Acta Agriculturae Zhejiangensis

Nutritional components and bioactivities of sweet potatoes with different flesh colors

XIE Ziyu, WANG Ke’er, ZHAO Wenliang, WEN Zuhui, CHEN Linrun, XU Lishan

2021, 33(2): 183-192. DOI: 10.3969/j.issn.1004-1524.2021.02.01

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In order to define the difference and correlation of nutritional components and bioactivities of sweet potatoes with different cultivars, the content of nutritional components (dry matter, reducing sugar, soluble sugar, starch, soluble protein, carotenoids, anthocyanin and polyphenols) and bioactivities [DPPH· scavenging activity, trypsin-inhibitory activity and polyphenol oxidase (PPO) activity] of sweet potatoes cultivars with different flesh colors (purple, orange, yellow and white) in Zhejiang Province were analyzed by using difference significance analysis, correlation analysis, factor analysis and cluster analysis. The results showed that there were significantly differences in the content of nutritional components in 12 cultivars (P＜0.05). The PPO activity of purple flesh cultivars was significantly higher than those of other flesh color cultivars, and showed obvious advantages in DPPH· scavenging activity and trypsin-inhibitory activity. The results of correlation analysis showed that there was an extremely significantly positive correlation between DPPH· scavenging activity and content of soluble protein, anthocyanin and polyphenols. Except for the content of reducing sugar and soluble sugar, trypsin-inhibitory activity and PPO activity were significantly correlated with the other nutritional components. The cluster analysis divided 12 cultivars of sweet potato into four categories, and the results were consistent with the distribution of each cultivar on the scatter diagram of factor score. The results could provide reference for postpartum utilization and breeding of sweet potato.

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Effects of sowing date and density on population structure and lodging resistance of winter wheat under drip irrigation

WANG Tangang, SUN Ting, WANG Jichuan, LI Huiqin, GAO Zhen, SHI Yuanqiang

2021, 33(2): 193-202. DOI: 10.3969/j.issn.1004-1524.2021.02.02

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To study the effects of different sowing dates and sowing densities on population dynamics and lodging resistance of winter wheat under drip irrigation, Xindong 22 (less-spike type) and Handan 5316 (multi-spike type) were used as the test materials, the field test design of the split area was adopted, and the main area had three sowing dates: September 23 (B1), October 4 (B2) and October 15 (B3); the sub-area had four seeding densities: 3.15×10⁶·hm^-2 (M1), 5.10×10⁶ hm^-2 (M2), 7.05×10⁶ g hm^-2 (M3) and 9.00×10⁶ hm^-2 (M4). The results showed that: (1) The growth period of winter wheat under drip irrigation was shortened with the delay of sowing date. Under B3 sowing date, the growth period of Xindong 22 and Handan 5316 were 11 d shorter than B2 and 22 d shorter than B1. Density had little effect on the growth process. (2) The population size and leaf area index (LAI) increased with the increase of density and decreased with the delay of sowing date. Late sowing population tended to catch up with the normal sowing date at the later stage of growth; Population size and leaf area dynamics of B2 treated under the same density and M2 or M3 treatments in the same sowing date were the smallest with the growth process, showing better leaf regulation function. (3) With the increase of density, basal internode and barycenter height increased, basal diameter, mechanical strength and lodging resistance index decreased; With the delay of sowing date, basal internode became shorter, center of gravity height decreased, diameter increased, mechanical strength and lodging resistance index increased. Effect of density on stem character was greater than that of sowing date. In the actual production, the interaction effect of density and sowing date should be brought into full play, and the density of late sowing treatment should be appropriately increased to optimize individual growth and ensure the formation of high yield. (4) The average yield of B2 treatment was 8.09%-17.52% and 16.01%-21.07% higher than that of B1 and B3. The yields of B2M3 treatment of Xindong22 and B2M2 treatment of Handan 5316 were the highest, reaching 8 541.04 kg·hm^-2 and 9 218.08 kg·hm^-2, respectively. (5) From the perspective of population growth, Xindong22 was more sensitive to density, Handan 5316 was more sensitive to sowing date. In production, large panicle varieties should pay attention to the adjustment of sowing date under the premise of reasonable density, while multi spike varieties should pay attention to the adjustment of sowing amount under the premise of appropriate sowing date, so as to give full play to the potential of yield increase of wheat varieties.

