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01 June 2024, Volume 57 Issue 11

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Scientia Agricultura Sinica. 2024, 57(11):  0. 

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SPECIAL FOCUS: SOYBEAN DISEASE RESISTANCE, YIELD AND QUALITY CORRELATION

Soybean Disease Resistance, Yield and Quality Correlation

ZHAN YuHang, WANG Jie, LI YongGuang, HAN YingPeng

Scientia Agricultura Sinica. 2024, 57(11):  2061-2064.  doi:10.3864/j.issn.0578-1752.2024.11.001

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Identification and Gene Mapping of Hard Seededness Mutant M_zp661 in Soybean

MIAO Long, SHU Kuo, HU YanJiao, HUANG Ru, HE GenHua, ZHANG WenMing, WANG XiaoBo, QIU LiJuan

Scientia Agricultura Sinica. 2024, 57(11):  2065-2078.  doi:10.3864/j.issn.0578-1752.2024.11.002

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【Objective】Hardness, a structural feature of seed physical dormancy, is an important trait in soybean domestication. Although hardness is beneficial for seeds to survive in unfavorable environments, it will seriously reduce the emergence rate of soybean in the field, and detrimental to yield and processing quality. Analyzing the QTL and candidate genes using bulked segregant analysis sequencing (BSA-Seq), can provide a theoretical reference for understanding the molecular mechanism of hard seededness in soybean.【Method】The hard seed mutant M_zp661 was obtained from the seeds of Zhongpin 661 induced by ethyl methane sulfonate (EMS), and was crossed with cultivated soybean Zhonghuang 13 (male parent) to construct recombinant inbred line (RIL) population. The progeny lines were investigated for seed hardness, water absorption capacity and anatomical structure of seed coats. Two types of extreme lines in the RIL population, with hard seeds or with imbibed seeds, were selected to construct DNA mixed pools respectively, and then BSA-Seq technology was used to detect genotype differences in extreme-mixed pools and parents. Euclidean distance (ED), delta SNP-index, and delta InDel-index methods were applied to associate hard seed genetic loci of soybean. Combining with bioinformatics analysis, transcriptome data of different soybean tissues and gene annotation information, candidate genes within significant association regions were predicted.【Result】In the progenies of M_zp661, all areas of imbibitive seeds had the penetration ability, and the seed volume increased continuously with the soaking time. However, no changes were observed for hard seeds over 36 hours. With the prolonged of soaking time, the seed coat of hard seeds began to shrink locally and gradually spread to other parts, and finally cotyledons recovered their imbibition ability. The hard seed not only has smooth and compact seed coat, but also has regular network structure of cuticle and thicker palisade layer, while numbers of stomata and loose structures, tiny cracks and thinner palisade layer were existed in the imbibed seeds. These results suggest that the seed hardness of M_zp661 may be caused by the impermeability of the seed coat. ED, delta SNP-index and delta InDel-index association analysis methods not only identified the reported seed physical dormancy locus qHS1, but also simultaneously detected the candidate region Chr.06: 45897227-47746047, which contains a total of 189 genes. Further, transcriptome data and gene annotation predicted that Glyma.06G275300, which is specifically and highly expressed in seeds, might be the candidate gene for this associated region to regulate soybean seed hardness.【Conclusion】Seed hardness of soybean mutant M_zp661 was caused by the impermeability of the seed coat, and Glyma.06G275300 was predicted as a candidate gene affecting the structure of seed coat using BSA-Seq.

Genome Wide Association Analysis of Soluble Sugar Content in Fresh Seeds of Soybean Landraces

ZHANG YuMei, DING WenTao, LAN XinLong, LI QingHua, HU RunFang, GUO Na, LIN GuoQiang, ZHAO JinMing

Scientia Agricultura Sinica. 2024, 57(11):  2079-2091.  doi:10.3864/j.issn.0578-1752.2024.11.003

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【Objective】Soluble sugar content is one of the important quality traits of vegetable soybean. The genetic variation and genetic mechanism of soluble sugar content in fresh soybean seeds were studied to provide a basis for germplasm innovation and quality breeding of vegetable soybean.【Method】Using 133 soybean landraces from the Northeast region, the North region, the Huanghuaihai region and the South region, the soluble sugar content of fresh seeds was determined in the three environments of Lianjiang in spring, Fuqing in spring and autumn, in 2021. In combination with 82 187 high-quality SNP markers, the whole genome association analysis of soluble sugar content was conducted based on the mixed linear model MLM (Q+K), and the SNP loci with significantly related to soluble sugar content were identified. The candidate intervals were selected by the significant SNP loci and the extension of 119.07 kb linkage disequilibrium decay distance at both ends. The candidate genes were predicted according to the annotation and tissue expression information of the genes in the candidate intervals.【Result】The variation range of soluble sugar content in fresh seeds under three environments was 3.37-33.84 mg·g^-1, the genetic variation coefficient was 24.59%-32.69%, and the heritability of soluble sugar content was 68.14%. 6, 8 and 22 SNPs were significantly associated with the soluble sugar content of fresh seeds were detected in Lianjiang in spring, Fuqing in spring and autumn, respectively, and phenotypic variation was 12.43%-29.27%. A total of 86 genes were obtained in the candidate regions of 9 significant SNP loci with higher interpretation rate of phenotypic variation, and 9 candidate genes were further screened by gene annotation and tissue expression information. These candidate genes are mainly involved in biological processes such as transcription factors, glycoprotein families and carbohydrate synthesis and transport. Among them, Glyma.01g016500, Glyma.13g042100, Glyma.16g131800 and Glyma.16g155300 were more highly expressed in soybean seeds and pods, which can be used as the most potential candidate genes for soluble sugar in fresh soybean seeds.【Conclusion】Through genome-wide association analysis, 36 SNPs significantly associated with soluble sugar content in fresh seeds were detected, and 9 candidate genes were further screened out, which may be involved in the regulation of soluble sugar content in fresh soybean seeds. Among them, Glyma.01g016500, Glyma.13g042100, Glyma.16g131800 and Glyma.16g155300 can be the key candidate genes for regulating soluble sugar content in fresh soybean seeds.

