Scientia Agricultura Sinica

Drought Resistance Identification and Genetic Resource Mining in Wheat

MAO HuDe, DU LinYing, KANG ZhenSheng

Scientia Agricultura Sinica. 2024, 57(9): 1629-1632. doi:10.3864/j.issn.0578-1752.2024.09.001

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Research Progress on Root System Architecture and Drought Resistance in Wheat

ZHANG YuZhou, WANG YiZhao, GAO RuXi, LIU YiFan

Scientia Agricultura Sinica. 2024, 57(9): 1633-1645. doi:10.3864/j.issn.0578-1752.2024.09.002

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Wheat is the most important cereal crop, and drought is the most significant abiotic stress factor that severely affects wheat growth and development. Plant root system, as a primary organ for crops to acquire water and nutrients, directly determines the efficiency of soil water utilization. In recent years, increasing evidence has shown that plant root system architecture (RSA) plays an important role in plant tolerance to drought stress. This review summarizes the current research progress on the regulation of wheat drought tolerance determined by RSA. First, we present how root tropism especially root gravitropism shapes the RSA, summarize the relevant genes and molecular regulatory mechanism involved in root gravitropic growth, and explain how the root tropism-regulated RSA is implicated in wheat adaptation to drought stress. In addition to root tropic growth, the root development also participates in the RSA formation and the plant adaptability to drought stress. Therefore, this review further summarizes how wheat regulates root development to alter its root system morphology (including increasing root length, modifying lateral root number and root hair density, etc.), thereby enhancing its water acqusition from the soil and its adaption to drought environment. The identified genes involved in wheat root development under drought stress conditions are also systematically summarized. Furthermore, as the underground part of plants, the revelation of RSA has always been a challenging task, which hinders our understanding of the relationship between RSA and plant drought tolerance. Therefore, this review also summarized the available techniques used to analyze the RSA at two- and three-dimension levels. These techniques can measure and analyze wheat root length, density, growth direction, and morphology parameters, laying technical support for an insightful understanding of the relationship between wheat RSA and drought resistance. Finally, we discuss the prospect of the improvement of RSA in breeding wheat drought-resistant varieties, as well as provide an outlook for how to identify genes regulating wheat RSA and pinpoint their regulatory mechanism. In summary, the relationship between wheat RSA and drought resistant is closely associated. The continuous development of sequencing techniques, along with the deepening research on the regulatory mechanism of wheat RSA, will provide new means and strategies for the further breeding of drought-tolerance wheat varieties.

Identification of Drought Resistance of 244 Spring Wheat Varieties at Seedling Stage

ZHOU Quan, LU QiuMei, ZHAO ZhangChen, WU ChenRan, FU XiaoGe, ZHAO YuJiao, HAN Yong, LIN HuaiLong, CHEN WeiLin, MOU LiMing, LI XingMao, WANG ChangHai, HU YinGang, CHEN Liang

Scientia Agricultura Sinica. 2024, 57(9): 1646-1657. doi:10.3864/j.issn.0578-1752.2024.09.003

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【Objective】Drought is a major environmental factor limiting global wheat production, and breeding drought-tolerant varieties is a key challenge faced by wheat breeders worldwide. Spring wheat, which has a short growth period, plays a vital role for national food security and planting structure, therefore, it is of great importance to identify and select drought tolerance of spring wheat varieties for breeding of high-yielding and drought-tolerant wheat.【Method】In this study, 244 spring wheat varieties (lines) from 10 different regions were used to assess the drought tolerance of spring wheat varieties during the seedling stage, this study used the controlled water content method to impose drought stress during the seedling stage, 5 seedlings with uniform and consistent growth were selected during the trefoil stage. Thirteen seedling stage indicators including maximum root length (MRL), first leaf length (FLL), first leaf width (FLW), coleoptile length (CL), shoot fresh weight (SFW) and root fresh weight (RFW) were measured. Comprehensive evaluation of drought resistance of various spring wheat varieties (lines) was conducted through methods such as using descriptive statistics, membership function, principal component analysis, cluster analysis, and correlation analysis. 【Result】The drought tolerance of spring wheat varieties (lines) exhibits a large variation. The coefficient of variation of the measured traits under drought treatment conditions ranges from 2.1% to 32.9%, while the coefficient of variation of the control group ranges from 1.0% to 29.3%. Compared with the control, the coleoptile length, root dry weight, fresh weight root to shoot ratio, and dry weight root to shoot ratio under drought treatment were all greater than those under the control treatment. The original 13 indexes were summarized into 5 principal components, and the contribution rate reached 79.56%, and the D value of the comprehensive drought resistance coefficient was calculated according to the characteristic vector of each principal component and the drought resistance coefficient of each trait index, then the D value was clustered and analyzed, which could be divided into 5 subgroups. Therefore, the root biomass (underground fresh weight and dry weight) was screened as an effective comprehensive index for the identification of drought resistance at the seedling stage. We conducted correlation analysis between the seedling stage drought index and the agronomic traits of maturity stage showed that the coleoptile length, first leaf length was significantly positively correlated with flag length, plant height, spike length, the number of spike and grain length. Additionally, and the seedling biomass was significantly positively correlated with thousand-grain weight.【Conclusion】Twenty-two highly drought-tolerant varieties were screened, and root biomass (both fresh and dry weight of the underground part) was identified as an effective comprehensive indicator for evaluating seedling stage drought tolerance.