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Grain starch quality characteristics of Yunnan soft rice landraces

CHEN Dan, TANG Cuifeng, DONG Chao, GAN Shuxian, LI Jun, A Xinxiang, ZHANG Feifei, YANG Yayun, NIU Saisai, DAI Luyuan

2021, 33(2): 203-214. DOI: 10.3969/j.issn.1004-1524.2021.02.03

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Soft rice is a unique, high-quality rice germplasm resource with a long history of cultivation in Yunnan Province, China. It is important to study the grain starch quality characteristics for elucidating the mechanism of high-quality rice and improving rice taste. In this study, 36 Yunnan soft rice landraces and control materials including high-amylose content (high-AC) rice varieties, glutinous rice varieties, Yunnan soft rice cultivars and other cultivars were planted and harvested in different environments. The apparent amylase content (AC), gel consistency (GC), gelatinization temperature (GT), and rapid visco analyzer (RVA) profile characteristics were determined and analyzed using correlation and variance analysis. The main starch quality characteristics of the 36 Yunnan soft rice landraces were that the AC and GC were in the middle; the GT was the highest, but there were no significant differences with the control groups (P>0.05); in the RVA profile, the peak viscosity (Peak-1) and breakdown value (Breakdown) were more higher, the hot paste viscosity (Trough-1), final viscosity (Final-Visc), and setback value (Setback), peak time (Peak-Time) and pasting temperature (Pasting-Temp) were basically between high-AC and glutinous rice varieties. Variance analysis indicated significant differences in Trough-1, FinalVisc, and Setback of RVA profile between the Yunnan soft rice varieties (general term for Yunnan soft rice landraces and Yunnan soft rice cultivars) and high-AC rice varieties, glutinous rice varieties, and other cultivars. Correlation analysis showed that there were significant correlation between AC and the RVA in Yunnan soft rice varieties (P<0.05), especially landraces. In addition, the starch quality of the Yunnan soft rice landraces were most affected by the environment compared with those of the control groups. In all 10 traits, except GT, 9 traits had showed significant differences between different environments (P<0.05). The starch quality of the Yunnan soft rice landraces were found to be related to their original sites: significant differences of starch quality were found between landraces from the paddy and upland rice planting region in the south margin and the single or double-season indica rice planting region in southern Yunnan. In summary, it is concluded that AC can be used as a basic index, Trough-1, FinalVisc, and Setback of RVA profiles should also be considered as auxiliary indexes for describing the main starch quality characteristics of Yunnan soft rice varieties. Moreover, it should also be noted that the starch quality of Yunnan soft rice landraces is strongly influenced by environmental factors. It is difficult to breed wide adaptable soft rice varieties.

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Establishment and preliminary application of fluorescence quantitative PCR method for duck NF-κB1 gene

ZHANG Piao, HE Xinwei, YANG Xia, ZENG Maoqin, LIU Yanhan, ZHANG Yangzi, YANG Ying, WEN Guilan, CHENG Zhentao, WEN Ming

2021, 33(2): 215-222. DOI: 10.3969/j.issn.1004-1524.2021.02.04

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In order to establish a fluorescent quantitative PCR method for the detection of nuclear factor-kappa B (NF-κB) gene in ducks, the expression of NF-κB 1 gene in duck embryo fibroblasts (DEF) was detected with the method established in this study. Based on the conserved sequence of NF-κB1 gene in GenBank, a specific primer was designed, and the reverse transcription of NF-κB 1 mRNA from duck embryo fibroblast was used to construct the NF-κB 1 gene cloning plasmid, the qPCR assay was used to detect NF-κB1 gene in ducks, and the specific, repeatable and sensitive tests were carried out. The transcription changes of NF-κB1 gene with time after DEV infection were detected by the established method. The results showed that the standard curve of NF-κB1 gene was typical s-type, the equation was y=-3.12x+44.086(R²=1), the amplification efficiency was 109.2%, the Tm value of the fusion temperature was (83.5±0) ℃, and the curve showed specific single peak, the intra- and inter-assay coefficients of variation were less than 0.3% and 0.2%, respectively, and the detection sensitivity was 1.79 copies. The transcription level of NF-κB 1 gene in DEF cells was not regular with time after being infected with DEV, but the expression level of NF-κB 1 gene in DEF cells was higher than that in normal cells (P<0.05), 36-84 h NF-κB1 gene transcription level was significantly different from that in normal cells (P<0.01). In this study, a fluorescent quantitative PCR method for the detection of duck NF-κB1 gene was successfully established, and the transcription level of NF-κB1 gene in DEV infected DEF cells was studied.

