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25 December 2022, Volume 43 Issue 12 Previous Issue   
Omics & Biotechnology
Cloning and Expression Analysis of HbRPW8 Gene from Hevea brasiliensis
GUAN Xin, TU Min, CAI Haibin, WANG Yunyue, HU Yanshi, ZENG Xia
2022, 43 (12):  2395-2404.  doi: 10.3969/j.issn.1000-2561.2022.12.001
Abstract ( 37 )   HTML ( 1 )   PDF (5003KB) ( 19 )  

RPW8 (resistance to powdery mildew locus 8) is a broad-spectrum resistance gene locus to many plant diseases, especially powdery mildew. In this study, the cloning and expression analysis of RPW8 gene in Hevea brasiliensis were carried out to lay the foundation for the analysis of powdery mildew resistance mechanism and molecular breeding. HbRPW8 gene coding region (CDS) was cloned from rubber tree ‘Reyan 73397’ by RT-PCR. Bioinformatics analysis was carried out, and qRT-PCR method was used to determine the expression of RPW8 gene after seven hormones and powdery mildew infection at different times and disease grades. The full-length cDNA of HbRPW8 was 570 bp, encoding 189 amino acids. The molecular weight of HbRPW8 was 21.73 kDa, the isoelectric point was 9.23, the fat coefficient was 86.30, and the total average hydrophilicity index was -0.404, which was a hydrophilic protein with eight phosphorylation sites. The protein was located in the nucleus without transmembrane domain and signal peptide, and had a conserved domain of RPW8. The main components of the secondary structure of HbRPW8 protein were α-helix and random coil, accounting for 70.90% and 22.22% of the amino acid sequence, respectively. Phylogenetic relationships analysis showed that HbRPW8 gene had the highest similarity with cassava RPW8 gene. Hydrogen peroxide, salicylic acid, ethephon, gibberellin and abscisic acid could rapidly induce the expression of HbRPW8 transcript, and reached the highest level at 0.5 h after treatment, which was about 14, 6, 75, 2.5 and 4 folds of the control, respectively; methyl jasmonate treatment reached the highest level at 6 h after treatment, about 10 times that of the control; HbRPW8 transcript was significantly down-regulated after auxin treatment; with the increase of infection time and disease grade of powdery mildew, the expression level of HbRPW8 increased first and then decreased. The results of this study preliminarily showed that HbRPW8 may be involved in the resistance response mechanism of rubber tree, providing a reference for the study of rubber tree resistance breeding.

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Gene Cloning, Subcellular Localization and Multimerization Analysis of HbPIP1;1 from Hevea brasiliensis
QIAO Xueying, ZHENG Yujiao, YANG Jianghua, ZENG Changying, ZOU Zhi
2022, 43 (12):  2405-2412.  doi: 10.3969/j.issn.1000-2561.2022.12.002
Abstract ( 12 )   HTML ( 2 )   PDF (24124KB) ( 5 )  

Aquaporins (AQPs), a class of integral membrane proteins facilitating the passive transport of water, are widely present in all living organisms. Evidence shows that AQPs function in homotetramers or hereotetramers in biological membranes. On the basis of the sequence similarity and subcellular localization, plant AQPs could be divided into five main subfamilies, i.e. PIP (plasma membrane intrinsic protein), TIP (tonoplast intrinsic protein), NIP (NOD26-like intrinsic protein), SIP (small basic intrinsic protein), and XIP (X intrinsic protein). Among them, PIPs, which are located in the plasma membrane, represent the main channel mediating water transport between cells. Para or Brazilian rubber tree (Hevea brasiliensis Muell. Arg.), a perennial big tree native to the Amazon basin, is the main commercial source of natural rubber currently. Compared with other plants, the water balance is particularly important for rubber tree, because a large amount of water loss could be caused by periodic bark-tapping as well as transpiration. Previous studies showed that the rubber tree genome encodes a high number of 51 AQP genes, which include five PIP1s and ten PIP2s. To uncover the molecular mechanism of PIP-mediated water balance in rubber tree, a key gene named HbPIP1;1 was cloned using the RT-PCR (reverse transcription polymerase chain reaction) technique, followed by investigation of the subcellular localization and multimerization of its coding peptide. Results showed that the CDS (coding sequence) length of HbPIP1;1 is 864 bp (base pairs), putatively encoding 287 aa (amino acids), which includes a MIP (major intrinsic protein) domain specific to the AQP family; it was predicted to be an instable, hydrophobic, and basic protein that harbors the theoretical molecular weight (Mw) of 30.80 kDa, the isoelectric point (pI) of 8.59, the instability index (II) of 49.27, the aliphatic index (AI) of 22.34, and the grand average of hydropathicity (GRAVY) value of 0.639; it was also shown to contain six transmembrane regions that harbor 20-23 residues. Moreover, various expression vectors for subcellular localization, bimolecular fluorescence complementation, and yeast two-hybrid were constructed. Consistent with the bioinformatics analysis, transient overexpression of HbPIP1;1 in tobacco (Nicotiana tabacum) leaves via the Agrobacterium tumefaciens-medicated transformation revealed that the protein is located in the plasma membrane. Further bimolecular fluorescence complementation and yeast two-hybrid experiments showed that HbPIP1;1 could not form a homomultimer. The findings presented in this study suggest that HbPIP1;1 may be involved in water balance in the form of heteromultimer, though detailed mechanisms are to be further studied.