Genome-Wide Association Study of Drought Tolerance at Seedling Stage in ICARDA-Introduced Wheat

ZHANG Ying, SHI TingRui, CAO Rui, PAN WenQiu, SONG WeiNing, WANG Li, NIE XiaoJun

Scientia Agricultura Sinica. 2024, 57(9): 1658-1673. doi:10.3864/j.issn.0578-1752.2024.09.004

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【Objective】Drought is one of the most destructive environmental stresses limiting wheat production. The novel germplasm with excellent drought tolerance as well as their candidate loci were identified and characterized to enrich the genetic basis of drought tolerance and lay a material foundation for wheat genetic improvement in China. 【Method】In this study, the drought tolerance of 198 wheat accessions introduced from International Dry Area Agriculture Research (ICARDA) were investigated at seedling stage through hydroponic method with PEG6000 simulating drought. Drought tolerance index (DTI) was calculated using the shoot fresh weight, root fresh weight, total biomass and root-shoot ratio, respectively. Genome-wide association analysis was performed using 660K SNP array genotyping to obtain the SNP loci and chromosome regions associating with drought tolerance index. Combined with the expression patterns in root and other tissues, the potential candidate genes were identified, and then they were further verified by qRT-PCR approach with the most drought-tolerant accession IR214 and the most drought-sensitive accession IR36 as materials. Finally, the excellent haplotypes of key candidate genes were analyzed. 【Result】Compared to normal control condition, the growth and development of wheat were significantly impaired under drought treatment. There were also significant phenotypic variations among different accessions with all of the four traits displayed normal distribution. The coefficient of variation ranged from 0.363 to 0.760 with genetic diversity from 0.310 to 0.400. Using the weighted membership function value (D value), the drought tolerance of these accessions was evaluated. Results showed that accession IR214 had the highest D value with 0.851, followed by IR92, IR213, IR235, and IR218, which could be considered as the novel excellent drought-tolerance germplasm. Furthermore, through genome-wide association study (GWAS) analysis, a total of 102 loci were significantly associated with the DTI values based on these four traits, with the phenotypic variation explained value (PVE) from 1.07% to 38.70%, of which 60 loci were associated with above-ground fresh weight, 1 locus associated with underground fresh weight, 36 loci associated with biomass and the remaining 5 loci associated with root-shoot ratio. Then, 31 candidate genes were predicated based on genomic annotation information and LD block. Combined with the expression patterns of them in roots and other tissues, 4 candidates displaying differential expression between CK and drought conditions were obtained. Finally, the expression levels of these 4 candidates were further verified by qRT-PCR method with the most drought- tolerant accession IR214 and the most drought-sensitive accession IR36 as materials to obtain two key candidates associating with drought tolerance. Additionally, their haplotype effects were investigated. It was found that the different genotypes of AX-86174509 locus in TraesCS6A02G048600 gene showed significant differences in drought tolerance, which might be considered as a causal locus.【Conclusion】Totally, 102 loci and 2 key candidate genes (TraesCS5B02G053500 and TraesCS6A02G048600) underlying drought tolerance at seedling stage were detected in ICARDA-introduced wheat, and AX-86174509 in TraesCS6A02G048600 was a potential functional locus.

Drought Resistance Evaluation of Synthetic Wheat at Grain Filling Using UAV-Based Multi-Source Imagery Data

YAN Wen, JIN XiuLiang, LI Long, XU ZiHan, SU Yue, ZHANG YueQiang, JING RuiLian, MAO XinGuo, SUN DaiZhen

Scientia Agricultura Sinica. 2024, 57(9): 1674-1686. doi:10.3864/j.issn.0578-1752.2024.09.005

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【Objective】To evaluate the drought resistance of synthetic wheat germplasm based on multi-source images collected by unmanned aerial vehicle (UAV) and yield data, explore high-throughput indices for drought resistance evaluation, and identify synthetic wheat germplasm resources with drought resistance. This provides technical support and germplasm materials for accelerating the expansion of drought-resistant genetic resources for wheat and enhancing the level of breeding for dryland wheat.【Method】Eighty synthetic wheat germplasm and the control variety Xin Chun 37 were used as plant materials, which were sown in the field and treated with a water regime of drought stress and irrigation. Multi-source images of test materials during filling stage were collected by multi-spectral and thermal infrared cameras equipped with unmanned aerial vehicle, and the spectral index of each test material was extracted by threshold segmentation. The analyses of Pearson’s correlation and principal component were performed to identify drought resistance-related spectral indices, and the drought resistance of each synthetic wheat germplasm was determined by single index and comprehensive evaluation methods. 【Result】The drought resistance coefficients of 19 spectral indices of 80 synthetic wheat germplasm were calculated based on multisource imagery data obtained from unmanned aerial vehicles. The correlation analysis between the spectral indices and the yield-based drought index (DRI) showed that among the drought resistance coefficients of the 19 spectral indices, OSAVI exhibited the highest correlation with the drought index, while NDVI, CI_re, and NDRE demonstrated relatively strong associations with the drought index. However, the different drought indices showed a high correlation, resulting in redundant information. The drought resistance coefficients of the 19 spectral indices were transformed into three independent comprehensive indicators through principal component analysis, with contribution rates of 59.6%, 12.0% and 9.6%, respectively. The comprehensive drought resistance index (D) for each synthetic wheat germplasm were calculated by aggregating the three independent comprehensive indicators using the weighted membership function method. 6 and 5 synthetic wheat germplasms with strong drought resistance were identified based on DRI and D, respectively. Among them, 2 germplasms (SW004 and SW009) with high drought resistance were detected based on both DRI and D. Furthermore, the drought resistance of the 80 synthetic wheat germplasms was graded based on the drought resistance coefficient of OSAVI, and the grading results were found to be consistent with that based on the D value. Among the six strongly drought-resistant germplasms identified based on the drought resistance coefficient of OSAVI, five of them were also classified as strongly drought-resistant germplasms based on comprehensive drought resistance evaluation.【Conclusion】The spectral indices NDVI, OSAVI, CI_re and NDRE extracted from UAV-based multi-source images, as well as the drought resistance comprehensive evaluation value can be used to assist in the identification of drought resistance of wheat germplasm.

