Table of Content

01 May 2023, Volume 56 Issue 9

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Principle, Optimization and Application of Mixed Models in Genome- Wide Association Study

TAN LiZhi, ZHAO YiQiang

Scientia Agricultura Sinica. 2023, 56(9):  1617-1632.  doi:10.3864/j.issn.0578-1752.2023.09.001

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Genome-wide association study (GWAS) is an effective method to locate genomic loci that are significantly associated with traits. With the accumulated phenotypic data, the continuous development of high-throughput genotyping technology, and the improved statistical methods, it promotes the wide application of GWAS in area of human disease and animal and plant genetics. False positives are one of the important concerns that impair the reliability of genome-wide association results. To control the false positives, in addition to correcting the P-values, GWAS models have been continuously improved from the naive methods like ANOVA (for quantitative trait) or Chi-square test (for quality trait), to general linear model (GLM), which incorporates fixed-effect covariates, to the mixed linear model (MLM), which incorporates random effects. Fitting individual genetic effects into random effects defined by the genomic relationships matrix (GRM) is commonly adapted currently. Since the parameter estimation of MLM consumes a lot of computational resources, researchers have tried to optimize solving models and constructing GRM (which also improves computing efficiency), and the time complexity gradually decreased from O(MN³) to O(MN) for MLM-based methods, achieving a great leap in computational speed and statistical efficacy. For inflations caused by unbalanced case-control data, researchers further correct the generalized mixed linear model (GLMM). This paper comprehensively introduces the basic principles and development of GWAS, with specific emphasis on the model improvement and optimization details. We also list the applications of MLM in GWAS in agriculture, including progress on animals, plants and microbes, as well as the application of haplotype in GWAS. Finally, we give prospects on the future developments of GWAS from the viewpoints of further model optimization and experimental design.

Overexpression of Wheat TaCYP78A5 Increases Flower Organ Size

PENG HaiXia, KA DeYan, ZHANG TianXing, ZHOU MengDie, WU LinNan, XIN ZhuanXia, ZHAO HuiXian, MA Meng

Scientia Agricultura Sinica. 2023, 56(9):  1633-1645.  doi:10.3864/j.issn.0578-1752.2023.09.002

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【Objective】The function and mechanism of TaCYP78A5 regulating flower organ size was preliminarily analyzed by means of expression pattern analysis, transgenic overexpression and cytological observation. The results provide genetic resources and theoretical basis for crop genetic improvement. 【Method】According to the sequence information of CYP78A family members of different species in EnsemblePlants genome database, sequence alignment and evolutionary analysis were carried out for the homologous genes of TaCYP78A5 in wheat and other species. The gene and protein structures and the expression patterns of different organs of wheat TaCYP78A5 were analyzed by bioinformatics. Through the strategy of constitutive overexpression and local specific overexpression in reproductive organs of TaCYP78A5 in Arabidopsis, it is clear that TaCYP78A5 has the function of regulating flower organ size. The cytological characteristics of flower organs of different transgenic Arabidopsis were observed under microscope, and the cytological mechanism of TaCYP78A5 regulating flower organ size was analyzed. The function of TaCYP78A5 in regulating wheat spike size and other spike traits was clarified by using the strategy of transgenic overexpression in wheat. The correlation analysis of haplotype data and spike phenotype data of 323 wheat accessions was used to explore the effect of TaCYP78A5 expression on spike size and other spike traits of different wheat accessions. 【Result】The gene and protein sequence similarity of wheat TaCYP78A5 and Arabidopsis AtCYP78A5 is low, but the gene and protein structure similarity is high. Wheat TaCYP78A5 and Arabidopsis AtCYP78A5 are widely expressed in many organs, but highly expressed in flower organs. Compared with wild type, the constitutive overexpression of TaCYP78A5 in Arabidopsis could lead to the enlargement of flower organs and a significant increase in petal area of 13.5%-35.4%. Moreover, the specific overexpression of TaCYP78A5 only in the ovule was enough to cause the enlargement of the flower organ of Arabidopsis, and the petal area increased significantly by 9%-22.1%. On the contrary, the flower organ of Arabidopsis cyp78a5 mutant was significantly smaller than that of wild type, and the petal area was significantly reduced by 27%. The constitutive overexpression of TaCYP78A5 in Arabidopsis resulted in a significant increase in the size of petal epidermal cells by 49%-54% compared with wild type, and a significant decrease in the number of cells by 11%-19% compared with wild type. Locally specific overexpression of TaCYP78A5 in Arabidopsis also resulted in a significant increase in the size of petal epidermal cells by 20%-49% compared with wild type, and a significant decrease in the number of cells by 8%-24% compared with wild type. The constitutive overexpression of TaCYP78A5 in wheat resulted in the increase of wheat spike length by 7.9%-8.9%, glume area by 9.6%-14.7%, and grain number per spike by 12.4%-23.8%. The spikelet number per spike and grain number per spikelet showed different degrees of change. The results of haplotype analysis showed that among 323 wheat accessions, wheat accessions with higher TaCYP78A5-A expression level had longer spike length, more grains per spikelet and fewer spikelets per spike than wheat accessions with lower TaCYP78A5-A expression level, but there was no significant difference in grain number per spike. 【Conclusion】TaCYP78A5 promoted the growth of flower organs in a non cellular self-made mode. The overexpression of TaCYP78A5 in wheat and Arabidopsis could lead to the enlargement of flower organs.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY·AGRICULTURE INFORMATION TECHNOLOGY

Effects of Increasing Density on the Granule Size Distribution and Viscosity Parameters of Endosperm Starch in Spring Maize Kernel

LU MengLi, ZHANG YaTing, REN Hong, WANG TuJin, HAN YiMing, LI WenYang, LI CongFeng

Scientia Agricultura Sinica. 2023, 56(9):  1646-1657.  doi:10.3864/j.issn.0578-1752.2023.09.003