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Aggregation-related Proteins Binding to Rubber Particles with Different Diameter in Rubber Tree
DING Huan, WU Shaohua, XIA Zhihui, HUANG Xi, SHI Minjing
2022, 43 (12):  2413-2421.  doi: 10.3969/j.issn.1000-2561.2022.12.003
Abstract ( 17 )   HTML ( 3 )   PDF (17958KB) ( 8 )  

Rubber tree (Hevea brasiliensis Muell.Arg.) is an important rubber-producing plant, and the secondary laticifer in the trunk bark is the major tissue for the synthesis and storage of natural rubber. Natural rubber is extracted from the latex in laticifer by tapping (mechanical wounding) and synthesized by a special organelle, named the rubber particle. Rubber particle is a spherical structure surrounded by a lipid monolayer and membrane-bound proteins, in which the natural rubber is stored. The peripheral membrane is bound to a variety of proteins that are closely related to the functions of rubber particles. At present, there are many studies on proteins related to natural rubber synthesis, but the proteins related to rubber particle aggregation still remains unclear. Using the latex collected from the clone ‘RY7-33-97’ as the material, rubber particles with different particle sizes were obtained by fractionation at different centrifugal speeds. Subsequently, the rubber particle samples were cleaned by buffer for three times and collected for electrophoresis, respectively. The binding proteins on rubber particles were compared and analyzed by Tricine- SDS-PAGE and Western-blotting techniques. There were obvious differences in the content of bound proteins on rubber particles with different particle size. Accompanied by the decrease of rubber particle size, the content of small rubber particle membrane protein (SRPP) increased significantly, while the content of rubber elongation factor protein (REF) remained stable and had little relationship with the rubber particle size. Hevb7 latex allergen protein (Hevb7) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) in C-serum could bind to the rubber particles, and β-1,3-glucanase (Glu), hevein (Hev) and chitinase (Chit) in B-serum could also bind to rubber particles, but in which the binding ability of chitinase to rubber particles was the weakest. After cleaning, as the main membrane protein of rubber particles, the content of SRPP decreased significantly with the times of cleaning, but the content of REF protein did not change obviously, indicating that the binding ability of SRPP to rubber particle membrane is not as strong as that of REF. The content of agglutination-related proteins from C-serum and B-serum decreased significantly with the times of cleaning, usually, the proteins could not be detected after the second cleaning. Small rubber particles with about 0.16 μm mean diameter were incubated with different protein samples in vitro, the results showed that rubber particles could bind a variety of different proteins, in which some proteins were related to the aggregation of rubber particles. In this study, the aggregation-related proteins bound to rubber particles with different particle sizes were preliminarily analyzed, the results would lay a foundation for elucidating the mechanism of latex flow of rubber trees.

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Cloning and Bioinformatics Analysis of Pepper PnCAD Gene by Race
SUN Yeqiao, WANG Jue, HU Lisong, WU Baoduo, HAO Chaoyun, FAN Rui
2022, 43 (12):  2422-2430.  doi: 10.3969/j.issn.1000-2561.2022.12.004
Abstract ( 19 )   HTML ( 1 )   PDF (10402KB) ( 15 )  

Lignin has some functions in plants, such as transporting water, supporting plants and strengthening plants against damage, etc. It is one of the important products of phenylpropane metabolism. Among them, cinnamyl alcohol dehydrogenase (CAD) is an important rate-limiting enzyme in the lignin synthesis pathway. In this experiment, on the basis of pepper transcriptome sequencing, the RACE method was used for gene cloning, bioinformatics analysis of the full-length PnCAD gene, and many analyses of its protein such as physicochemical properties, subcellular localization and phylogenetic tree. It was analyzed by qPCR. The cinnamyl alcohol dehydrogenase gene was cloned by the race method. Finally, a full-length cDNA with a length of 1364 bp was obtained, including 1071 bp open reading frame (ORF), encoding 356 amino acids. The predicted relative molecular weight was 3.879 kDa and the isoelectric point was 6.27. It belonged to hydrophilic protein. It contained three N-glycosylation characteristic sequences and nine phosphorylation sites, which were likely to be in the cytoplasm. Domain analysis showed that CAD protein contained NAD (P) binding sites, multiple catalytic zinc and structural zinc binding sites. Phylogenetic tree analysis showed that pepper CAD was closely related to Asarum CAD 6, and the highest homology was 76%, both of which belonged to primitive dicotyledons. Through fluorescence quantitative analysis, it could be found that the expression of P. flaviflorum under the infection of Phytophthora capsici increased, reached the highest value at 8 h, about 10 times that of the control, then increased slightly at 24 h, about 6 times that of the control group, and then decreased. Generally speaking, the gene expression level of P. flaviflorum at all time was higher than that of P. nigrum cv. Reyin-1 and was significantly different. The experimental data could provide reference data for the future study of the anti abiotic stress function of black pepper, and also provide a theoretical basis for the functional study of gene PnCAD.

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Identification and Evolutionary Analysis of Maize DUF1685 Gene Family
LUO Xuan, LIN Zhengyu, CHEN Zhang, LEI Bo, LI Jie, QUAN Jinying, LIU Hailan
2022, 43 (12):  2431-2442.  doi: 10.3969/j.issn.1000-2561.2022.12.005
Abstract ( 30 )   HTML ( 2 )   PDF (5163KB) ( 25 )  

A total of 211 DUF1685 gene family members in 16 monocotyledonous and dicotyledon and Selaginella moellendorffii were identified in this study. Analysis of protein physicochemical properties showed that the amino acid sequences of 211 DUF1685 genes ranged in length from 83 to 1071 aa, molecular weights from 9.2 to 116.3 kDa, and theoretical isoelectric points from 3.66 to 11.90. Phylogenetic evolution analysis showed that the DUF1685 gene family were divided into three subfamilies (Class I, Class II and Class III). The events of A1 and A2, B1 and B2 in the Class I and Class II subfamilies occurred after the differentiation of monocotyledonous plants, and A1 and B2 branches (members were all dicotyledonous genes) had gene expansion phenomenon. The results of conserved motifs and gene structure analysis showed that the conserved motifs among members of the same subfamily were similar. Most of the 211 DUF1685 family genes contained one intron, and a few genes contained two or more introns or no introns. Selection pressure analysis showed that the related loci of DUF1685 family genes were positively selected during the evolution process, which may be the reason for the functional changes of some genes. Collinearity analysis indicated that fragment duplication events may be a potential driver of DUF1685 gene amplification and evolution in the maize. The results of cis-element analysis in the gene promoter region showed that the promoter region of maize DUF1685 gene contained light-responsive elements, ABA and cis-acting elements related to abiotic stress. It was speculated that the genes may be involved in the response of maize to abiotic stress. Transcriptome data analysis revealed that the maize DUF1685 gene was associated with the growth and development of specific tissues (mature pollen). This study explored the function and evolution of the maize DUF1685 gene family in various aspects to provide a theoretical reference for the in-depth study of the biological function and evolutionary relationship of the maize DUF1685 gene in the future.