Classification and Identification of Nitrogen Efficiency of Wheat Varieties Based on UAV Multi-Temporal Images

ZANG ShaoLong, LIU LinRu, GAO YueZhi, WU Ke, HE Li, DUAN JianZhao, SONG Xiao, FENG Wei

Scientia Agricultura Sinica. 2024, 57(9): 1687-1708. doi:10.3864/j.issn.0578-1752.2024.09.006

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【Objective】To explore the potential of UAV remote sensing in nitrogen efficiency classification and recognition, a nitrogen efficiency classification method for wheat varieties was constructed, so as to provide the theoretical basis and technical support for nitrogen efficient variety screening.【Method】Six agronomic indicators related to nitrogen efficiency at maturity stage (yield, plant nitrogen accumulation, nitrogen physiological use efficiency, plant dry biomass, total nitrogen uptake of grains, and N harvest index) were used to construct the principal component synthesis value, and K-Means cluster analysis was performed on them. The 121 wheat varieties were divided into three types: high, medium, and low nitrogen efficiency types. A UAV remote sensing platform equipped with a multi-spectral camera was used to obtain remote sensing images of wheat at the jointing, booting and flowering stages, and 34 vegetation indices were extracted to analyze the correlation between vegetation index and nitrogen efficiency comprehensive value. The accuracy of nitrogen efficiency classification models of support vector machine (SVM), random forest (RF), and K-nearest neighbor (KNN) classification methods were compared, and the overall classification accuracy (OA) and Kappa coefficient were used to compare the classification and recognition ability of wheat varieties in different growth periods. Three different feature set screening methods(ReliefF algorithm, Boruta algorithm and RF-RFE algorithm) were used to comprehensively evaluate the optimized feature subsets, and an appropriate classification and recognition method for wheat varieties nitrogen efficiency was established.【Result】With the progress of wheat growth stage, the correlation between vegetation index and the comprehensive value of nitrogen efficiency gradually increased, which reached the highest correlation coefficient at flowering stage (r=0.502). The full feature set of vegetation indices was used to classify the nitrogen efficiency of wheat varieties. For the data of single growth stage, SVM model had the best classification accuracy at flowering stage (OA=77.1%, Kappa=0.591), and the worst classification accuracy at jointing stage (OA=65.6%, Kappa=0.406). In general, the classification accuracy of nitrogen efficiency of varieties with multi-growth stage data fusion was higher than that of single growth stage, among which SVM model with jointing stage + booting stage + flowering stage had the best classification accuracy (OA=80.6%, Kappa=0.669). In order to reduce the number of feature set variables in multi-growth period data fusion, the feature optimization effects of RF-RFE, Boruta and ReliefF algorithms were compared and analyzed. The optimal feature subset based on RF-RFE algorithm had the highest classification accuracy, and its OA and Kappa coefficients were 4.0% and 10.1% higher than those of the full feature set classification model, respectively. Among them, the data fusion of three growth stages had the best classification accuracy (OA=85.4%, Kappa=0.749).【Conclusion】The nitrogen efficiency evaluation method with six nitrogen efficiency indexes - principal component analysis -K-Means were established in this study. The RF-RFE algorithm effectively optimized the number of characteristic subsets of the multi-growth period combination, and obtained high classification accuracy. A nitrogen efficiency classification model of wheat varieties based on the fusion of multi-growth period combination and RF-RFE-SVM technology was established, which provided the theoretical basis and technical support for the rapid and accurate classification and identification of wheat varieties with nitrogen efficiency.

Compensation Potential of Dense Planting on Nitrogen Reduction in Maize Yield in Oasis Irrigation Area

FAN Hong, YIN Wen, HU FaLong, FAN ZhiLong, ZHAO Cai, YU AiZhong, HE Wei, SUN YaLi, WANG Feng, CHAI Qiang

Scientia Agricultura Sinica. 2024, 57(9): 1709-1721. doi:10.3864/j.issn.0578-1752.2024.09.007

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【Objective】To address the issue of excessive nitrogen fertilizer use for maize production in an oasis irrigation area, this study investigated the compensation effect for nitrogen fertilizer reduction through dense planting on maize yield.【Method】From 2019 to 2021, a two-factor split-plot experiment was carried out to explore the effect of different maize densities on yield and yield components under nitrogen reduction conditions. The main plot was two nitrogen application rate, including 25% reduction (N₁, 270 kg·hm^-2) and local habitual nitrogen application (N₂, 360 kg·hm^-2), and sub-plot was three planting densities of maize, including traditional (M₁, 78 000 plants/hm²), medium (M₂, 104 000 plants/hm², 33% increase), and high planting density (M₃, 129 000 plants/hm², 66% increase).【Result】(1) The grain yield and biomass of maize under N₁decreased by 4.0% and 4.9% than that under N₂respectively due to nitrogen reduction, which could be compensated by dense planting. The grain yield of N₁M₂ was increased by 4.1% compared with that of the control treatment (N₂M₁), while the biomass of treatment of high density and nitrogen reduction (N₁M₃) had the largest compensation effect, which was increased by 14.2% compared with that under the control. (2) According to the regression analysis, at the N₁ level, the density of 84 000 plants/hm² could get the equal grain yield of the control treatment, and reached the maximum grain yield of 13 537 kg·hm^-2 at 106 000 plants/hm², achieving a 4.9% increase in grain yield. (3) Compared with N₂, N₁ reduced maize ear number, kernel number per ear, and 1 000-kernel weight by 5.0%, 3.3%, and 3.4%, respectively, but had no significant effect on the harvest index. M₂ and M₃ increased the maize ear number by 27.9% and 49.7%, reduced kernel number per ear by 3.8% and 8.4%, respectively, and decreased 1 000-kernel weight by 5.2% and 8.9%, respectively. M₂ had no significant effect on the harvest index, while M₃ significantly reduced the harvest index by 14.2%. Therefore, compared with N₂M₁, N₁M₂ compensated for the decrease in ear number, kernel number per ear, and 1 000-kernel caused by nitrogen reduction through the increase of ear number. (4) N₁ decreased the maize growth rate from the jointing stage to the tasseling and silking stage by 7.2%-8.4%, while M₂ and M₃ significantly increased the maize growth rate by 27.3% and 60.3% compared with traditional density from the seedling stage to the trumpet stage. (5) Compared with N₂M₁, N₁M₂ increased maize leaf,stem, and sheath dry matter transportation amount (DTA) by 9.6%, 13.6%, and 3.7%, respectively, and the contribution rate of vegetative organs to grain (GCR) by 5.3% and 9.0%, respectively.【Conclusion】In the oasis irrigation area, the maize grain yield decrease caused by nitrogen reduction could be compensated by reasonably dense planting. Increasing the density to 104 000 plants/hm² based on 25% nitrogen reduction could maximize the yield compensation effect, which was a feasible measure to save nitrogen for a stable and high yield of maize.