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Function of porcine non-coding RNA lnc-000649 during PRRSV infection

WU Junjing, QIAO Mu, ZHOU Jiawei, MEI Shuqi, PENG Xianwen

2021, 33(2): 223-229. DOI: 10.3969/j.issn.1004-1524.2021.02.05

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Long noncoding RNA (lncRNA) plays a role in immunity and the host response to viral infection. In this study, a novel porcine lncRNA lnc-000649, with a total length of 1 483 bp, was found in porcine alveolar macrophage (PAM) cells. The expression level of lnc-000649 in PAM cells before and after PRRSV infection was detected by quantitative PCR, and it was found that the expression of lnc-000649 was significantly (P<0.01) down-regulated after PRRSV infection. In order to further study the function of this lncRNA, lnc-000649 overexpression vector lnc-000649-pcDNA3.1 was constructed and transfected into PAM cells. After PRRSV inoculation, the results showed that PRRSV RNA level in PAM cells which transfected with lnc-000649-pcdna3.1 was significantly (P<0.01) lower than that in transfected pcDNA3.1(+) and non-transfected group. It indicated that lnc-000649 could inhibit the proliferation of PRRSV. However, its specific mechanism remains to be further studied.

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Pathogenicity of Acinetobacter pittii from beef cattle in mice

FAN Lihong, GUO Hongrui, WU Jiang, YI Jun, MA Xiaoping, GOU Liping, XIE Yue, YE Gang, ZUO Zhicai

2021, 33(2): 230-238. DOI: 10.3969/j.issn.1004-1524.2021.02.06

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In order to explore the pathogenicity of two strains of Acinetobacter pittii from bovine respiratory disease complex (BRDC) infected beef cattle to mice, the related virulence genes were detected and the pathogenicity test of mice was carried out, which mainly included clinical symptom observation, pathological examination, histopathological observation, and determination of median lethal dosage (LD₅₀) and bacterial load in various organs. The results showed that ZZCNC1807-6 and ZZCSF1807-9 stains were highly lethal to mice, and their LD₅₀ reached 4.487×10⁷ CFU·mL^-1 and 3.177×10⁸ CFU·mL^-1, respectively. After pathology autopsy, it was seen that Acinetobacter pittii mainly caused subcutaneously hyperemia, lung congestion and swelling, intestinal pneumatosis and effusion and other symptoms in mice. And it could cause infection of many organs, such as heart, liver, spleen, lung, kidney and brain. Histopathological observation showed that the pathological changes of various organs in mice were mild, mainly manifested in a small amount of inflammatory cells infiltration in liver and lung, and necrosis and fibrous hyperplasia of white pulp cells in spleen. Among them, the pathological changes of mice in ZZCNC1807-6 group were more serious than those in ZZCSF1807-9 group. The analysis of bacterial load showed that the invasiveness of the two strains to the liver, heart, spleen, lung and kidney of mice had little difference, but ZZCNC1807-6 strain had stronger invasiveness to the brain than ZZCSF1807-9. To sum up, the virulence of strain ZZCNC1807-6 was stronger than that of ZZCSF1807-9.

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Isolation, culture and identification of pigeon intestine epithelium cells

LIU Lei1, WANG Xun, LUO Yi, LIANG Jiyuan, YAN Peiqi, LI Xinyi, LIU Wei, LIU Chenkai, LI Jiajia

2021, 33(2): 239-247. DOI: 10.3969/j.issn.1004-1524.2021.02.07

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To establish a set of method to isolate, culture and identify pigeon intestine epithelium cells, and provide a primary cell model to research the mechanism of nutrient transportation and absorption, cell proliferation and metabolism in vitro, pigeon intestine epithelium cells were isolated by collagenase digestion and tissue explants adherent method. Isolated pigeon intestine epithelium cells were identified by immunofluorescence analysis and PCR analysis. The results showed that pigeon intestine epithelium cells were successfully isolated by using collagenase digestion and tissue explants adherent method. The isolated cells were arranged in the shape of paving stones. Cytokeratin 8 immunofluorescence staining was positive, and both CLDN-3 and CLDN-4 gene of tight junction proteins were expressed. The cell growth curve was S shape. In summary, we successfully established a set of method to isolate, culture and identify pigeon intestine epithelium cells, and provided a cell model for the further research on intestinal nutrition of pigeon squabs.

