Table of Content

12 September 2021, Volume 47 Issue 9

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EDITORIAL

Editorial: strengthening the research on the interaction between cultivated measures and environment/resource allocation of field economic crops to promote the development of industry with high efficiency and high quality

ZHOU Guang-Sheng, WANG Jing, KUAI Jie, WANG Bo

Acta Agronomica Sinica. 2021, 47(9):  1633-1638.  doi:10.3724/SP.J.1006.2021.04633

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RESEARCH PAPERS

Identification of gene co-expression modules of peanut main stem growth by WGCNA

WANG Ying, GAO Fang, LIU Zhao-Xin, ZHAO Ji-Hao, LAI Hua-Jiang, PAN Xiao-Yi, BI Chen, LI Xiang-Dong, YANG Dong-Qing

Acta Agronomica Sinica. 2021, 47(9):  1639-1653.  doi:10.3724/SP.J.1006.2021.04223

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This study was investigated the difference of transcriptome using three different peanut varieties with high main stem by RNA-seq. Transcriptomics combined with weighted gene co-expression network analysis (WGCNA) was used to explore the hub genes related to main stem growth and the molecular mechanisms of morphological formation of peanut stems. Results showed that 5872 differential expressed genes (DEGs) were detected in the Df216 and Huayu 33 comparation group, while 6662 DEGs were detected in the Df216 and Shanhua 108 comparation group. GO analysis suggested that these DEGs were mainly involved in molecular function and biological process, including the primary and secondary cell wall organization and biogenesis, phenylpropanoid biosynthetic and metabolic process, lignin biosynthetic process, and cellulose synthase activity, respectively. There were 33 modules were identified by WGCNA, among which five modules (Grey60, Cyan, Darkolivegreen, Brown, and Blue) were highly significant association with main stem height. According to the connectivity of genes in modules, caffeoyl-CoA O-methyltransferase, transcription factorATAF2, WAT1 (walls are thin1), and GDSL esterase/lipase were the hub genes, respectively. The results of hub gene networks by weighted values indicated that coumaroylquinate 3’-monooxygenase, 4-coumarate-CoA ligase, shikimate O-hydroxycinnamoyltransferase, rapid alkalinization factor,COBRA-like protein, and zinc finger protein had high connections with ADRL3Lin the Grey60 module, while β-1,4-galactosyltransferase, LRR receptor-like serine/threonine-protein kinase, pectin acetylesterase, leucine-rich repeat extensin-like protein had high connections with TZB0A2 in the Brown module. The identification of co-expression modules and their hub genes, and the analysis of gene function and gene networks of key genes will be helpful for revealing the genetic basis of the main height in peanut.

Effects of row spacings and nitrogen or mepiquat chloride application on canopy architecture, temperature and relative humity in cotton

YAN Wei, LI Fang-Jun, XU Dong-Yong, DU Ming-Wei, TIAN Xiao-Li, LI Zhao-Hu

Acta Agronomica Sinica. 2021, 47(9):  1654-1665.  doi:10.3724/SP.J.1006.2021.04167

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Mechanical harvesting is an inevitable trend of cotton production in the Yellow River Valley of China. However, the current row spacings for manual harvest do not match those of spindle-type pickers. Therefore, it is necessary to determine the appropriate row spacings within the adjustable range of cotton spindle pickers (76-102 cm) and to identify supporting agronomic measures. Field study was conducted under stalk incorporation in Hejian city, Hebei province, during 2016-2018, and consisted of two independent experiments of row spacing and nitrogen (N) rate, and row spacing and mepiquat chloride (1,1-dimethyl piperidinium chloride; DPC) rate. A split-plot design with four replicates was adopted; row spacings (76, 92, and 102 cm) were assigned as main plots at equal population of 90,000 plants hm ^-2, and N (0, 105, 210 kg hm^-2) or DPC rates (0, 140, 281, and 394 g hm^-2) as subplots. In normal years of 2016 and 2017, the wider row spacings (92 and 102 cm) showed a slight increase in leaf area index (LAI) and a slight decrease in diffuse non-interceptance (DIFN) relative to narrow row spacing (76 cm); however, in the hot and dry year of 2018, the LAI of wider rows was obviously lower and the DIFN was greater than that of 76 cm rows. The application of N fertilizer showed limited influences on the canopy structure, while the DPC application had strong effects characterized by a significant reduction in LAI and an increase in DIFN. Compared with 76 cm rows, the wider rows increased the average canopy temperature and decreased the relative humidity to different extents. The effect of N fertilizer on canopy microclimate was negligible, and DPC-treated canopy showed a mildly higher temperature and a mildly lower relative humidity. The row spacings did not interact with N or DPC rates to affect the cotton canopy architecture and microclimate.