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【Objective】Dense planting is one of the main measures to improve the high yield cultivation of maize, and density has a significant effect on the formation of maize starch. Therefore, this study analyzed the granule size distribution and viscosity parameters of different types of spring maize kernels under different increasing density conditions for improving the quality of maize starch. 【Method】 The field experiments were conducted at the Gongzhuling experimental base in Jilin province in 2019 and 2020. In the present experiments, eight main maize varieties in Northeast China, such as Xianyu 335, Zhengdan 958 and Nonghua 101, etc, were selected as experimental materials, and two planting densities of 67 500 and 97 500 plants/hm² were set. The granule size distribution and viscosity parameters of starch in different treatments were measured by diffraction particle size analyzer and viscosity analyzer, and the relative quality of maize was measured by near-infrared analyzer, and the correlation analysis was conducted to clarify the effects of increasing density on the granule size distribution and viscosity parameters of endosperm starch in spring maize.【Result】The results showed that with the increase of planting density, maize grain yield and starch content increased significantly, and the increase of density significantly increased the volume, surface area and number percentage of large (>17 μm) starch granules, while the opposite trend was observed in the volume, surface area and number percentage of small (<3 μm) starch granules. It could be seen that with the increase of planting density, the volume and number percentage of small starch granules in maize kernels decreased significantly, and the volume and number percentage of large starch granules increased, indicating that increasing density was beneficial to the increase of the volume ratio of large starch granules, that is, increasing density promoted the accumulation of starch and increased the number of large starch granules and the formation of individual volume. At the same time, it was found that the peak viscosity, trough viscosity, breakdown and final viscosity of maize starch were significantly increased after increasing density. The results of correlation analysis showed that the starch content, yield and viscosity parameters of maize grain were negatively correlated with the volume percentage of small starch granules, significantly or extremely significantly negatively correlated with the volume percentage of medium (3-17 μm) starch granules, and significantly or extremely significantly positively correlated with large (>17 μm) starch granules.【Conclusion】Increasing planting density could increase maize grain yield, starch content and its viscosity parameters by mainly affecting the granule size distribution of endosperm starch, namely increasing the proportion of large starch granules and reducing the proportion of small and medium-sized ones.

Effects of Squares and Bolls Abscission on Photosynthate Accumulation and Its Strength as an Auxiliary Source of Cotton Sympodial Leaves

KAN JiaQiang, LIU Yu, ZHOU ZhiGuo, CHEN BingLin, ZHAO WenQing, HU Wei, HU ShaoHong, CHEN Yang, WANG YouHua

Scientia Agricultura Sinica. 2023, 56(9):  1658-1669.  doi:10.3864/j.issn.0578-1752.2023.09.004

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【Objective】The abscission rate of squares and bolls is often more than 60%, and the sympodial leaves after squares and bolls shedding are often used as “auxiliary sources” to play an important role in the development of adjacent bolls. In order to enrich the “source-sink” regulation theory and provide theoretical basis for the regulation of cotton yield compensatory development, the activity changing characters of the “auxiliary sources” was explored after the shedding of their squares or bolls.【Method】In this study, two sowing dates (May 10 and June 1, 2021) of Zhongmian 425 were used to carry out a field experiment at the Pailou Experimental Station of Nanjing Agricultural University in Nanjing, Jiangsu province (118° 50′ E, 32° 02′ N). Under the conditions of fruiting branch phloem blocking, the changes of related indicators of leaf source capacity, such as cotton sympodial leaves morphological characteristics, gas exchange parameters, carbon and nitrogen substances and endogenous hormone content, were studied after defruiting (isolate the “source-sink” system on the first node at the fourth, fifth or sixth fruiting branches by chemical blocked the phloem, and then simulated the boll abscission condition by manual remove the bud or young bolls of the system).【Result】(1) The defruiting treatment significantly increased the content of fructose, sucrose, starch and cellulose in sympodial leaves, but significantly decreased the glucose content. With the extension of time, the increase of starch was the largest at 1 day after treatment (DAT), while that of cellulose was significantly larger at 3 DAT and that of sucrose, cellulose and starch was relatively larger at 5 DAT. (2) After treatment, carbohydrates accumulated more in the form of non-reducing sugars; photosynthates were more distributed to starch; polysaccharides/oligosaccharides decreased at first and then increased; while the C/N of sympodial leaves increased at first and then decreased. (3) The defruiting treatment significantly decreased the net photosynthetic rate and chlorophyll content of sympodial leaves. (4) The sympodial leaves showed purplish red locally, and compared with the control, the anthocyanin content increased by about 2 times. (5) After treatment, the content of ABA, JA, SA in sympodial leaves significantly increased compared with the control, and the content of IAA increased at first and then decreased, while the content of GA₃ was significantly lower than the control. (6) The dynamic balance of endogenous hormones in sympodial leaves changed after treatment: ABA/IAA and JA/IAA decreased at first and then increased, while ABA/GA₃ and JA/GA₃ increased continuously. 【Conclusion】After squares and bolls shedding, the forms of sugar accumulation and distribution as well as endogenous hormone signals in sympodial leaves changed significantly and had a significant effect on source capacity. In a short period of time (1-3 days), the overall content of sugars in sympodial leaves increased, especially the accumulation of non-reducing sugars, and the source capacity strengthen rapidly. However, with the passage of time, the enhancement of source capacity diminished, and the leaves had a tendency of senescence, while chlorophyll degradation accelerated. That was, after abscission, the “auxiliary source” function of the sympodial leaves increased rapidly in a short period of time (about 3 days), then decreased rapidly, and made limited contribution to the development of the adjacent bolls in the later stage.