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Cloning and Activity Identification of High Efficiency Ubiquitin Promoters from Sorghum
XIA Qiyu, HE Pingping, ZHANG Lili, ZHANG Yuliang, XIAO Susheng, ZHAO Hui
2022, 43 (12):  2443-2452.  doi: 10.3969/j.issn.1000-2561.2022.12.006
Abstract ( 13 )   HTML ( 3 )   PDF (13080KB) ( 3 )  

In the research of transgenic plants, promoter is one of the important factors affecting the efficiency of transgenic expression. Plant ubiquitin gene promoters have been widely used in monocotyledons because of its high starting efficiency, relatively low methylation degree and stable genetic traits. Among them, the Ubi-1 promoter of maize is one of the most commonly used Ubiquitin promoters. The purpose of this study is to obtain high-efficiency ubiquitin promoters of sorghum and provide a new constitutive promoter selection for the genetic transformation of sorghum and other monocotyledonous plants. In this study, multiple polyubiquitin genes were found from NCBI database, and the sequence of 3000 bp upstream of its starting codon was downloaded. According to the characteristics of Ubiquitin promoter, the sequence with 5′ UTR intron and appropriate size was selected, and the promoter was analyzed through the online promoter prediction website. Finally, two genes LOC8076096 and LOC8063786 were selected for promoter cloning, and their promoter sequences were named U1 and U5 respectively. After PCR amplification, the two promoter fragments were connected to the plant expression vector Ubi-GUS containing Gus reporter gene to obtain recombinant expression vectors U1-GUS and U5-GUS. The recombinant vector was transformed into rice and green bristlegrass by the Agrobacterium-mediated method. The positive transformed seedlings were screened by PCR. GUS staining analysis was carried out on the positive transformed seedlings to identify the promoter activities of U1 and U5. GUS staining showed that the roots, stems and leaves of all positive transformed seedlings of rice and green bristlegrass with U1 and U5 as promoters showed darker blue, which was slightly darker than that of positive transformed seedlings with maize Ubi-1 as promoter, and the blue of positive transformed seedlings with U5 as promoter was deeper than that of U1 as promoter, while non-transgenic rice and green bristlegrass seedlings could not be stained with blue at all. Therefore, the promoters U1 and U5 have the activity of constitutive strong promoters in rice and green bristlegrass, and can be used as new constitutive promoters to study the genetic transformation of sorghum, rice, green bristlegrass and other monocotyledonous plants.

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Plant Cultivation, Physiology & Biochemistry
Hyperspectral Estimation for Magnesium Content of Rubber Tree Leaves
CHEN Guiliang, LIU Zhongmei, XU Muguo, DING Huaping, LI Xiaoqing
2022, 43 (12):  2453-2460.  doi: 10.3969/j.issn.1000-2561.2022.12.007
Abstract ( 15 )   HTML ( 1 )   PDF (1739KB) ( 4 )  

Magnesium is closely related to the growth and rubber production of rubber trees. Rapid and accurate determination of magnesium content in rubber tree leaves is of great significance for the evaluation of magnesium nutritional status and application of formula fertilization. In this study, the mature fresh leaves of rubber trees with multiple regions, varieties and tapping ages were collected to obtain leaf samples with different levels of magnesium content including deficiency, normal and rich. Spectral reflectance and magnesium content of leaf samples were obtained synchronously using FieldSpec4 and chemical methods. After noise band removal and resampling of spectral reflectance, kennard-Stone (KS) algorithm was used to divide the sample set into calibration set and validation set. The differential transformation by Savitzky-Golay (SG) was used to preprocess the spectral reflectance of leaves. Based on differential spectra of different transformation modes with the whole spectrum and magnesium content data, partial least squares (PLS) and leave-one-out cross validation method were used for modelling. Through screening, the optimal differential transformation mode was obtained as follows: differential order 2, filter window size 71 and polynomial degree 2 or 3. Twenty-three differential spectral characteristic variables were obtained by partial least squares regression coefficient characteristic wavelengths selection. Based on the optimum differential spectral characteristic variables and magnesium content data, the hyperspectral estimation models of rubber tree leaf magnesium were established using PLS. The results showed that the predicting accuracy of the model constructed based on differential spectral characteristic variables was improved obviously compared with the model constructed based on original spectral reflectance. The R2 increased from 0.666 to 0.805, the RMSE decreased from 0.475 g/kg to 0.372 g/kg, and the RPD increased from 1.739 to 2.217. SG differential transformation and PLS regression coefficient characteristic wavelengths selection can significantly improve the accuracy of model estimation. The RPD of the model is between 2.0 and 2.5, and the estimation ability is good.