Effects of interaction between calcium and nitrogen fertilizers on dry matter, nitrogen accumulation and distribution, and yield in peanut

WANG Jian-Guo, ZHANG Jia-Lei, GUO Feng, TANG Zhao-Hui, YANG Sha, PENG Zhen-Ying, MENG Jing-Jing, CUI Li, LI Xin-Guo, WAN Shu-Bo

Acta Agronomica Sinica. 2021, 47(9):  1666-1679.  doi:10.3724/SP.J.1006.2021.04186

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The purpose of this study was to investigate the effects of calcium and nitrogen fertilizer on dry matter, nitrogen accumulation and distribution, and yield in peanut. A field experiment was conducted using Huayu 25 with two calcium (Ca) rates (0 and 600 kg hm^-2), and five nitrogen (N) rates (0, 75, 150, 225, and 300 kg hm^-2) in Jiyang (JY) and Yinmaquan (YMQ) in 2019. The results showed that compared with Ca₀, the dry matter accumulation of peanuts under Ca₆₀₀ treatment was significantly increased by 13.5% in the Jiyang, by 12.6% in Yinmaquant. Compared with N₀, nitrogen fertilizer significantly promoted the accumulation of dry matter in peanut, and the N₇₅, N₁₅₀, N₂₂₅, N₃₀₀ treatments increased dry matter accumulation by 12.8%, 17.7%, 26.3%, 21.0% in Jiyang and 16.7%, 28.4%, 24.9%, 22.9% in Yinmaquan, respectively. The dynamic curve of peanut dry matter and nitrogen absorption accumulation conformed to the Logistic model, and the maximal nitrogen accumulation (Y_m) was obtained under Ca₆₀₀N₂₂₅treatment in Jiyang and Ca₆₀₀N₁₅₀ treatment Yinmaquan. Compared to the average, the maximal speed of accumulation (V_m), the maximal biomass, duration of rapid accumulation (T), were increased at two plots by 12.4% and 10.6%, 14.9% and 13.7%, 2.3% and 3.1%, respectively. The starting date of rapid accumulation period (t₁) was 7.5 days and 9.4 days earlier for nitrogen than for dry matter, indicated that the nutrient absorption of peanut was the premise of dry matter accumulation. The pod yield of peanut of Ca₆₀₀N₂₂₅ in Jiyang and Ca₆₀₀N₁₅₀ and Ca₆₀₀N₂₂₅ in Yinmaquan was higher than other treatments. Effects of interaction between calcium rates and nitrogen rates had a significant impact on peanut yield. Increasing calcium fertilizer application was an important way to improve nitrogen use efficiency, which increased pod number and 100-pod weight and promoted stably high yield in peanut. In this study, calcium fertilizer (600 kg hm^-2) and nitrogen fertilizer (75 kg hm^-2) were applied as the optimal fertilization scheme in the cultivation of less-fertilizer, stable-yield, and improved-efficiency treatment, while calcium fertilizer (600 kg hm^-2) and nitrogen fertilizer (150-225 kg hm^-2) as high-yield and high-efficiency treatment.

Different response of cotton leaves to heat stress is closely related to the night starch degradation

ZHAO Wen-Qing, XU Wen-Zheng, YANG Liu-Yan, LIU Yu, ZHOU Zhi-Guo, WANG You-Hua

Acta Agronomica Sinica. 2021, 47(9):  1680-1689.  doi:10.3724/SP.J.1006.2021.04220

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The export rate of photosynthetic products from leaves is an important manifestation of their source capacity. Heat induced source capacity shortage is one of the major reasons for cotton yield reduction and quality deterioration. To explore the difference and mechanism of leaf carbohydrate export in response to short-term heat stress between cotton cultivars with different heat sensitivity, pot experiments were carried out using two cotton cultivars PHY370WR (heat tolerance) and Sumian 15 (heat sensitivity) as experimental materials in 2015 and 2016. Two temperature treatment (CK, average temperature 26℃; HT, average temperature 34℃) was conducted at flowering and boll forming stages lasting for five days. Results showed that cotton boll weight was significantly decreased and specific leaf weight was increased by HT. The reduction of boll weight and increase of specific leaf weight of PHY370WR were lower than that of Sumian 15. The results of ¹³C labeled photosynthetic products showed that the carbohydrate export efficiency (CEE) of cotton leaves was significantly reduced by HT. Compared with CK, the decrease rate of CEE in Sumian 15 was 22.1% and the decline slope was -2.48, significantly higher than that of PHY370WR by 15.7% and -1.82, respectively. The decrease after five days of recovery in CEE diminished, but the differences at five days of HT between varieties were increased from 6.4% to 10.2% compared with at five days after HT released. The recovery slope of CEE in Sumian 15 was only 0.44, far less than 0.89 of PHY370WR. In addition, compared with HT, the difference of daily variation amplitude of sucrose content was decreased and the difference of daily variation amplitude of starch content was increased between cultivars after five days recovery. The latter was consistent with the trend of CEE in response to HT. Correlation analysis revealed that starch content of daily variation amplitude was more significantly correlated with CEE than sucrose. Further analysis showed that at both five days of HT and five days after HT released, the difference of increase in the minimum (night) starch content between cultivars was more significant than that of decrease in the maximum (day) starch content. The differences between cultivars at five days after HT released were significantly larger than that at five days of HT. In conclusion, there were the differences of cotton leaf CEE with different heat sensitivities not only during high temperature stress but also after the relief of stress. The heat tolerant cultivar PHY370WR indicated stronger resistance to HT and better recovery ability after HT released, which was closely related to a better starch degradation ability with a less increase in the minimum starch content in leaves at night.