Monitoring Wheat Lodging Based on UAV Multi-Spectral Image Feature Fusion

WEI YongKang, YANG TianCong, ZANG ShaoLong, HE Li, DUAN JianZhao, XIE YingXin, WANG ChenYang, FENG Wei

Scientia Agricultura Sinica. 2023, 56(9):  1670-1685.  doi:10.3864/j.issn.0578-1752.2023.09.005

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【Objective】The wheat lodging seriously affected the process of photosynthesis and maturity, which led to the reduction of yield and quality. In order to obtain lodging information quickly and accurately, UAV ability of remotely monitoring wheat lodging was evaluated, and a wheat lodging monitoring model was built, so as to provide a technical support for disaster assessment, insurance claims and post-disaster remediation.【Method】Five original multispectral band images, including red, green, blue, red-edge and near-infrared, were acquired by near-ground UAV. The wheat canopy image with flying height of 50 m was preprocessed to obtain digital orthophoto map (DOM) and digital surface model (DSM) with a resolution of 1.85 (cm/pixel), three types of feature information were extracted, namely spectral features, height features, and texture features. Support Vector Machine (SVM) and Random Forest (RF) were used to compare the lodging classification of six different feature set combinations, and accuracy (Acc), precision (Pre), recall (Re) and harmonic mean (F1) were used to determine the best feature combination and classifier. At the same time, three different feature set screening methods (Lasso algorithm, random forest recursive algorithm RF-RFE and Boruta algorithm) were used to comprehensively evaluate the optimized feature subset, and to establish an appropriate evaluation method for lodging classification.【Result】The results showed that the single feature spectrum and texture as well as their combinations had poor classification and evaluation results for wheat lodging, and the “salt and pepper phenomenon” was serious. On this basis, the classification accuracy of DSM information fusion was significantly improved. The random forest classifier was used to combine spectral features, texture features and height features, and the classification accuracy of wheat lodging identification reached 91.48%. In order to reduce the number of feature set variables, three feature optimization methods were adopted. Compared with the full feature set, Lasso algorithm and the RF-RFE algorithm, the optimized feature subset based on the Boruta algorithm had higher classification accuracy and better overall stability. From the perspective of the mean value of the three feature combinations containing DSM, the overall classification accuracy and Kappa coefficient were improved by 0.17% and 0.01 (full feature set), 2.45% and 0.05 (Lasso), 2.87% and 0.05 (RF-RFE), respectively. Among them, spectrum-texture-DSM was the best, with the overall classification accuracy of 92.82% and Kappa coefficient of 0.86.【Conclusion】The study showed that the Boruta algorithm could effectively optimize the number of feature subsets of the spectrum-texture-DSM combination, allow fewer feature parameters to participate in the classification, and obtain higher classification accuracy. Meanwhile, a multi-feature combination-Boruta-RFC technology model was established for accurately monitoring wheat lodging, which provided a reference for wheat disaster assessment and the formulation of remediation measures.

PLANT PROTECTION

Early Molecular Diagnosis of Southern Corn Rust Based on Conventional PCR and Nested PCR Assays

MA HongXia, SUN Hua, GUO Ning, LIU ShuSen, ZHANG HaiJian, SHI Jie

Scientia Agricultura Sinica. 2023, 56(9):  1686-1695.  doi:10.3864/j.issn.0578-1752.2023.09.006

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【Objective】The objective of this study is to establish a rapid detection method for Puccinia polysora during the incubation period based on the nested PCR, and to provide support for prediction and control of southern corn rust.【Method】The nested PCR primers for the specific detection of P. polysora were designed using the variant region of the ITS sequence, including outer primer NX471-F/ITS4 and inner primer NX255-F/NX255-R. For amplification, the 20 µL PCR reaction mixture contained: Ex Taq DNA polymerase (5 U·μL^-1) 0.15 μL, 10×Ex Taq Buffer (Mg²⁺ plus) 2 μL, dNTP Mixture (2.5 mmol·L^-1 each) 1.6 μL, forward and reverse primers (10 μmol·L^-1) 0.3 μL each, template DNA 1 μL, ddH₂O 14.65 μL. The PCR program was performed as follows: the outer primer NX471-F/ITS4 was used for the first amplification and denaturation at 95℃ for 7 min, 30 cycles of denaturation at 95℃ for 30 s, annealing at 55℃ for 30 s, extension at 72℃ for 45 s, and a final extension at 72℃ for 7 min. The product was diluted 20 times and used as the template for the second run of the nested PCR, which was amplified with the inner primer NX255-F/NX255-R, and the PCR program was denaturation at 95℃ for 7 min; 30 cycles of 95℃ for 30 s, 66℃ for 30 s, and 72℃ for 26 s; 72℃ for 7 min. At the same time, the inner primer was selected for conventional PCR, in which the reaction mixture was the same as the nested PCR, and the amplification conditions were the same as the second run, except that the number of reaction cycles was 38. Under these conditions, the specificity was detected for P. polysora, Puccinia sorghi, Melampsora laricipopulina and seven other common maize pathogens, and the sensitivity of nested PCR was tested using genomic DNA of P. polysora and DNA from artificially inoculated leaves.【Result】Nested PCR could specifically detect P. polysora from all tested fungi, with a 255 bp target fragment. The lowest detection limit of the nested PCR was 10 fg·μL^-1, and the sensitivity was 500 times that of the conventional PCR. For the samples containing 500-2.5×10⁴ urediniospores per gram of artificially inoculated leaves, the detection rates of conventional PCR and nested PCR were 0 and 85.71%, respectively. Nested PCR could detect at least 1 000 urediniospores. For the samples containing 1-7 uredia per gram of artificially inoculated leaves, the detection rates of conventional PCR and nested PCR were 76.19% and 100%, respectively. Conventional PCR and nested PCR could detect at least 2 and 1 uredia, respectively. For the samples containing 1-7 infection sites per gram of artificially inoculated leaves, the detection rates of conventional PCR and nested PCR were 14.29% and 66.67%, respectively. Conventional PCR and nested PCR could detect at least 6 and 3 infection sites, respectively.【Conclusion】With NX471-F/ITS4 as the outer primer and NX255-F/NX255-R as the inner primer, a detection method for P. polysora was established based on the nested PCR, which could quickly, efficiently and accurately detect the P. polysora during the incubation period in maize leaves.