Mitochondrial Protein-Coding Genes Nad5, Nad6 and Atp6 are Involved in Phosphine Resistance of Cryptolestes ferrugineus

CHEH ErHu, YUAN GuoQing, CHEN Yan, CHEN MengQiu, SUN ShengYuan, TANG PeiAn

Scientia Agricultura Sinica. 2024, 57(9): 1722-1733. doi:10.3864/j.issn.0578-1752.2024.09.008

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【Background】Cryptolestes ferrugineus is one of the most economically important stored-grain pests, and its phosphine resistance is particularly prominent. Mitochondria are important organelles in living organisms, which are the core site for insects to undergo respiratory metabolic reactions. Mitochondrial protein-coding genes (PCGs) are involved in regulating physiological processes of insects, such as respiratory rate, energy metabolism, and cell signal transduction.【Objective】The objective of this study is to clarify the roles of mitochondrial PCGs in phosphine resistance of C. ferrugineus.【Method】The respiratory rates of different phosphine resistant populations of C. ferrugineus were measured by using a CO₂ detector. The Taicang and Shanghai populations of C. ferrugineus with greatest differences in phosphine resistance levels and respiratory rates were selected to analyze the expression patterns of mitochondrial PCGs by using RT-qPCR technology, and the activities of mitochondrial complexes I and V were measured as well. The expression levels of three key mitochondrial PCGs including Nad5, Nad6 and Atp6, and the activities of mitochondrial complex I and V were determined after phosphine fumigation treatments in C. ferrugineus. RNA interference (RNAi) was used to silence Nad5, Nad6 and Atp6, and then the changes of respiratory rate and phosphine sensitivity of C. ferrugineus were analyzed.【Result】There was a negative correlation between the respiratory rate and phosphine resistance levels of C. ferrugineus, that is, the respiratory rates significantly decreased with the increase of phosphine resistance levels. The RT-qPCR results showed that the expression levels of mitochondrial PCGs in the highly phosphine resistant population (Taicang population, RR=1 906.8) of C. ferrugineus were significantly lower than those in the relatively sensitive population (Shanghai population, RR=1.4), and the enzyme activities of mitochondrial complexes I and V were consistent with the expression patterns of mitochondrial PCGs. The expression levels of three key mitochondrial PCGs, Nad5, Nad6 and Atp6, and the activities of mitochondrial complexes I and V were significantly inhibited after phosphine fumigation treatments in C. ferrugineus. The key mitochondrial PCGs, Nad5, Nad6 and Atp6 were silenced by injecting dsRNA, which resulted in a significant decrease in respiratory rate and phosphine sensitivity of C. ferrugineus.【Conclusion】The mitochondrial PCGs are involved in phosphine resistance of C. ferrugineus.

Screening, Compounding and Safety Evaluation of Herbicides Suitable for Peach Nursery

GUO Lei, HUANG ChenYan, SONG HongFeng, SHEN ZhiJun, ZHANG BinBin, MA RuiJuan, SUN Meng, HE Xin, YU MingLiang

Scientia Agricultura Sinica. 2024, 57(9): 1734-1747. doi:10.3864/j.issn.0578-1752.2024.09.009

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【Objective】Weed control is an important step for fruit tree production. To investigate the safety of different herbicides, suitable herbicides for peach nurseries and orchards were screened in peach production, which can provide theoretical basis for the application of chemical herbicides in the peach industry.【Method】To preliminarily screen the safety of 13 herbicides, the peach seedlings combined with Lolium perenne, Cynodon dactylon, Alternanthera philoxeroides, Trifolium repens and Medicago falcata were evaluated in pot. Based on the results of the phytotoxicity index of each herbicide, 10% quizalofop-p-ethyl and 60% quinclorac were mixed. According to the effective doses of 25, 50, and 75 mL·hm^-2 of quizalofop-p-ethyl and 150, 300, 450 g·hm^-2 of quinclorac, a total of 9 herbicide mixtures were established. After 7, 14, and 21 d of stem and leaf spraying treatment, the weed inhibition rate was investigated. After 30 d of the treatment, the plant height, stem diameter, aboveground and underground biomass, electrolyte permeability of the leaf and root tip cells, total root length, total root surface area, root volume and root tip number of peach seedlings were also measured. Based on principal component analysis, the safety of different treatments was comprehensively evaluated.【Result】After spraying on the stems and leaves of peach seedlings, 11 herbicides caused phytotoxicity in peach seedlings, resulting in varying degrees of symptoms such as chlorosis, wilting, and withering. However, quizalofop-p-ethyl and quinclorac had no significant effect on the growth of peach seedlings. After spraying weeds with a single agent of quizalofop-p-ethyl for 21 d, the inhibition rate of quizalofop-p-ethyl on gramineous weeds was 100%. However, it had no effect on broad-leaved weeds. On the contrary, the inhibition rate of spraying quinclorac on gramineous weeds was 0, and the inhibition rate range of M. falcata, T. repens and A. philoxeroides was 80% to 100%. After being mixed with quizalofop-p-ethyl and quinclorac, the total weed inhibition rate under 9 compound preparations could reach over 90% after 21 d. Meanwhile, each formulation had no significant effect on the height of peach seedlings, aboveground and underground biomass, electrolyte permeability of the leaf and root tip cells. The comprehensive analysis showed that the effective dose of quizalofop-p-ethyl had a significant impact on the comprehensive evaluation D value of the mixed formulation. When the effective dose of quizalofop-p-ethyl increased to 75 mL·hm^-2, the comprehensive evaluation D value of the mixed formulation exceeded 0.563, but there was no trend between the increasing D value and the increase of the effective dose of quinclorac.【Conclusion】Peach seedlings are sensitive to most herbicides, and mixing is an effective measure to improve the comprehensive weed inhibition rate of quizalofop-p-ethyl and quinclorac. After mixing an effective dose of 75 mL·hm^-2 quizalofop-p-ethyl with 300 g·hm^-2 quinclorac, the comprehensive evaluation D value of the formulation is the highest, which can achieve the best weed inhibition rate while ensuring the safety of peach seedlings.