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Character Identification and Ornamental Value Evaluation of SP1 Generation of Space-induced Agapanthus praecox
GUO Xiangxin, DAI Yifeng, ZHANG Yan, LI Xiaoqing, TANG Qianwen, LI Qingyun, SHEN Xiaohui, CHEN Guanqun
2022, 43 (12):  2461-2470.  doi: 10.3969/j.issn.1000-2561.2022.12.008
Abstract ( 12 )   HTML ( 1 )   PDF (12092KB) ( 5 )  

Space mutation is an effective method for breeding new varieties. In this study, the morphological indicators of 29 SP1 plants of Agapanthus praecox flowering for 8-10 years induced by space were observed and determined under the guidance of the international DUS test guidelines for A. praecox. Six principal components were extracted from 15 morphological indicators using principal component analysis. Then the integral ornamental evaluation was performed by the fuzzy comprehensive evaluation method. Due to the diversity of inflorescence, the ornamental value of inflorescence was assessed by the hierarchical-relational analysis. The tested plants showed significant differences in the 15 morphological indicators. There were extremely significant or significant correlations between each indicator, with correlation coefficients concentrated in 0.2 to 0.6. Based on the principal component analysis and factor analysis, plant height and inflorescence type significantly affected the ornamental value and were easily varied. The comprehensive evaluation was established to estimate the ornamental properties of 29 tested plants. Several plants with high integral ornamental quality were screened out. For example, plants No.506, 445, and 319 performed large floret number and high inflorescence height, that were suitable for vegetative propagation to maintain the excellent characters. According to the calculation of the weighted grey correlation analysis of the 15 indicators of the flower, the top 6 indicators were floret number C1, florescence C13, flower color C7, inflorescence diameter C2, early flowering degree C14, and bud color C8. The total weight of the above indicators exceeded 70%, and the weight of each indicator exceeded 6%. Through two years of continuous field investigation, it was found that some indicators such as flower color, pedicel color, floret number, early flowering degree were relatively stable. The indicators were less susceptible to be influenced. Plant No.445 was screened through this analysis. It was suitable for hybridization to propagate more ornamental offspring because of the gradient flower color. This study has initially established an ornamental evaluation method for A. praecox, providing a useful reference to the breeding of A. praecox. Heat map was used to evaluate the character changes of the adult plants of space-induced A. praecox during different growth phase. In this research, the mutation selection of a single indicator was carried out by combining the single indicator evaluation and integral ornamental value evaluation.

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Effects of Cadmium Stress on Yield and Cadmium Absorption of Agaricus blazei and Its Control Techniques
CHEN Hua, LIU Penghu, YE Jing, LIN Yi, WENG Boqi, WANG Yixiang
2022, 43 (12):  2471-2481.  doi: 10.3969/j.issn.1000-2561.2022.12.009
Abstract ( 18 )   HTML ( 2 )   PDF (1344KB) ( 9 )  

Cadmium (Cd) accumulation is an important problem influencing Agaricus blazei industry. Therefore, breeding low-Cd content varieties and exploring Cd prevention and control technology in A. blazei were of great importance. In this study, the effect of Cd on their yield and cadmium absorption of two varieties of A. blazei J37 and J1 under Cd stress treatments were investigated. The effect of CaSO4 application on cadmium absorption of A. blazei also was investigated. The effects of different Cd stress treatments on the traits of fruit bodies of J37 and J1strains. With the increase of exogenous Cd concentration, the pileus weight, stipe weight, pileus thickness, pileus diameter, stipe length, and stipe diameter decreased, respectively. The yield of J37 under different Cd stress increased by 32.5%, 45.1%, 31.0%, 38.2% and 36.5% than those of J1 in the first tides, respectively. Moreover, the yield of J37 was also higher than that of J1 in the second and third tides. The sensitive Cd concentration on protein quality of J1 and J37 was 10 mg/kg and 20 mg/kg, respectively. Under 20 mg/kg Cd treatment, the polysaccharide content of J1 was 8.2% higher than that of J37. But the Cd accumulation in J1 was all higher than that of J37 with the increase of Cd stress. Under the conditions of 10 mg/kg and 20 mg/kg Cd stress, the effects of CaSO4 application with 45 mg/kg on cadmium poisoning of J1 and J37 were the most obvious. The average control rate of cadmium poisoning by applying calcium fertilizer was 36.2% and 47.6%, respectively. Under the conditions of this experiment, 20 mg/kg cadmium content in the culture was the sensitive node of A. blazei to tolerate cadmium poisoning, and the yield of A. blazei decreased by more than 40.0% in the first tide. When the Cd concentration in the culture was less than 10 mg/kg, A. blazei could tolerate Cd stress. Results also showed that the weight or cap diameter or stalk diameter might be used as a direct indicator for judging the Cd toxicity.

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Microscopic Observations of Gills, Basidiospores and Mycelium in Agaricus brasiliensis
ZHOU Yu, HUANG Zaixing, BAO Xinglu, LI Jing, LIU Penghu
2022, 43 (12):  2482-2488.  doi: 10.3969/j.issn.1000-2561.2022.12.010
Abstract ( 11 )   HTML ( 3 )   PDF (4820KB) ( 3 )  

Agaricus brasiliensis is a precious edible and medicinal mushroom, which is not only rich in nutrition but also has high medicinal value, and its industrial development has a broad prospect. However, the lack of germplasm resources of A. brasiliensis and insufficient knowledge of the genetic background of A. brasiliensis have hindered the development of its hybrid breeding technology, and the existing germplasm resources can hardly meet the practical needs of production. A. brasiliensis strains J1 was used as research materials, it is proposed to investigate the biological properties related to A. brasiliensis by micro-morphological observation of the reproduction-related structures of A. brasiliensis. The microscopic morphological characteristics of gills, basidiospores and mycelium in different growth and development stages were observed by scanning electron microscope and fluorescence microscope. The gills and trama were in the developmental stage and the hyphae lamellae were not obvious, and the gill sheets were not obvious during the morula state. The gill sheets were obviously observed, arranged parallel to each other, composed of trama and the fruiting layers on both sides, which were closely arranged, uniform in thickness, and a small amount of basidia were borne after the coral stage, but the trama was irregularly arranged. During the forming stage, the gills were clear and regular, and the inner veil was not ruptured, the gill space contains basidiospores and disorganized duct-like cells arranged in raised surface, and the duct-like cells in the gill were closely related. During the forming stage, the gill basidium was relatively full and wrinkled. There were 3 or 4 sporozoites on the gill basidia, and there were small connecting filaments between the basidiospores. The observation of basidiospore nuclei by DAPI staining showed that the most basidiospores were dinuclear spores, and a few were mononuclear and enucleated spores. The observation of mycelial nuclei by DAPI staining showed that the mycelium of A. brasiliensis mycelium was multinucleated and had septa, but there was no lock-like association. This study would clarify the microscopic morphological characteristics of gills, basidia, basidiospores and mycelium in different growth and development stages of A. brasiliensis, enrich the knowledge of biological studies and life history processes of A. brasiliensis, and lay a foundation for the hybrid breeding, basidiospore mating types, genetics transformation system of A. brasiliensis.

