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25 August 2020, Volume 32 Issue 8 Previous Issue    Next Issue
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Crop Science
Animal Science
Horticultural Science
Plant Protection
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Crop Science

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Effects of no tillage and straw mulching on soil nitrogen, water content and yield of spring wheat in dryland farming area ZHANG Tongshuai, YAN Lijuan, LI Guang, CHEN Guopeng, LUO Yongzhong 2020, 32(8):  1329-1341.  DOI: 10.3969/j.issn.1004-1524.2020.08.01 Abstract ( 1204 )   HTML ( 2147483647 )   PDF (1367KB) ( 2223 )   In the present study, a field experiment was conducted with randomized block design, including conventional tillage (CT), no tillage (NT), conventional tillage+straw mulching (TS), no tillage+straw mulching (NTS), to explore the water and fertilizer effect and yield characteristics of spring wheat under different treatments in dryland farming area. The soil bulk density, contents of total nitrogen, ammonium nitrogen, nitrate nitrogen, soil water content, and wheat yield were determined. It was shown that after two years' experiment, the soil bulk density of NT and NTS in 0-10 cm soil layer was significantly (P<0.05) higher than that of CT and TS. Compared with CT, TS and NTS increased soil water content and total nitrogen content in soil surface layer (0-40 cm). According to the average of two-year results, the soil water content of TS, NT and NTS was increased by 8.33%, 3.17% and 3.82% than that of CT, respectively. The soil total nitrogen content of TS and NTS was significantly (P<0.05) increased by 1.78% and 3.48% than that of CT, respectively. However, TS, NT and NTS significantly (P<0.05) decreased the content of ammonium nitrogen and nitrate nitrogen compared with CT. Based on the average of two-year result, compared with CT, TS and NTS increased the yield of spring wheat, while NT decreased the yield of spring wheat. References | Related Articles | Metrics

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Effects of planting space on growth and development of tobacco seedlings XU Na, WANG Dahai, DU Chuanyin, DU Shasha, WANG Xiaomeng, ZHANG Yan, ZHANG Yuqin, WU Yuanhua, GUAN Ensen, SHI Yi 2020, 32(8):  1342-1350.  DOI: 10.3969/j.issn.1004-1524.2020.08.02 Abstract ( 798 )   HTML ( 5 )   PDF (3178KB) ( 2187 )   In order to study the effects of different planting spaces on growth and development of tobacco seedlings, flue-cured tobacco K326 was used as experimental material to research the root, stem, leaf development and correlative physiological index under treatments with same rhizosphere space (90 cm3) and different planting spaces (3, 6, 9 cm). The results showed that, different planting spaces could significantly influence the colony structure, emergence speed of new leaf, leaf number, leaf area, photosynthetic characters, stem height, stem radius of each node, stem pitch, lignified degree of stem, root architecture and root activity of seedings. The plant-type and the maximum elongation node were constant among different treatments. It was concluded that, different planting spaces could affect the colony structure, phenotype and physiological index of tobacco seedlings. The rhizosphere space of 90 cm3 and the planting space of 6 cm were beneficial to seedlings growth and development. References | Related Articles | Metrics

Animal Science

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Quantitative analysis of mRNA expression of Tan sheep coat color candidate genes MC1R and TCF25 WANG Xiaowei, FAN Yi, MA Xiaoming, MA Lina, YUE Caijuan, WANG Jin, ZHAO Zhengwei, MA Qing 2020, 32(8):  1351-1356.  DOI: 10.3969/j.issn.1004-1524.2020.08.03 Abstract ( 749 )   HTML ( 4 )   PDF (720KB) ( 1921 )   In order to explore the relationship between the melanocortin-1-receptor gene (MC1R) and transcription factor 25 gene(TCF25), which affect the coat colors of mammals, and the coat colors of Tan sheep, real-time fluorescent quantitative PCR (qRT-PCR) technique was used to study the mRNA expression of MC1R gene and TCF25 gene in skin tissues of 15 Tan sheep with different coat colors (pure white, brown spot and black spot). The results showed that MC1R gene and TCF25 gene were expressed in three different kinds of coat colors of Tan sheep. Expression quantity of MC1R gene in skin tissues of different coat colors of Tan sheep was black spot>brown spot>pure white. The black spot group was significantly higher than the pure white group (P<0.01), the brown spot group was significantly higher than the brown spot group (P<0.05), and the brown spot group was significantly higher than the pure white group (P<0.05). The expression quantity of TCF25 gene in skin tissues of different coat colors of Tan sheep was pure white>brown spot>black spot, with no significant difference among groups (P>0.05).The results showed the relationship between the expression level of target gene and the coat colors of Tan sheep, and provided references for the color breeding and improvement of Tan sheep in the future. References | Related Articles | Metrics

