Acta Agriculturae Zhejiangensis

State quo of utilization of high-quality hybrid rice varieties in China during 2001-2017

FANG Yuwei, ZHANG Wei, CHEN Youyuan, HOU Fan, XU Linfeng, TANG Changhua, LI Rongde

2020, 32(1): 1-14. DOI: 10.3969/j.issn.1004-1524.2020.01.01

Abstract ( 540 )

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To understand state quo of the utilization of high-quality hybrid rice varieties in China, the information of high-quality hybrid rice varieties with promotion area exceeded 6 700 hm² during 2001-2017 were collected and analyzed. The results showed that: (1) The number of high-quality hybrid rice combinations sharply increased from 19 to 214 during the 17 years, and the proportion of their planting area increased from 10% (1 232 000 hm²) in 2001 to 60% (7 062 000 hm²) in 2017; (2) The numbers of high-quality two-line and three-line hybrid rice combinations with annual promotion area exceeded 6 700 hm² were 133 and 382 respectively, with total annual promotion area of 25 659 000 hm² and 53 750 000 hm² , respectively; (3) The quality indexes including the head rice rate, amylose content, gel consistency, chalky grain percentage and chalkiness degree of the main planting varieties were significantly improved; (4) The seed companies were more focused on the high-quality two-line hybrid rice breeding and promotion, while the public breeding institutions had advantage in the high-quality three-line hybrid rice breeding; 5) The photo-thermo-sensitive genic male sterile (PTGMS) lines used large-scale in the high-quality two-line hybrid rice breeding were Y58S, Guangzhan 63S and Guangzhan 63-4S, etc., while the cytoplasmic male sterility (CMS) lines used large-scale in the high-quality three-line hybrid rice breeding were Zhong 9A, Yixiang 1A and Tianfeng A, etc. Yangdao 6, Guanghui 998, Shuhui 527 and Huazhan, etc. were the key restorer lines for high-quality three-line hybrid rice breeding. In addition, problems existed in high-quality rice breeding were analyzed, and countermeasures for the quality improvement were proposed. This study could provide guidance for breeding and promotion of high-quality hybrid rice in future.

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Study on hybrid rice purity of special combining pattern testing with functional marker of wide compatibility gene S5-n

ZHANG Xinyue, LI Youfa, LIU Jiangning, FU Haowei

2020, 32(1): 15-19. DOI: 10.3969/j.issn.1004-1524.2020.01.02

Abstract ( 893 )

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The combining pattern of japonica male sterile line/widely compatible restorer lines has been widely adopted in Zhejiang Province in recent years. Moreover, hybrid rice purity could be quickly tested with the functional marker of wide compatibility S5-n. To verify the effectiveness of functional marker of wide compatibility S5-n for identifying the F₁ hybrid of the combining pattern of japonica male sterile line/widely compatible restorer lines, field statistics and functional marker of wide compatibility S5-n were conducted for the F₁ hybrid of Changjing 1A and six restorer lines. The results showed that the alien plants resulted from pollen contamination could not be specifically tested; hence, the result of functional marker of wide compatibility S5-n was 1.0%-2.0% higher than that of field statistics. Therefore, we suggested that the specificity of functional marker of wide compatibility gene should be further optimized to improve the accuracy of molecular detection, which had important practical significance for the safety production of hybrid rice.

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Genetic analysis of dwarf gene for dwarf mutant“819” in Panicum miliaceum L.