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Effects of different storage temperature on quality and lignin accumulation in postharvest oyster mushrooms

LI Tianzhu, SUN Yuwen, WANG Jitao, GAN Defang, HU Keling

2021, 33(2): 248-258. DOI: 10.3969/j.issn.1004-1524.2021.02.08

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Fresh oyster mushrooms were stored in natural open polyethylene (PE) fresh bag in a biological refrigerator at 1 ℃ and 5 ℃ to investigate the changes of firmness, weight loss, malondialdehyde (MDA) content, antioxidant enzyme activity, nutrient content and lignin synthesis related enzyme activity. The results showed that the weight loss, MDA content, soluble sugar and total phenol were better inhibited by 1 ℃ treatment, maintain higher firmness, soluble protein, cellulose and lignin content. The activities of peroxidase (POD), phenylalanine ammonia-lyase (PAL), cinnamyl alcohol dehydrogenase (CAD), and catalase (CAT) in the early stage of storage were improved. In summary, the storage quality of oyster mushrooms was better maintained at low temperature, the biosynthesis and accumulation of lignin were promoted, and the quality of oyster mushrooms stored at 1℃ was better.

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Plasticity of a karst endemic plant Juglans regia L. f. luodianense Liu et Xu in response to soil moisture

CHENG Jing, LIU Jiming, WANG Shu, WANG Deng, LI Lixia, XU Guorui, CHEN Meng, HUANG Luting

2021, 33(2): 259-269. DOI: 10.3969/j.issn.1004-1524.2021.02.09

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To understand the adaptability and the plasticity difference of Karst endemic plants to different water conditions, taking 1-year-old Juglans regia L. f. luodianense Liu et Xu as the study material, the differences in plasticity of morphological, biomass allocation, physiological characteristics of seedlings of J. regia L. f. luodianense Liu et Xu were discussed under different water conditions [(100±5)%, (80±5)%, (60±5)%, (40±5)%]. The results showed that, compared with CK group, the response of J. regia L. f. luodianense Liu et Xu under high and low water stress was as follows: seedling height, ground diameter growth, root length, leaf area and specific leaf area all decreased; fleshy degree of leaves significantly decreased, and compactness of leaf tissue structure increased under moderate low water stress (40±5)%. Distribution of plant stem and leaf resources decreased, the root resource input and the root-cap ratio increased under moderate low water stress, and total biomass decreased. Net photosynthetic rate (P_n) and transpiration rate (T_r) were all reduced, stomatal conductance (G_s) was slightly increased at mild high water level (100±5)%, and intercellular CO₂ concentration (C_i) was basically stable. The content of chlorophyll b and total amount of chlorophyll only increased under mild high water stress. Based on the plasticity indexes (ranging from 0.02 to 0.50) of seedlings of J. regia L. f.luodianense Liu et Xu under different water conditions, the net photosynthetic rate was up to 0.50, followed by leaf area and stem biomass, and chlorophyll a had a minimum plasticity of 0.02. There were significant differences in the sensitivity and regulatory mechanism to the plastic responses of different water conditions of seedlings of J. regia L. f. luodianense Liu et Xu, which were regulated by leaf area, stem biomass, and net photosynthetic rate. Under normal water supply (80±5)% and mild high water stress (100±5)%, the water demand for the growth of seedlings of J. regia L. f.luodianense Liu et Xu could be satisfied.

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Effects of root pruning on growth and expression of related genes in Poncirus trifoliata

HUANG Yongming, SONG Fang, WANG Ce, YAO Jinglei, WANG Zhijing, HE Ligang, WU Liming, JIANG Yingchun

2021, 33(2): 270-277. DOI: 10.3969/j.issn.1004-1524.2021.02.10

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In this study, Poncirus trifoliata seedlings were chosen as the test materials. The effects of four different root pruning levels (no cutting, cutting off 1/3 taproot, cutting off 1/2 taproot and cutting off 2/3 taproot) on the plant growth, root architecture system and nutrient contents of Poncirus trifoliata seedlings were investigated by a repeated experiment for two years, and the expression of key genes involved in the lateral roots development was analyzed under root pruning treatments. The results showed that cutting off 1/2 taproot treatment enhanced the height, stem diameter, shoot and root fresh weights, and improved the root system architecture parameters (the number of lateral roots, the total root length, the root surface area and average length), and also increased the contents of K, P, Ca, B, Fe, Na and Zn in roots of Poncirus trifoliata seedlings. In addition, quantitative real-time PCR (qRT-PCR) revealed that the expression levels of lateral root development related genes HOX1 and CYP2 were induced, but IAA11 and IAA13 were reduced under root pruning treatments. Overall, the moderate root pruning might regulate the development of lateral roots and improve the root architecture through up-regulating of HOX1 and CYP2 genes, and down-regulating of IAA11 and IAA13 genes, thus leading to the improvement of nutrient absorption and growth of Poncirus trifoliata seedlings.