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Detection of leukaemia virus antigen and analysis of GP85 gene sequence in local chicken breeds in Zhejiang Province NI Zheng, CHEN Liu, HUA Jionggang, YE Weicheng, YUN Tao, ZHU Yinchu, ZHANG Cun 2020, 32(8):  1357-1362.  DOI: 10.3969/j.issn.1004-1524.2020.08.04 Abstract ( 899 )   HTML ( 2 )   PDF (873KB) ( 1791 )   To investigate the infection of J subgroup avian leukosis virus (ALV-J)in local chicken breeds of Zhejiang Province, and to explore the molecular characterization of epidemic strains, infection of ALV-J was analyzed by detecting p27 antigen from samples collected from suspected infected chicken flocks of some area in Zhejiang Province. Five strains of ALV-J were isolated and GP85 genes were amplified by PCR and sequencing. Results demonstrated that ALV-J antigen positive occurred in all tested 19 lines of local chicken breeds, among of them, the positive rate of ALV p27 antigen was the highest in Line 101 and the positive rate was 40.48% in hen group, 16.54% in cock group; Line 126 took the second place, the positive rate was 28.87% in hen group, 3.30% in cock group; the positive rate was the lowest in Line171, the infection rate was 4.08% in hen group, and none was infected in cock group. Results of sequence determination and analysis demonstrated that GP85 amplified from 5 strains were all 924 bp in length, accord with the prediction; these sequences shared 90.8%-98.5% identification at nucleotide acid levels. The nucleotide similarity was 90.3%-97.0% with HPRS103, and 86.5%-99.0% with other domestic isolates. The isolates showed the highest homology with the isolates from Fujian FJ201308 strain and Guangdong WF13 strain. In conclusion, different lines of local chicken breeds in most parts of Zhejiang were infected with ALV-J to varying degrees, and the isolated strains showed different mutants to some extent, which suggested that the purification of ALV-J in Zhejiang Province should be strengthened. References | Related Articles | Metrics

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Investigation and genotyping of Giardia duodenalis infection in South China Sea WANG Zhekan, ZHOU Haolan, LI Danlei, ZHAO Ayong 2020, 32(8):  1363-1368.  DOI: 10.3969/j.issn.1004-1524.2020.08.05 Abstract ( 537 )   HTML ( 2 )   PDF (1052KB) ( 1789 )   Giardia duodenalis, a parasitic intestinal parasite that is zoonotic, was spread all over the world. Moreover, its infection rate had a great relationship with the region and the environment. To understand the infection situation of canine duodenal Giardia duodenalis in the neighboring countries and regions of the South China Sea, and determine whether marine isolation is an important factor affecting Giardia duodenalis transmission.From June 2018 to July 2019, 616 canine fecal samples were collected from Guangzhou, China, Ho Chi Minh City, Vietnam, Kuala Lumpur, Malaysia, Singapore, and Manila, Philippines. DNA of canine fecal samples from each region were extracted, and a nested PCR was prepared by using the TPI gene and BG gene of Giardia duodenalis. The extracted canine fecal genomic DNA was used as a template for nested PCR amplification to determine its positive infection rate. PCR-positive products were sequenced and the results were compared with Giardia duodenalis sequences in GenBank to determine their typing.Among the 616 samples, tested results of 48 samples were positive for Giardia duodenalis infection, with a positive rate of 7.79% (48/616). The infection rates in different regions were 4.81% in Guangzhou, China, 6.90% in Ho Chi Minh City, Vietnam, 9.09% in Kuala Lumpur, Malaysia, 2.86% in Singapore, and 11.52% in Manila, Philippines. Among them, 48 samples were detected at TPI and BG sites, and the positive rates were 7.63% and 5.19%, respectively. The positive samples were then sequenced and compared for the BG and TPI gene sites, and it was learned that the BG site had conglomerate B type (3.33%), conglomerate C type (86.67%), and conglomerate D type (10%). TPI site had conglomerate B type (2.12%), conglomerate C type (85.1%), and conglomerate D type (12.76%). After statistical analysis and comparison, the difference between Giardia duodenalis genotypes in various regions was not significant. Giardia duodenalis infection existed in the surrounding areas of the South China Sea, and the infection rate was relatively low in areas with relatively good public health. The genotyping distribution of canine Giardia duodenaliswas not significantly affected by the isolation of marine areas. References | Related Articles | Metrics