JIA Xiaoping, WANG Zhenshan, ZHU Xuehai, YANG Dezhi, KOU Shujun, LIU Xingxing

2020, 32(1): 20-27. DOI: 10.3969/j.issn.1004-1524.2020.01.03

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In order to uncover the genetic characteristics of dwarf gene from a dwarf mutant “819”, and provide theoretical basis for the subsequent locating of dwarf mutant gene ten traits' including plant height, ear length, neck length, tiller number, stem node number, length of second panicle branch 1, length of second panicle branch 2, length of second panicle branch 3 and so on were investigated for Panicum miliaceum L. crossing parents dwarf mutant “819”, high-stem material J12 and their 674 F₂ individuals, and further variance analysis, cartesian inspection, correlation and regression analysis, principal component analysis were performed for these traits. The results showed that dwarf trait of dwarf mutant “819” was a recessive trait controlled by a single gene. A significantly positive correlation was found between plant height and ear length, tiller number, stem node number, secondary branch length 1, secondary branch length 2, secondary branch length 3, secondary branch distance 1 (P<0.01), and a significant positive correlation was found between plant height and secondary branch spacing 2 (P<0.05). The regression equation of plant height (Y) and other agronomic traits was as follow: Y=-18.446+1.491X₁+1.222X₂+6.827X₄+1.319X₇+0.746X₈, and the fitting degree of which was 0.811. The regression equation reached significant level (P<0.01) and could be used to predict the plant height. Three principal components were obtained by principal component analysis for 10 characters of F₂ population, which accounted for 72.656% of the cumulative contribution rate. These three principal components were named as length factor, stem node number factor and branch spacing factor respectively. The results above provided basis for locating dwarf gene and evaluating, selecting of dwarf offsprings.

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Genome-wide association studies for coat color in Tan sheep

WANG Xiaowei, MA Qing

2020, 32(1): 28-34. DOI: 10.3969/j.issn.1004-1524.2020.01.04

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Tan sheep, not only famous for its delicious meat, but also enjoys high reputation at home and abroad for its one-month lamb's fur. Therefore, the coat color is an important economic trait of Tan sheep. To detect the genomic regions which affecting the coat color of Tan sheep, the genome-wide association studies (GWAS) were performed based on Logistic regression method using genotypes from the America Affymetrix 600K genotyping chips for this trait. Genotyping was performed on 96 representative tan sheep of Yanchi, Ningxia, which had pure white bodies, white bodies with black heads and white bodies with brown or yellow heads. By Bonferroni correction, we have found five SNPs significantly associated with coat color, which were located within or close to 2 known genes (MC1R and TCF25). The MC1R is involved in the regulation of melanin synthesis that has been shown to be related to the color of sheep by numerous studies. The TCF25 is located nearby MC1R, so the identification of TCF25 maybe a result of linkage disequilibrium between these two genes. Our studies explained the genetic mechanism of coat color of Tan sheep, and provided scientific basis for assisted breeding by mark the color traits of Tan sheep.

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Sequence variation and molecular phylogeny of mitochondrial Cyt b gene segments from four Sillago species

YUAN Donghao, YANG Tianyan, MENG Wei, ZHENG Yao, ZHENG Deyu

2020, 32(1): 35-42. DOI: 10.3969/j.issn.1004-1524.2020.01.05

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Mitochondrial DNA cytochrome b gene sequence fragments of four Sillago species (Sillago aeolus, S. asiatica, S. sihama and S. japonica) were sequenced and analyzed to compare the sequence differences, phylogenetic relationships and taxonomic status among them. The results showed that the average nucleotide composition of the four species was T 29.9%, C 29.2%, A 21.5% and G 19.3%, and the average interspecific genetic distance was between 0.157 and 0.280. The maximum likelihood (ML) phylogenetic tree showed that S. japonica and S. asiatica clustered together first, and then clustered with S. sihama and S. aeolus, respectively. S.aeolus was the latest to divergent from other Sillago species. The genetic divergence time of four Sillago fishes based on the nucleotide divergence rate of Cyt b gene sequence was 785-1400 years ago in the Miocene period.

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Isolation and identification of pseudorabies virus and molecular characterization of its main virulence genes in Anhui

YUAN Xianyu, YANG Longbin, HE Zanzan, MAO Tianjiao, HE Changsheng, ZHAN Songhe, SUN Pei, WEI Jianzhong, LI Yu