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Effects of different culture medium composition on pollen germination and pollen tube growth of 5 strains of Chimonanthus praecox

SHEN Zhiguo, SUN Meng, DING Xin, CHENG Jianming, CHEN Dixin

2021, 33(2): 278-287. DOI: 10.3969/j.issn.1004-1524.2021.02.11

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Five strains of Chimonanthus praecox fresh pollens collected from Xuchang City, Henan Province were used as materials to test and screen the best culture medium for pollen germination of C. praecox. Effects of different culture medium composition on pollen germination and pollen tube growth of C. praecox were investigated with in-vitro culture method. The results showed that PEG-4000 was the key factor for pollen in-vitro germination and its tube growth of C. praecox, and the pollen failed to germinate when there was no PEG-4000 in the medium. On the contrary, sucrose was unnecessary factor for pollen in-vitro germination and high concentration sucrose inhibited pollen germination; While boric acid and calcium nitrate could promote pollen germination effectively, which played an auxiliary role in pollen germination. The optimum medium formulation for C. praecox var. concolor and C. praecox var. patens was 250 g·L^-1 PEG-4000+10 mg·L^-1 Ca (NO₃)₂·4H₂O+20 mg·L^-1 H₃BO₃, the pollen germination rates of Yusu No.1, Yusu No.2 and Yuhong No.1 were 25.38%, 25.34% and 23.46%, respectively, and their pollen tube lengths were 302.31 μm, 297.64 μm and 285.68 μm, respectively. The optimum medium formulation for C. praecox var. intermedius was 250 g·L^-1 PEG-4000+5 mg·L^-1 Ca(NO₃)₂·4H₂O+15 mg·L^-1 H₃BO₃, the pollen germination rates of Yuqiao No.1 and Yuqiao No.2 were 24.43% and 24.93%, their pollen tube lengths were 288.27 μm and 286.37 μm, respectively. The influence trend of the same factors in the culture medium was the same for the five kinds of pollen, but under the most suitable conditions, the pollen vitality of C. praecox var. concolor was better, and its germination rate was slightly higher than that of the other two types.

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Effects of different cultivation methods on growth and carbohydrate accumulation of Chinese chives

WANG Qizhang, ZHANG Guangnan, WANG Lihui, TIAN Jie

2021, 33(2): 288-297. DOI: 10.3969/j.issn.1004-1524.2021.02.12

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In order to explore the effects of different cultivation methods on growth and carbohydrate accumulation of Chinese chives, with variety Xuejing 208 as material, the dynamic changes of agronomic characters and contents of soluble sugar components under soil cultivation, nutrient solution cultivation and substrate cultivation were measured. Based on grey relational analysis method, the primary and secondary relations between growth or soluble sugar factors and yield under different cultivation methods were analyzed, and the suitable cultivation methods for Chinese chives with different commercial characters were screened out. The results showed as follows: (1) Among the three cultivation methods, nutrient solution cultivation would easily promote the Chinese chives growth. Using nutrient solution cultivation, the growth rate of plant height, maximum leaf length, number of leaves and pseudostem length were the fastest; Substrate cultivation followed; The values of above-mentioned four indexes in soil cultivation were the lowest. However, soil cultivation was conducive to the growth of leaf width and pseudostem diameter. (2) Different cultivation methods could significantly affect the yield. Nutrient solution cultivation would enhance yield per plant rapidly. During the entire growth period, the aboveground fresh weight and dry weight in nutrient solution cultivation remain higher than those of other cultivations. On the 35th day, the fresh weight in nutrient solution cultivation respectively increased by 50.16% and 63.70%, and the dry weight in nutrient solution cultivation respectively increased by 11.07% and 16.04%, compared with those of soil cultivation and substrate cultivation. (3) The difference of carbohydrate content in different organs of Chinese chives under the three cultivation methods were significant. Nutrient solution cultivation would accelerate the accumulation of total soluble sugar and fructose in pseudostems. From the 7th day to the 35th day, content of total soluble sugar and their components in different organs with nutrient solution cultivation was higher than the values of soil cultivation and substrate cultivation. On the 35th day, growth of total soluble sugar content in pseudostems was significantly higher than that in leaves, and contents of sucrose, glucose and fructose in pseudostems increased by 13.83%, 12.31% and 29.14% respectively, comparing with those in leaves. (4) Grey relational analysis results showed that the indices closely related to Chinese chives yield per plant in three cultivation methods were the components and contents of soluble sugar. The key factors affecting nutrient solution cultivation, substrate cultivation and soil cultivation were sucrose content in pseudostems, sucrose content in leaves, glucose content in leaves, respectively. In summary, among the three cultivation methods, nutrient solution cultivation would be the most conductive way to grow rapidly and accumulate soluble sugar in Chinese chives, sucrose content in pseudostems was the key factor for the yield formation of Chinese chives under nutrient solution cultivation, which indicated that the accumulation of sucrose played an important role in the nutrient solution high-yield cultivation of Chinese chives.