Cuticle Protein Genes are Involved in Phosphine Resistance of Cryptolestes ferrugineus

CHEH ErHu, SHEN DanRong, DU WenWei, MENG HongJie, TANG PeiAn

Scientia Agricultura Sinica. 2023, 56(9):  1696-1707.  doi:10.3864/j.issn.0578-1752.2023.09.007

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【Objective】As an important structural component of insect cuticle, the cuticle protein (CP) plays an important role in the formation of cuticle penetration resistance to pesticides. The phosphine resistance of Cryptolestes ferrugineus is increasingly prominent, and the current study was conducted to reveal the roles of CP genes in the formation of phosphine resistance in C. ferrugineus.【Method】According to the phosphine bioassay method that recommended by the Food and Agriculture Organization of the United Nations (FAO), the difference in phosphine sensitivity from five geographical populations (Zhangjiagang, Xiangyin, Huaian, Huaihua and Taicang populations) of C. ferrugineus was analyzed. The four CP genes were identified from the previous transcriptome data of C. ferrugineus, and then the phylogenetic tree of CPs was constructed and the corresponding amino acid sequence of C. ferrugineus CPs was further analyzed. Afterwards, the RT-qPCR was used to analyze the spatio-temporal (different developmental stages and different tissues of adults) expression patterns of four CP genes, and their expression levels under different phosphine resistance levels, as well as the expression patterns of four CP genes in response to phosphine stress were explored. Subsequently, a specific CP gene (CfRR2-1) was selected to be knocked down by using RNAi (RNA interference) technology, and the change of phosphine sensitivity of C. ferrugineus was determined.【Result】The results of phosphine sensitivity bioassay analysis showed that there were significant differences in phosphine resistance levels of different geographical populations, and the range of insecticide resistance ratio (RR) was 7.2-1 906.8. The further sequence analysis suggested that the four CPs all contained chitin binding domain, which belonged to the RR2 subfamily of CPR family, and they were named as CfRR2-1, CfRR2-2, CfRR2-3 and CfRR2-4, respectively. The gene expression patterns demonstrated that four CP genes were specifically highly expressed in the pupal stage of C. ferrugineus, and the high expression levels of four CP genes were detected in the peripheral tissues of C. ferrugineus as well. Besides, the CP genes were highly expressed in the phosphine resistant population (Taicang population, RR=1 906.8), and their expression levels could be significantly induced by phosphine in C. ferrugineus. Lastly, a CP gene CfRR2-1 was selected for the further functional study. After the gene expression level of CfRR2-1 was significantly knocked down in phosphine resistance (TC) population of C. ferrugineus via the injection of dsRNA, the sensitivity of C. ferrugineus to phosphine was significantly increased.【Conclusion】The over-expression of CP gene is involved in the formation of phosphine resistance.

SOIL & FERTILIZER·WATER-SAVING IRRIGATION·AGROECOLOGY & ENVIRONMENT

Effects of Long-Term Film Mulching and Application of Organic Fertilizer on Yield and Quality of Spring Maize on the Loess Plateau

WEI YaNan, BO QiFei, TANG An, GAO JiaRui, MA Tian, WEI XiongXiong, ZHANG FangFang, ZHOU XiangLi, YUE ShanChao, LI ShiQing

Scientia Agricultura Sinica. 2023, 56(9):  1708-1717.  doi:10.3864/j.issn.0578-1752.2023.09.008

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【Objective】The aim of this study was to investigate the effects of long-term film mulching and application of organic fertilizer on yield, quality, dry matter accumulation and nitrogen uptake of spring maize through long-term localized field experiments. 【Method】 The long-term experiment began in 2009 at the Changwu Agri-Ecological Station, and the samples were collected in 2020 and 2021. The field experiments were conducted with four treatments: mulching, no N (F), no mulching, N 225 kg·hm^-2 (N), mulching, N 225 kg·hm^-2 (FN), and mulching, N 225 kg·hm^-2 and apply organic fertilizer (FSN). Plant samples for measuring total biomass were collected at silking stage (R1) and harvest stage (R6). The samples were divided into different parts as required, and the total N content was determined. Crude protein, crude fat and crude amylum concentrations of maize grain were determined at harvest. 【Result】(1) Mulching under nitrogen application significantly increased the yield of spring maize, while additional application of organic fertilizer under mulching further increased the yield. Compared with the control, the N treatment increased the yield by 106%-176%. The FN treatment increased the yield by 21%-75% on this basis, and the FSN treatment was further increased by 5.6%-8.4%. (2) Mulching under nitrogen application significantly increased the dry matter accumulation and N uptake of spring maize, and the two indicators were further improved after the application of organic fertilizer. (3) The crude protein content under N treatment was 8.67%-8.94%, while the crude protein content under FN treatment increased to 8.99%-9.34%. The crude protein content of the FSN treatment was not further improved. There were no significant differences in crude fat and crude amylum content between the treatments. 【Conclusion】FN treatment significantly increased the yield and crude protein content of spring maize. The application of organic fertilizer under FSN further increased the yield on the basis of maintaining the crude protein content of the grain, and realized the high yield and high quality of spring maize.

Effects of Long-Term Fertilization on Nitrogen Accumulations and Organic Nitrogen Components in Soil Aggregates in Yellow-Mud Paddy Soil

WANG Fei, LI QingHua, HE ChunMei, YOU YanLing, HUANG YiBin

Scientia Agricultura Sinica. 2023, 56(9):  1718-1728.  doi:10.3864/j.issn.0578-1752.2023.09.009