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Relationship of plumage color with expression and polymorphism of GNAS gene in Korean quail LIU Kunju, ZHANG Xiaohui, PANG Youzhi, ZHAO Shujuan, QI Yanxia, WANG Qiankun 2020, 32(8):  1369-1377.  DOI: 10.3969/j.issn.1004-1524.2020.08.06 Abstract ( 1050 )   HTML ( 4 )   PDF (2425KB) ( 2037 )   The present study was undertaken to explore the correlation between GNAS gene expression, polymorphism and plumage color in Korean quail. Trizol method was used to extract total RNA from different wing tip tissues of maroon Korean quail embryos and white Korean quail embryos at different development stages, and RT-qPCR was used to detect the mRNA expression level of GNAS gene in wing tissues of Korean quail embryos at different development stages and different feather colors; The full CDS sequence of the GNAS gene was cloned and analyzed by bioinformatics; Genomic DNA was extracted from wing tip tissue of embryos, incubated for 10 days, and the specific sequence of the GNAS gene was amplified by PCR. Asymmetrical PCR-SSCP method combined with sequencing was used to determine the genotype to analyze the effect of different genotypes on the formation of plumage color in Korean quail. The results showed that the expression level of GNAS gene in maroon quail embryos was significantly higher (P<0.01) than that in white quail embryos at 8-14 days. The open reading frame of the CDS region of the GNAS gene is 1 140 bp in length, contains 14 exons, and encodes a stable hydrophilic protein containing 379 amino acids. Two SNP loci were detected in the Korean quail GNAS gene, namely g.119221T>A in exon 12 region and g.121181A>G in 3'UTR region. The frequency distribution of the three genotypes (AA, AB and BB) of maroon plumage Korean quail in g.121181A>G mutation site in 3'UTR region was significantly different from that of white plumage Korean quail (P<0.01). These results suggest that the expression level of GNAS gene in Korean quail tissue was related to the formation of plumage color. The g.121181A>G mutation on the 3'UTR of the GNAS gene had a significant correlation with the plumage color traits of Korean quail. GNAS can be used as a candidate gene for studying plumage color of Korean quail. References | Related Articles | Metrics

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Correlation analysis of HSP70 gene polymorphism and semen quality in Xuefeng Black-bone chicken YU Zonggang, JIANG Jun, YAO Yaling, GUO Ying, LI Chuang, YAN Haifeng 2020, 32(8):  1378-1384.  DOI: 10.3969/j.issn.1004-1524.2020.08.07 Abstract ( 872 )   HTML ( 4 )   PDF (1140KB) ( 1959 )   To study HSP70 gene polymorphism of Xuefeng black-bone chicken and its relationship with frozen semen quality of chicken. Molecular markers related to freezing resistance of chicken semen were screened out to provide technical support for freezing preservation and molecular breeding of chicken semen. One hundred mature white Xuefeng black bone roosters of the same batch were selected. The semen volume, semen density and frozen semen vitality of rooster were measured. Blood was collected from the pterygium vein. gDNA was extracted from the blood sample and HSP70 gene was amplified. Three mixed pools of low, medium and high semen quality were constructed and sequenced. After sequencing a single sample, the genotyping was completed by comparing the sequencing peak diagram. The number of individuals with different genotypes was counted and the correlation analysis of semen quality was further carried out. The results showed that there was a mutation G>A at 436 bp in HSP70 gene, and G was the dominant gene. The population was divided into AA, AG and GG genotypes with the frequencies of 22%, 44% and 34%, respectively. The genetic diversity analysis PIC of this locus was 0.371 4, which was a moderate polymorphic locus. Hardy-Weinberg equilibrium fitness test showed χ2=1.1480 (P>0.05), which showed that the population conformed to Hardy-Weinberg equilibrium law. Correlation analysis between gene polymorphism and semen quality showed that the sperm volume and semen density of GG genotype individuals were significantly higher than those of AG type and AA type individuals (P<0.01). The viability after freezing of GG genotype individuals was significantly higher than that of AG type individuals (P<0.05), and was significantly higher than that of AA type individuals (P<0.01). The semen collection volume and semen density of AG type individuals were significantly higher than those of AA type individuals (P<0.01), and the difference of frozen semen activity was not significant. To sum up, the mutant G>A site of HSP70 gene was significantly related to the frozen semen quality of chicken. The locus could be used as a candidate gene for individual semen antifreeze of Xuefeng black-bone chicken. The individual with genotype GG had the best semen anti-freezing, followed by AG type individual. References | Related Articles | Metrics