Effects of waterlogging on rhizosphere microorganisms communities of different soybean varieties

YU Tao-Bing, SHI Qi-Han, NIAN-Hai , LIAN Teng-Xiang

Acta Agronomica Sinica. 2021, 47(9):  1690-1702.  doi:10.3724/SP.J.1006.2021.04137

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Waterlogging affects the composition of rhizosphere microbial community of different soybean varieties. The tolerance of soybean plant with different genotypes to waterlogging is quite different. In this study, waterlogging tolerant soybean genotype (Qihuang 34) and waterlogging sensitive soybean genotype (Jidou 17) were selected. The bacterial diversity, community composition, and network characteristics in the rhizosphere of the two genotypes under different waterlogging time were analyzed via fluorescence quantitative qPCR and Illumina Miseq high-throughput sequencing. The results showed that the biomass of waterlogging tolerant genotype and bacterial abundance in its rhizosphere were significantly higher than those for waterlogging sensitive genotype. The PCoA analysis showed that the difference in microbial community composition between waterlogging tolerant and sensitive soybean genotypes changed with waterlogging time (P < 0.05). Under the condition of waterlogging, Yonghaparkia and Unclassified-WD2101, OTU274 (Clostridium) and OTU2334 (Desulfosporosinus) enriched in the rhizosphere of the waterlogging tolerant genotype. The enrichment of these bacteria might be related to waterlogging tolerance. This study provides evidence of the microbial potential in the rhizosphere of soybean against waterlogging.

Characterization of the promoter and 5'-UTR intron in AhFAD2-1 genes from peanut and their responses to cold stress

SHI Lei, MIAO Li-Juan, HUANG Bing-Yan, GAO Wei, ZHANG Zong-Xin, QI Fei-Yan, LIU Juan, DONG Wen-Zhao, ZHANG Xin-You

Acta Agronomica Sinica. 2021, 47(9):  1703-1711.  doi:10.3724/SP.J.1006.2021.04247

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Delta-12 fatty acid desaturase 2 (FAD2) catalyzes the conversion of oleic acid to linoleic acid and is the determination of the level of oleic to linoleic acid ratio (O/L) in peanut oil. Peanuts with high oleic acid content are more susceptible to cold stress than those with normal oleic acid content, suggesting that FAD2 plays important roles in response to cold stress. To explore the role ofFAD2s during the process of cold stress acclimation in peanut, the genomic structures of AhFAD2-1A/Bwere determined; the function of promoters, intron of AhFAD2-1A/Band their response to cold stress were characterized by using β-glucuronidase (GUS) gene reporter system in transgenic Arabidopsis. The results were as follows: AhFAD2-1A/B genes consisted of two exons and one intron within their 5'-UTR; promoter ofAhFAD2-1A was too weak to be detected and the promoter of AhFAD2-1B poorly activated the expression level of GUS in cotyledon tip of seedlings; the promoter of AhFAD2-1pseudogene activated GUS expression limited to cotyledon, hypocotyl, and seed. The intron of AhFAD2-1B demonstrated promoter-like activity which was restricted in cotyledon and hypocotyl, and not only enhanced the gene expression efficiency but also expanded gene expression range. Intron-mediated enhancement was an essential aspect of AhFAD2-1expression. Activities of 5'-flanking region of AhFAD2-1A/B were repressed by the cold stress.