Establishment of Evaluation System and Screening of Disease- Resistant Accessions for Phomopsis Seed Decay in Soybean Germination Stage

MIAO Long, YANG Lei, XU JingHao, LI Na, WANG FeiYu, QIU LiJuan, WANG XiaoBo

Scientia Agricultura Sinica. 2024, 57(11):  2092-2101.  doi:10.3864/j.issn.0578-1752.2024.11.004

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【Objective】An accurate and rapid indoor evaluation system was established by using soybeans with different resistance levels to Phomopsis seed decay as test materials. And then 170 soybean germplasm accessions were employed to screened out disease-resistant varieties, so as to provide methods and material basis for high-throughput assessment of Phomopsis seed decay in soybean and cultivation of resistant varieties.【Method】In terms of establishing a reliable evaluation method for Phomopsis seed decay, Qihuang 34, Williams, Zhongzuo 09-560, z13-631-2, ZDD26268, Chenxiqingpidou 1 and Tongxianhuangdou were selected as experimental materials. For each soybean accession, the seeds with uniform size and undamaged seed coat were germinated in the dark after disinfection. At different germination stages, the pathogen of Phomopsis seed decay was inoculated for 24 h, 48 h, 72 h and 96 h. The mycelium coverage rate and seed decay rate of seed surface under different infection time were counted to determine the optimal identification period for evaluating Phomopsis seed decay in soybean. Then, the resistance of 170 different soybean germplasms in natural population was identified by using the coverage rate of mycelium on the surface of seeds and the decay rate of seeds as evaluation indexes. The high disease resistance varieties were screened based on 5 disease resistance levels.【Result】The soybean accessions showed the most significant differences in disease resistance levels after 96 h of germination when mycelium coverage rate and seed decay rate of soybean surface were used as evaluation indexes. Further comparison of the incidence of 24 h, 48 h, 72 h and 96 h after infection showed that the difference in disease resistance between different varieties after infection for 72 h was the most obvious. Therefore, it was the most suitable period, 72 h of infection at the bud stage after 96 h of germination, for evaluating the resistance level of different soybean varieties to Phomopsis seed decay. The resistance of 170 soybean varieties to Phomopsis seed decay was identified and classified into five disease resistance grades, namely, high resistance, medium resistance, medium susceptibility, susceptibility and high susceptibility. Among them, there were 30 varieties of grade I (high resistance to disease), 51 varieties of grade Ⅱ (medium resistance to disease), 71 varieties of grade Ⅲ (medium disease susceptibility), 4 varieties of grade Ⅳ (disease susceptibility) and 14 varieties of grade V (high disease susceptibility), idicating that there are extensive variations in the resistance to Phomopsis seed decay of soybean germplasm resources in China.【Conclusion】In this study, the most optimum stage of disease identification was considered as soybean seeds after 96 h germination to infect the Phomopsis longicolla for 72 h. After that, the mycelium coverage rate and seed decay rate of soybean surface were counted as evaluation parameters. The evaluation system has high accuracy and reliability, which can provide an effective method for high-throughput identification of different varieties in the laboratory. And 30 highly resistant varieties were further screened to provide a material basis for the breeding of resistant varieties.

Genome-Wide Association Analysis of Soybean Nodulation-Related Traits in the Northern Hebei

SHOU XinYue, LIU Zhi, CHEN YueHan, LI ChenHui, SUN BinCheng, SUN RuJian, HAN DeZhi, LU WenCheng, SHEN YongHui, WANG XiaoBo, YAN Long

Scientia Agricultura Sinica. 2024, 57(11):  2102-2113.  doi:10.3864/j.issn.0578-1752.2024.11.005

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【Objective】Exploring efficient nodulation soybean germplasm adapted to the ecological conditions of the Bashang area, identifying genetic loci and candidate genes regulating soybean-rhizobium symbiotic nodulation, and improving soybean symbiotic nitrogen fixation efficiency.【Method】This study utilized a natural population of 260 soybean germplasms as the research object, rhizobium strain USDA110 was inoculated under outdoor potted conditions in the Bashang of Hebei Province. The single plant nodule number and single plant nodule dry weight data were used as phenotypic values. Combined with genotype data of the 260 germplasms, a genome-wide association analysis was conducted to explore genes related to soybean-rhizobium symbiotic nodulation.【Result】A total of 18 SNPs significantly associated with soybean nodule number were detected, located on chromosomes 2, 7, 8, 13, 18, and 19. Among them, the significant associated locus BARC_2.01_Chr02_43161654_A_G on chromosome 2 was identified as the main locus controlling soybean nodule number (LOD=3.89). Linkage disequilibrium analysis within the 200 kb interval upstream and downstream of this locus containing BARC_2.01_Chr02_43161654_A_G identified 10 candidate genes regulating soybean nodule number. There was a significant difference in the number of nodules among the materials corresponding to different haplotypes of Glyma.02G243200 (P<0.05), the expression pattern of this gene was queried in the SoyBase database, and it was expressed in root hairs, indicating that Glyma.02G243200 may be a key gene influencing soybean nodule number. Additionally, six SNPs significantly associated with soybean nodule dry weight were identified, located on chromosomes 6, 18, and 20. Among them, the significant associated loci BARC_2.01_Chr06_6069381_G_A and BARC_2.01_Chr06_6192925_T_C on chromosome 6 were identified as the main loci controlling soybean nodule dry weight (LOD=3.49 and LOD=3.35, respectively). Linkage disequilibrium analysis within the 100 kb interval upstream of BARC_2.01_ Chr06_6069381_G_A and downstream of BARC_2.01_Chr06_6192925_T_C identified 14 candidate genes regulating soybean nodule dry weight. Haplotype analysis revealed significant differences in nodule dry weight for the genes Glyma.06G079600 and Glyma.06G079900 between different haplotype materials (P<0.01, P<0.001), the expression pattern of this gene was queried in the SoyBase database, and they were expressed in roots, indicating that these two genes may be key genes influencing soybean nodule dry weight.【Conclusion】This study identified a candidate gene significantly associated with nodule number on chromosome 2 and two candidate genes significantly associated with nodule dry weight on chromosome 6, providing new genetic resources and references for genetic improvement of soybean nodulation traits.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY·AGRICULTURE INFORMATION TECHNOLOGY

Yield and Quality Analysis of Japonica Varieties from Cold Region Cultivated as Double Cropping Early Season Rice in the Lower Reaches of the Yangtze River

XU YaNan, TAO Yi, YE ShuZhen, XU ChunMei, CHEN Song, CHU Guang, WANG DanYing, OUYANG YouNan