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【Objective】Nitrogen is an important limiting factor for soil productivity in sticky and thin medium-low-yield paddy soil in southern China. In order to provide the basis for reasonable fertilization and soil nitrogen pool management, the effects of long-term fertilizations on nitrogen accumulations and organic nitrogen components in soil aggregates in a yellow-mud paddy soil were investigated.【Method】 In the 36^th year, soil samples from the plough layer under different fertilization treatments in the long-term experiment of yellow-mud paddy soil were collected to analyze the nitrogen accumulation and the content of organic nitrogen components as well as their distributions in aggregates by wet screening and Bremner organic nitrogen classification method. The treatments included: no fertilization (CK), application of chemical fertilizer (NPK), chemical fertilizer plus cow dung (NPKM), and chemical fertilizer plus total rice straw returning (NPKS). 【Result】 The content of total nitrogen in >2 mm aggregate was significantly increased by 12.7%-51.9% in fertilization treatments compared with that in CK (P<0.05). The cumulative contribution ratios of TN in >2 mm aggregate to total nitrogen in bulk soil under NPKM and NPKS treatments were 24.7 and 20.0 percentage points significantly higher than that under CK (P<0.05), respectively. The content of acid-hydrolyzable nitrogen (AHN) and non-hydrolyzable nitrogen (NHN) in >2 mm aggregate in fertilization treatments were increased by 10.1%-36.3% and 20.7%-100.5% compared with those under CK, respectively, and the cumulative contributions of the two components to total nitrogen in bulk soil were increased as well, especially for NPKM and NPKS treatments. In >2 mm aggregate, the content of acid-hydrolyzable ammonia nitrogen (AMMN) in fertilization treatments were significantly increased by 17.2%-40.4% compared with that in CK (P<0.05), and the largest increasement was found under NPKM treatment. The content of acid-hydrolyzable amino acid nitrogen (AAN) and acid-hydrolyzable unknown nitrogen (HUN) were increased most significantly under NPKS and NPKM treatments, which were 24.0% and 52.1% higher than those under CK (P<0.05), respectively. The content of NHN and AMMN in >2 mm and 0.25-2 mm aggregates were all significantly positively correlated with the content of alkaline nitrogen in corresponding aggregates (P<0.05). Compared with NPKM, NPKS was more conducive to the accumulation of NHN in >2 mm aggregate. In >2 mm aggregate, NPKM had the biggest contribution to the increase of AMMN and HUN contents, and their cumulative contribution ratios to total nitrogen in bulk soil, while NPKS had the largest contribution to the increase of AAN content and their cumulative contribution ratio to total nitrogen in bulk soil. Redundant analysis (RDA) showed that the nitrogen uptake of rice plant was mainly affected by NHN components in >2 mm and 0.25-2 mm aggregates. The nitrogen uptake of rice plant was more affected by soil organic nitrogen components under NPKM and NPKS treatments than that under NPK and CK treatment.【Conclusion】The content of total nitrogen in >2 mm aggregate and their cumulative contributions to total nitrogen in bulk soil were increased in plough layer of yellow-mud paddy soil under long-term fertilizations, especially for the combined application of organic and inorganic fertilizers. The contents of NHN, AHN and AMMN in >2 mm aggregate were closely related to alkaline nitrogen and the nitrogen uptake of rice plant in yellow-mud paddy soil, which were important available nitrogen pool.

Effects of Different Biochar Application Rates on Soil Aggregate Characteristics and Organic Carbon Contents for Film-Mulching Field in Semiarid Areas

PANG JinWen, WANG YuHao, TAO HongYang, WEI Ting, GAO Fei, LIU EnKe, JIA ZhiKuan, ZHANG Peng

Scientia Agricultura Sinica. 2023, 56(9):  1729-1743.  doi:10.3864/j.issn.0578-1752.2023.09.010

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【Objective】The aim of this study was to investigate the effects of long-term plastic film mulching farmland combined with different biochar input rates on soil aggregate stability and organic carbon in northwest China, in order to provide a scientific basis for improving the soil fertility and maintaining the sustainability of crop production for film-mulching field in semiarid regions. 【Method】Based on continuous years of double ridge furrow film mulching (D), the full film double ridge furrow mulching planting and traditional flat without film mulching planting were set as the main treatment, and four biochar input rates (no returning (N), 3 t·hm^-2 (L), 6 t·hm^-2 (M), and 9 t·hm^-2 (H) ) were set as the secondary treatment respectively to investigate the effects of different biochar input rates on soil aggregate distribution, aggregate stability, aggregate organic carbon and maize yield.【Result】The film mulching could significantly (P<0.05) increase the soil mechanical stable (6.1%-8.7%) and water-stable macro-aggregate contents (15.9%-83.6%) and maize yield (35.0%-41.8%). Under the film mulching planting, biochar inputs treatments could significantly (P<0.05) increase mechanical macro-aggregate and water macro-aggregate by 6.8% and 29.6% on average, respectively, and the effects gradually increased with the increase of biochar inputs rate. In addition, biochar inputs could also increase the soil organic carbon and aggregate organic carbon content in film mulching farmland, and the effects under DH (9 t·hm^-2) were better than other treatments, with an average increased by 13.9% and 25.9%, respectively. Maize yield was significantly correlated with biochar addition rates ( λ=0.42, P<0.001 ), and DH had the highest yield with 12.8 t·hm^-2. 【Conclusion】Biochar input could significantly improve soil aggregrate characteristics and organic carbon content in plastic film mulching farmland, thus increase the maize yield and promote soil carbon sequestration, especially with 9 t·hm^-2.

HORTICULTURE

An Overview of the Worldwide Plum Breeding

LIU Shuo, XU Ming, LIU JiaCheng, ZHANG QiuPing, MA XiaoXue, LIU Ning, ZHANG YuPing, ZHANG YuJun, ZHAO HaiJuan, LIU WeiSheng

Scientia Agricultura Sinica. 2023, 56(9):  1744-1759.  doi:10.3864/j.issn.0578-1752.2023.09.011