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Effect of Selenium on Growth, Flowering and Activities of Antioxidant Enzymes of Arachis hypogaea Seedlings under Hydroponic Conditions
SHI Heping, ZHANG Xiaoyuan, XU Sheng
2022, 43 (12):  2489-2495.  doi: 10.3969/j.issn.1000-2561.2022.12.011
Abstract ( 14 )   HTML ( 4 )   PDF (17612KB) ( 13 )  

Selenium (Se) is an essential trace element for human and animals. Selenium deficiency in soil environment can lead to many diseases in the animals such as white muscle disease and Keshan disease. Increasing the selenium content of plants, especially crops, by applying selenium fertilizer is regarded as one of the effective measures to prevent selenium deficiency diseases. Arachis hypogaea is one of the most important oil crops in China and even in the world. In order to lay an experimental foundation and provide the possibility for improving peanut yield and its selenium content by applying selenium fertilizer to oil crop A. hypogaea in agricultural production in the future, the effects of different concentrations of selenium (Se) on growth and flowering and activities of antioxidant enzymes superoxide dismutase (SOD) and peroxidase (POD) and MDA content in A. hypogaea seedlings were investigated in hydroponic solution culture. The results showed that Se concentration less than or equal to 0.5 mg/L stimulated the growth of peanut seedlings, the best growth was obtained at 0.1 mg/L Se. Se concentration less than 1 mg/L was shown to enhance the flowering of peanut seedlings, the highest flowering frequency was 27 per plant, which was 90% higher than that of the control. When added more than 1 mg/L Se in the medium, the growth was gradually inhibited, the root was thicker and shorter, its tips became browner and the stems became shorter and redder and the number of flowers of seedlings was significantly decreased with the increasing Se concentration. No flower was even observed at 5.0 mg/L, the highest concentration of Se in the solution. Compared to the control, lower concentration of Se (≤1.0 mg/L) enhanced POD and SOD activities but decreased the MDA content of peanut seedlings; Higher concentrations above 3 mg/L Se could only enhance POD and SOD activities in A. hypogaea seedlings at 5 days of culture, with prolonged time, the activities of SOD and POD in A. hypogaea seedlings gradually decreased while its MDA content increased. This has would lay an experimental and technical foundation for enhancing Se content and yield of peanut through application of Se fertilizations.

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Plant Protection & Bio-safety
Evaluating the Adaptation of Spodoptera frugiperda to Various Plants in Corn Field via Artificial Diet Method
LIAO Huimin, GUO Yeshan, HUANG Zian, WANG Peiyue, YE Yuhan, SHU Yinghua, WANG Jianwu
2022, 43 (12):  2496-2506.  doi: 10.3969/j.issn.1000-2561.2022.12.012
Abstract ( 9 )   HTML ( 3 )   PDF (5704KB) ( 4 )  

Understanding the effects of different host plants on the biological characteristics of herbivorous insects is the basis for the study of insect-plant interactions, and is of great significance for effective pest management strategies. The invasive pest, fall armyworm Spodoptera frugiperda, may damage plants as many as 353 species, but the effects of most host plants on its biological characteristics are still not clear. Feeding the fresh plant leaves to the larvae of herbivorous insects is the common method, but it is limited by climate, geographical location, plant growth cycle and so on. In this study, Zea mays was used as a reference, and 6 crops and weeds in and around corn fields were collected as experimental materials, including Glycine max, Vigna unguiculata, Ipomoea batatas, Artemisia argyi, Lactuca sativa and Cucumis sativus. The fresh leaves of the above plants were uniformly collected and then ground to powder. The powder of different plants was added to the artificial diets at a ratio of 1%, then was used to feed the larvae of S. frugiperda respectively. The survival (i.e., larval survival rate, pupation rate, eclosion rate), growth (i.e., larval gain weight, pupal weight, relative growth rate), development period (i.e., larval period, prepupal period, pupal period), food utilization (i.e., relative consumption rate, approximate digestibility, efficiency of conversion of ingested food, efficiency of conversion of digested food) were investigated to explore the biological characteristics of S. frugiperda after feeding the above diets. In order to verify the feasibility of the plant leaves powder feed method, the fresh leaves of the above plants were also collected uniformly and fed to the larvae of S. frugiperda respectively. The results showed that G. max and V. unguiculata were the suitable host plants for S. frugiperda. While I. batatas, A. argyi and L. sativa presented negative effects on S. frugiperda, which may reduce the harm to corn when the plants were intercropped with corn. With the help of analytic hierarchy process (AHP), a quantitative grading index evaluation system was established to compare the two methods quantitatively. As a result, the effects of diets and fresh leaf feeding were consistent, and the plant leaves powder diet method has few restrictions and easy operation, which is better evaluating the effects of farmland plants on the biological characteristics of S. frugiperda.