Scientia Agricultura Sinica. 2024, 57(11):  2114-2124.  doi:10.3864/j.issn.0578-1752.2024.11.006

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【Objective】The aim of the study was to evaluate the differences between rice yield and its components, as well as quality of double cropping early japonica rice which was selected from various accumulated temperature zones in cold region to plant in the lower reaches of the Yangtze River, so as to provide a theoretical basis to select the proper japonica varieties as the double cropping early season rice in this area.【Method】Field experiments were carried out at Taizhou (121°13′ E, 28°78′ N) and Hangzhou (119°94′ E, 30°08′ N) of Zhejiang province in 2018, 2021 and 2022. Six (2018), thirteen (2021) and forty-one (2022) japonica varieties were selected from different accumulated temperature zones in Heilongjiang province, respectively, and the early indica rice Zhongzao 39 was picked out as a control in 2018 and 2022. The differences of productive panicle number, spikelets number per panicle, percentage of filled grain, thousand grains weight, number of spikelets unit area, yield, and harvest index were analyzed among double-cropping early japonica and indica rice; the quality indexes were compared among this two types rice too, such as head rice rate, diaphaneity, gel consistency, amylose content, chalkiness degree, and chalky grain rate.【Result】The harvest dates of early japonica rice with beforehand sowing were about 0-15 days earlier than that of local double-season early indica rice. The total mean yield of early japonica rice was 6 637.77 kg·hm^-2 in 2018; and the yield of Kongyu 131 were the highest with 7 724.70 kg·hm^-2. Moreover, the field production verification in 2022 suggested that the yield of Kongyu 131 could reach 7 194.77 kg·hm^-2. The averages of chalkiness degree, diaphaneity, gel consistency and amylose content in all varieties met the quality of second-class edible rice variety criterion, but the head rice rate was low. The total mean yield early japonica rice was 6 630.45 kg·hm^-2 in 2022, in order as follows: Longken 257 (8 324.99 kg·hm^-2), Longken 263 (8 170.94 kg·hm^-2), and Liandao 1 (8 108.34 kg·hm^-2). Compared with Zhongzao 39, the productive panicle number in early japonica rice were higher, however, the spikelets number per panicle, percentage of filled grain, thousand grains weight were lower than the control, which induced the yield decrease of 54.75%-93.28%. The average yield of the third accumulated zone was higher than that of other accumulated zones due to the relative superior percentage of filled grain. The correlation analysis within yield and its components of different japonica cultivars showed that, the yield had significantly positive correlation with productive panicle number (P<0.05) and number of spikelets unit area (P<0.01).【Conclusion】It was practicable to plant double cropping early japonica rice varieties in the Yangtze River area selected from different accumulated temperature zones in Heilongjiang province, confirmed by appropriate performances on growth duration, yield and quality. It was suggested that Kongyu 131, Longken 257, Longken 263, and Liandao 1 could be selected as double cropping early japonica rice for the next large-scale demonstration planting.

Effects of Layered Fertilization Under Different Irrigation Conditions on Vertical Distribution of Soil Nutrients and Root Growth and Function of Wheat

BU MingNa, YANG XiWen, TENG ZhengKai, HU NaiYue, ZHANG Shuo, WANG ChunYan, YANG Jian, LIANG WenXian, MA WenQi, HE DeXian, ZHOU SuMei

Scientia Agricultura Sinica. 2024, 57(11):  2125-2142.  doi:10.3864/j.issn.0578-1752.2024.11.007

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【Objective】In order to explore the effects of fertilization on soil nutrients and wheat (Triticum aestivum L.) root growth, and to shape a good root architecture, so as to provide a theoretical basis for scientific fertilization and high-yield and high-efficiency production of wheat field.【Method】The experiment was conducted in Yuanyang Scientific and Educational Park of Henan Agricultural University from 2021 to 2023. The pool planting positioning experiment is adopted. And three fertilization treatments (F₀: no fertilization; F₁: shallow application of N, P, K fertilizer; F₂: 1/3 shallow application plus 2/3 deep application of N, P, K fertilizer) and three irrigation treatments (W₁: prior to sowing irrigation; W₂: prior to sowing irrigation plus irrigation at jointing stage; W₃: prior to sowing irrigation plus irrigations both at jointing and anthesis). A total of 9 treatment combinations were used to determine concentration dynamics of soil nutrients and root morphological and physiological traits at different soil layers within 0-100 cm.【Result】Under different irrigation frequencies, the concentrations of available N, P, K nutrients were relatively high in top soil layer and decreased with the soil depth. In the soil layer of 0-60 cm, the trend of concentrations of available N, P, K nutrients under different treatments was as F₂>F₁>F₀. Especially, the nutrient concentrations were significantly increased in 20-40 cm soil layer in layered application treatment (F₂). Compared with those in shallow application (F₁), the concentrations of nitrate nitrogen, ammonium nitrogen, available phosphorus, and available potassium increased by 16.03%, 7.67%, 8.82%, and 6.32% under F₂ under different irrigation frequencies from anthesis to maturity, respectively. Also, under F₂ treatments, the concentrations of both nitrate nitrogen and total nitrogen increased in 80-100 cm soil layer, and irrigation enhanced the treating effects. The distribution of available potassium concentration in 0-100 cm soil layer exhibited an S-shaped curve, and K concentration increased at maturity stage suggesting the phenomenon of potassium excretion. The wheat roots were mainly located in the 0-40 cm soil layer. Morphological & quantitative traits and physiological function of roots were significantly improved under F₂ in the 20-40 cm soil layer: compared with those under F₁, the root length density, root surface area density, root volume ratio, root dry weight density, root vigor, and root physiological potential were increased by 38.42%, 16.93%, 25.65%, 43.07%, 33.12%, and 31.10%, respectively. The correlation analysis showed that concentrations of available N, P, K nutrients in 0-20 cm soil layer were significantly positively correlated with root morphological & quantitative traits (P<0.01). Root physiological potential in 0-60 cm soil layer was significantly positively correlated with soil nitrate nitrogen, ammonium nitrogen, available phosphorus, and available potassium, respectively.【Conclusion】The layered N, P, K fertilization combined with key irrigations at three stages achieved a high degree of coordination between root configuration, growth, physiological functions, and appropriate distribution of available N, P, K nutrients, and enhanced the root biomass in 20-40 cm soil layer, indicating more absorptions of nitrogen, phosphorus, and potassium from the soil and a higher grain yield.