Study on the Matching Relationship Between Pattern of Grain Production and Arable Land Resources in Hubei Province Based on Geomorphological Divisions

ZHANG JunFeng, DING JianCheng, WENG YuWei, ZHANG Xiong

Scientia Agricultura Sinica. 2024, 57(9): 1748-1765. doi:10.3864/j.issn.0578-1752.2024.09.010

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【Objective】The matching relationship between grain production pattern and regional arable land resources in different geomorphologic zones was studied to provide decision-making basis for grain production distribution and arable land resources protection.【Method】Concentration index, coefficient of variation method, spatial center of gravity model, matching degree and LMDI model were used.【Result】From 1990 to 2020, the proportion of grain output of Western Mountains, Central Heights, Eastern Hills and Jianghan Plain in the total grain output of Hubei Province was gradually adjusted to 11.2%, 30.6%, 26.2% and 32.0%. There are significant differences in the concentration and changing trends of grain crop production with different geomorphological division in Hubei Province from 1990 to 2020. Grain production in Hubei Province has a clear tendency to concentrate in Central Heights, mainly wheat and corn, while soybean production is concentrated in Jianghan Plain. In the past 30 years, the barycenter of grains planting and the barycenter of grains production in Hubei Province have both shifted to the northwest, with a distance of 5.37 km and 14.63 km, respectively. However, the barycenter of grain production in the Central Heights moves to the northeast, while the Jianghan Plain and the Western Mountains move to the southwest. The average spatial distances between grains production and the barycenter of arable land resources in the Western Mountains, the Central Heights, the Eastern Hills and the Jianghan Plain of Hubei Province are 6.20 km, 3.35 km, 10.57 km and 6.82 km. And their average index of consistency of change are 0.49, 0.44, 0.40 and 0.27, respectively. The Gini coefficients of grain production and arable land resources in Hubei Province are all greater than 0.5 and tend to increase, while the imbalance indices of Western Mountains and Jianghan Plain are positive, and the imbalance indices of Central Heights and Eastern Hills are negative. The quantity effect and intensive effect of arable land for grain production change in the four geomorphological divisions in the last 30 years are negative, and the utilization effect and quality effect of arable land are positive, among which the decreasing effect of arable land planting structure change on grain production in the Eastern Hills reaches 3.097 million t, while the increasing effect of replanting index change on grain production in the Central Heights reaches 3.0046 million t.【Conclusion】In the past 30 years, the incremental effect of quality and structure of arable land in the geomorphological divisions of Hubei Province is weakening, and the decreasing effect of quantity is increasing. Grain production in Hubei faces the planting risk of decreasing quality cropland and the yield risk of grain planting structure adjustment. Grain production and arable land resources have long been mismatched in the geomorphological divisions of Hubei Province and show obvious regional characteristics. The spatial layout of grain production and the adjustment of planting structure should fully consider the natural geography and arable land resource endowment characteristics of different geomorphological divisions to promote the coordinated development of food production and arable land use.

Effects of Different Nitrogen Application Rates on Carbon and Nitrogen Content of Soil Aggregates and Wheat Yield

HAN XiaoJie, REN ZhiJie, LI ShuangJing, TIAN PeiPei, LU SuHao, MA Geng, WANG LiFang, MA DongYun, ZHAO YaNan, WANG ChenYang

Scientia Agricultura Sinica. 2024, 57(9): 1766-1778. doi:10.3864/j.issn.0578-1752.2024.09.011

