil nutrients and crop yield in rice-rapeseed rotation

CHE Pin-Gao, CHEN Guo-Hui, CAO Guo-Jun, GAO Bing-Ke, CHEN Yan-Fang, XIONG Wen, YING Zhi-Hong, ZHOU Qing-You

Acta Agronomica Sinica. 2024, 50(12):  3118-3128.  doi:10.3724/SP.J.1006.2024.32045

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A seven-year field study from 2016 to 2023 was conducted on typical paddy soil in Jiujing city, Jiangxi province, to evaluate the effects of different straw returning methods on soil nutrients and crop yield in a rice-rapeseed rotation system in the middle-lowerYangtze Plain of China. The study included four treatments: no straw returning (CK), rice straw returning during the rapeseed season (T1), rapeseed straw returning during the rice season (T2), and straw returning during both the rape and rice seasons (T3). Measurements of shoot and root dry matter, crop yield, and soil nutrient content were taken at key growth stages during the 2022 rice season and the 2022-2023 rape season. The results indicated that, compared with CK, straw returning significantly increased soil pH and the contents of organic matter, and N, P, K, and other nutrients. The T3 treatment was particularly effective, significantly increasing soil pH by 9.7% and 12.9%, alkali-nitrogen by 32.9% and 25.5%, available phosphorus by 33.5% and 24.3%, available potassium by 56.3% and 58.6%, total nitrogen by 22.9% and 33.0%, and organic matter by 26.6% and 50.8% (P < 0.05) in the rice and rape seasons, respectively. Dry matter accumulation in rice initially increased and then decreased as the growth period extended. The T2 treatment significantly promoted dry matter accumulation, whereas the T3 treatment inhibited it during the early stages of rice growth. Compared with straw removal, straw returning increased rice grain yield, with the largest increase of 13.9% observed in the T2 treatment (P < 0.05). In rapeseed, dry matter accumulation continued to increase with the growth period, and the T2 treatment most significantly promoted this accumulation. Compared with CK, the T2 treatment resulted in the largest increase in rapeseed grain yield, by 20.0% (P < 0.05). Correlation analysis showed that available potassium was significantly positively correlated with the rice seed setting rate (r = 0.84^**, P < 0.01). Total nitrogen and available potassium were significantly positively correlated with the number of pods per plant (r = 0.705^*, r = 0.623^*, P < 0.05) and rape yield (r = 0.623^*, r = 0.690^*, P < 0.05). These findings suggest that the major reason for the yield increase may be the elevated content of soil total nitrogen and available potassium due to straw returning. Considering soil nutrients, dry matter accumulation, and crop yield, rape straw returning during the rice season (T2) performed best and could be recommended for promotion and application in the middle and lower reaches of the Yangtze River.

Compensation mechanism of green manure on grain yield and nitrogen uptake of wheat with reduced nitrogen supply

WEI Jin-Gui, MAO Shou-Fa, JIANG Yu-Xin, FAN Zhi-Long, HU Fa-Long, CHAI Qiang, YIN Wen

Acta Agronomica Sinica. 2024, 50(12):  3129-3143.  doi:10.3724/SP.J.1006.2024.41026

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Long-term continuous cropping, excessive nitrogen input, and low nitrogen use efficiency are prevalent issues in wheat production in the Northwest Oasis irrigation area. This study examined the compensatory mechanism on grain yield and nitrogen utilization by reducing nitrogen input in wheat and multi-cropping of green manure after wheat harvest. The goal was to provide a theoretical basis for developing efficient wheat production technologies with reduced nitrogen input. This long-term field experiment, initiated in 2018, collected data from 2020 to 2022. The main plot included four green manures: multi-cropped common vetch mixed with hairy vetch (HCV), common vetch (CV), rapeseed (R), and fallow (F) after the previous wheat harvest. Subplots applied three nitrogen rates: the local conventional rate (N3, 180 kg hm^-2), reduced by 20% (N2, 144 kg hm^-2), and reduced by 40% (N1, 108 kg hm^-2). Our results indicated that reducing conventional nitrogen by 20% and 40% significantly decreased both grain yield and nitrogen uptake. However, multi-cropped hairy vetch mixed with common vetch after wheat harvest could compensate for the yield and nitrogen uptake losses caused by a 40% nitrogen reduction. When combined with a 20% nitrogen reduction, grain yield and nitrogen uptake increased by 21.4% and 6.9%, respectively (P < 0.05). Additionally, this cropping pattern compensated for the decreased nitrogen use efficiency resulting from a 40% nitrogen reduction and, when combined with a 20% nitrogen reduction, enhanced nitrogen use efficiency by 13.4% (P < 0.05). The compensation mechanism was attributed to: (1) Under a 40% nitrogen reduction, multi-cropped hairy vetch mixed with common vetch compensated for nitrogen uptake rate, increased net nitrogen assimilation rate by 34.3% (P < 0.05), maintained nitrogen distribution in the ear, and enhanced the nitrogen transportation rate from the stem by 6.6% (P < 0.05). (2) Compared with fallow after wheat harvest and the conventional nitrogen application rate, multi-cropped hairy vetch mixed with common vetch under a 20% nitrogen reduction increased mean nitrogen uptake efficiency and net nitrogen assimilation rate by 7.2% and 34.1%, respectively (P < 0.05). It also improved nitrogen distribution in the ear from early filling to maturity stages by 6.7% (P < 0.05) and enhanced the contribution rate of nitrogen transportation from stem and leaf to ear by 17.8% and 8.9%, respectively (P < 0.05). Therefore, multi-cropped hairy vetch mixed with common vetch after wheat harvest is a viable measure to reduce nitrogen fertilizer input. When combined with a 20% nitrogen reduction, it can increase grain yield and nitrogen use efficiency in wheat by improving nitrogen uptake rate, net nitrogen assimilation rate, and the contribution rate of nitrogen transportation from leaf and stem to ear, thereby promoting nitrogen distribution in the ear in arid oasis irrigated areas.