Source-sink characteristics and classification of peanut major cultivars in North China

GAO Fang, LIU Zhao-Xin, ZHAO Ji-Hao, WANG Ying, PAN Xiao-Yi, LAI Hua-Jiang, LI Xiang-Dong, YANG Dong-Qing

Acta Agronomica Sinica. 2021, 47(9):  1712-1723.  doi:10.3724/SP.J.1006.2021.04164

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To explore whether and how source-sink theory was involved in mediating peanut high yield formation, a field experiment was conducted using 13 major peanut cultivars in North China. Principal component analysis and cluster analysis were used to evaluate natural indicators for the characterization and classification of source-sink types such as leaf area (LA) per plant, number of flowers, and pod rate. The results showed that LA per plant, number of flowers, pod rate, and pod plumpness at the pod-setting and pod-filling stages could be the major characteristics to evaluate source-sink relationship. Based on the source-sink indicators and yield components, these peanut cultivars could be classified into four categories, including source-sink coordination type, large source-few sink type, sufficient source-few sink type, and sufficient source-large sink type. The source-sink coordination type varieties could achieve high yield mainly due to the higher net assimilation rate at the pod-setting stage, the moderate florescence and number of flowers, and the higher economic pods ratio and pod fullness. Large source-few sink type cultivars had higher LA, but lower net assimilation rate and smaller contribution of the leaf area to the yield formation, thus decreased the pod yield. Sufficient source-large sink type cultivars had longer florescence and more flowers compared to others types, leading to reduce the pod rate and pod plumpness, which was the main limiting factor to increase the pod yield. On the contrary, both florescence and the number of flowers per plant of sufficient source-few sink type cultivars were less than others types. In summary, to prevent the redundancy of leaf source, more flowers but less pegs, and more pods but less kernels and to promote the effective proportions and pod fullness resulting in higher pod yield in peanut production, corresponding measures should be taken to control leaf area and amount of flowering according to different source-sink types peanut cultivars.

Effects of planting density on yield and lodging related characters of reciprocal hybrids in Brassica napus L.

LOU Hong-Xiang, JI Jian-Li, KUAI Jie, WANG Bo, XU Liang, LI Zhen, LIU Fang, HUANG Wei, LIU Shu-Yan, YIN Yu-Feng, WANG Jing, ZHOU Guang-Sheng

Acta Agronomica Sinica. 2021, 47(9):  1724-1740.  doi:10.3724/SP.J.1006.2021.04253

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High yield and lodging resistance are two goals in rapeseed production that are hard to reconcile, which restrict severely the further improvement of economic performance. This contradiction is particularly prominent in the high-density and mechanize farming mode. Due to maternal inheritance, there are obvious differences in yield and lodging resistance related traits among reciprocal hybrids, but the effects of planting density on these key traits are not clear. Here, Huahang 901 and Zheyou 50, which are conventional rapeseed varieties and their reciprocal hybrids, were planted with gradient density. The yield and lodging related traits were measured and the heterosis of each trait was calculated. In order to provide the basis for the selection of parents under the high-density and direct seeding farming mode, the effects of planting density on yield and lodging related traits of parents and reciprocal hybrids were investigated. The results showed that the actual yield and economic coefficient of two parents and their reciprocal hybrids were first increased and then decreased with the increase of the planting density. Interesting, the dynamic change pattern and the values of both traits of reciprocal hybrids under gradient density were well consistent with those of paternal parent. The variation of lodging index with increased density at two sites was different, but the values and the dynamic change patterns of reciprocal hybrids were consistent with that of the maternal parent. In 2017 in Xining, the actual yield of reciprocal hybrids had obvious heterosis and Huahang 901×Zheyou 50 showed higher heterosis than that of Zheyou 50×Huahang 901. Meanwhile, the Huahang 901×Zheyou 50 had greater heterosis of lodging resistances, but there was no such heterosis in Zheyou 50×Huahang 901. In conclusion, to obtain hybrids rapeseed varieties with high yield lodging resistance and dense planting under the high-density and direct seeding farming mode, it was better to select those varieties with high-yield as paternal parents and those varieties with strong lodging resistance as maternal parents.

Screening and comprehensive evaluation of shade tolerance of forage soybean varieties

SONG Li-Jun, NIE Xiao-Yu, HE Lei-Lei, KUAI Jie, YANG Hua, GUO An-Guo, HUANG Jun-Sheng, FU Ting-Dong, WANG Bo, ZHOU Guang-Sheng

Acta Agronomica Sinica. 2021, 47(9):  1741-1752.  doi:10.3724/SP.J.1006.2021.04149