Horticultural Science

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Analysis of highly cited papers in 10 core Chinese journals of horticulture CHEN Juan, ZHU Miao, BAO Yong 2020, 32(8):  1385-1396.  DOI: 10.3969/j.issn.1004-1524.2020.08.08 Abstract ( 523 )   HTML ( 2 )   PDF (1533KB) ( 1728 )   Statistical analysis was made on the highly cited papers of 10 horticultural journals selected in A Guide to the Core Journals(the 2017 edition). Five hundred highly cited horticultural papers were determined by the selection methods of selecting papers with the top 50 citation frequencies. Among the highly cited papers of the 10 horticultural journals from 2009 to 2018, the publication years were mainly concentrated in 2009—2013; most of the highly cited papers were supported by funds, which were mainly at national, ministerial and provincial levels; authors of the highly cited papers were mainly distributed in 9 provinces and autonomous regions such as Beijing and Liaoning; the papers co-authored by 2-8 scholars accounted for 92.8%, in which those co-authored by 5 scholars were the majority, and most of the papers were cooperated by 2-3 institutions; and the authors were mainly scientific researchers with doctoral degrees and senior titles. Twenty-two papers cited more than 100 times were mainly published in four journals: Acta Horticulturae Sinica, China Vegetables, Journal of Fruit Science and Northern Horticulture. These papers were mainly from universities (20 papers), and nearly half (10 papers) were review papers. If the editors consciously organize influential authors to write a review with a topic, it will have a positive effect of improving the influence of the journals. References | Related Articles | Metrics

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Application of protoplast fusion technology to breed new strains of Pleurotus ostreatus and Pleurotus eryngii WU Qiuying, ZHANG Yunfeng, ZHANG Shuhong, GAO Fengju, LIU Haiying, FAN Yongshan 2020, 32(8):  1397-1404.  DOI: 10.3969/j.issn.1004-1524.2020.08.09 Abstract ( 1129 )   HTML ( 8 )   PDF (5356KB) ( 2119 )   In order to breed new strains combining the elite complementary traits of Pleurotus ostreatus and Pleurotus eryngii, Pleurotus ostreatus variety CCEF89 with the properties of high yield and strong ability to resist contamination, and Pleurotus eryngii variety PL7 with the properties of high quality and strong adaptability were used as the parent strains to build the PEG (polyethylene glycol)protoplast fusion system.Under the optimal protoplast fusion condition of 1∶1 quantity ratio of the parent strains, 32 ℃ water bath, 30% PEG 6000, 0.01 mol·L-1 Ca2+ and 30 min co-incubation, the fusion rate was up to 0.010 1%-0.028 2%. 12 protoplast fusants (P1-P12) were identified by antagonistic reaction test and Rep-PCR molecular identification from 515 protoplast fusion regeneration isolates. After the mushroom cultivation experiments, P1 and P5 were identified as new strains of P. eryngii, and the other 10 protoplast fusants were new strains of P. ostreatus. The mushroom yield and biological efficiency of new strains P1 and P5 were significantly higher than those of their parent PL7, and their ability to resist contamination were increased significantly. Comparing to the parent CCEF89, the time of medium cultivation and mushroom primordia formation of P. ostreatus new strains P4, P10 and P11 were 5.5-7.3 days earlier, the yield of the first harvest mushroom and the total biological efficiency increased by 18.0%-24.0% and 21.00%-27.67%, respectively.Using the protoplast fusion technology, we acquired P. ostreatus and P. eryngii new strains with excellent complementary properties of the parents simultaneously, and proposed a new pathway to innovate new germplasm resources and bred new varieties of two different edible fungiat the same time. References | Related Articles | Metrics

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Effects of pH on physiological characters in somatic embryo induction stage of Agapanthus praecox YUE Jianhua, DONG Yan, LI Wenyang, LI Meng, ZHANG Yan 2020, 32(8):  1405-1414.  DOI: 10.3969/j.issn.1004-1524.2020.08.10 Abstract ( 680 )   HTML ( 1 )   PDF (1238KB) ( 1986 )   Suitable medium pH maintains a suitable pH environment in the process of in vitro culture, which ensures the normal physiological metabolism of cells. To improve somatic embryogenesis efficiency in Agapanthus praecox, the medium pH parameter was optimized, and the regulatory effects of pH on plant hormones, carbon sources and oxidative stress during somatic embryogenesis were investigated. Pedicel originated embryogenic callus were used as materials, the induction efficiency of young somatic embryos (YSE) and mature somatic embryos (MSE) with gradient medium pH (5.6, 5.8, 6.0 and 6.2) in somatic embryo induction stage were revealed, respectively. Furthermore, physiological differences were detected by the ELISA technique, and correlation analyses among pH, embryo number and physiological indices were conducted. The results showed that the optimal pH values in YSE and MSE induction stages were 6.0 and 6.2, respectively. In YSE induction stage, content of endogenous IAA was positively correlated with YSE number (P<0.01), while content of GA1 was negatively correlated with YSE number (P<0.05). In MSE induction stage, pH was positively correlated with MSE quantity, IAA oxidase activity, and sucrose content (P<0.05), respectively. Then IAA oxidase activity was positively correlated with MSE quantity (P<0.01), and the correlation between GA4 content, sucrose content and MSE quantity were also strong. H2O2 content and YSE numbers showed a positive correlation, while the correlation between H2O2 and MSE numbers was negative. POD activity was negatively correlated with YSE numbers (P<0.05). pH in the process of YSE and MSE induction stages were optimized in this study, the results showed that endogenous IAA might be the crucial factor for somatic embryo induction under different pH conditions, GA4 and sucrose contents played important roles in MSE induction. References | Related Articles | Metrics