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Extraction of Karanjin from Pongamia pinnata and Its Insecticidal Activity Against Bactrocera dorsalis
REN Junhua, ZHAO Yongliang, WANG Hui, LI Jiuhui, ZHAO Chunjie, LU Shaopeng, XIONG Yan, WU Suran
2022, 43 (12):  2507-2514.  doi: 10.3969/j.issn.1000-2561.2022.12.013
Abstract ( 9 )   HTML ( 1 )   PDF (1205KB) ( 1 )  

Bactrocera dorsalis is a destructive pest, which can harm more than 200 fruits. At present, prevention and control measures of B. dorsalis are toxic, environmentally unfriendly, or costly. In this study, Pongamia pinnata pod, which is cheap and easily available, was as the raw material, and ultrasonic-assisted extraction was performed to extract karanjin from its powder. Effect of ethanol concentration, material ratios of ethyl acetate, petroleum ether, n-hexane and ethanol on extraction rate of karanjin were compared by single factor experiments to obtain the optimal solvent and material/solvent ratio. Egg hatching inhibition activity of EPP against B. dorsalis and its gastric toxicity on 1st instar larvae of B. dorsalis was measured by the immersion method and leaf disc method, respectively. The optimal concentration of ethanol was 60%, and the best material-liquid ratios of ethyl acetate, petroleum ether, n-hexane and 60% ethanol was 1∶30, 1∶20, 1∶30 and 1∶25, respectively, with the extraction rates 0.48%, 0.31%, 0.37% and 0.44%, respectively, suggesting that the optimal solvent is ethyl acetate with material-liquid ratio 1∶30. The results of insecticidal activity showed that 2% EPP had the strongest egg hatching inhibition activity on B. dorsalis with corrected inhibition rate 58.53%, and 6% EPP the second, with corrected hatching inhibition rate was 46.46%; 4% EPP had the best gastric toxicity against 1st instar larvae of B. dorsalis, with 24 hours corrected mortality 54.05%, and 48 hours corrected mortality 95.94%. Extraction rate of karanjin from the pod powder of P. pinnata was the highest when the solvent was ethyl acetate, and solid-liquid ratio was 1∶30, with the extraction rate 0.48%. EPP had an egg hatching inhibition activity against B. dorsalis and gastric toxicity activity on its 1st instar larvae, so it is expected to be developed as a plant-derived pesticide against B. dorsalis.

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Antifungal Activity of 13 Phenylpropanoid Metabolites Against Six Colletotrichum Species
WU Pengpeng, AN Wei, XU Yunfeng, LUO Lijuan, JIANG Lingyan
2022, 43 (12):  2515-2526.  doi: 10.3969/j.issn.1000-2561.2022.12.014
Abstract ( 6 )   HTML ( 1 )   PDF (9266KB) ( 1 )  

Colletotrichum is a fungal pathogen which causes a destructive disease called anthracnose and affects a wide range of tropical crop plants. Development of green pesticide is important for the prevention and control of anthracnose disease. Early transcriptome and metabolome studies of stylo (Stylosanthes spp.) have shown that the phenylpropanoid metabolic pathway is significantly up-regulated in response to Colletotrichum infection. In this study, an in vitro antifungal test was used to determine the inhibitory effects of 13 phenylpropanoid metabolites on the mycelial growth of six Colletotrichum species, including stylo C. gloeosporioides, rubber C. gloeosporioides, rubber C. acutatum, yam C. gloeosporioides, mango C. gloeosporioides and papaya C. gloeosporioides. The metabolites with higher inhibitory effects and the pairwise combinations were used to test the activity on the inhibition of the mycelial growth of six Colletotrichum species. In addition, the effects on conidial germination of five Colletotrichum species were also examined using the metabolites and their pairwise combinations. The results showed that 13 metabolites displayed different inhibitory effects on the six Colletotrichum species. Among all the tested metabolites, pterostilbene had the best inhibitory effect on the mycelial growth of the six Colletotrichum species at both 500 μmol/L and 1000 μmol/L. The inhibition rates of pterostilbene ranged from 47.47% to 80.74% at 1000 μmol/L. Phloretin and coumarin also showed inhibitory effects on the mycelial growth of the six Colletotrichum species at a 1000 μmol/L, but the rest nine metabolites did not show significant inhibitory effects. Then, pterostilbene, phloretin, coumarin, ferulic acid, naringin, resveratrol were combined in pair to test the effects on the mycelial growth and conidial germination of the six Colletotrichum. The results showed the combinations containing pterostilbene had a significant inhibitory effect on the mycelial growth of the six Colletotrichum species, and the inhibition rates ranging from 31.07% to 89.05%. For the conidial germination, pterostilbene and its combinations showed a significant inhibitory effect on five Colletotrichum. Therefore, the IC50 values of pterostilbene and its combinations on conidial germination of five Colletotrichum species were determined. Overall, the metabolites or combinations with best inhibition effects on stylo C. gloeosporioides, rubber C. gloeosporioides, rubber C. acutatum, mango C. gloeosporioides and papaya C. gloeosporioides were pterostilbene+phloretin, pterostilbene+ferulic acid, pterostilbene+ferulic acid, pterostilbene+phloretin and pterostilbene with IC50 values of 293.475 μmol/L, 67.660 μmol/L, 184.764 μmol/L, 108.671 μmol/L and 68.417 μmol/L, respectively. The metabolites and its combination identified from this study could provide candidates for further development of green pesticide.