2020, 32(1): 43-56. DOI: 10.3969/j.issn.1004-1524.2020.01.06

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Porcine pseudorabies (PR) is an acute and hot infectious disease caused by pseudorabies virus (PRV). Since the end of 2011, PRV had been mutated. The traditional attenuated PRV vaccine can not provide complete protection for PRV mutants, which brings great challenges to the prevention and control of PRV in China. To understand the molecular characteristics of major virulence genes of PRV clinical epidemic strains in Anhui Province, PCR,cell-inoculation tests, transmission electron microscopy (TEM), indirect immunoinfluscent assay (IFA) and animal test were used to isolate and identify the pathogen. The major virulence genes (gE, gI, TK, gB, gC and gD) of PRV strains were cloned and sequenced by PCR with 6 pairs of specific primers. A total of 15 PRV strains of clinical cases were isolated and identified from Anhui Province during 2016-2018. The sequences of gE, gI, TK, gB, gC and gD genes of PRV were highly homologous with those of PRV mutants which were prevalent in China after 2011. Compared with the sequence of domestic PRV classical strains before 2011, there are multiple substitutions, insertions or deletions of multiple sites in the gE, gB, gC and gD gene sequences of PRV isolates, and some mutations were located in important epitope regions. The above results indicated that 15 PRV strains isolated from Anhui Province from 2016 to 2018 were all variant strains, which have become the main epidemic strains in Anhui Province. The gene sequences of gI and TK of 15 PRV isolates were relatively conservative, but the mutation of amino acids in the epitopes of gE and gC protein might change their virulence and antigenicity. The homology of PRV sequence between some PRV isolates from neighboring areas was 100%, which may be related to the frequent trans-provincial transfer and trans-regional introduction of pigs.

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Screening of strain for inactivated vaccine of Streptococcus suis type 2

CHEN Zhang, WU Huajian, MAO Tianjiao, HAN Yeqin, SUN Pei, WEI Jianzhong, LI Dongfeng, LI Yu

2020, 32(1): 57-64. DOI: 10.3969/j.issn.1004-1524.2020.01.07

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To screen out the strains of Streptococcus suis type 2 (SS2) vaccine with strong pathogenicity, excellent antigenicity and relatively pure and stable genetic traits. In this study, 6 clinical isolates of SS2 virulent strains, numbered HF1, XC1, HF2, HF3, BZ1, BB1, were used as tested strains. The half lethal dose (LD₅₀) of strain was determined by modified Karber's method, the reactivity was determined by ELISA in detection of antibody titer of New Zealand white rabbit and Kunming mice serum, the immunogenicity was determined by immune challenge test in Kunming mice and zebrafish. At the same time, the tested strains were cultured continuously, the genetic stability of the tenth, twentieth, thirtieth generation of the tested strains were evaluated by the half lethal dose (LD₅₀), serum antibody titer and immune protection rate. The results showed that the LD₅₀ of BB1, BZ1, XC1, HF1, HF2 and HF3 for Kunming mice were 3.72×10⁹, 3.31×10⁸, 1.58×10⁹, 1.00×10⁹, 5.01×10⁸ and 3.24×10⁸ CFU·mL^-1, respectively, the LD₅₀ for zebrafish were 3.31×10³, 0.93×10², 6.03×10³, 3.39×10⁴, 0.62×10² and 2.34×10³ CFU·mL^-1, respectively. ELISA antibody titer determination, immune challenge test showed that the reactivity and immunogenicity of HF2, HF3 and BZ1 were better than those of HF1, XC1 and BB1. The pathogenicity of HF2, HF3, BZ1 decreased at the 10th generation, among which BZ1 still showed a downward trend at the 20th and 30th generations, while HF2 and HF3 tended to be stable. The serum antibody titers of inactivated whole cell HF3 and HF2 decreased from 1∶51 200 at the 10th generation to 1∶12 800 at the 30th generation, while BZ1 decreased from 1∶12 800 to 1∶6 400. The immune protection rates of HF2, HF3 and BZ1 were 100%-80%, 80%-60%, 80%-40% and 66.7%-60%, 80%-60%, 60%-53.3%, respectively. The results showed that HF2 and HF3 had the characteristics of strong virulence, excellent antigenicity and genetic stability which could be used as strains for SS2 seedling production.

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Optimization of CDDP-PCR reaction system in Fortunella japonica