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Maize intercropped with soybean can significantly increase the protein yield of feed, and the selection of shade tolerant soybean varieties is particularly important. In this study, five treatments including soybean intercropped with maize, monocropping, shading at seedling stage, shading at branching stage, shading at flowering and podding stage were conducted. The biomass, morphology, and nitrogen content were investigated at filling stage among the treatments. The shade tolerance coefficient (STC) of each index was used to measure the shade tolerance of each tested variety. A few key indexes at key growth stages under shading were screened out by stepwise regression analysis to predict the shade tolerance of soybean varieties, which could be used to simplify the screening protocol. The results showed that there were significant differences of shade tolerance between soybean varieties under intercropping. Shade tolerance of shading at flowering and podding stages was positive correlation to shade tolerance of intercropping. Thus, the treatment of shading at flowering and podding stages could be used to screen out feed soybean varieties suitable for intercropping with maize. According to the comprehensive evaluation of shade tolerance under shading at flowering and podding stages, the varieties used in this study were clustered into three groups, and the results were highly consistent with the shade tolerance of intercropped with maize. The regression equation was used to predict the shade tolerance of the tested varieties, and the results of which were highly consistent with the comprehensive evaluation values (D-values). These results suggested that the regression equation established by STC of a few indexes at flowering and podding stages could be used for rapid evaluation and screening of shade tolerant materials under intercropped with maize.

Establishment of comprehensive evaluation system for cold tolerance and screening of cold-tolerance germplasm in peanut

ZHANG He, JIANG Chun-Ji, YIN Dong-Mei, DONG Jia-Le, REN Jing-Yao, ZHAO Xin-Hua, ZHONG Chao, WANG Xiao-Guang, YU Hai-Qiu

Acta Agronomica Sinica. 2021, 47(9):  1753-1767.  doi:10.3724/SP.J.1006.2021.04182

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Low temperature in early spring is the key factor limiting the yield and quality of peanut in Northeast China, which mainly occurs at germination and seedling stages. The selection and breeding of cold-tolerant cultivars are the most direct and effective means to solve the problem of chilling injury in agricultural production. In this study, 68 peanut cultivars mainly planted in Northeast China were used as experimental materials, and their cold tolerance was evaluated at germination and seedling stages in the climatic chamber and field, respectively. At germination stage, we found that the cold treatment at 6℃ for seven days could be the suitable condition for cold tolerance evaluation of large-scale peanut germplasm by the comprehensive membership function analysis and the standard normal distribution test according to the seed vigor of peanut cultivars after treatments at 10℃, 8℃, 6℃, and 4℃ for seven days. At seedling stage, after treatment at 6℃ for seven days, plant height, leaf area, fresh weight of aerial parts, fresh weight of root, dry weight of aerial parts, dry weight of root, and cold tolerance grade were measured to evaluate the cold tolerance of various peanut cultivars. Correlation analysis revealed that the leaf area, fresh weight of aerial parts and cold tolerance grade had the most significant relationships with cold tolerance and could be used as the main evaluation indicators for the identification of cold tolerance at seedling stage in peanut. In the field, cold tolerance of various cultivars were evaluated by emergence rate, emergence ability, and yield component factors through the early sowing and sowing by stages. Finally, based on the multiple phenotypic analysis, the most cold-tolerant peanut (cultivar NH5) and the most cold-sensitive peanut (cultivar FH18) were identified at germination and seedling stages, suitable for planting in Northeast China. This study provided the reference for peanut planting in high-latitude and cold regions and the excellent germplasm of cold tolerance mechanism in peanut.

Effects of cold stress on germination in peanut cultivars with normal and high content of oleic acid

XUE Xiao-Meng, WU JIE, WANG Xin, BAI Dong-Mei, HU Mei-Ling, YAN Li-Ying, CHEN Yu-Ning, KANG Yan-Ping, WANG Zhi-Hui, HUAI Dong-Xin, LEI Yong, LIAO Bo-Shou

Acta Agronomica Sinica. 2021, 47(9):  1768-1778.  doi:10.3724/SP.J.1006.2021.04170

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High oleate (HO) peanut is highly popular for its improved nutrient value and strengthened storage stability among customers and peanut processing enterprises. In recent years, with the adoption of HO peanut in our country, the cold tolerance of peanut at germination stage in high altitude or high latitude area has become a major concern. To figure out the relationship between the seed oleic acid content and the cold tolerance at germination stage in peanut, the germination rate and germination index of seeds under cold stress were investigated among six peanut cultivars with normal content of oleic acid (NO) and their backcross-derived HO lines, respectively. The results showed that the oleic acid content was not significantly correlated with the cold tolerance at germination stage. The contents of eight main fatty acids under cold stress at germination stage were tracked in Quanhua 551 (Quanhua 551-NO) and its HO offspring line (Quanhua 551-HO), and the germination rate of Quanhua 551-HO was significantly lower than that of Quanhua 551-NO under cold stress. The oleic acid content of Quanhua 551-NO was significantly decreased while the linoleic acid content was significantly increased under cold stress. However, the contents of oleic acid and linoleic acid exhibited the same trend in Quanhua 551-HO, and there was no significant difference. The expression profiles offatty acid desaturase 2 (AhFAD2) genes in both Quanhua 551-NO and Quanhua 551-HO under cold stress revealed that the relative expression level of AhFAD2-1A/B was significantly up-regulated, while that of AhFAD2-4A/B was significantly down-regulated under cold stress in Quanhua 551-NO. Conversely, the relative expression level of AhFAD2-1A/B was significantly decreased, but the relative expression level of AhFAD2-4A/B was significantly increased under cold stress in Quanhua 551-HO. These results implied that the up-regulation of AhFAD2-4A/Bin HO peanut may partly compensate for lost function of AhFAD2-1A/Bin response to cold stress. In conclusion, the oleic acid content in seed was not the main factor to determinate the cold tolerance at germination stage.