Plant Protection

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Toxicity difference of EoNPV of two sibling species of tea genometrids LI Hong, TANG Meijun, GUO Huawei, WANG Zhibo, XIAO Qiang 2020, 32(8):  1415-1419.  DOI: 10.3969/j.issn.1004-1524.2020.08.11 Abstract ( 636 )   HTML ( 1 )   PDF (592KB) ( 1578 )   The EoNPV is an important pathogenic microorganism. And EoNPV can cause the death of Ectropis obliqua Prout and Ectropis grisescens in tea plantation. In order to further clarify the virulence difference of EoNPV to two sibling species of E. obliqua and E. grisescens. The leaf disk method feeding with two sibling species 3th instar larvae was used to find out the difference in virulence. The results showed that LD50 of E. grisescens was 28.9 times as E. obliqua. The LT50 of E. obliqua was less than E. grisescens. It showed that toxicity was different in two sibling species of tea genometrids. EoNPV had higher pathogenicity to E. obliqua. It had practical significance for using EoNPV to control the two sibling species of tea plantation. References | Related Articles | Metrics

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Effects of genotype and environment on downy mildew of cauliflower in different developmental stages HUANG Lei, LI Guangqing, YAO Xueqin, LIU Chunqing, XIE Zhujie, GENG Chunnü 2020, 32(8):  1420-1426.  DOI: 10.3969/j.issn.1004-1524.2020.08.12 Abstract ( 925 )   HTML ( 2 )   PDF (1431KB) ( 1924 )   Cauliflower downy mildew is one of the major fungal diseases affecting its production and quality. In order to explore the effects of genotype, environment and their interaction effect on the disease index of cauliflower downy mildew, four varieties of cauliflower (Xiamei 80, Xueyuan 80, 830-F and Huang 80) were artificially inoculated, and the disease index in three developmental stages under four field conditions with different temperatures and relative humidities were investigated. The correlations between the disease index of cauliflower downy mildew and five meteorological factors including temperature, humidity, temperature difference between day and night, accumulated temperature and sunshine hours were also analyzed.The results showed that the contribution rate order to the resistance of cauliflower downy mildew was genotype>environment>genotype and environment interaction,the variation ranges were 77.52%~87.04%, 12.33%~19.94%, 0.63%~2.54%, respectively. Huang 80 had strong resistance to downy mildew and could be used as a resistance resource for breeding.The resistance to downy mildew was significant positive correlated with daily average humidity and temperature difference between day and night,significant negative correlated with daily average temperature and accumulated temperature, and had no significant relationship with sunshine hours. Above all, low temperature and high humidity might aggravate the incidence of downy mildew cauliflower. Measures such as selecting resistant varieties, paying attention to heat preservation, maintaining ventilation in autumn and winter could effectively reduce downy mildew. References | Related Articles | Metrics

Environmental Science

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Predictive analysis of soil organic matter content in black soil region based on combined model LU Muyuan, LIU Yuan, LIU Guijian 2020, 32(8):  1427-1436.  DOI: 10.3969/j.issn.1004-1524.2020.08.13 Abstract ( 658 )   HTML ( 2 )   PDF (2573KB) ( 1903 )   To improve the prediction accuracy of soil organic matter content in typical black soil region via spectral processing and optimization of model methods, partial least squares regression (PLSR) model, back propagation neural network (BPNN) model and support vector machine (SVM) model were established based on the ground measured data and the first-order, second-order differential and principal component analysis data of image reflectance, and the best characteristic band selection and regression prediction of soil organic matter content in the study area were carried out. The results showed that different mathematical transformation of image band could enlarge some fine absorption characteristics of image data and highlight sensitive spectral information. The contribution rate of the spectral data after treatment was quantified by using the PLSR standardized model, and the best characteristic band was screened out along with the correlation coefficient. Among all the established models, the decision coefficient, root mean square error, and relative percent difference of the SVR model on the test set were 0.89, 2.81 g·kg-1 and 2.14, respectively, which exhibited the best performance. The present study could provide a new method for the selection of the best characteristic band in the inversion modeling of soil organic matter content in black soil region, and provide reference for selection of the best soil organic matter content inversion model. Meanwhile, the established SVR model could be used for rapid monitoring of soil organic matter content in typical black soil region, and could provide digital support and theoretical basis for the future effective development of cultivated land. References | Related Articles | Metrics