CHEN Yanli, TANG Zhipeng, OU Kewei, LU Yefei, ZHANG Yu

2020, 32(1): 65-71. DOI: 10.3969/j.issn.1004-1524.2020.01.08

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To construct and optimize the CDDP-PCR reaction system of Fortunella japonica and select the ideal primers for the CDDP-PCR analysis of Fortunella japonica, so as to provide reference basis for using CDDP marker technology to assist germplasm identification and molecular breeding, the DNA of Fortunella japonica genome was used as the template, and the orthogonal optimization test design scheme was adopted to design the 5 factor and 4 level test for dNTPs concentration, primer concentration, template DNA dosage, Mg²⁺ concentration and Taq DNA polymerase concentration. Range analysis method, variance analysis method and Duncan multiple comparison method were used to analyze the test results. The results showed that polymorphic bands could be amplified from 21 common primers of CDDP using 5 Fortunella japonica varieties. The optimal reaction system was as follows: DNA dosage 120 ng, Mg²⁺ concentration 1.5 mmol·L^-1, Taq DNA polymerase concentration 0.25 U, primer concentration 1.0 μmol·L^-1, dNTPs concentration 0.15 mmol·L^-1, and the remaining volume was supplemented by ddH₂O to 20 μL. The influences of various factors on the reaction system from the largest to the smallest were dNTPs>primer>template DNA>Mg²⁺>Taq DNA polymerase.

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Evaluation of heat tolerance and response of enzymatic antioxidant system to heat stress in Brassica parachinensis L.

PANG Qiangqiang, ZHOU Man, SUN Xiaodong, ZHANG Wen, CAI Xinglai

2020, 32(1): 72-79. DOI: 10.3969/j.issn.1004-1524.2020.01.09

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In order to identify the heat tolerance of different varieties of Brassica parachinensis L., heat damage index was used as an evaluation index to evaluate the heat tolerance of 19 materials. On this basis, the response of enzymatic antioxidant system to simulated high temperature stress was studied. The results showed that through the analysis of heat damage index, 5 heat-resistant varieties, 11 medium heat-resistant varieties and 3 heat-sensitive varieties were screened out. The heat-resistant variety CX10, medium-heat-resistant variety CX17 and heat-sensitive variety CX13 under high temperature treatment showed that conductivity, MDA contents, activities of SOD, POD and CAT, expression levels of the related genes Mn-SOD, POD and CAT were increased compared with the control. The increase of conductivity and MDA content in heat-resistant varieties was significantly lower than that in heat-sensitive varieties. SOD, POD and CAT activity, as well as the expression of Mn-SOD, POD and CAT genes in the heat-resistant varieties, increased largest. After 3 days' recovery, compared with the treatment under stress, all indicators showed a downward trend, but higher than the control. These results indicated that high temperature stress affected the normal metabolism of enzymatic antioxidant system in Brassica parachinensis L. Even after high temperature was relieved, it could not return to the normal state. However, heat-resistant varieties could alleviate the damage caused by stress by regulating their protective system.

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Growth dynamic and nutrient uptake law of common bean cultivar Liyun 2

MA Ruifang, MA Jinchuan, MA Junwei, ZHOU Dayun, WANG Qiang, DING Chaohong

2020, 32(1): 80-85. DOI: 10.3969/j.issn.1004-1524.2020.01.10

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Growth dynamic and nutrient uptake of common bean (Phaseolus vulgaris L.) cultivar Liyun 2 were studied in this research to clarify the nutrient uptake over the growth period so as to provide a basis for more scientific nutrient management. Field experiments were carried out in Lishui City, Zhejiang Province in 2016. The agronomic management measures in the production of common beans were consistent with local farmers' practice. In seedling stage, stretch tendril stage, flowering stage, pod setting stage and harvest stage, plant samples were taken to determine and analyze the dry material accumulation and nutrient element content. Results indicated that the dry material accumulation of common bean showed an increasing trend over the growth period, and the harvest stage had the largest accumulation of dry material, 2 304.6 kg·hm^-2. The nutrient demands of common bean in different growth stages were showed as follows: harvest stage>pod setting stage>stretch tendril stage>seedling stage and flowering stage. During the common beans production, the nutrient uptake ratio for N, P, K was 1.0∶0.4∶1.0, and nearly 79.0% of all N, P, K uptake were redistributed to economic yield, respectively. The nutrient requirement for N, P and K at the yield level of 30 000 kg·hm^-2 were N 155-181 kg·hm^-2, P₂O₅ 82-103 kg·hm^-2, K₂O 136-156 kg·hm^-2, which were evaluated according to the yield level, nutrient concentration and N/P/K use efficiency. This study can provide a basis for the nutrient management in common bean production and the control of environmental risk caused by fertilizer over application.