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【Objective】The influence mechanism of varying nitrogen (N) rates on the carbon (C) and N content of soil aggregate, as well as wheat yield were investigated in this study, so as to provide a scientific basis for the rational application of N fertilizer.【Method】The 11-year experiment was conducted in Zhangpan Town, Xuchang City, Henan Province, with four different N levels, including 0 (N0), 180 kg·hm^-2 (N1), 240 kg·hm^-2 (N2), and 300 kg·hm^-2 (N3). The study systematically analyzed changes in soil carbon and nitrogen content, cluster distribution and their carbon and nitrogen content in different soil layers as a result of long-term N application, and investigated the regulatory pathways of long-term N application on wheat yield and its composition.【Result】There was a transformation in the composition of soil aggregates in every soil layer, specifically from larger macroaggregates (>0.25 mm) to microaggregates (0.25-0.053 mm) and silt and clay particles (<0.053 mm), as well as an increase in N rate. Additionally, the application of N resulted in a significant decrease in the mean weight diameter (MWD). As N application rates increase, the C and N content of the soil increased in the 0-20 cm layer, the C and N content of the soil in the 20-40 cm soil layer showed the trend to increase at first and then decrease. Compared with the N0 treatment, N application increased soil organic carbon (SOC) and soil total nitrogen (STN) content by 13.1%-37.2% and 19.4%-29.4% in the 0-20 cm layer and by 15.3%-32.2% and 6.1%-29.3% in the 20-40 cm layer, respectively. The N treatment significantly increased the SOC content of each particle size aggregates compared with N0 treatment, with the SOC content of macroaggregates increasing by 31.6%-62.0%, the SOC content of microaggregates increasing by 8.7%-61.2% and the SOC content of silt and clay increasing by 14.0%-81.7%. As N application rates increased, the STN content of the soil increased in the 0-20 cm layer. With the STN content of macroaggregates increasing by 32.6%-51.0%, the STN content of microaggregates increased by 25.7%-35.9% and the STN content of silt and clay increased by 3.2%-9.7%, the N3 treatment had the highest STN content of all particle size aggregates. In the 20-40 cm soil layer, the STN content of all particle size aggregates tended to increase at first and then decrease. With the STN content of macroaggregates increasing by 17.6%-35.2%, the STN content of microaggregates increased by 11.7%-24.0% and the STN content of silt and clay increased by 1.1%-12.9%, and the N1 treatment had the highest STN content of all particle size aggregates. The study results indicated that long-term nitrogen application had a significant impact on the spike number and grain number per spike in wheat, resulting in increased yield. Compared with the N0 treatment, the application of N1, N2, and N3 treatments resulted in a significant increase in wheat yield, with improvements of 188.1%, 177.3%, and 173.2%, respectively. The correlation and structural equation modelling analyses revealed a significant and positive correlation between wheat yield and soil carbon and nitrogen content, as well as carbon and nitrogen content in aggregates. Additionally, the long-term application of nitrogen was found to influence wheat yield formation by affecting carbon and nitrogen content in microaggregates.【Conclusion】In summary, the application of nitrogen over a long period of time raised the content of carbon and nitrogen in both soil and aggregates, enhanced soil fertility, ultimately promoting wheat yield. The optimal nitrogen application rate was 180 kg·hm^-2under the condition of this experiment.

Identification and Analysis of Genes Related to Bitter Gourd Saponin Synthesis Based on Transcriptome Sequencing

QI RenJie, NING Yu, LIU Jing, LIU ZhiYang, XU Hai, LUO ZhiDan, CHEN LongZheng

Scientia Agricultura Sinica. 2024, 57(9): 1779-1793. doi:10.3864/j.issn.0578-1752.2024.09.012

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【Objective】As the main source of bitterness in bitter gourd fruit, saponin possesses various medicinal values including hypoglycemic and anticancer properties. This paper aimed at identifying the metabolic pathways and genes involved in the regulation of bitter gourd saponin biosynthesis, so as to provide the theoretical basis for further analysis of the molecular mechanism of bitter gourd saponin formation.【Method】Using the bitter gourd high-generation inbred line GK24 as the test material, fruit tissues were sampled at the ovary stage (T1), young fruit stage (T2), commodity fruit stage (T3), and maturity fruit stage (T4). The saponin content of bitter gourd at different periods were determined by the vanillin-glacial acetic acid method, and the differentially expressed genes (DEGs) were identified using the method of transcriptome sequencing. 【Result】From T1 to T4, the endogenous saponin content of bitter gourd showed significant decrease with fruit development. A total of 17 504 genes were identified by transcriptome sequencing, and the number of down-regulated genes was higher than that of up-regulated genes in the comparison of the three groups of T1-vs-T2, T2-vs-T3, and T3-vs-T4. GO enrichment analysis showed that phosphorus-containing complex metabolic process, kinesin complex and 2-succinyl-6-hydroxy-cyclohexadiene-1-carboxylic acid synthetase activity were the most significantly enriched terms in biological process, cellular component and molecular function, respectively. KEGG analysis showed that global and overview mapping, carbohydrate metabolism, and amino acid metabolism were the most significantly enriched pathways in all three comparative groups. The genes could be categorized into 20 profiles based on their expression patterns. Genes in profile 0 gradually decreased from T1 to T4, showing similar pattern of saponin content changes with bitter gourd fruit development. 14 genes related to bitter gourd saponin biosynthesis were identified from profile 0, including AAT1, HMG1, MVK, PMK, MVD2, and FPS1 in the terpene skeleton biosynthesis pathway, SS12, SQE1, and CPQ in the sesquiterpene and triterpene biosynthesis pathway, and the postmodifying enzyme genes CYP97A3, CYP71AN24, UGT94E5 and UGT73C6. The results of RNA-seq were validated by qRT-PCR method.【Conclusion】The saponin content of bitter gourd decreased with the fruit development. Bitter gourd saponin was synthesized through the terpenoid bone biosynthesis (ko00900) metabolic pathway to accumulate terpenoid saponin skeleton in the first, and then produce saponins through the sesquiterpene and triterpene biosynthesis (ko00909) metabolic pathway and the modification of oxidoreductase and glycosyltransferase successively. A total of 14 genes related to the saponin biosynthesis of bitter gourd have been identified in the present study.

Stem Sap Flow and Water Consumption of Chestnut During Growth Season

GUO Yan, ZHANG ShuHang, ZHANG XinFang, LI Ying, LIU JinYu, FAN LiYing, LIU ShiYuan, GAO Qian, WANG GuangPeng

Scientia Agricultura Sinica. 2024, 57(9): 1794-1806. doi:10.3864/j.issn.0578-1752.2024.09.013