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Plum is a significant fruit tree worldwide, with the two main species being P. domestica and P. salicina. Chinese plum, originating from China, exhibits high genetic heterogeneity and abundant genetic variation in fruit traits. It is speculated that wild Chinese plums still exist in the Yangtze River basin. Throughout Chinese history, the plum cultivation and varieties were recorded by many secretaries of the Qin Dynasty, the Han Dynasty, the Jin Dynasty, the Northern Song Dynasty, and the Ming Dynasty. Similarly, in other countries, such as Greece, France, Finland, the Czech Republic, and Russia, there are written records of plum, describing its origin and 14 varieties. Plum was gradually introduced into the European continent during the Roman era, and numerous new varieties have since been cultivated to improve the fruit’s quality, commercial value, and meet market demand. There were currently 88 independently bred plum varieties in China that have passed variety approval and been officially published. Breeding traits of common concern include fruit size, peel color, polyphenols, soluble solids, fruit maturity, cold resistance, disease resistance, etc. Breeding methods range from traditional methods to molecular-assisted breeding, tissue culture, and transgenic breeding. Many excellent varieties with good fresh food quality, storage and transportation resistance, and adaptability have been bred through continuous improvement of breeding methods, promoting the development of the global plum industry. China is the world’s largest plum producer, accounting for 54.94% of total production and 74.75% of total cultivation area worldwide. The rich natural resources of plum in China provide solid material and diversity guarantee for germplasm exploration and breeding application. To further strengthen the international advantages of plum germplasm resources and cultivation areas in China, and to enhance the core competitiveness of national breeding, this study reviewed the global history process of plum breeding and improvement, including the origin, dissemination, early cultivation history of plum in the world, recent research on the main breeding traits, and commercial breeding strategies for modern plum.

Determination and Analysis of Flavonoids Metabolites in Different Colors Cultivars and Blooming Stages of Prunus mume

WU SiHui, ZHU HuanHuan, ZHANG JunWei, BAO ManZhu, ZHANG Jie

Scientia Agricultura Sinica. 2023, 56(9):  1760-1774.  doi:10.3864/j.issn.0578-1752.2023.09.012

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【Objective】Flower color is an extremely important ornamental trait of Prunus mume (P. mume), and flavonoids are the main pigments in the petals of P. mume. However, there are few systematic studies on the composition of flavonoids and the relationship between flower color and flavonoids in P. mume. The study on flavonoids can provide a reference for the mechanism of flower color formation and the development of flavonoids resources in P. mume.【Method】In this study, the petals of four P. mume cultivars with representative flower color in the blooming stage and the key period of flower color change of two cultivars were selected as materials. The flower color phenotype of petals was measured with the Royal Horticultural Society Color Card (RHSCC) and colorimeter. Flavonoids in those petals of flowers were determined by high-performance liquid chromatography and mass spectrometric (HPLC-MS) detectors. Then, Duncan test and OPLS-DA were used to analyze the difference of metabolites among these four cultivars and the major blooming stages. 【Result】In total, 25 flavonoids were determined in P. mume. The main components of red Baixu Zhusha and purple-red Huqiu Wanfen were anthocyanins. But the contents of cyanidin and its derivatives between Baixu Zhusha and Huqiu Wanfen were different. In addition, from the big budding stage to the blooming stage, the red color of Baixu Zhusha gradually became lighter, and the contents of cyanidin-3-O-glucoside and peonidin-3-O-glucoside also gradually decreased. Yellow-green Bian Lv’e and pure white Sanlun Yudie were most enriched with quercetin and its derivatives. The contents of quercetin derivatives between Bian Lv’e and Sanlun Yudie were different. 【Conclusion】The flavonoid metabolic profiles differed among the different colored petal of P. mume, and flavonoids with medicinal value were distributed in all varieties. The difference in the contents of cyanidin and peonidin might be related to petal color differences of red P. mume. Quercetin derivatives might affect the color of yellow-green P. mume. In this study, the flavonoids metabolites of different color P. mume were identified and analyzed for the first time, and the differences in flower color P. mume varieties and the blooming process were preliminarily understood from the metabolic level. The results provided a reference for understanding the difference of flower color formation and development of flavonoid resources of P. mume.

FOOD SCIENCE AND ENGINEERING

The Mechanism of Effects of Konjac Gum on the Gel Property and Water Holding Property of Pork Myofibrillar Protein Based on Phase Separation Behavior and Moisture Stabilization

LUO Cheng, WANG Huan, CHEN YinJi, LI Chao, ZHUANG XinBo

Scientia Agricultura Sinica. 2023, 56(9):  1775-1786.  doi:10.3864/j.issn.0578-1752.2023.09.013

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【Objective】 The purpose of this experiment was to study the effects of konjac gum on the microstructure and phase-separated structure of pork myofibrillar proteins, and then to explain the regulation mechanism of konjac gum on the gel property and water holding property of myofibrillar proteins. 【Method】 The simulated system with different ratios of konjac gum and myofibrillar protein was used to measure the texture property, stress and strain during fracture deformation, the water distribution and water holding capacity of the composite gel, and to observe the phase separation behavior of konjac gum and myofibrillar protein and the microstructure of myofibrillar protein gel network. 【Result】 When the addition ratio of konjac gum was less than 0.8%, the gel strength, final value of storage modulus and stress at fracture deformation of the composite protein gels significantly increased to 179.21 g, 1 192 Pa and 9 139.37 Pa respectively with the increase of the addition ratio (P<0.05). When the addition ratio of konjac gum was greater than or equal to 0.8%, the gel strength, storage modulus, stress and strain at fracture deformation of the composite protein gels significantly decreased to 83.03 g, 566 Pa, 4 964.07 Pa and 0.64 (P<0.05) respectively with the increase of the addition ratio. Low-field NMR results showed that the relaxation time and the percentage of free water in the composite gel system of immobilized water decreased significantly (P<0.05) with the increase of the addition ratio of konjac gum less than 0.8%, while the percentage of immobilized water increased significantly (P<0.05), and the water holding capacity of the composite gel increased significantly from 67.18% to 80.47% in the control group (P<0.05). In contrast, the high percentage addition of konjac gum (greater than or equal to 0.8%) significantly increased the relaxation time and the percentage of free water in the immobilized water (P<0.05), while the percentage of immobilized water significantly decreased (P<0.05), and the water holding capacity significantly decreased to 55.24% (P<0.05). Paraffin sections showed konjac gum was embedded in the composite protein gel backbone in a physically filled form with many cavities of various sizes and shapes. Scanning electron microscopy showed that the cavities and gullies in the protein gel network structure of the control group were filled with many moisture phases. The addition ratio of konjac gum less than 0.8% could reduce the interlocking water gullies in the protein network structure and make the protein gel network structure denser and more homogeneous. The high addition of konjac gum (greater than or equal to 0.8%) increased the number and volume of water gullies in the system, resulting in a looser microstructure of the composite gel. The results of image processing analysis showed that the fractal dimension of the composite protein gel network structure with 0.4% konjac gum was the highest (P<0.05), and the lowest (P<0.05) with the lacunary value of 0.264.【Conclusion】The low concentration of konjac gum on myofibrillar protein gel property and water-holding property had a significant improvement effect, but the upper limit of the addition of konjac gum ratio was 0.8%, because a high percentage of the addition (greater than or equal to 0.8%) would make the composite protein gel texture deteriorated.