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Study on chromosome technique of Calendula officinalis and its karyotype

LONG Haimei, ZHANG Nanqing, LI Zongyan, WANG Qin, FU Chao

2020, 32(1): 86-92. DOI: 10.3969/j.issn.1004-1524.2020.01.11

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In order to explore the optimal chromosome technique of Calendula officinalis, its root tips were used to investigate the effects of sampling time, root length, pretreatment methods and different reagent. The results indicated that Calendula officinalis could maintain vigorous mitotic-activity with more cells at mitotic metaphase if the roots were sampled from 8:30 am to 9:30 am when they had 1.0-1.5 cm length. It was better for Calendula officinalis to be treated with saturated solution of p-dichlorobenzene for 6 h at 6 ℃. It showed that the autosomes number of Calendula officinalis was 28 consisting of median region and submedian region types of chromosomes. Moreover, the percentage of all chromosome' relative length varied from 5.93% to 8.46%. The mean indice of relative length ranged from 0.83 to 1.18. Maximum value of arm ratio was 2.34. Besides standard chromosomes, there were bar-like or point-like B-chromosomes in its somatic cells and its number varied from 11 to 18. The analysis showed that the karyotype formula was 2n=18m+10sm and its karyotype belonged to 2B based on Stebbins classification system.

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Cloning and expression of the PpFBD1 involved in primordium formation of Pleurotus pulmonarius

WANG Weike, SONG Jiling, LU Na, YUAN Weidong, YAN Jing, CHEN Guanping

2020, 32(1): 93-97. DOI: 10.3969/j.issn.1004-1524.2020.01.12

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Through transcriptome sequencing and differential expression gene analysis of Pleurotus pulmonarius samples at different developmental stages induced by low temperature in the previous study, it was found that the gene with ID Cluster-6377.64510 (named as PpFBD1) was highly expressed at the prophase of primordium formation. To further understand and analyze its expression characteristics and functions, the full-length cDNA sequences of PpFBD1 was cloned from Pleurotus pulmonarius by RT-PCR method with the specific primers designed based on transcriptome data. The PpFBD1 was composed of 342 nucleotides that encode a protein consisted of 113 amino acids. The relative molecular weight of this protein is about 11 ku. Phylogenetic tree analysis showed that the protein encoded by PpFBD1 had the closest relationship with hydrophobin1 of Pleurotus ostreatus. GO functional analysis showed that the PpFBD1 mainly involved in the synthesis of fungal cell walls. Fluorescence quantitative RT-PCR detection found that the expression of the gene was the highest in the phase of mycelium recovery to room temperature after induction at low temperature. It suggested that the gene may be involved in the regulation of primordium morphogenesis in Pleurotus pulmonarius. The results of this study provided a reference for elucidating the formation mechanism of the primordium of Pleurotus pulmonarius.

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Efficiency of soil solarization on control of Chinese cabbage clubroot

SHEN Lu, LI Qinchao, TAKASHI Tanaka, TATSUYA Inamura, IRBIS Chagan

2020, 32(1): 98-107. DOI: 10.3969/j.issn.1004-1524.2020.01.13

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In order to investigate the effect of solar heat treatment on the Chinese cabbage clubroot disease, the variety of Chaojixiaohuangbai was used as the test material to determine the physical and chemical properties of the soil before and after solar heat treatment, the number of dormant spores, the microbial diversity and the incidence of disease and disease index of the roots. The results showed that the pH of the soil increased from 4.96 to 5.60 at 0-10 cm after heat treatment in the sun, and the concentration of dormant spores in the dry soil decreased from 1.09×10⁶ g^-1 to 5.74×10⁵ g^-1. The results of denaturing gradient gel electrophoresis (DGGE) showed that the solar heat treatment increased the bacterial microbial diversity of the soil. The Shannon-Wiener index of soil microbial community at 0-10cm and 10-20 cm increased from 1.51 and 0.91 to 1.98 and 1.53, respectively. The incidence of clubroot disease was reduced from 87.10% to 49.12%, and the disease index was reduced from 45.24 to 16.96. This study provided a theoretical basis for the application of solar heat treatment in actual agricultural production and the prevention of clubroot disease.