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Phenotypic variation and resource value evaluation of natural hybrid progenies of seventeen Huangjinju tea plants

WANG Zhihui, PENG Hua, YANG Puxiang, JIANG Xinfeng, LI Wenjin, YUE Cuinan, LI Chen, LI Yansheng

2021, 33(2): 298-307. DOI: 10.3969/j.issn.1004-1524.2021.02.13

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The phenotypic characters of natural hybrids of yellow tea variety Huangjinju are different, in order to explore the phenotypic variation and diversity of them, excellent individual plants were screened. The variation and diversity of 23 phenotypic traits of 17 individuals from natural hybrid progenies were analyzed, and excellent phenotypic plants were screened, and the biochemical quality was evaluated by principal component analysis. The results showed that the variation coefficient of descriptive characters of natural hybrids ranged from 0 to 57.23%, with an average value of 33.88%. The diversity index ranged from 0 to 1.78, with an average of 0.81; Among them, there were no variation in tree type and tree posture, and the color variation of bud and leaf was the largest; The variation coefficient of quantitative traits ranged from 10.33% to 19.82%, with an average of 14.68%. The diversity index ranged from 1.14 to 1.95, with an average of 1.75. The contents of free amino acids and simple catechins of some individual plants were significantly increased by natural hybridization, while the contents of tea polyphenols, total catechins and ester catechins were significantly decreased. There was no significant difference in caffeine among the excellent phenotypic plants (P>0.05). Finally, five plants with better phenotypic and biochemical quality were selected by principal component analysis, the buds of HJJ-12 and HJJ-1 were green, those of HJJ-7 and HJJ-11 were yellow, and that of HJJ-17 was purple.

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Effects of irrigation amount and nitrogen forms on production and nitrogen metabolism of broccoli

ZHANG Hui, CHE Xusheng, LYU Jian, GOU Zhaohui, QIN Qijie, LUO Jian, ZHANG Guobin

2021, 33(2): 308-315. DOI: 10.3969/j.issn.1004-1524.2021.02.14

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In the present study, broccoli cv. Bilyu was selected as experimental material, and a two-factor interactive experimental design was adopted. Three irrigation amounts, namely, W1 (80% of the maximum field capacity), W2 (60% of the maximum field capacity), W3 (40% of the maximum field capacity) and 3 nitrogen forms, namely, N1 (pure$NO^{-}_{3}-N$), N2 (proportion of $NO^{-}_{3}-N$ to $NH^{+}_{4}-N$ was 7∶3), N3 (proportion of $NO^{-}_{3}-N$ to $NH^{+}_{4}-N$ was 5∶5) were set. The effects of different irrigation amounts and nitrogen forms on dry matter accumulation (dry weight), yield, water and nitrogen use efficiency and nitrogen metabolism of broccoli were studied. It was shown that under the same nitrogen form, the dry weight, yield, and partial factor productivity from applied nitrogen of broccoli exhibited a trend of increase first and decrease later with the decreasing irrigation amount. Under the same irrigation amount, the glutamine synthetase (GS) activity, glutamate synthase (GOGAT) activity and soluble protein content of broccoli increased with the elevated proportion of $NH^{+}_{4}-N$, while the changes of nitrate reductase (NR) activity was the opposite. All in all, under the experiment condition, the performance of yield, water and nitrogen use efficiency, dry weight of broccoli was the best under W2N3 treatment. In other words, it was a suitable combination for local broccoli production when the irrigation amount was 60% of the maximum field capacity, and the proportion of $NO^{-}_{3}-N$ to $NH^{+}_{4}-N$ was 5∶5.