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Constructions of hyperspectral remote sensing monitoring models for heavy metal contents in farmland soil in Zhangjiagang City QIAN Jiawei, LIU Xiaoqing, ZHANG Jingjing, ZHOU Weihong, LI Jianlong 2020, 32(8):  1437-1445.  DOI: 10.3969/j.issn.1004-1524.2020.08.14 Abstract ( 839 )   HTML ( 6 )   PDF (1432KB) ( 2069 )   In the present study, soil samples were prepared from Zhangjiagang City to establish the quantitative inversion models of the soil heavy metals contents. The contents of the soil heavy metals and the visible and near-infrared spectra of the soil samples were obtained in a darkroom. Firstly, the original hyperspectral data was smoothed and the spectral transformations such as first derivative, reciprocal of first derivative, logarithm of reciprocal of first derivative, square root of first derivative and continuum removal were carried out. Secondly, the characteristic bands of different transform spectra were extracted through correlation analysis. Finally, quantitative estimation models of heavy metals contents were established by stepwise regression. The results showed that Cd, Hg, Cu and Zn in the farmland soil of Zhangjiagang City exhibited certain pollution risk. The correlation coefficient within the first derivative or the continuum removal and heavy metals contents were higher than that of other transformation forms. Eight quantitative estimation models of soil heavy metals contents and hyperspectral data possessed good prediction accuracy. The fitting degrees of the actual and verified values of the estimated models for Cd, Hg, Cr, As, Cu, Zn, Ni and Pb were 0.874, 0.879, 0.800, 0.646, 0.513, 0.655, 0.603 and 0.542, respectively. Therefore, hyperspectral data could be used to predict the contents of soil heavy metals in farmland in Zhangjiagang City. References | Related Articles | Metrics

Foods Science

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Isolation and identification of intestinal culturable bacteria of Dendrolimus punctatus and screening of protease-producing bacteria JIANG Yuhang, LI Hongwei, CAI Saibo, LIN Lianbing, ZHANG Qilin 2020, 32(8):  1446-1456.  DOI: 10.3969/j.issn.1004-1524.2020.08.15 Abstract ( 981 )   HTML ( 4 )   PDF (1143KB) ( 1804 )   To isolate and identify intestinal bacteria from Dendrolimus punctatus larvae and to tap resources of protease-producing bacteria. D. punctatus larvae was used as experimental material in this paper, several intestinal bacteria were obtained by conventional bacterial culture method in vitro. 16S rDNA was used to identify these bacteria, and protease-producing strains were screened by casein protein selection medium. Protease activity was determined according to GB/T 23527—2009 “protease preparation” test method. The results showed that 18 different species of non-anaerobic bacteria were obtained, including Bacillus genera belonging to Firmicutes, and Sulfurobacillus, Staphylococcus, Psychrobacter, Pantoea, Pseudomonas, Acinetobacter and Citrobacter belonging to Proteobacteria. Six strains of the protease-producing bacteria all belonging to Bacillus genus were screened by casein selective medium. The results of enzyme activity showed that all of these protease-producing bacteria had high protease-producing ability, especially strain MW-39 (Bacillus licheniformis), the highest enzyme activity reached to 255.36 U·mL-1, followed by MW-50 (Bacillus amyloliquefaciens) and MW-4 (Bacillus subtilis), their highest enzyme activity reached to 193.85 U·mL-1 and 165.81 U·mL-1, respectively. Enzymatic characteristics of protease produced by three bacterial species with the highest enzymatic activity were further analyzed, and their proteases showed a certain thermal stability and acid-base tolerance. One-way ANOVA analysis showed that protease activity of investigated bacteria were high at pH 5.0-9.0 and 30-50 ℃, and the optimum pH of protease produced by MW-39, MW-4 and MW-50 were 8.0, 7.5 and 8.0, respectively, and the optimum temperatures were 45 ℃, 40 ℃ and 40 ℃. This study revealed various species of intestinal bacteria in larvae of D. punctatus, enriched resources of protease-producing bacteria, and could provide reference for further development and utilization of protease-producing bacteria in insect intestine. References | Related Articles | Metrics

Biosystems Engineering

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Cotton recognition based on transfer learning WANG Jian, TIAN Guangbao, ZHOU Qin 2020, 32(8):  1457-1465.  DOI: 10.3969/j.issn.1004-1524.2020.08.16 Abstract ( 973 )   HTML ( 12582916 )   PDF (6482KB) ( 2061 )   An important way to improve the efficiency of the intelligent cotton picker is to realize the identification of single cotton, overlapped cottons, blocked cottons to avoid false picking and missed picking. The conventional feature extraction method is difficult to achieve satisfactory results for the identification of different types of cotton. Methods based on transfer learning and feature extraction based on transfer learning combined with extreme learning machine (ELM) was proposed. Firstly, the classification layer of AlexNet, GoogleNet and ResNet-50 models was changed and the relevant parameters were set, and the trained transfer model was used to identify the cotton validation set; secondly, the trained transfer model was used to extract the characteristics of cotton data set, and then the characteristics of the training set were used to train the ELM model to calculate the accuracy of the ELM model with different hidden layer neurons. The recognition rates of AlexNet, GoogleNet and ResNet-50 transfer models were 92.03%, 93.19% and 93.68%, respectively. The accuracy of the method of feature extraction combined with ELM was 1.97, 1.34 and 1.55 percentage points higher than that of the corresponding transfer model. The results showed that the transfer model could obtain higher accuracy for small sample cotton recognition. The method based on feature extraction and ELM could further improve the accuracy. References | Related Articles | Metrics