PLANT PROTECTION

Effects of Exogenous Addition of L-Proline on the Occurrence of Cotton Verticillium Wilt and Its Soil Microbial Community in Rhizosphere

ZHAO WeiSong, GUO QingGang, CUI NaQi, LU XiuYun, LI SheZeng, MA Ping

Scientia Agricultura Sinica. 2024, 57(11):  2143-2160.  doi:10.3864/j.issn.0578-1752.2024.11.008

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【Objective】Root exudates are signal mediators for the interaction between plants and soil microorganisms, which have important regulatory functions for plant disease occurrence and plant growth. The objective of this study is to clarify the microecological mechanism of L-proline in root exudates of cotton against the occurrence of Verticillium wilt, reveal the relationship of L-proline-mediated interaction between rhizosphere microorganisms and the occurrence of cotton Verticillium wilt, and to provide a new perspective for the construction of beneficial bacterial communities for the biological control of soil-borne diseases.【Method】Through greenhouse pot experiments, different concentrations of L-proline (0, 50, 100, 200, and 400 mmol·L^-1) were set as experimental treatments, and real-time fluorescence quantitative PCR and metagenomic sequencing techniques were used to determine the DNA copy numbers of Verticillium dahliae and microbial community structure and function of soil samples treated with L-proline. The microbial community structures of rhizosphere soils under different concentrations of L-proline were compared using principal component analysis. Redundancy analysis was used to study the correlations between soil nutrient factors and microbial community structure, and Spearman correlation analysis was focused on the relationships between microbial community structure and functional metabolic pathways.【Result】Compared with the blank control, the occurrence of cotton Verticillium wilt could not reduce under low concentration (50 mmol·L^-1) L-proline treatment, while the disease indexes under high-concentration (100, 200, and 400 mmol·L^-1) L-proline treatments were decreased by 22.51%, 60.23%, and 64.23%, respectively. The results of qPCR showed that L-proline treatment did not significantly decrease the copy numbers of V. dahliae in soil. The metagenomic sequencing analysis showed that the Shannon index of bacterial diversity significantly increased after L-proline treatment, while the Shannon index of fungal diversity showed a downward trend. At the genus level, the relative abundances of Nocardioides, Lysobacter, Arthrobacter, Phycicoccus, Pseudomonas, and Mucor were increased after treatment with L-proline. Linear discriminant analysis (LDA) showed that the enrichment of microbial KEGG pathways in rhizosphere soil changed after exogenous addition of L-proline, except for L-proline at the concentration of 100 mmol·L^-1. Redundancy analysis showed that bacterial community composition was significantly influenced by pH, conductivity, nitrate nitrogen, ammonium nitrogen, and organic matter (OM), while fungal community composition was significantly correlated with ammonium nitrogen. Spearman correlation analysis showed that the bacterial KEGG pathways were negatively correlated with pH, OM and ammonium nitrogen, while positively correlated with conductivity and nitrate nitrogen. Most of the KEGG pathways of fungi had poor correlation with soil nutrients.【Conclusion】The exogenous addition of an appropriate amount of L-proline can influence the occurrence of cotton Verticillium wilt through altering the structure and function of soil bacterial communities, increasing the relative abundance of beneficial microorganisms, but it cannot change the DNA copy numbers of pathogen. Meanwhile, the composition and function of bacterial community are related to soil nutrients.

The Effects of Potato Root Exudates on the Hatching and Chemotaxis of Globodera rostochiensis and Verification of Exogenous Acid Substances

YIN YanDie, YANG YanMei, FU QiChun, WANG Qin, LI YongQing, DUAN JinFeng, LIU YuZhu, WANG QiaoMei, HU XianQi

Scientia Agricultura Sinica. 2024, 57(11):  2161-2175.  doi:10.3864/j.issn.0578-1752.2024.11.009

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【Objective】The objective of this study is explore the effects of root exudates from different resistant potato varieties and different growth stages on the hatching and chemotaxis of Globodera rostochiensis, so as to provide a theoretical basis for the green prevention and control of G. rostochiensis.【Method】The root exudates of four potato varieties at three growth stages were collected. The effects of root exudates on the hatching and chemotaxis of G. rostochiensis were studied by the soaking method and filter paper method. The components of root exudate were analyzed by GC-MS. Eight standard exogenous acids, caffeic acid, succinic acid, 3-phenylpropionic acid, 3-hydroxypropionic acid, 3-amino-3-methyl-butyric acid, glycolic acid, stearic acid, and L-lactic acid, were selected, and the effects of the main acids of root exudates on the hatching and chemotaxis of G. rostochiensis were verified by the soaking method and filter paper method.【Result】The efficiency of stimulating hatching of G. rostochiensis by root exudates of susceptible varieties Qingshu 9 and Huize 2 was higher than that of resistant varieties Xuanshu 6 and Yunshu 505. At three growth stages (15 d (germination stage), 30 d (seedling stage), 55 d (tuber formation stage)), the effect of susceptible varieties on hatching stimulation was stronger than that of resistant varieties, and the effect of stimulating hatching of each variety root exudate at 30 d (seedling stage) was better than that at 15 d (germination stage) and 55 d (tuber formation stage). The stimulating hatchability of root exudates from Qingshu 9 was 7.20%, 27.30%, and 5.70% at 15, 30 and 55 d, respectively; that of Huize 2 was 10.50%, 38.00%, and 9.40%, Xuanshu 6 was 5.40%, 20.40%, and 16.30%, Yunshu 505 was 13.20%, 21.80%, and 3.10% at 15, 30 and 55 d, respectively. Among the root exudates of four potato varieties, Qingshu 9 was more attractive to G. rostochiensis. At three growth stages, except for Xuanshu 6, the root exudates of the other three varieties at 15 d had a better attraction effect than at 30 and 55 d. The attraction rate of root exudates of Qingshu 9 at 15, 30 and 55 d was 13.73%, 9.68%, and 6.13%, respectively, that of Huize 2 was 5.65%, 4.76%, and 4.89%, Yunshu 505 was 4.86%, 4.13%, and 2.91%, Xuanshu 6 was 4.11%, 5.77%, and 6.47% at 15, 30 and 55 d, respectively. According to GC-MS analysis and identification, potato root exudates mainly contain 9 kinds of substances, including 24 acids, 13 amino acids, 5 salts, 3 alcohols, 3 hydrocarbons, 3 carbohydrates, 2 phenols, 1 ketone, and 1 lipid. From the species and proportion, acids, amino acids, phenols and alcohols are the main components of potato root exudates. The experiment of 8 kinds of exogenous acid substances showed that succinic acid and 3-hydroxypropionic acid had a significant effect on the hatching stimulation of G. rostochiensis. Caffeic acid and 3-phenylpropionic acid had a significant effect on the chemotaxis of G. rostochiensis. However, compared with the effects of root exudates from four varieties at 30 d on G. rostochiensis, it was found that the hatching stimulation effects of above acids with significant effects were significantly lower than those of root exudates, and there was no significant difference in chemotaxis.【Conclusion】The root exudates from different potato varieties and different growth stages all have effects on the hatching and chemotaxis of G. rostochiensis. The effects of hatching and chemotaxis of G. rostochiensis by root exudates from susceptible varieties were higher than those of resistant varieties. The effects of susceptible and resistant varieties on G. rostochiensis began at 15 d (germination stage) when the root system appeared, were strongest at 30 d (seedling stage), and weakened at 55 d (tuber formation stage). The potato root exudates are diverse, the main components are acids, amino acids, and alcohols, and the resistance and susceptible varieties are slightly different. Succinic acid and 3-hydroxypropionic acid had a significant effect on hatching, caffeic acid and 3-phenylpropionic acid had a significant effect on chemotaxis. Single acid had significantly less effect on hatching of G. rostochiensis than root exudates.