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Isolation and Identification of Leaf Pathogen from Pandanus amaryllifolius Roxb.
GOU Yafeng, XUE Chao, GAO Shengfeng, SUN Shiwei, QIN Xiaowei, YU Huan, TIAN Tian, LIU Shichao
2022, 43 (12):  2527-2533.  doi: 10.3969/j.issn.1000-2561.2022.12.015
Abstract ( 8 )   HTML ( 1 )   PDF (1750KB) ( 5 )  

Pandanus amaryllifolius, a new food flavor, is loved by consumers. The main edible part is leaves. Leaf diseases have become the primary restrictive factor affecting the development of P. amaryllifolius industry. There are few reports on the research of leaf diseases on P. Amaryllifolius. In order to control the pathogens causing leaf diseases, this study investigated the occurrence and epidemic of leaf diseases, defined the main incidence period and disease types, isolated and identified the pathogens of different leaf diseases, and it would provide technical support for promoting the development of P. amaryllifolius industry. The occurrence of leaf diseases mainly began from the middle and late November of each year to the end of April of the next year. The pathogenicity of 28 isolated pathogens was determined in vitro leaves and in vivo potted seedlings. Through the observation of pathogen colony morphology, spore microstructure, universal identification of fungal primers ITS1/ITS4 and pathogenicity determination, strains BDC4121, BDC11221, BDC4112, BDC21112, XYS211, LSS112, LSS214, LSS213 and LSS221 were finally obtained through Koch’s rule verification. Through the screening of sporulation medium, BDC11221 was found to produce spores in mung bean liquid medium and shaking table for 5-7 days, LSS214 to spores in PDA at 28℃ for about 30 days, and BDC4121, BDC4112, XYS211, LSS112, LSS221 and LSS213 to produce spores in PDA at 28℃ for 7-10 days. Combined with ITS1/ITS4 identification and spore microstructure observation, the pathogens were in Talaromyces, Fusarium, Colletotrichum, Epicoccum, Pestalotiopsis, Phomopsis, Alternaria and Acrocalymma. The pathogens will be clarified with multigenome sequencing technology.

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Identification, Biological Characteristics and Fungicide Screening of Tobacco Leaf Spot Disease Pathogen Epicoccum latusicollum
AN Xuanxian, SANG Weijun, LU Yanhui, KONG Fei, WANG Wuquan, LI Haoxi, YANG Jiangmin, PENG Lijuan, YANG Maofa
2022, 43 (12):  2534-2544.  doi: 10.3969/j.issn.1000-2561.2022.12.016
Abstract ( 10 )   HTML ( 3 )   PDF (2978KB) ( 7 )  

Leaf spot disease is one of the main tobacco diseases in the field period, which is mainly caused by fungal infection. It is easy to happen and spread, and has a great impact on the quality and yield of tobacco. In this study, the strain was isolated and purified from the leaves with typical leaf spot diseases of tobacco variety ‘K326’ in Guangxi Zhuang Autonomous Region by tissue separation, and through pathogenicity determination combined with morphological characteristics and molecular biological methods to identify pathogens. The mycelium growth rate method was used to measure the mycelium growth of pathogens in different media, temperature, pH, carbon source, nitrogen source, light, lethal temperature treatment and 10 common chemical conditions. In the early period of tobacco leaf spot disease, the typical symptoms of the leaf spot disease are gray white small round spots. As the disease worsens, the round spot gradually diffuses into irregular shape, and the center of the spot forms a perforation, the color is gray white, the edge is brown, and accompanied by a yellow halo. We isolated and purified two strains and named them as HZFC36 and HZZS76. The pathogenicity test results showed that both strains could cause disease spots on the leaves of healthy ‘K326’ tobacco plant under the condition of no leaf injury. Epicoccum latusicollum was identified as the pathogen causing tobacco leaf spot disease in Guangxi, based on morphological characteristics of pathogen and phylogenetic analysis of multiple loci (LSU, ITS, RPB2 and TUB2). The mycelia of the pathogen grew the fastest on CMA medium, and the optimal growth temperature was 28℃, the optimal pH was 6, the optimal carbon was sucrose and nitrogen source was beef extract powder. 24 h continuous light is favorable to the growth of the mycelia, and the mycelia did not grow after being continuously treated in water bath at 47℃ for 10 min. Preliminary screening results of chemical fungicides in the laboratory showed that 50% boscalid and 25% pyraclostrobine had the best inhibitory effect on the pathogen with EC50 value 4.752×10-2 mg/L and 4.989×10-2 mg/L respectively. The results of the study would provide a theoretical basis for the field control of tobacco leaf spot caused by E. latusicollum.

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Post-harvest Treatment & Quality Safety
Influence of Screw Extrusion Expansion Drying on Structure and Properties of Natural Rubber
CHEN Guojing, WANG Bingbing, LUO Ting, LI Gaorong, ZHANG Fuquan, LIAO Jianhe, LIAO Lusheng
2022, 43 (12):  2545-2553.  doi: 10.3969/j.issn.1000-2561.2022.12.017
Abstract ( 6 )   HTML ( 1 )   PDF (2638KB) ( 7 )  

Natural rubber is mainly dried by hot air. However, natural rubber is a poor conductor of heat and has strong self-adhesion, which leads to low drying efficiency, sticky rubber and entrapment in hot air drying, and adversely affects the performance of the product. Screw extrusion expansion drying process, a new drying method, has been widely used in the synthetic rubber industry due to the high drying efficiency, high automation level and stable process. And the drying process also has a good application prospect in the production of natural rubber (NR). In this paper, the structure of NR prepared by traditional hot air drying and screw extrusion expansion drying (respectively denoted as NT and NCT) was compared, and the performance characteristics of NCT were analyzed to explore the feasibility of screw extrusion expansion drying process in the production and processing of natural rubber. For raw rubber, the screw extrusion expansion drying process could reduce the thermo-oxidative degradation of the NR molecular chain during the drying process because of its low drying temperature and short drying time, so NCT had higher initial plastic value, Mooney viscosity and gel content than NT. The screw extrusion drying process had little effect on the non-rubber components, so the change range of the non-rubber components such as protein and volatiles was low. For the pure compound vulcanizate, NT exhibited a faster cure rate than NT. The contribution of the internal network structure of the vulcanizate was fitted using the Mooney-Rivlin equation. The effective crosslink density and the number of chemical crosslink networks after NCT vulcanization were relatively low. The conventional mechanical properties such as tensile strength, tear strength and modulus of NCT were lower than those of NT, and NCT exhibited higher fatigue temperature rise and higher degree of creep during dynamic loading. For carbon black vulcanizate, the conventional mechanical properties of NCT and NT were not significantly different., this may be due to the faster vulcanization rate of vulcanization accelerator N-tert-butylbenzothiazole-2-sulphenamide. However, NCT had longer fatigue life and better dynamic fatigue properties, which means the screw extrusion drying process could improve the dispersion of carbon black.