Regulation of carbon and nitrogen metabolism in leaf of soybean cultivar Suinong 26 at seed-filling stage under drought stress by exogenous melatonin

CAO Liang, DU Xin, YU Gao-Bo, JIN Xi-Jun, ZHANG Ming-Cong, REN Chun-Yuan, WANG Meng-Xue, ZHANG Yu-Xian

Acta Agronomica Sinica. 2021, 47(9):  1779-1790.  doi:10.3724/SP.J.1006.2021.04151

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The grain-filling stage is the most complex stage of carbon and nitrogen metabolism. Drought stress inevitably inhibits the assimilation, distribution, and transition of carbon and nitrogen at grain-filling stage in soybean, resulting in less soybean yield. The objective of this study was to investigate the effects of exogenous melatonin on the carbon and nitrogen metabolism genes and pathways under drought stress in soybean. Transcriptome analysis showed that, compared with drought stress treatment, 37 and 493 genes were jointly up-regulated and down-regulated in soybean leaves treated with normal water supply and treated with exogenous melatonin under drought stress, respectively. The up-regulated genes included functional genes directly and indirectly involved in carbon and nitrogen metabolism, such as the key genes involved in the cysteine synthesis pathway, photosynthesis, carbohydrate metabolism, and glucose metabolism. Metabolomic analysis revealed that, compared with drought stress treatment, 17 and 43 metabolites were jointly up-regulated and down-regulated in soybean leaves treated with normal water supply and treated with exogenous melatonin under drought stress, respectively. Most (14/17) of up-regulated metabolites were amino acids, lipids, organic acids, and carbohydrates, which further indicated that exogenous melatonin could improve soybean carbon and nitrogen metabolism and drought resistance in soybean. Combined with transcriptome and metabolomic profile, melatonin promoted the relative expression level of β-D-Glucosidase gene due to regulate the pathway of amino acid metabolism and starch and sucrose metabolism, improved the contents of L-Asparagine and D-glucose-6P metabolites, and ultimately improves the ability of drought resistance in soybean.

Effects of exogenous melatonin on morphology, photosynthetic physiology, and yield of spring soybean variety Suinong 26 under drought stress

ZHANG Ming-Cong, HE Song-Yu, QIN Bin, WANG Meng-Xue, JIN Xi-Jun, REN Chun-Yuan, WU Yao-Kun, ZHANG Yu-Xian

Acta Agronomica Sinica. 2021, 47(9):  1791-1805.  doi:10.3724/SP.J.1006.2021.04154

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It is of great significance to study the mechanism of improving the drought resistance ability of soybean seedlings for the growth of soybean seedlings in Northeast China. This experiment was conducted using ‘Suinong 26’ as the experimental material with four treatments to investigate the physiological indexes and yield of soybean under drought stress, including the normal nutrient solution (CK), the drought stress treatment (D), the drought stress + foliar spraying melatonin treatment (LM), and the drought stress + irrigation melatonin treatment (RM). The results indicated that the gas exchange parameters, the dry matter accumulation of organ at seedling stage, the activities of antioxidant enzyme, and the content of soluble protein were increased under LM and RM compared with D. The net photosynthetic rate and stomatal conductance were significantly increased at V2 and V4 stages, and the transpiration rate and intercellular carbon dioxide concentration were significantly increased at V4 stage with P < 0.05; POD and CAT of RM were significantly increased at P < 0.05; the content of soluble protein was significantly increased after drought stress at V2 and V4 stages at P < 0.05. Compared with D, the yield of soybean with LM at V2 and V4 stages was increased by 24.2% and 19.1% at P < 0.05, RM increased by 38.6% and 56.3% at P < 0.05. Compared with LM, the yield of soybean with RM at V2 and V4 stages was increased by 11.6% and 31.3% at P < 0.05. These results revealed that the application of melatonin increased the yield of soybean under drought stress and the yield of soybean with irrigation melatonin treatment was higher than that of foliar spraying melatonin treatment.