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

Response of Zinc Concentration and Distribution in Wheat Grain to Soil Zinc Fertilization in Dryland of Loess Plateau

DING YuLan, HUANG Cui, WANG XingShu, ZHANG XueMei, XU JunFeng, HUANG Ning, DANG HaiYan, GUO ZiKang, SUN RuiQing, WANG ZhaoHui

Scientia Agricultura Sinica. 2024, 57(11):  2176-2188.  doi:10.3864/j.issn.0578-1752.2024.11.010

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【Objective】The changes in available soil zinc (Zn), wheat grain yield and grain Zn concentration were identified, so as to provide the important basis for optimizing Zn biofortification of wheat grain technology.【Method】Based on the location-fixed field trial initiated in 2017 in drylands of the Loess Plateau, the samples were collected to analyze the available soil Zn, wheat yield, yield components, Zn concentrations in grain and its tissues, Zn uptake and distribution in various plant parts under different Zn application rates in the wheat growing seasons of 2020-2021 and 2021-2022.【Result】Zn application did not significantly affect the wheat yield and yield components, but Zn concentration was increased by 28.8%-46.0% in grain and maximized to 31.1 mg·kg^-1 at Zn application rate of 24.9 kg·hm^-2; Zn concentration was increased by 31.8%-58.8% in bran and maximized to 87.6 mg·kg^-1 at Zn application rate of 27.3 kg·hm^-2; Zn concentration was increased by 26.3%-41.3% in flour and maximized to 11.3 mg·kg^-1 at Zn application rate of 24.0 kg·hm^-2. The grain Zn was found mainly distributed in bran, accounting for 77.7%-80.0%, with the average Zn concentration of 78.9 mg·kg^-1; and 20.0%-22.3% Zn in flour, with the average Zn concentration of 10.8 mg·kg^-1. With the Zn application rate increase, Zn concentration increased much more in bran than that in the flour. Available soil Zn was increased by 235.2%-1233.8% and 207.4%-825.9% in the 0-20 and 20-40 cm soil, respectively, and reached 9.47 and 2.50 mg·kg^-1 at the maximum Zn application rate of 27.3 kg·hm^-2, respectively. Available Zn of 0-100 cm soil layers contributed differently to wheat Zn uptake, with that in top soil contributed much more than that in deep soil layers.【Conclusion】Obviously, soil Zn application significantly increased soil available Zn and wheat grain Zn concentrations in drylands of the Loess Plateau, and for further improvement of wheat grained Zn nutritional and explore the increase potential in wheat grain Zn concentration, an integrative optimization should be implemented on Zn rates and application methods, and other agronomical measures, such as water, N and phosphorus supply, as well as green manure planting.

Soil Water Use Characteristics of Spring Wheat with Multiple- Cropping Green Manure and Nitrogen Reduction in Northwest Irrigated Areas

ZHANG DianKai, LI Pan, FAN Hong, HE Wei, FAN ZhiLong, HU FaLong, SUN YaLi, TAN XiangNian, YIN Wen, CHEN GuiPing

Scientia Agricultura Sinica. 2024, 57(11):  2189-2201.  doi:10.3864/j.issn.0578-1752.2024.11.011

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【Objective】The aim of this study was to explore the effects of multiple-cropping green manure and reduced nitrogen (N) application on water use characteristics of spring wheat in northwest irrigated areas, so as to provide a theoretical basis for optimizing the efficient use of water resources in spring wheat production.【Method】A split-zone design was adopted, with two cropping patterns of multiple-cropping green manure (W-G) and post-wheat fallow (W) in the main zone, three N fertilizer levels in the sub-plot: conventional N fertilizer application (180 kg·hm^-2, N3), N fertilizer reduction of 15% (N2, 153 kg·hm^-2), and N fertilizer reduction of 30% (N1, 126 kg·hm^-2). The effects of multiple-cropping of green manure and nitrogen reduction on yield, water consumption and water use efficiency of spring wheat were studied from 2020 to 2021.【Result】The multiple-cropping green manure combined with moderate reduction of nitrogen fertilizer increased the pre-sowing soil water storage of spring wheat, and W-G increased the pre-sowing soil water storage of spring wheat by 11.5% to 13.5% compared with W pattern, while the multiple-cropping green manure combined with N reduction of 15% (W-GN2) and multiple-cropping green manure combined with N fertilizer reduction of 30% (W-GN1) increased the pre-sowing soil water storage of spring wheat compared to control post-wheat fallow combined with conventional N fertilizer application (W-N3) by 12.1% to 20.2% and 15.2% to 16.6%, respectively. W-G reduced water consumption of spring wheat by 12.6% to 13.7% compared with W-GN1, and W-GN2 reduced water consumption of spring wheat by 15% compared to W-N2 and W-N3, respectively. W-G effectively harmonized the water demand characteristics of spring wheat before and after the reproductive period by reducing the evapotranspiration modulus coefficient of spring wheat at the early stage of nodulation and filling, and increasing the evapotranspiration modulus coefficient of pre-sowing to jointing and early-filling to maturity (the proportion of water consumption of the two stages to the total water consumption of the whole reproductive period was 60.5% to 64.1%). Finally, the synchronization of water supply and demand during the growth and development of spring wheat was enhanced. W-G had the advantage of yield increase, with 13.5% to 14.1% under W pattern. W-GN2 and W-N3 had yield increases of 16.7% to 18.4% and 13.6% to 14.6% under W-N2 and W-N3, respectively. Thus, W-G improved water use efficiency by 29.4% to 31.0% compared with the W pattern, and among the multiple-cropping green manure, W-GN2 improved water use efficiency by a greater extent than W-N2 and W-N3 by 44.2% to 46.8% and 39.1% to 43.5%, respectively, and W-GN1 and W-GN3 by 36.2% to 50.7% and 9.1% to 17.0%, respectively.【Conclusion】The multiple-cropping green manure combined with 15% N fertilizer reduction (i.e., 153 kg·hm^-2 of N fertilizer) improved spring wheat yield and water use efficiency compared with conventional water and N fertilizer management, and could be recommended as a production technique for efficient water use in spring wheat in dry irrigated areas.