RESEARCH NOTES

Salt tolerance evaluation and transcriptome analysis of maize mutant caspl2b2

ZHANG Jin-Hui, XIAO Zi-Yi, LI Xu-Hua, ZHANG Ming, JIA Chun-Lan, PAN Zhen-Yuan, QIU Fa-Zhan

Acta Agronomica Sinica. 2024, 50(12):  3144-3154.  doi:10.3724/SP.J.1006.2024.43017

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Salt stress-sensitive mutants are crucial genetic materials for studying the genetic basis and molecular mechanisms of salt tolerance in crops. In this study, the maize inbred line LY8405 and the mutant caspl2b2 were used to investigate phenotype, physiological, and biochemical indices at the seedling stage under normal growth and salt stress conditions. The results showed that, compared to LY8405, the survival rate of caspl2b2 significantly decreased under salt stress, and the growth of aboveground parts was notably inhibited. The content of Na⁺ ions and malondialdehyde (MDA) in aboveground parts significantly increased, while transpiration rate, stomatal conductance, and intercellular CO₂ concentration also increased significantly. Conversely, the net photosynthetic rate significantly decreased. To uncover the molecular basis of the phenotypic differences under salt stress, transcriptome analysis was performed on leaf tissues of LY8405 and caspl2b2 under normal growth and salt stress conditions. The results revealed that differentially expressed genes (DEGs) were mainly concentrated in glutathione transferase activity, glutathione metabolism, REDOX enzyme activity, and cell homeostasis, with glutathione metabolism being the most significant. This study not only provides important germplasm resources for the genetic basis analysis of crop salt tolerance, but also lays a foundation for the identification of salt tolerance genes and the analysis of genetic regulatory networks.

Cloning and expression analysis of transcription factor AhWRI1s in peanut

YIN Xiang-Zhen, ZHAO Jian-Xin, HAO Cui-Cui, PAN Li-Juan, CHEN Na, XU Jing, JIANG Xiao, ZHAO Xu-Hong, WANG En-Qi, CAO Huan, YU Shan-Lin, CHI Xiao-Yuan

Acta Agronomica Sinica. 2024, 50(12):  3155-3164.  doi:10.3724/SP.J.1006.2024.44054

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Peanut is one of the widely cultivated oil and economic crops worldwide and has become a major source of oil and protein for humans due to its high oil and protein content. With the increasing global demand for vegetable oil, improving the fatty acid composition and increasing the lipid content of peanut seeds has become a top priority in peanut breeding. Transcriptional regulators can modulate the expression of a series of genes in metabolic pathways related to lipid synthesis, significantly affecting lipid synthesis and metabolism. In this study, two transcription factors, AhWRI1-1 and AhWRI1-2, were cloned from the leaves of Huayu 33. The ORF of AhWRI1-1 was 1101 bp, encoding 366 amino acids, and the ORF of AhWRI1-2 was 1128 bp, encoding 375 amino acids. Bioinformatics analysis revealed that both AhWRI1-1 and AhWRI1-2 contained two AP2/EREBP conserved domains. The expression patterns of AhWRI1-1 and AhWRI1-2 in different tissues were detected by qRT-PCR. The results showed that AhWRI1-1 had the highest expression in seeds, suggesting its involvement in the regulation of fatty acid synthesis and oil accumulation, while AhWRI1-2 had the highest expression in hypocotyls, indicating its role in hypocotyl development. Additionally, the differences in the responses of AhWRI1-1 and AhWRI1-2 to abiotic stresses suggested that these transcription factors may play different roles under such conditions. Transcriptional activation experiments in yeast showed that both AhWRI1-1 and AhWRI1-2 possess transcriptional activation activities. This study lays the foundation for future in-depth functional studies of AhWRI1-1 and AhWRI1-2.