ANIMAL SCIENCE·VETERINARY SCIENCE

In Vivo Estimation of Lean Percentage, Fat Percentage, and Intramuscular Fat Content of Boars by Computed Tomography

REN ZhiQiang, WANG ChenYang, KOU ZhongYun, CAI Rui, YANG GongShe, PANG WeiJun

Scientia Agricultura Sinica. 2023, 56(9):  1787-1799.  doi:10.3864/j.issn.0578-1752.2023.09.014

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【Objective】 The aim of this study was to investigate the accuracy of computed tomography (CT) technology in the in vivo estimation of carcass and meat quality traits in boars, so as to achieve intelligent measurements of the phenome, and thus provide technical parameters for selection and feeding management of boars. 【Method】 In the present study, 40 Duroc boars of similar weight ((42.02±1.05) kg) and in good health were selected and starved for 24 h. After that, general anaesthesia was administered by intravenous injection of anaesthetic at the ear margins. The boars were placed on the CT scanning bed in the prone position of the head, front and tail, and the original image sequences were obtained by 16-slice spiral CT scanning. The images were then subjected to thin layer reconstruction with denoising, multi-planar reconstruction, and segmentation by image processing techniques in order to quantitatively analyze the images, and combined with B-ultrasound in vivo measurement and slaughter measurement to evaluate the carcass traits of boars, such as carcass composition, backfat thickness, eye muscle depth, eye muscle area, carcass straight length, and carcass sloping length. A prediction model for carcass leanness of breeding boars was constructed using partial least squares regression analysis with slaughter-measured leanness as the dependent variable and CT-measured backfat thickness, eye muscle depth, eye muscle area, carcass straight length, and carcass sloping length as the independent variables. The Soxhlet extraction method was used to determine the content of intramuscular fat (IMF) in the longissimus thoracis, gluteal medius, and semimembranosus samples, and then the correlation analysis was performed with the intramuscular fat content in the corresponding parts of the CT in vivo assessment.【Result】When analyzing the correlation between CT in vivo evaluation and slaughter determination of lean percentage, fat percentage, bone percentage, and skin percentage, it was found that the correlation coefficient (r) between the two parameters was above 0.85, showing a strong correlation (P<0.01); subsequently, after a one-variable linear regression analysis, the coefficient of determination (R²) was 0.832, 0.820, 0.800, and 0.740, respectively. In addition, there was no significant difference (P>0.05) between CT and slaughter measurements of backfat thickness, eye muscle depth, carcass straight length, and carcass sloping length. When measuring backfat thickness at the thoracolumbar junction (P2 point), the difference between B-ultrasound and slaughter measurements was significant (P<0.05), while the difference between CT in vivo assessment and slaughter measurements was not significant (P>0.05). In a regression model using partial least squares to predict the carcass lean percentage of boars, the root mean square error of prediction (RMSEP) and R² were 0.1472 and 0.934, respectively. Furthermore, the content of intramuscular fat was measured by CT, and CT estimation and slaughter measurements of the longissimus thoracis, gluteus medius, and semimembranosus were strongly correlated (P<0.01), with correlation coefficients (r) of 0.837, 0.815, and 0.786, respectively. One-variable linear regression analysis revealed a highly significant positive linear correlation (P<0.01) between in vivo CT assessment and post-slaughter measured intramuscular fat content.【Conclusion】CT technology allowed accurate in vivo determination of carcass traits, such as lean percentage, fat percentage, bone percentage, backfat thickness, and eye muscle depth, as well as intramuscular fat content of meat quality indicators, which provided a technical support for the continuous improvement of breeding performance and thus more accurate selection of relevant traits.

Effects of Holstein Bulls Fed Mixed Silage of Potato Chips Processing by Product with Rice Straw on Fattening Performance and Blood Biochemical Indexes

WEN YuanYuan, LI Yan, LI JianGuo, WANG MeiMei, YU ChangHui, SHEN YiZhao, GAO YanXia, LI QiuFeng, CAO YuFeng

Scientia Agricultura Sinica. 2023, 56(9):  1800-1812.  doi:10.3864/j.issn.0578-1752.2023.09.015