Distribution of Wheat and Maize Straw Resources in Shandong Province and Fertilizer Reduction Potential Under Straw Return

CHAI RuShan, ZHU LiQing, LIU MengYang, LUO LaiChao, ZHANG LiangLiang, CHENG QiPeng, ZHANG ChaoChun

Scientia Agricultura Sinica. 2024, 57(11):  2202-2214.  doi:10.3864/j.issn.0578-1752.2024.11.012

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【Objective】Shandong Province is the main wheat and maize producing province in North China. Clarifying the spatial distribution characteristics of wheat and maize straw resources and nutrient substitution potential of straw return of this province could provide the decision support for comprehensive utilization of crop straw and fertilizer reduction.【Method】In this research, the wheat and maize straw yield and substitution potential of nutrient by straw return in different areas of Shandong Province were estimated by straw-to-grain ratio method, based on statistic yearbook data and published literature review.【Result】The annual outputs of wheat and maize straw were 29.28 and 22.52 million tons, respectively, in Shandong Province during 2019-2021. The proportions of wheat and maize straw resources in different regions were ranked as follows: North Shandong (34.9% and 34.7%)>Southwest Shandong (27.6% and 24.9%)>Central Shandong (20.2% and 21.4%)>East Shandong (9.1% and 11.3%)>Southeast Shandong (8.2% and 7.8%). The order of collectable wheat straw per unit area was North Shandong (5 573 kg·hm^-2)>Southwest Shandong (5 380 kg·hm^-2)>Central Shandong (5 361 kg·hm^-2)>Southeast Shandong (5 088 kg·hm^-2)>East Shandong (4 968 kg·hm^-2). The order of collectable maize straw per unit area was Southwest Shandong (5 121 kg·hm^-2)>North Shandong (5 034 kg·hm^-2)>Southeast Shandong (4 807 kg·hm^-2)>Central Shandong (4 790 kg·hm^-2)>East Shandong (4 709 kg·hm^-2). At the municipal level, the straw resources were mainly distributed in Heze, Dezhou, Liaocheng, Jining and Weifang. The wheat and maize straw yields of these cities accounted for 57.5% and 55.5%, respectively. However, the proportions of wheat and maize straw outputs from Dongying, Zibo, Rizhao and Weihai were only 7.2% and 8.0%, respectively. In Shandong Province, the amounts of nutrient from wheat straw were 0.1394 million tons of N, 0.0513 million tons of P₂O₅, and 0.5090 million tons of K₂O. For maize straw, the outputs of nutrient were 0.1665 million tons of N, 0.0658 million tons of P₂O₅, and 0.3660 million tons of K₂O. In the regional scale, the substituting potentials of N, P₂O₅ and K₂O through wheat straw return were 16.7-18.7, 7.8-8.7 and 110.4-123.8 kg·hm^-2, respectively. The maize straw incorporation could substitute chemical fertilizers of N 25.4-27.6, P₂O₅ 11.8-12.8 and K₂O 83.2-90.5 kg·hm^-2 theoretically.【Conclusion】In summary, there were some differences in total straw yield and collectable straw per unit area among different wheat-maize rotation areas of Shandong Province. Therefore, these appropriate policies should be formulated based on local conditions to promote efficient utilization of wheat and maize straw resources. The fertilizer replacement potential of returned straw should be considered for nutrient management in wheat-maize rotation system, which was conducive to chemical fertilizer reduction and green agricultural development.

HORTICULTURE

Effect of Nitrogen Form on Root Growth, pH in Root Zones and Cell Wall Components of Pakchoi

HAN RuiFeng, GUO YuQin, WANG YuZhuo, CHENG YongSan, HOU LeiPing, ZHANG Yi

Scientia Agricultura Sinica. 2024, 57(11):  2215-2226.  doi:10.3864/j.issn.0578-1752.2024.11.013