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Construction of plant root tip mesenchymal sensors and their effects on urea sensing dynamics NIU Bo, LI Lina, PANG Guangchang, LU Dingqiang 2020, 32(8):  1466-1474.  DOI: 10.3969/j.issn.1004-1524.2020.08.17 Abstract ( 933 )   HTML ( 2 )   PDF (2239KB) ( 2118 )   The plant root tip tissue sensor was constructed to quantitatively measure the root tip tissue's ability to sense urea and to explore the dynamics of the interaction between the two. In this study, sodium alginate-starch gel was used as a fixative. The meristems of corn, pepper, cauliflower and cucumber were fixed between two nuclear microporous membranes to make a “sandwich” urea sensing membrane. It was fixed and sealed on a glassy carbon electrode to make a plant root tip meristem sensor. Electrochemical workstations and time-current curve methods were used to determine the changes in electrochemical signals produced by the interaction of urea with root meristem sensors of corn, pepper, cauliflower, and cucumber. Compared with the blank control group, the root-tip meristem sensors of four plants showed a clear functional relationship to different concentrations of urea. Corn, pepper, cauliflowerand cucumber exhibited enzymatic response characteristics (linked allosteric effect) was similar to enzyme and substrate responses in the range of 10-8-10-4,10-16-10-6,10-19-10-10 and 10-20-10-10mol·L-1 urea. Further analysis showed that the linked allosteric constants Ka (similar to the Mie constants Km of enzyme-bottom catalytic kinetics) of corn, pepper, cauliflower, cucumberand urea were: 7.197 0×10-9, 4.537 0×10-16, 9.908 5×10-20 and 6.462 8×10-21mol·L-1. It was indicated that corn's ability to sense urea was at least 7 orders of magnitude worse than that of the other three plants. Corn and pepper were cultivated under the condition that urea was the only exogenous nitrogen nutrient. The experimental results showed that at a concentration lower than the corn's ability to sense urea (1×10-10mol·L-1), the corn died within 10-15 days and peppers could grow normally. It was proved that the linkage allosteric constant Ka obtained in this study reflected the true sensing ability of plant root-tip meristems to ureaand that corn's sensing of urea has some defects. References | Related Articles | Metrics

Agricultural Economy and Development

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Rural residential land reform and promotion of farmers' income: based on panel data of 6 pilot counties (cities, districts) with difference-in-difference analysis ZHANG Gongwang, ZHU Mingfen 2020, 32(8):  1475-1484.  DOI: 10.3969/j.issn.1004-1524.2020.08.18 Abstract ( 707 )   HTML ( 6 )   PDF (1257KB) ( 1788 )   Based on 885 households panel data from 6 pilot counties (cities, districts) of rural residential land reform, propensity score matching and difference-in-difference approach were applied to analyze the influence of rural residential land reform on farmers' income increase under the control of household fixed effect and year fixed effect, with farmers' annual per capita income and annual per capita property income as explanatory variables. It was shown that the rural residential land reform could increase farmers' annual per capita property income, but it had no significant impact on farmers' annual per capita income. In order to promote farmers' income through rural residential land reform, measures should be focused on how to promote farmer's property income. Therefore, suggestions were proposed including promoting urbanization, applying market mechanism and offering other related supporting reform measures. References | Related Articles | Metrics

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Comprehensive evaluation of land use benefit in early stage of pastoral complex construction: taking Lujia Village as an example HU Qiaolian, YANG Jun, SHAO Jingsong, ZHOU Pengquan, GUO Jiarui, HOU Manping 2020, 32(8):  1485-1492.  DOI: 10.3969/j.issn.1004-1524.2020.08.19 Abstract ( 666 )   HTML ( 5 )   PDF (901KB) ( 1899 )   The present study took the pastoral complex in Lujia Village as an example to establish a comprehensive evaluation system of land use benefit. Both analytic hierarchy process and variation coefficient method were applied to determine the weight of indexes, and the land use benefit was analyzed from aspects of social benefit, economic benefit and ecological benefit, respectively. It was shown that the proportion of social benefit, economic benefit and ecological benefit decreased successively in the early stage of pastoral complex construction in case of Lujia Village, and the comprehensive land use benefit achieved significant growth after the construction of pastoral complex. The social benefit and economic benefit increased rapidly during 2016-2017, yet the growth was limited in 2017-2018. The ecological benefit grew steadily by a little extent during 2016-2018. In general, the construction of pastoral complex had positive impact on social and economic development and environment protection, and posed remarkable impact on social and economic benefits, while its enhancement on ecological benefit was not obvious in the short term. References | Related Articles | Metrics