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【Objective】The purpose of this experiment was to explore the effects of different proportions of mixed silage of raw potato chips processing by product with rice straw (hereinafter referred to as “mixed storage”) instead of whole plant corn silage (hereinafter referred to as “silage”) on fattening performance, nutrient apparent digestibility, rumen fermentation parameters, blood biochemical indexes and economic benefits of Holstein bulls, so as to provide a theoretical basis for the use of potato processing by-products in cattle production.【Method】Sixty healthy Holstein bulls with similar body weight ((461.33 ± 33.47) kg) were randomly divided into four groups with 15 replicates in each group and one bull per replicate, including T20 group (concentrate + 20% mixed silage + 80% silage), T40 group (concentrate + 40% mixed silage + 60% silage), T60 group (concentrate + 60% mixed silage + 40% silage), and T80 group (concentrate + 80% mixed silage + 20% silage). The ratio of concentrate to roughage and the composition of concentrate were the same in the experimental group. Adaptation and experimental periods lasted for 10 and 150 d, respectively.【Result】(1) there was no significant difference in average daily gain (ADG) of Holstein bulls with different proportions of mixed silage instead of whole plant maize silage (P>0.05). The dry matter intake (DMI) of T20 group was 4.30% higher than that of T40 group (P<0.01), 5.24% higher than that of T60 group (P<0.01), and 6.01% higher than that of T80 group (P<0.01). The feed gain ratio (F/G) of T40 group was the lowest, which was 4.08% (P<0.01), 3.14% (P<0.05), and 5.60% (P<0.01) lower than that of T20, T60, and T80 groups, respectively. (2) Compared with T80 group, the apparent digestibility of dry matter (DM), neutral detergent fiber (NDF), acid detergent fiber (ADF) and ether extract (EE) of the first three groups were significantly increased (P<0.05). The apparent digestibility of crude protein (CP) of T20 group was significantly higher than that of T60 and T80 groups (P<0.05), but there was no significant difference between T20 group and T40 group (P>0.05). (3) The rumen pH, propionic acid and butyric acid contents were not affected by increasing the proportion of mixed storage (P>0.05). However, the concentrations of ammonia nitrogen (NH₃-N) and total volatile fatty acids (TVFA) of T60 and T80 groups were significantly lower than those of T20 group (P<0.05), and the content of acetic acid was significantly higher than that of T20 group (P<0.01). The ratio of acetic acid to propionic acid of T80 group was significantly higher than that of T20 and T40 groups (P<0.05). (4) Albumin (ALB) content of T20 group was significantly higher than that of T60 and T80 groups (P<0.05). Urea nitrogen (UN) concentration of T80 group was significantly increased (P<0.01), 29.05%, 20.96% and 11.31% higher than that of T20, T40 and T60 groups, respectively. Glucose (Glu) concentration of T20 group was significantly higher than that of T60 and T80 groups (P<0.01), and there was no significant difference between T20 group and T40 group (P>0.05). (5) The economic benefit of T40 group was the highest (17.96 yuan·head^-1·d^-1), followed by T20 (16.91 yuan·head^-1·d^-1), T60 (16.79 yuan·head^-1·d^-1) and T80 (15.91 yuan·head^-1·d^-1).【Conclusion】In conclusion, with the increase of the proportion of mixed silage instead of silage, the digestibility of nutrients, rumen fermentation and blood biochemical indexes would be affected to some extent. When replacing 40% whole plant maize silage, the production performance was the best and the economic benefit was the highest.

Chicken Quality Analysis and Screening of Key Flavor Substances and Genes

JU XiaoJun, ZHANG Ming, SHAN YanJu, JI GaiGe, TU YunJie, LIU YiFan, ZOU JianMin, SHU JingTing

Scientia Agricultura Sinica. 2023, 56(9):  1813-1826.  doi:10.3864/j.issn.0578-1752.2023.09.016

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【Objective】This experiment was conducted to screen flavor substances and genes in different breeds of chicken, and to provide a scientific basis for better breeding and development and utilization of chicken products. 【Method】 Firstly, the main selection factors of broiler chickens were investigated. Secondly, local chickens (Wenchang chicken and Luyuan chicken), cultivated chickens (817, Huashan chicken) and introduced white broilers (Ross 308) were selected, and 30 chickens (15 male and 15 female) with close to average body weight of each breed were slaughtered. Both breast muscles were taken immediately after slaughter and used for taste evaluation, routine meat quality, myofiber characteristics, inosinic acid, fatty acid amino acid content and gene expression. Finally, Partial Least Squares (PLS) method was used to analyze the correlation between the results of taste evaluation and the results of physical and chemical determination, and to explore the influence of flavor substances in taste evaluation.【Result】 (1) The flavor was the main choice factor for broiler chickens. The sweetness and umami taste of Wenchang chicken breast were significantly higher than those of Ross 308 (P≤0.05). (2) The average myofiber area of Wenchang chicken and Luyuan chicken breast was significantly lower than that of other breeds (P≤0.05), and the average myofiber diameter of Wenchang chicken and Luyuan chicken breast was significantly lower than that of Huashan chicken and Ross 308 (P≤0.05). The inosinic acid content of Wenchang chickens was significantly higher than that of other breeds (P≤0.05). The saturated fatty acid content in breast muscle of Wenchang and Luyuan chickens was significantly higher than that of other breeds (P≤0.05), and the unsaturated fatty acid content in breast muscle of Ross 308 was significantly higher than that of Wenchang, Luyuan, and 817 chickens (P≤0.05). Except lysine, the content of other amino acids of Wenchang chickens were relatively high, and the content of umami amino acids were significantly higher than those of other breeds (P≤0.05). Except lysine, the content of most amino acids in breast meat of Ross 308 was relatively low. The glutamate ATV value of Wenchang chicken, Luyuan chicken, 817 chicken and Huashan chicken was greater than 1, and the order was as follows: Wenchang chicken > Luyuan Chicken >817 chickens > Huashan chicken. The ATV value of Alanine in Wenchang chicken breast was greater than 1. (3) The ACOX1 gene expression in breast muscle of Wenchang chickens was significantly higher than that of 817 chickens and Ross 308 (P≤0.05), and the GADL1 gene expression of Wenchang chickens and Luyuan chickens was significantly higher than that of other breeds (P≤0.05). The GLUD1 gene expression of Wenchang chickens was significantly higher than that of 817 chickens, Huashan chicken and Ross 308 (P≤0.05). (4) Most fatty acids had a positive effect on the salty and sour taste of chicken, most amino acids had a positive effect on sweet and umami taste, and inosinic acid had a positive effect on the sweet and umami taste of chicken. Palmitic oleic acid, α-linolenic acid, linoleic acid, inosinic acid and other free amino acids except lysine had a positive effect on the flavor level of chicken. 【Conclusion】It could be concluded that the content of inosinic acid and amino acid was one of the main reasons that the flavor of local chickens was better than that of introduced chickens. GADL1 and GLUD1 were related genes that affected the difference of chicken flavor. Inosinic acid, glutamic acid, alanine, palmitoleic acid, α-linolenic acid, and linoleic acid might be the key flavor substances for different varieties of chicken meat.