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Geometric morphometric analysis of wing shape variation and phylogenetic relationships among six subgenera of genus Culicoides (Diptera: Ceratopogonidae)

NING Yuan, DUAN Chen, CHANG Qiongqiong, HOU Xiaohui

2020, 32(1): 108-114. DOI: 10.3969/j.issn.1004-1524.2020.01.14

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In order to identify and analysis phylogenetic relationships of the subgenus Culicoides, wing shapes were compared and analyzed by using geometric morphology method. Various geometric methods were used to analyze wing shape variation of 20 species from six subgenus Culicoides, including landmarks, centroid size, procrustes superimposition, principal component analysis, canonical variate analysis and cluster analysis. Kruskal-Wallis of centroid size results showed as follow: Avaritia>Trithecoides>Beltranmyia>Culicoides>Monoculicodie>Oecacta, but there was no significant difference, indicating the size of wings could not be used as the basis for distinguishing subgenus. Principal component analysis showed that principal component 1 (73.648%) and principal component 2 (12.372%) accounted for 86.020% of the total variation, which could explain the main difference between the wings of the six subgenera. The grid diagram showed that the differences were mainly concentrated in radial-median crossvein, basal portion, first radial cell, second radial cell and fourth medial cell. Canonical variate analysis results showed that there were significant differences in the wing shape (P<0.05), the most significant difference in the wing shape between the subgenus Monoculicodie and Trithecoides, and the smallest difference between the subgenus Beltranmyia and Oecacta. Therefore we could accurately identify the species of the different subgenus by the variation of wing shape. Cluster analysis showed that the genetic relationship between the subgenus Beltranmyia and Oecacta were the closest, between the subgenus Trithecoides and Culicoides were the second, between the subgenus Monoculicodie and Trithecoides were the farthest. This result was consistent with that of canonical correlation analysis. Geometric morphology was a useful assistant tool to study the relationship and taxonomy within the genus Culicoides.

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Impact of intercropping and arbuscular mycorrhizal fungi on soil fertility and corn yield in a newly cultivated mountain land

TAO Jing, WU Qifeng, SHI Jiang, LI Songhao, GE Jiangfei, CHEN Junhui, XU Qiufang, LIANG Chenfei, QIN Hua

2020, 32(1): 115-123. DOI: 10.3969/j.issn.1004-1524.2020.01.15

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In the present study, a field experiment was conducted to investigate the effect of arbuscular mycorrhizal fungi (AMF) and planting pattern on soil nutrients and corn yield. Corn (Zea mays L.), sweet potato (Ipomoea batatas Lam.) and soybean (Glycine max Merr.) were used as test plants, and Acaulospora laevis 90034 was used as the test fungal species. The experiment was set with split block design, with the main factor of AMF inoculation and interactive factor of planting pattern, such as corn monoculture (C), intercropping of corn-sweet potato (C-P) and corn-soybean (C-S) system. The results showed that intercropping significantly (P<0.05) increased the yield of corn than that of corn monoculutre, but AMF inoculation had no significant impact on it. The soil pH and available nitrogen increased significantly (P<0.05) in C by AMF inoculation. Compared with the treatments without AMF inoculation,the percentage of macroaggregates (>2 mm) was significantly (P<0.05) higher in C by AMF inoculation. AMF significantly (P<0.05) increased soil protease, acetyl glucosaminidase activities in C, and urease, cellobiohydrolase activities in C-P, but decreased β-glucosidase, phosphatase activities in C-S system. Redundancy analysis showed that soil organic matter and available nitrogen contents had significant (P<0.01) impact on soil enzyme activities. In conclusion, C-P intercropping system with AMF inoculation could improve corn yield, and increase soil available phosphorus content, as well as soil enzyme activities, thus had great potential in improving soil fertility of newly cultivated mountain land.

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Effects of different bulking agents on compost of straw biogas residue