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【Objective】This study analyzed the characteristics of transpiration water consumption of chestnut (Castanea mollissima Bl.), so as to provide a theoretical reference for the formulation of scientific and reasonable water management measures in chestnut orchards.【Method】The thermal diffusion probe method was used to continuously monitor the stem flow rate of Dabanhong chestnut continuously during the whole growing season from March 1, 2022 to March 1, 2023, and seven related environmental factors (solar radiation, air relative humidity, air temperature, wind speed, vapor pressure deficit, soil temperature, and soil relative humidity) were observed simultaneously to analyze the stem flow rules and water consumption characteristics of chestnut trees and their correlation with environmental factors. 【Result】The obvious stem flow of chestnut trunk started on May 3 and ended on October 26, which lasted for 176 days. The diurnal variation of stem flow rate of chestnut showed a single-peak curve in sunny days during the whole growing season. The daily start and peak time of stem flow rate in June, July and August were earlier than those in May, September and October, while the decline time was later than those in May, September and October, so that the peak duration of stem flow rate in June, July and August was longer than that in May, September and October. The daily average stem flow rate, daily average water consumption and monthly water consumption in the whole growing season of chestnut were ranked from high to low as August>July>June>September>May>October, the significance test showed that there was no significant difference between July and August, but it was significantly higher than other months. The nocturnal sap flow percentage was ranked from high to low as October>September>May>June>July>August, and the significance test showed that October, September and May were significantly higher than June, July and August. The stem sap flow rate of chestnut during the whole growing season was significantly positively correlated with solar radiation, water vapor pressure deficit, air temperature and wind speed, and significantly negatively correlated with air relative humidity. Six regression models of stem flow rate from May to October and seven environmental factors were established.【Conclusion】The obvious stem flow of chestnut began at the beginning of May and ended at the end of October. The key water demand period of chestnut was July to August. Regression models of chestnut sap flow rate and environmental factors, which could be used to estimate the water requirement of plants in different months and the whole growing season through environmental factors.

Cloning and Identification of Differentially Expressed lncRNAs in Follicles of Meishan Pigs and Duroc Pigs with Their Correlation Analysis with miRNAs

ZHANG HuaPeng, ZHANG QingZe, HE Fan, QI MengFan, FU BinBin, LI QingChun, LI MengXun, MA LiPeng, LIU Yi, HUANG Tao

Scientia Agricultura Sinica. 2024, 57(9): 1807-1819. doi:10.3864/j.issn.0578-1752.2024.09.014

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【Objective】The objective of this study was to clone and identify the differentially expressed lncRNA-ALDBSSCT0000005583 in M2 follicles on the fourth day of follicular stage in Meishan pigs and Duroc pigs, and to analyze the correlation between the expression of miRNAs in porcine granulosa cells, so as to provide a theoretical basis for exploring the role of lncRNAs in the development of follicles in sows by regulating miRNAs. 【Method】Based on the differentially expressed lncRNA- ALDBSSCT0000005583 screened in Meishan and Duroc M2 follicles in our early research, the full-length sequence of ALDBSSCT0000005583 was verified by RT-qPCR and cloned by RACE; the coding ability of this lncRNA was predicted by the coding potential assessment tool of CAPT and CPC, which was further identified by the primary expression test; the coding ability of this lncRNA was identified by the primary expression test; the subcellular coding ability of NA-ALDBSSCT0000005583 was identified by the nucleoplasmic separation experiment and tested to identify its coding ability; the subcellular localization of lncRNA-ALDBSSCT0000005583 by nucleoplasmic isolation assay and its expression level in various tissues were detected by RT-qPCR; miRBase website was used to locate the miRNA database of pigs, and the combination of RNAhybrid and miRanda online software was used to predicte the relationship with the lncRNA-ALDBSSCT0000005583. The inter-species conserved miRNAs that interacted with lncRNA-ALDBSSCT0000005583 were predicted by TargetScan and miRanda, the target genes that interacted with lncRNA-ALDBSSCT0000005583 were predicted by TargetScan and miRanda, and their target genes were subjected to GO enrichment and KEGG signaling pathway analyses; the effects of target genes on miRNA expression were verified by overexpression as well as interference with lncRNA. 【Result】The expression level of lncRNA-ALDBSSCT0000005583 in M2 follicles of Duroc pigs was significantly higher than that in Meishan pigs, and the size of lncRNA 5′RACE and 3′RACE fragments was 569 bp and 546 bp, respectively, and the sequencing analysis showed that the size of lncRNA-ALDBSSCT0000005583 was 588 bp. Bioinformatics predicted that the encoding potential was low, and the results of prokaryotic expression assay further proved that it did not code for proteins. Tissue expression profiling showed that lncRNA-ALDBSSCT0000005583 was expressed in the adrenal gland, spleen, liver and ovaries, and low in the hypothalamus and heart, while the subcellular localization results showed that the lncRNA was mainly present in the cytoplasm. After bioinformatics analysis, a total of 9 conserved miRNAs were screened for potential interaction with lncRNA-ALDBSSCT0000005583, including two miRNAs related to ovarian development: miR-193a-5p and miR-361-3p. KEGG and GO enrichment analysis showed that the target genes of miR-193a-5p and miR-361-3p were related to phylogenetic processes and biological processes such as cell-to-cell signaling. It was also significantly involved in oxytocin, Ras, NF-κB gonadotropin- releasing hormone secretion and other pathways. Subsequently, lncRNA-ALDBSSCT0000005583 was overexpressed in granulosa cells, and the expressions of miR-193a-5p and miR-361-3p were significantly down-regulated by RT-qPCR (P<0.05), but there was no significant effect after interference with lncRNA-ALDBSSCT0000005583. 【Conclusion】 lncRNA-ALDBSSCT0000005583 was a lncRNA that did not have the ability to code for proteins. There was a significant difference in the expression level between the medium follicles of Meishan and Duroc pigs, and the expression level was higher in the adrenal glands, spleen, liver and ovaries, which is mainly found in the cytoplasm of granulosa cells, and might be involved in the development of porcine ovarian granulosa cells by interacting with miR-193a-5p and miR-361-3p.