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【Objective】Nitrogen (N) is a critical factor in regulating the growth of vegetable crops. The purpose of this study was to explore how different N forms affect root growth and cell wall components in pakchoi, and to identify the relationship between root zone pH changes and PM H⁺-ATPase, so as to provide a theoretical basis for further research on nitrogen regulation of plant root growth and development.【Method】Pakchoi (Brassica campestris ssp. Chinensis L.) was used as the test material. Three N forms, including nitrate nitrogen (NO₃^--N), ammonium nitrogen (NH₄⁺-N), and glycine nitrogen (Gly-N), were utilized in a hydroponic nutrient solution experiment. The intrinsic mechanisms by which inorganic and organic nitrogen regulate the pH in the root zone and the cell wall components on the root growth of pakchoi were explored, and the effects of nitrogen nutrition on root auxin (IAA) and plasma membrane (PM) H⁺-ATPase were investigated. The root scanning and physiological experiments were used to determine the root morphology indicators, including total root length, volume, surface area, and tip number; along with physiological indicators including medium pH, PM H⁺- ATPase activity, IAA content, the main components content of cell wall, pectin methylesterase (PME) and vasodilator (EXP) content, and finally the correlation between root morphology and various physiological indicators were analyzed.【Result】Both Gly-N and NO₃^--N treatments increased the medium pH, and even Gly-N showed a greater capacity for alkalization than the NO₃^--N treatment, while NH₄⁺-N acidified the medium pH. Compared with NO₃^--N treatment, Gly-N treatment significantly decreased the dry matter content in shoots and roots, primary root length, total root length, surface area, tip number, root forks, number of internal, and external links of pakchoi by 40.23%, 21.74%, 55.15%, 58.63%, 53.12%, 73.07%, 65.39%, 40.91%, and 73.94%, respectively, and increased the root cell wall extraction rate, pectin, cellulose, EXP content, PM H⁺-ATPase activity, root/shoot ratio, topological index, and fractal dimension by 22.00%, 47.74%, 25.30%, 109.53%, 15.42%, 30.33%, 11.43%, and 4.32%, respectively. Compared with NO₃^--N treatment, NH₄⁺-N treatment significantly reduced the plant’s shoot dry matter content, primary root length, root forks, number of internal and external links, root PME activity, and IAA content by 22.98%, 34.30%, 35.32%, 26.22%, 29.02%, 36.38%, and 8.74%, respectively, while enhancing root PM H⁺-ATPase activity, cell wall extraction rate, pectin, and hemicellulose content by 14.60%, 19.38%, 22.98%, and 74.33%, respectively. The correlation analysis between root morphology indicators and physiological indicators revealed that total root surface area was highly significantly positively correlated with total root length, the total number of root tips and root forks (P<0.01), and also positively with primary root length, and negatively correlated with root diameter, expansin, and topological index (P<0.01), as well as with pectin, cellulose, and fractal dimension (P<0.05). The root diameter showed a strongly significant positive correlation with expansin, cellulose, fractal dimension, and topological index (P<0.01), while significantly positively correlated with pectin (P<0.05).【Conclusion】Both Gly-N and NH₄⁺-N treatments enhanced cell wall content of the root system, thereby inhibited the elongation and growth of pakchoi roots. Among them, Gly-N facilitated the accumulation of pectin and cellulose, and NH₄⁺-N promoted the accumulation of hemicellulose.

Construction and Application of SSR Marker Identification System for Bitter Gourd Varieties

SU GuoZhao, LI AiAi, LIU ZhongHua, CHEN YuHua, ZHANG XiuJie, MA YingXue, YANG XuHong, DENG Chao, XU ZhenJiang

Scientia Agricultura Sinica. 2024, 57(11):  2227-2242.  doi:10.3864/j.issn.0578-1752.2024.11.014

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【Objective】In order to provide a practical support for authenticity identification, purity identification and protection of new variety rights of bitter gourd, a set of SSR core primers were screened, and then, the molecular identification system and SSR fingerprint database were established.【Method】Firstly, by using 8 representative varieties with large phenotypic differences, the preliminary 138 pairs SSR primer screening were carried out through 6% polyacrylamide-gel electrophoresis, and the preliminarily screened primers were synthesized into fluorescent primers. Secondly, the primer re-screening was carried out by fluorescence capillary electrophoresis against 95 bitter gourd varieties with diverse geographical sources. Then, the discrimination rate, PIC value, number of alleles, and other parameters of each re-screened primer were calculated respectively, and a set of SSR primer combinations with high discrimination rate and good polymorphism were selected. Finally, the total of 208 bitter gourd varieties were tested by the re-screened primers and a set of SSR core primers were further selected and used to construct a DNA fingerprint database of bitter gourd varieties.【Result】45 pairs of SSR primers with high specificity, high polymorphism and clear bands were screened by polyacrylamide gel electrophoresis. 20 pairs of SSR core primers were finally screened from small populations to large populations by fluorescence capillary electrophoresis. The core primers were divided into 4 groups for multiple electrophoresis, and DNA fingerprint data of 208 bitter gourd varieties were collected. The total of 65 alleles and 102 genotypes were detected by 20 pairs of SSR core primers. 12 reference varieties were selected, which could cover all alleles. Through phylogenetic tree construction, 208 bitter gourd varieties were divided into 2 categories, indicating that 20 pairs of SSR core primers were suitable for genetic diversity analysis of bitter gourd population. 202 of 208 bitter gourd varieties could be identified by core primers, and the discrimination rate was 97.11%. 11 groups of parents and hybrid materials were used to analyze genetic relationship and then conformed to Mendel’s genetic law. There were only 1 locus of fragment loss in each 2 groups, which provided a reference for the decision threshold value of identification of bitter gourd hybrids.【Conclusion】In this study, the identification system of bitter gourd varieties constructed based on 20 pairs of SSR core primers had superior applicability and excellent identification effect, and could also be used for authenticity identification, purity identification, hybrids identification of bitter gourd varieties, similar varieties selection in DUS test and protection of new variety rights of bitter gourd.

ANIMAL SCIENCE·VETERINARY SCIENCE

The Efficiency of Haplotype-Based Genomic Selection Using Genotyping by Target Sequencing in Pigs

LIU YanLing, QIU Ao, ZHANG ZiPeng, WANG Xue, DU HeHe, LUO WenXue, WANG GuiJiang, WEI Xia, SHI WenYing, DING XiangDong

Scientia Agricultura Sinica. 2024, 57(11):  2243-2253.  doi:10.3864/j.issn.0578-1752.2024.11.015