RESEARCH NOTES

Fungi diversity analysis of rhizosphere under drought conditions in cotton

YUE Dan-Dan, HAN Bei, Abid Ullah, ZHANG Xian-Long, YANG Xi-Yan

Acta Agronomica Sinica. 2021, 47(9):  1806-1815.  doi:10.3724/SP.J.1006.2021.04162

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Plant rhizosphere microorganisms play important roles in plant growth and the adaptability of plants to adverse environmental stresses. In this study, cotton rhizosphere fungal communities were analyzed under drought conditions, aiming to explore the effects of drought stress on the diversity and community structures of cotton rhizosphere fungi, and to provide a theoretical basis for improving cotton water use efficiency by using beneficial microorganisms. Drought stress was applied to upland cotton (Gossypium hirsutum cv. Jin 668) at flowering stage (SDP), while the soil without plants was also subjected to drought (SOPD). Simultaneously, the plants (SPN) and pots without plants (SNPN) regularly watered were used as controls. The soil samples were collected, the microbial DNA was isolated, and Illumina Miseq was conducted for a high-throughput sequencing of fungi ITS1 regions to study the diversity of the rhizosphere fungal communities. As a result, a total of 970 OTUs were identified, and the numbers of fungal OTUs in the samples of SNPN, SOPD, SPN, and SDP were 481, 528, 743, and 752, respectively, among which 288 OTUs were shared by all samples. The OTUs were classified to different levels of phyla, class, order, family, and genus of fungi. The rhizosphere fungal community of cotton was predominantly consisted of the phyla Ascomycota (82.70%) and Basidiomycota (10.15%). The abundance of Sordariomycetes, Sordariales, and Chaetomiaceae decreased, while the abundance of Eurotiales, Trichocomaceae, Aspergillus, and Penicillum increased significantly under drought stress. Moreover, the diversity of fungal community in the soil with cotton plants significantly higher than that in the soil without cotton plants. Meanwhile, the fungi community structures of SPN and SDP resembling each other and differing greatly from SNPN and SOPD. These results revealed that the cotton rhizosphere had a rich pool of fungal communities, and drought stress had a significant effect on the abundances and diversity of fungi in cotton rhizosphere. This study provided new insights for the researches of improving drought tolerance of cotton in terms of soil microorganisms.

Estimation of feed rapeseed biomass based on multi-angle oblique imaging technique of unmanned aerial vehicle

ZHANG Jian, XIE Tian-Jin, WEI Xiao-Nan, WANG Zong-Kai, LIU Chong-Tao, ZHOU Guang-Sheng, WANG Bo

Acta Agronomica Sinica. 2021, 47(9):  1816-1823.  doi:10.3724/SP.J.1006.2021.04211

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To obtain above-ground biomass information quickly and accurately facilitating crop growth monitoring and yield prediction, this study was to evaluate a new method to extract the biomass of feed rapeseed based on UAV with visible-light cameras. The experiment was conducted at the rapeseed experimental base of Huazhong Agricultural University in 2018. To estimate above-ground biomass of rapeseed, a UAV (unmanned aerial vehicle) platform equipped with a five-camera oblique photography system was used to simultaneously obtain images of rapeseed during final flowering period from multiple angles. Three flight altitudes (40, 60, and 80 m) and three seeding densities (3.00×10⁵, 5.25×10⁵, and 7.50×10⁵ plant hm^-2) were carried out to assess biomass predictions in a single-camera vertical imaging pattern. Firstly, the rapeseed canopy coverage and plant height information from the image of the UAV were extracted. Secondly, the volume model of rapeseed was obtained by the addition of plant height on the covering area. Finally, a linear regression model was established based on volume model and measured biomass to predict the dry weight of rapeseed. The results were as follows: (1) With the decrease of the flight height of the UAV of the three flight altitudes, the accuracy of biomass prediction was on the rise, and when the flight height was 40 meters, the accuracy of rapeseed biomass estimation was the best (calibration set: r = 0.792, RMSE = 125.0 g m ^-2, RE = 13.2%; validation set: r = 0.752, RMSE = 139.1 g m ^-2, RE = 15.3%). (2) When the planting density of rapeseed was higher, the actual biomass was smaller, and the prediction of biomass had a better result by volume model. (3) There was no significant difference in the accuracy of rapeseed biomass estimation between multi-angle imaging and single-camera vertical imaging, both of which had the best results at the flight height of 40 meters with correlation coefficients rof 0.772 and 0.742, respectively. This study indicated that it was feasible to obtain images for extracting rapeseed biomass by a UAV, which could provide the reference for efficient and accurate phenotypic information of field crops.