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Empirical study and early warning on spatial differentiation of arable land pressure and its influencing factors in main grain-producing regions based on county scale LUO Haiping, ZHOU Jingyi, HE Zhiwen 2020, 32(8):  1493-1506.  DOI: 10.3969/j.issn.1004-1524.2020.08.20 Abstract ( 652 )   HTML ( 1 )   PDF (1648KB) ( 1759 )   Based on the county scale, an empirical study was carried out on the spatial attributes and influencing factors of arable land pressure of 157 major grain-producing counties (including county-level city, district, autonomous county, banner and autonomous banner) in China's main grain-producing regions from 2000 to 2015. The arable land pressure from 2016 to 2030 was also fitted and forecasted with the help of GM(1,1) model. It was shown that the 157 major grain-producing counties had a heavy load of arable land. Due to the continuous increase in grain yield per unit area, the overall arable land pressure index of 157 major grain-producing counties dropped from 0.88 in 2000 to 0.66 in 2015. In 2015, a total of 99 major grain-producing counties in the study were in safe stress zones, 20 major grain-producing counties were in potential stress zone, and 31 major grain-producing counties were in mild stress zones. Whereas, seven major grain-producing counties, including Pizhou City in Jiangsu Province, and Anyue County, Jianyang City, Xuanhan County, Yuechi County, Nanbu County, Zizhong County in Sichuan Province were in moderate stress zones, and were under a potential risk of arable land pressure. The spatial distribution of arable land pressure in the 157 major grain-producing counties varied significantly, and their Matthew effect increased, and showed a trend of high in the South and low in the North, high in the West and low in the East. During the study period, the overall bearing coefficient of arable land pressure continued to decrease, yet the sensitivity coefficient of arable land pressure fluctuated significantly, showing a “W” wave dynamic trend. Without considering serious natural disasters, it was predicted that by 2030, the arable land pressure in 157 major grain-producing counties would ease. A model of influencing factors that could change the arable land pressure was established, and was used to empirically analyze the significant effects of factors such as arable land quality, fertilizer input, planting structure, urbanization level, and farmers' income on arable land pressure. Therefore, it was still the priority to ease the arable land pressure by improving planting structure and arable land quality and increasing the grain yield per unit area. References | Related Articles | Metrics

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Analysis of factors influencing operating income of village level collective economy: based on survey data of Jinhua City, Zhejiang Province LOU Yujie, ZHANG Benxiao, WANG Zhenzhen 2020, 32(8):  1506-1512.  DOI: 10.3969/j.issn.1004-1524.2020.08.21 Abstract ( 673 )   HTML ( 2 )   PDF (769KB) ( 1753 )   The development of rural collective economy is conducive to realize rural revitalization and tackle poverty. This article took the village collective economic data in 2019 of Jinhua City, Zhejiang Province, as the research object, through multiple regression analysis to study the critical influencing factors that affect the village collective operating income and proposed corresponding policy recommendations. The results showed that the number of village Party members and the government's financial subsidies to the village had significant impacts on the aggregate operating income of Jinhua Village, which were the key factors affecting the village's aggregate operating income and positive correlation with the village collective operating income. The results put forward suggestions to give full play to the role of party members in the village and make full use of the government's financial subsidies to the village. References | Related Articles | Metrics

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Research progress of main flavor compounds in tomato fruits WANG Tonglin, YE Hongxia, ZHENG Jirong, LI Ming 2020, 32(8):  1513-1522.  DOI: 10.3969/j.issn.1004-1524.2020.08.22 Abstract ( 1682 )   HTML ( 27699 )   PDF (1238KB) ( 2213 )   Flavor is an important quality index of tomato, which has been widely concerned in recent years. The flavor of tomato includes sweetness, acidity and fragrance, which are related to the content of soluble sugar, organic acid and volatile aromatic compounds. In this paper, starting from the important components that affect the flavor of tomato and their contribution to the flavor of tomato, the main flavor contributing substances and their biosynthesis pathway of tomato fruit and the main enzymes involved were discussed, and the international research on the genetic mechanism of these substances formation were comprehensively discussed. The existing problems in the study of tomato fruit flavor were analyzed and the prospect of tomato quality research was proposed in order to provide reference for tomato quality research and breeding in the future. References | Related Articles | Metrics