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【Objective】This study explored the efficiency of haplotype-based genomic selection using genotyping by target sequencing technology in order to provide the useful experience for molecular breeding of pigs in China.【Method】The growth traits records of 1 267 Large White pigs and the reproduction trait records of 800 Large White pigs were collected and genotyped by using the porcine 50K liquid-phase SNP panel (liquid-phase 50K) based on the Genotyping by Target Sequencing (GBTS) as well as its target resequencing data. Three strategies for haplotype block partition, including fixed SNP number, fixed length, and target block, were proposed to construct haplotypes, and the corresponding haplotype-based genomic prediction were compared with single SNP genomic prediction. The target block partition strategy was mainly based on target resequencing data obtained by the GBTS, and one haplotype block contained one target site in liquid-phase 50K and its upstream and downstream SNPs (mSNP) within 400 bp from target resequencing data. In this study, after phasing haplotype using Beagle 5.1 within each haplotype block, the different haplotypes were recoded as haplotype alleles, and then haplotype allele matrix was constructed using haplotype dosage model. A single-step GBLUP model (ssGBLUP) was then used to estimate genomic breeding values for three traits of days at 100 kg body weight (AGE), backfat thickness at 100 kg (BF), and total number of born (TNB). A two-trait animal model was implemented for two growth traits of AGE and BF, and repeatability model for TNB. Younger validation population and five-fold cross validation were carried out to assess the efficiency of genomic prediction. The correlation coefficients between estimated breeding values and genomic estimated breeding values were measured as the accuracy of genomic prediction, and the regression coefficients of genomic estimated breeding values on estimated breeding values were measured unbiasedness, respectively.【Result】The results from the younger validation population showed that the target resequencing data yielded lower accuracies of genomic selection on three traits than liquid-phase 50K SNP, even its number of SNP after genotype quality control was increased from 42 302 in liquid phase 50K to 88 105. The haplotype blocks partitioned by target block strategy contained 2.08 SNPs and 5.67 haplotype alleles on average. The accuracies of haplotype-based genomic selection based on all three haplotype block partition strategies were improved, and the target block gained the largest improvement, yielding 4.80%, 1.98% and 6.04% higher accuracies on AGE, BF and TNB than liquid- phase 50K, respectively. In addition, the target block strategy generated the lowest bias in most scenarios as well. The five-fold cross-validation obtained similar results as younger validation population did, target block gained advantages over both single SNP and other haplotype block partition methods. The fixed length of 400 bp block partition strategy performed comparable with target block, while it was time demanding. Although fixed 2 and 5 SNP haplotype block partition methods performed better than single SNP method, they were worse than target block.【Conclusion】Due to the short length, the linkage disequilibrium between most of the target sites in liquid-phase 50K SNPs and their mSNPs in same blocks are strong, resulting in target block strategy obtained higher accuracy in haplotype-based genomic selection than single SNP and other haplotype block partition strategies, which could make use of the technique advantage of GBTS, and further broaden the application of liquid-phase chip.

Epidemiological Investigation of Respiratory Pathogens in Deceased Fattening Pigs in Major Pig Farming Area of Middle and Eastern China and Characterization of Pasteurella multocida

LUO SuXian, ZHOU Hong, LIN HuiXing, FAN HongJie

Scientia Agricultura Sinica. 2024, 57(11):  2254-2264.  doi:10.3864/j.issn.0578-1752.2024.11.016

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【Objective】This study aims to isolate and identify prominent bacterial respiratory pathogens from samples collected from fattening pigs that have died from respiratory diseases in major domestic pig farming area of middle and eastern China. And identifying these bacterial pathogens will offer valuable evidence for preventing and controlling the significantly prevalent respiratory diseases in recent years. Moreover, the characteristics of Pm were identified, providing reference for the development of Pm vaccines.【Method】The lungs of pigs died from respiratory disease were collected from large-scale farms in major pig farming area of middle and eastern China from 2021 to 2023. Blood agar and TSA were employed for the isolation of pathogens, which were then identified through microbiological and molecular biology methods. Additionally, MLST typing and virulence testing in mice were conducted on Pm isolates. The primers for PCR against seven housekeeping genes of adk, est, gdh, mdh, pgi, pmi and zwf of Pm were designed. Then the productions of amplicons were sequenced and submitted to perform MLST typing. The capsule and lipopolysaccharide typing were detected by PCR. The virulence factor genes were detected by PCR. Single isolates of A type and selected D and F types of Pm were evaluated for virulence in ICR mice. LD₅₀ of JS-65, JS-51 and JS-34 were detected in ICR mice.【Result】A total of 73 Pm isolates were obtained, with an isolation rate of 15.53%. Additionally, 71 SS isolates, 29 APP isolates, and 10 GPS isolates were obtained, with isolation rates of 15.11%, 6.17%, and 2.13% respectively. The typing results indicated that the prevailing subtype among Pm isolates was A:L3, accounting for 55%. Among SS isolates, subtype 9 was the prevailing type, accounting for 38.03%. Among APP isolates, subtype 15 was the prevailing type, accounting for 51.72%. Among GPS isolates, subtype 5/12 was the prevailing type, accounting for 60.00%. Co-infection included Pm+SS, Pm+APP, SS+APP and Pm+APP+GPS, accounting for 16.67% of the total pig population. Three capsule types were isolated: A (67%), D (30%), and F (3%). Two lipopolysaccharide types were found: L3 (56%) and L6 (44%). Nine ST genotypes were identified: ST79, ST50, ST7, ST74, ST13, ST27, ST9, ST287, and ST370, with proportions of 33%, 26%, 16%, 10%, 4%, 4%, 3%, 3%, and 1%, respectively. The results of virulence gene detection showed that the positivity rates of ptfA, fimA, hsf-2, exbB, exbD, tonB, fur, nanH, sodA, and sodC genes were greater than 95%. The positivity rates of hsf-1, pfhA, tadD, hgbA, hgbB, pmHAS, ompA, ompH, oma87, and plpB genes ranged from 40% to 90%. The positivity rates of tbpA and nanB genes were between 10% and 30%; the toxA gene was not detected. The virulence test results indicated that all mice died when exposed to less than 10² CFU of strain A, the mortality rate of mice was between 60% and 100% when exposed to 10³ CFU of strain D, and the mortality rate of mice was 60% when exposed to 5×10³ CFU of strain F. LD₅₀ of JS-65, JS-51, and JS-34 were detected in ICR mice, and the results showed that JS-65 LD₅₀<10 CFU, and JS-51 LD₅₀=6.3 × 10² CFU, JS-34 LD₅₀=3.98 × 10³ CFU.【Conclusion】Based on the bacterial pathogen isolates from 2021 to 2023, the primary pathogen bacterium of the respiratory tract in dead fattening pigs were Pm, SS, APP, and GPS. Pm had the highest number of isolates and isolation rate from lung tissue. The RIRDC identified a Pm strain of ST370 and extended MLST typing data in pigs. PCR typing results showed that the dominant serotype of Pm was A:L3:ST79, which exhibited the highest virulence in ICR mice with a minimum lethal dose of less than 10 CFU. These results serve as the foundation for the development of an inactivated Pm vaccine.