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Effects of different planting patterns on soil nematode community structure and soil properties of Chinese yam field

FAN Linjuan, LIU Zirong, XU Xueliang, WANG Fenshan, PENG Deliang, YAO Yingjuan

2021, 33(2): 316-325. DOI: 10.3969/j.issn.1004-1524.2021.02.15

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To investigate the effects of different planting patterns (two stubble intervals of 0, 3, 6, 10 years, recorded as YPI-0, YPI-3, YPI-6 and YPI-10, respectively) on soil environment, nematode classification methods and conventional soil analysis methods were adopted to reveal the effects of different planting patterns on soil nematode community and soil properties of Chinese yam yield at the seedling stage and maturity stage, to provide references for the control of plant parasitic nematodes by changing planting patterns of Chinese yam. The resultd showed that different planting patterns had no significant effect on soil pH value, and contents of organic matter and available potassium. But the content of available phosphorus under treatment of YPI-6 and YPI-10 was significantly (P<0.05) lower than that under YPI-0 and YPI-3 treatments. Meanwhile, compared with YPI-0, the relative abundance of bacterivores under treatments of YPI-10 at the seedling stage and maturity stage increased significantly (P<0.05), while the relative abundance of plant parasites was significantly (P<0.05) decreased. Redundancy analysis (RDA) indicated that the number of Tylenchus, Meloidogyne and Pratylenchus had significantly (P<0.05) positive correlations with soil available phosphorus and available potassium, and the number of most bacterivores had significantly (P<0.05) negative correlations with soil pH, and contents of organic matter, ammonium nitrogen. The Shannon diversity index (H’) and dominance index (λ) had no significant change under different planting patterns at both seedling stage and maturity stage, and the nematode channel ratio (NCR) value was all higher than 0.5, which indicated that the decomposition of soil organic matter under different planting patterns was mainly bacterial degradation, and the Wasilewska index (WI) and maturity index (MI) under treatments of YPI-6 and YPI-10 were significantly (P<0.05) higher than those under YPI-0 treatment, while the performance of plant parasite index (PPI) to MI (PPI/MI) was the opposite. In conclusion, increasing the two stubble interval of Chinese yam changed the community of soil nematodes, which not only reduced the abundance of harmful plant parasites, but also made the soil ecosystem mature and healthy, and the effect was better with the increasing interval years.

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Growth-promoting characteristics of Aspergillus niger TL-F2 and its effect on seed germination and cadmium content in seedlings of ryegrass under cadmium stress

LIU Ru, DONG Changru, ZHANG Yiwen, QU Minghui, ZHANG Wei, SA Haiyang, CHEN Haiyan, YE Wenling, FAN Ting

2021, 33(2): 326-334. DOI: 10.3969/j.issn.1004-1524.2021.02.16

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The growth-promoting characteristics of Aspergillus niger TL-F2, and its effects on seed germination, seedling growth and Cd content of ryegrass under Cd stress were studied. The results showed that the siderophore production of A. niger TL-F2 was significantly (P<0.05) decreased by 48.18%, and there was no significant change of indoleacetic acid (IAA) production and phosphate solubilization under low Cd (5 mg·L^-1) stress. However, under medium (20 mg·L^-1) and high (50 mg·L^-1) Cd stress, the IAA production, phosphate solubilization and siderophore production of A. niger TL-F2 was significantly (P<0.05) decreased by 55.76% and 65.69%, 50.07% and 78.19%, 69.71% and 80.08%, respectively. Inoculation of 1×10⁸ mL^-1 A. niger TL-F2 could benefit the seed germination and seedling growth of ryegrass, and the Cd content in shoots was significantly (P<0.05) increased by 17.95% than that without inoculation under high Cd stress. However, inoculation of 1×10⁶ mL^-1 A. niger TL-F2 showed no significant effect on seed germination and seedling growth of ryegrass. The results suggested that inoculation of proper amount of A. niger TL-F2 could promote seed germination and seedling growth of ryegrass, and enhance the accumulation of Cd in the shoots of ryegrass seedlings. Therefore, inoculation of A. niger TL-F2 had the potential as a new means to enhance the remediation of Cd polluted soil and water by using ryegrass.

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Screening, identification and application of high efficient nitrite degrading functional strains in Chinese characteristic fermented vegetables

XIN Xiaoting, LIU Daqun, ZHANG Chengcheng, WU Min, CHEN Denggao, ZHANG Jianming

2021, 33(2): 335-345. DOI: 10.3969/j.issn.1004-1524.2021.02.17

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Seventy two strains of lactic acid bacteria were isolated and purified from traditional fermented vegetables in China. Their ability to degrade nitrite was determined. Thirty strains of lactic acid bacteria with a degradation rate of more than 85% were screened out. Five strains with good tolerance for gastric acid and bile salt were obtained by acid and bile salt tolerance test. The morphology and 16S rDNA sequencing results showed that all strains were Lactobacillus plantarum. The results of fermentation characteristics showed that Lactobacillus plantarum JLSC2-6 had strong growth, strong acid production capacity, good salt tolerance and excellent function, and had the ability to degrade nitrite efficiently. The pH value and nitrite content of pickles fermented by Lactobacillus plantarum JLSC2-6 were determined. The results showed that the pH value and nitrite content of pickles fermented by JLSC2-6 were significantly different from those of natural fermentation pickles. Therefore, Lactobacillus plantarum JLSC2-6 can be used as an efficient and safe starter for fermented vegetables.