Response of agronomic traits and P/Fe utilization efficiency to P application with different P efficiency in soybean

ZHAO Jing, MENG Fan-Gang, YU De-Bin, QIU Qiang, ZHANG Ming-Hao, RAO De-Min, CONG Bo-Tao, ZHANG Wei, YAN Xiao-Yan

Acta Agronomica Sinica. 2021, 47(9):  1824-1833.  doi:10.3724/SP.J.1006.2021.04212

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The phosphorus content in soil is closely related to the iron absorption in plant. In this study, 15 agronomic traits were analyzed by principal component analysis in sand culture and split blot design, with P-efficient and P-inefficient soybean varieties screened in the early stage as the experimental materials. To analyze the relationship between agronomic traits and P/Fe utilization efficiency, and to provide the theoretical basis for the rational application of P and Fe fertilizer in soybean, the effects of different P:Fe ratios on biological traits and genotypic differences were studied in response to P-efficient and P-inefficient genotypes under different P:Fe treatments by factor scores in soybean. The results were as follows: (1) At R5 stage, plant height, stem diameter, root dry weight, and shoot dry weight of P-efficient genotypes were increased relatively rapidly under each treatment, and all of them were higher than those of P-inefficient genotypes. When P:Fe ratio was 100:100, root dry weight per plant at R5 stage was lower, while 100-seed weight was higher. In addition, when P:Fe ratio was 100:100, P utilization efficiency of the two soybean genotypes were the lowest. (2) Canonical correlation analysis revealed that stem diameter at R5 stage of P-efficient genotypes was positively correlated with Fe utilization efficiency in leaves, while shoot dry weight of P-inefficient genotypes was negatively correlated with P utilization efficiency in leaves. (3) The increase of P utilization efficiency of leaves at R3 stage and shoot dry weight at R8 stage were beneficial to the increase of seed weight per plant of P-efficient genotypes, while the increase of P-efficient genotypes at R3 stage would lead to the decrease of seed weight per plant of P-efficient genotypes. The increase of plant height at R3 stage, shoot dry weight at R3 and R8 stages contributed to the increase of seed weight per plant of P-inefficient genotypes, while the increase of stem diameter at R3, R5, and R8 stages, and Fe utilization efficiency of leaves at R5 stage resulted in the decrease of seed weight per plant of P-inefficient genotypes. Furthermore, shoot dry weight at R8 stage had the largest direct positive contribution to both P-efficient and P-inefficient genotypes. (4) Comprehensive evaluation by factor score showed that when P:Fe ≤ 100:100, the comprehensive performance of P-efficient genotypes and P- inefficient genotypes were the best when P:Fe ratio was 100:100. When P:Fe ≥ 500:100, the comprehensive performance of P-efficient genotypes and P-inefficient genotypes were the best when P:Fe ratio was 1000:100. In conclusion, the early stage of seed filling can be an important stage for screening soybean genotypes with different P efficiency. P:Fe ratio at 1:1 was better for both P-efficient and P-inefficient genotypes under sufficient Fe supply, considering the accumulation of phosphate fertilizer in soil and effect of phytates in seed on P efficiency.

Effects of hydrogen peroxide soaking on germination and physiological metabolism of seeds in peanut

HAO Xi, CUI Ya-Nan, ZHANG Jun, LIU Juan, ZANG Xiu-Wang, GAO Wei, LIU Bing, DONG Wen-Zhao, TANG Feng-Shou

Acta Agronomica Sinica. 2021, 47(9):  1834-1840.  doi:10.3724/SP.J.1006.2021.04187

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To investigate the effects of hydrogen peroxide soaking on peanut germination and seed physiological metabolism, the seed germination and related physiological indexes after seed soaking were determined using peanut variety Kainong 176 as experimental material. The results showed that the germination vigor of peanut was increased from 0 to 24.45%, and the germination percentage was increased from 39.33% to 90.99% by hydrogen peroxide soaking. Hydrogen peroxide treatment increased the content of gibberellin in peanut seeds and decreased the content of abscisic acid at germination stage. The contents of gibberellin in germinating seeds at 0, 24, and 48 hour(s) were 10.82%, 5.73%, and 18.64% higher than those of control, and the contents of abscisic acid were 44.98%, 36.45%, and 39.70% lower than that of control, respectively. At the same time, hydrogen peroxide treatment enhanced the activities of antioxidant enzyme SOD and CAT, increased the contents of soluble sugar and soluble protein, decreased the content of MDA, promoted the catabolism of macromolecular storage substances such as fat, protein, and starch, and provided more ATP and substrates for protein and nucleic acid synthesis. Studies revealed that hydrogen peroxide could promote peanut seed germination under low-temperature stress by mediating antioxidant enzymes, ABA and GA, and storage matter decomposition.