BAI Ling, SONG Feiyue, JI Mengmeng, DENG Yun, RUAN Wenquan

2020, 32(1): 124-133. DOI: 10.3969/j.issn.1004-1524.2020.01.16

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In order to understand the effects of different bulking agents on straw biogas residue composting, straw biogas residue was used as raw material, and seven bulking agents of sawdust, peanut straw, corn straw, wheat straw, soybean straw, reed straw and rice straw were introduced and mixed homogeneously with straw biogas residue at the ratio of 1∶5 (wet weight) in this experiment with 30 days of aerobic composting, respectively. The physical, chemical and biological characteristics were studied during the composting. Results indicated that all the test bulking agents could be used as the bulking agent for straw biogas residue composting, which could promote the piles produce a great deal of heat rapidly, make compost products harmless and sanitary. The thermophilic phase (≥55 ℃) duration of treatments with straws as bulking agent was longer than the that of the treatment with sawdust as bulking agent. The electrical conductivity (EC) was the lowest in the treatment with sawdust as bulking agent. The highest temperature reached 68 ℃ when soybean straw was used as the bulking agent. Under this treatment, the polyphenol oxidase activity was more active and helpful to promote the formation of humus. Rice straw could decrease pH, enhance nitrate nitrogen (NO3--N) content and cellulase activity, and promote the degradation of cellulose during straw biogas residue composting. The germination index reached 137.06% and 138.26% in treatment with soybean straw or rice straw as the bulking agent, respectively, which indicated that soybean and rice straw could promote root growth of seeds, and improve the quality of compost products.

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Study on hydrolysis characteristics of asparagus old stem in non-closed system

XU Suyun, CUI Minghao, YAN Yan, LI Qinfeng, WANG Yulei

2020, 32(1): 134-140. DOI: 10.3969/j.issn.1004-1524.2020.01.17

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The non-closed system can provide a facultative environment for the microbial hydrolysis of organic solid waste, and can effectively improve the hydrolysis efficiency of cellulose. In the present study, the feasibility of hydrolyzing asparagus old stem in a non-closed system was explored, and the effects of inoculum and aeration on the hydrolysis process and the formation of humic substances were explored. The results showed that the inoculation of cellulose bacteria accelerated the decomposition of old stems of asparagus. When the inoculation ratio was 0.3%, the maximum decomposition rates of total solids and cellulose from asparagus old stem were 75.43% and 51.03%, respectively. Infrared spectroscopy and three-dimensional fluorescence spectroscopy were used to reveal the evolution characteristics of cellulose and humic substances during hydrolysis. The humification index (HIX) and fluorescence index (FI) showed that inoculation and aeration could improve the hydrolysis and the degree of humification. The HIX of the hydrolysate was positively correlated with the germination index (GI), and the highest GI of the hydrolysate was 93.2% after 12 days. It showed that this non-closed facultative hydrolysis process could be applied independently to realize the reduction of vegetable straw.

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Effect of montmorillonite addition on aerobic composting and heavy metals passivation of pig manure

HUANG Jian, XIAO Jianzhong, TANG Shigang, ZHENG Qiang, DING Fenghua, ZHANG Dongxu

2020, 32(1): 141-148. DOI: 10.3969/j.issn.1004-1524.2020.01.18

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To further improve the composting process, montmorillonite was added during pig manure composting with straw. The temperature, pH values, electrical conductivity (EC) values, germination index (GI) and metal phases were determined to illustrate the effects of montmorillonite addition on the maturity of pig manure compost and the passivation effect of Cu and Zn. The results indicated that the addition of montmorillonite could increase the aerobic composting temperature of pig manure and prolong the high temperature period, effectively promote compost maturity and improve compost quality. The seed germination index could reach 92% when the montmorillonite addition amount was 5% of the dry weight of pig manure. Adding proper amount of montmorillonite could improve the passivation effect of heavy metals. The passivation rate of exchangeable Cu and Zn could reach 23.7% and 17.2%, respectively, when the addition amount was 5% of the dry weight of pig manure.

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Effect of selenium on spectral characteristics of chromium interaction with bovine serum albumin

LIU Kang, HU Chengxiao, CAI Miaomiao, GAO Lin, ZHANG Mengjiao, BA Lei, YANG Dandan, WANG Xu, ZHAO Xiaohu