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Analysis on farmers’ willingness to buy agricultural accessory risk based on regional index in China: a case study on cotton growers in Hebei Province

WEN Changcun, SUN Yuzhu

2021, 33(2): 346-354. DOI: 10.3969/j.issn.1004-1524.2021.02.18

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To avoid international trade dispute, the United States launched an agricultural accessory risk based on regional index, cumulative income protection plan (STAX), which could reduce the cost of investigation and personal moral hazard. At present, China faces multiple pressures, such as the adjustment of cotton support policy and the declining plantation willingness of cotton growers. If similar insurance like STAX was introduced in China, would farmers be willing to buy? To answer this question, we first analyzed the content of STAX, and then carried out a survey in cotton growers in Hebei Province, and adopted the Logit model to empirically study the farmers’ willingness to buy such insurance products. The results showed that, the premium and purchase of cotton insurance had significant (P<0.05) negative correlation with farmers’ willing to buy such insurance products. While, income from farming, the recognition of the role of insurance in stabilizing the income from farming and the purchase of insurance with the whole expected income as insurance subject by farmers’ relatives or neighbors had a significant (P<0.05) positive correlation with farmers’ willing to buy such insurance products. Based on these findings, it was suggested that the insurance products system should be improved and innovated. The guarantee level of insurance should be improved. And, the publicity of insurance knowledge should be strengthened to increase the farmers’ recognition toward agricultural insurance.

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Empirical analysis on scale effect of forest output of forest insurance premium subsidy policy in China: based on difference-in-differences model and event study model

FU Lisha, QIN Tao, PAN Huanxue, DENG Jing

2021, 33(2): 355-368. DOI: 10.3969/j.issn.1004-1524.2021.02.19

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The forest insurance premium subsidy policy has been implemented for more than 10 years in China, and the proposition of whether and to what extent it can promote forestry production is in urgent need of scientific and systematic empirical test. Combined with producer behavior theory, we explored the scale effect of forest insurance premium subsidy policy on forest output, and analyzed the mechanism of forest insurance premium subsidy policy on forest output. On this basis, by using panel data of 31 provinces (autonomous regions, municipalities) in China from 2001 to 2017, and taking the impact of China’s forest insurance premium subsidy policy in 2009 as a natural experiment, we explored the impact of the subsidy policy on the forest-related output value of the primary forestry industry via difference-in-differences model and event study model. Two placebo tests were also carried out to rule out the potential threat of conclusions. The results showed that the forest insurance premium subsidy policy had a significant (P<0.1) positive effect on forestry output, and the effect would increase with the prolonged time of implementation. After the implementation of the subsidy policy, the forest-related output value of the primary forestry industry in pilot regions increased by 1.04 million yuan compared with that in non-pilot regions. Moreover, the robustness test was carried out in 2010 as the year of policy impact, and the conclusions were consistent. Additionally, two placebo trials also ruled out two potential threats to the results. The study held a positive attitude towards the role of forest insurance under the central financial subsidy, and it was suggested that the subsidy policy should be further optimized from the aspects of subsidy scale and subsidy standard to enhance its output effect.

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Research progress of regulation techniques of rice seed dormancy

ZOU Wenxiong, WU Wei, GUAN Yajing, CAO Dongdong, BIAN Xiaobo, SHI Deyun, DING Liling

2021, 33(2): 369-379. DOI: 10.3969/j.issn.1004-1524.2021.02.20

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Seed dormancy is a self-protection way for plants to adapt to external environments to ensure its survival, reproduction and evolution, which is also directly affect agricultural production. In this paper, the regulation mechanism of rice seed dormancy, including the basics of genetics, respiratory and metabolic pathways, hormones and ecological factors were reviewed. The detection methods of seed dormancy characteristics and its influencing factors such as genetic characteristics, plant endogenous hormone and amylase activity were expounded. Meanwhile, this paper summarized and analyzed the researches on physical and chemical regulation techniques of rice seed dormancy, and the application of some technologies in agricultural production, such as planting management, plume removal, spraying preharvest sprouting inhibitor or dormancy breaking agent. Furthermore, the research direction was discussed in order to provide reference for further research on seed dormancy regulation technology.

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