Biological Characteristics of H6N1 Subtype Avian Influenza Virus from 2019 to 2022 in China

CHEN Yuan, CUI PengFei, SHI JianZhong, ZHANG YuanCheng, YU QingQing, YAN Cheng, ZHANG YaPing, WANG CongCong, ZHANG Jie, WANG Yan, DENG GuoHua, CHEN HuaLan

Scientia Agricultura Sinica. 2024, 57(9): 1820-1832. doi:10.3864/j.issn.0578-1752.2024.09.015

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【Background】H6 avian influenza virus (AIV) is widely prevalent in southern China, which is one of the most common subtypes of AIVs circulating in poultry in China. H6N1 AIVs frequently undergo gene reassortment events with other wild bird-origin virus, which can be a donor to provide internal gene segments to highly pathogenic AIVs, which may lead to the emergence of novel virus and threaten human health.【Objective】The aim of this study was to investigate the evolution and biological characteristics of H6N1 AIVs in China, so as to provide valuable data for the prevention and control of avian influenza in China.【Method】From 2019 to 2022, cloacal and throat swabs were collected from live poultry markets and breeding farms across 25 provinces or autonomous regions in China. 7 H6N1 viruses were isolated by inoculating into chicken embryos. The complete genome sequences were determined, followed by analyzing their phylogenetic relationships, receptor binding properties, as well as replication in SPF chickens and BALB/c mice.【Result】The phylogenetic analysis revealed that the genes of the 7 H6N1 AIVs were highly homologous to those of wild bird-origin viruses from North America and Southeast Asia, indicating a complex genetic origin with significant genetic diversity. According to the Bayesian evolution analysis, the HA gene of H6 subtype AIVs had many times of intercontinental transmission in the history, and the Eurasian lineage strains also had a long time of circulation in North America. The HA gene of one strain of the virus was highly homologous to that of the North American strain. Based on the results of Bayesian evolutionary analysis, it was hypothesized that the virus was introduced to China via wild birds after undergoing complex genetic reassortment in wild birds. Analysis of specific amino acid sites revealed that the cleavage site of HA protein was PQIETR↓GLF, which was the signature of low pathogenic AIVs. In addition, one other virus had a Y52H mutation in the NP protein, which was critical in BTN3A3 evasion. Receptor binding analysis demonstrated that some of the H6N1 AIVs bound to both avian-type receptor and human-type receptor, however, their affinity towards human receptors was weaker compared with avian receptors. Infectivity experiments on SPF chickens indicated that flocks was still able to shed virus up through oropharyngeal and cloacal routes after infection with A/chicken/Jiangxi/S40445/2019(H6N1) and that the virus could be transmitted via contact within flocks. Only a few chickens infected with A/duck/Jiangxi/S10941/2019(H6N1) shed virus through their oropharyngeal tract, and the virus could not be transmitted via contact among chickens. The infectivity experiments conducted on mice showed that H6N1 subtype AIVs could replicate in the respiratory organs of infected mice without prior adaptation, but display low pathogenicity levels in mice.【Conclusion】Most of the genes of H6N1 subtype AIV isolated in China from 2019 to 2022 were derived from wild bird-origin viruses, and those migratory birds could introduce the viruses into China via the East Asia-Australasian migratory flyway. Some of the H6 AIVs bound to human-type receptors and replicate in the respiratory organs of mice suggested that H6N1 viruses posed a potential threat to human health.

A Study on the Quality Stability of Wheat Grains at Designated Locations Across Multiple Years

ZHAO BoHui, ZHANG YingQuan, JING DongLin, LIU BaoHua, CHENG YuanYuan, SU YuHuan, TANG Na, ZHANG Bo, GUO BoLi, WEI YiMin

Scientia Agricultura Sinica. 2024, 57(9): 1833-1844. doi:10.3864/j.issn.0578-1752.2024.09.016

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【Objective】The stable quality of wheat raw grain can keep the processing technology and its parameters basically unchanged, reduce human intervention in the processing process and the loss of process adjustment, and ensure the stability of the quality of flour products. The evaluation of variety quality stability could provide the reference for processing enterprises to purchase stable quality raw grain.【Method】In this experiment, seven wheat varieties, including Shiluan 02-1, Jimai 22, Liangxing 99, Han 6172, Yingbo 700, Luyuan 502, and Gaoyou 2018, were planted in Xingtai and Handan cities from 2013 to 2019 and selected as trial samples. The coefficient of variation was used to quantitatively characterize the quality stability of varieties over multiple years and locations. The product of test weight, crude protein in grains, wet gluten content, and dough stability time was calculated, and its coefficient of variation was used as a comprehensive statistical measure of quality stability. Pairwise analysis of varieties in the same year and location was conducted to analyze the stability of their quality indicators.【Result】The fluctuation ranges of test weight, crude protein in grains, wet gluten content, dough stability time, and the coefficient of variation of the product of quality indicators were 0.06%-5.50%, 0.01%-12.21%, 0.03%-10.02%, 0.4%-138.69%, and 0.32%-140.01%, respectively. Pairwise analysis showed that the stability of test weight from high to low was Gaoyou 2018, Luyuan 502, Han 6172, Liangxing 99, Yingbo 700, Jimai 22, and Shiluan 02-1. The stability of crude protein in grains from high to low was Gaoyou2018, Han 6172, Yingbo 700, Luyuan 502, Liangxing 99, Jimai 22, and Shiluan 02-1. The stability of wet gluten content from high to low was Gaoyou 2018, Han 6172, Luyuan 502, Yingbo 700, Liangxing 99, Shiluan 02-1, and Jimai 22. The stability of dough stability time from high to low was Yingbo 700, Jimai 22, Gaoyou 2018, Luyuan 502, Han 6172, Liangxing 99, and Shiluan 02-1. The stability of the product of the above quality indicators from high to low was Yingbo 700, Gaoyou 2018, Luyuan 502, Liangxing 99, Han 6172, Jimai 22, and Shiluan 02-1. 【Conclusion】Among the tested quality indicators, test weight showed higher stability, while dough stability time exhibited lower stability. The stability of crude protein in grains and wet gluten content fell between the two. By using the coefficient of variation of the product of four quality indicators as the evaluation criterion, Yingbo 700 demonstrated higher quality stability among the trial varieties.

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