2020, 32(1): 149-159. DOI: 10.3969/j.issn.1004-1524.2020.01.19

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In order to determine whether Se(Ⅳ) affects the Cr(Ⅵ)-protein (bovine serum albumin, BSA) interaction system, and reduces the toxic effect of Cr(Ⅵ) on proteins, ultraviolet and fluorescence spectra were used to study the effect of Se(Ⅳ) on Cr(Ⅵ)-BSA interaction spectral characteristics, including binding characteristics, forces type, binding sites, etc. The results indicated that the addition of Cr(Ⅵ) increased the intensity of ultraviolet absorption peak of BSA, accompanied by red-shift and changes of spatial conformation. It could be deduced that there were some changes in the BSA conformation when Cr(Ⅵ) was bound to BSA. In addition, Se(Ⅳ) had no significant effect on the conformation and spectral characteristics of BSA. Cr(Ⅵ) resulted in fluorescence quenching of BSA, which was caused by the generation of substrates (1∶1) with no fluorescence. The binding constant of Cr(Ⅵ)-BSA was 4.568 8×10³ L·mol^-1 (298 K) and the quenching method belonged to static quenching. The thermodynamic parameters including enthalpy change (△H=-53.528 kJ·mol^-1), entropy change (△S=-0.110 kJ·mol^-1·K^-1) and Gibb's free energy (△G<0) were calculated using Van't Hoff equation. These negative values showed that hydrogen binding and van der Waals forces were the main interaction forces in the binding of Cr(Ⅵ) to BSA and the stabilization of the complex. Moreover, the interaction of Cr(Ⅵ) and BSA was spontaneous. Further studies revealed that the binding distance of BSA-Cr (Ⅵ) was 0.14 nm and the binding site was site II. The addition of Se(Ⅳ) had no significant effect on the conformation and spectral characteristics of BSA in BSA-Cr(Ⅵ) interaction system.

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Improvement of emulsifying properties of skipjack tuna protein by enzymatic hydrolysis

ZHANG Jilei, ZHOU Huan, ZENG Xiaohong, CAI Yanping, DING Yuting, LIU Shulai

2020, 32(1): 160-167. DOI: 10.3969/j.issn.1004-1524.2020.01.20

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Owing to the poor emulsifying properties, natural fish protein could not meet the needs of actual production. The protein could be modified by enzymatic hydrolysis to improve its emulsifying properties, meet production needs and broaden its application range. Effects of different enzymes (trypsin, flavourzyme and papain) and hydrolysis time on the preparation of protein hydrolysate and emulsifying properties of fish protein were compared to optimize the process parameters of enzymatic hydrolysis. After freeze-drying of the enzymatic hydrolysate, the differences in functional properties such as solubility, emulsification and foaming properties of fish protein before and after enzymatic hydrolysis were analyzed. The results showed that when the amount of trypsin was 2 000 U·g^-1, hydrolyzed for 10 min, the degree of hydrolysis (DH) of fish protein reached 8.2%, the emulsifying properties of modified fish protein were the best. Compared with the sample before enzymolysis, the emulsification activity and emulsification stability of modified fish protein after enzymatic hydrolysis were significantly improved, and its solubility, foamability and foam stability were improved to a certain extent. The skipjack tuna protein hydrolysate having better functional properties in a broad pH range will had braod application in food industry.

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International comparative analysis of current pesticide residues standards in tea and responding suggestion

YANG Mei, LUO Fengjian, ZHOU Li, LOU Zhengyun, ZHANG Xinzhong, SUN Hezhi, WANG Xinru, CHEN Zongmao

2020, 32(1): 168-175. DOI: 10.3969/j.issn.1004-1524.2020.01.21

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In order to master the current international standards for pesticide residues in tea, and further improve the quality and safety of tea in China, the pesticide maximum residue limits (MRLs) standards regarding tea all over the world were collected and sorted out. The present paper introduced the current MRLs standards and the situation of banned pesticides in tea of China, Codex Alimentarius Commission (CAC), the European Union, the United States, Japan, Korea, India, Morocco and other countries or international organizations. Comparative analysis results revealed that MRLs standards regarding tea in China were insufficient conformity with the international standards, and the standards system for analytical method of pesticide residues in tea should be improved. Also, some measures and suggestions about clean production of tea, developing and revising standards were put forward.

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Research progress of microRNA in rabbits

SHAO Jiahao, WANG Jie, JIA Xianbo, CHEN Shiyi, LAI Songjia

2020, 32(1): 176-182. DOI: 10.3969/j.issn.1004-1524.2020.01.22

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microRNA(miRNA), a class of endogenous non-coding single-stranded RNA molecules, plays an important role in gene regulation in animals by pairing with target gene mRNA to guide their functional expression. Studies had shown that miRNA was widely involved in the regulation of animal growth and development, reproductive regulation, metabolism, disease occurrence and other life processes. This review summarized the studies on miRNA in rabbits in recent years, such as promoting the proliferation and differentiation of muscle cells, regulating fat metabolism and affecting the occurrence of diseases, and explored the research status and development direction of miRNA in rabbits, in order to provide theoretical basis for the breeding and reproduction of rabbits.

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