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Comparative Study of Multiple Image Edge Detection Operators Applied to Size Measurement of Passiflora edulia Sims
LIU Xian, LIN Yingzhi
2022, 43 (12):  2554-2563.  doi: 10.3969/j.issn.1000-2561.2022.12.018
Abstract ( 4 )   HTML ( 1 )   PDF (1260KB) ( 0 )  

Size measurement was a very important and indispensable link in the postpartum sorting stage of passion fruit. This paper described a variety of edge detection operators and image recognition steps based on edge detection algorithm. A fruit image acquisition platform was constructed by simulating fruit sorting site. In order to increase the difficulty, forty passion fruits with certain wrinkle on the surface were obtained by using fruit image acquisition platform and forty images shoot from the top were selected as the test material. Based on the Visual Studio 2017 integrated development environment, called the OpenCV 3.2.0 machine vision library, C++ programming language was used to detect the edge of forty passion fruit images by Canny, Sobel, Laplacian and Scharr operators. The size of passion fruit was measured by photoshop 7.0.1 software based on images as the approximation of real fruit size and according to the value to measure the detection accuracy of algorithm. The detection parameters of the four operators were automatically optimized, and the detection parameters of each operator, the detection accuracy of the four operators and the single fruit detection time were statistically analyzed by SPSS software. The test results showed that the measurement accuracy of passion fruit size using Canny operator under (70, 105, 3) parameters was the highest, the average time consumed of the single fruit measurement was 1.98 ms, it was the fastest of four operators, which can satisfy the actual demand for the intelligent sorting of passion fruit.

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Identification and Evaluation on Leaf Bud Traits and Biochemical Components of Dominant Strains of Camellia tachangensis
LI Caiyun, SONG Qinfei, NIU Suzhen, ZHAO Zhifei, HE Yingqin, LI Fang, MA Anquan
2022, 43 (12):  2564-2575.  doi: 10.3969/j.issn.1000-2561.2022.12.019
Abstract ( 4 )   HTML ( 2 )   PDF (846KB) ( 4 )  

In order to scientifically and reasonably select new lines of high-quality Camellia tachangensis, seven dominant strains of C. tachangensis were used as the materials in this study, ‘Fuding Dabaicha’ as the check, to comprehensively analyze and systematically evaluate the leaf bud traits, basic quality traits, catechin components and amino acid components. The leaf bud traits of the seven lines were medium leaf or large leaf species with slightly elongated yellow-green bud leaves of shallow and blunt leaf teeth, without pilose or less pilose, in elliptic or long elliptic, with hard and crisp texture, and glossy leaf thickness.. Biochemical analysis showed that the water extracts, free amino acids and ECG contents of the seven lines were high, indicating that they were excellent tea germplasm resources. The variation range of water extract content, caffeine content, tea polyphenols content, amino acid content, crude fiber content, vitamin C content, protein content and water-soluble carbohydrate content was 47.02%-48.70%, 2.91%-3.42%, 19.03%-21.07%, 4.07%-4.84%, 7.43%-8.38%, 208.00-332.00 mg/100 g, 33.82-35.07 mg/100 g, 3.23%-3.85%, the variation range of phenol-ammonia ratio was 3.98-5.04. The content of main catechin was in the order of C>ECG>EC>EGCG>EGC, the content of C and ECG was high, which was significantly higher than that of CK, and the variation range was 5.25%-9.02% and 6.11%-7.64%, respectively. The contents of EGCG and EGC were low, which were significantly lower than that of CK, and the variation range was 0.08%-1.44% and 0.05%-0.31%, respectively. A total of 19 amino acids were detected in the seven lines. There were some differences in the types and contents of amino acids among different components. The five amino acids with high content were theanine>glutamic acid>arginine>aspartic acid>serine, accounting for more than 82.14 % of the total amino acids. There was a certain correlation between morphological traits and bochemical components. The results of principal component analysis based on 16 biochemical components showed that 16 biochemical components were simplified to 5 factors, and the cumulative contribution rate was 95.68%, which contained most of the star information of all traits. Comprehensive Evaluation based on biochemical components showed that L17, L22 and L06 ranked the top three among the seven lines. In this study, dominant lines L06, L17 and L20 with potential characteristics of suitable green tea and lines L12, L13, L21 and L22 with potential characteristics both for black and green tea production were identified.

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Preliminary Analysis of Aroma Components in Fruits of Different Geographical Sources of Fragaria nilgerrensis Schlecht
WANG Dong, CHEN lijuan, LI Hongwen, LIU Jia, ZAHNG Guowei, WANG Jianhui
2022, 43 (12):  2576-2585.  doi: 10.3969/j.issn.1000-2561.2022.12.020
Abstract ( 9 )   HTML ( 2 )   PDF (1703KB) ( 3 )  

Flavor improvement is one of the most important tasks in strawberry breeding. Fragaria nilgerrensis Schlecht has been widely concerned because of its special aroma components. There are abundant strawberry resources in southwest of China such as Sichuan, but the researches on its aroma components are not systematic. In this experiment, the aroma components of strawberry fruits from different geographical sources were analyzed. It could broaden the genetic background of cultivated strawberry and provide theoretical basis for innovative utilization of F. nilgerrensis Schlecht resources and breeding. In this study, headspace solid phase microextraction and gas chromatography-mass spectrometry (GC-MS) were used to analyze the differences of aroma components in six different geographical sources of F. nilgerrensis Schlecht. The results showed that a total of 89 aroma substances were detected. Different from the previously reported aroma components of cultivated strawberry, ester compounds did not account for the largest proportion in the other five geographical sources of F. nilgerrensis Schlecht, except Lijiang Yulong Snow Mountain. A total of 56 volatile substances with relative content greater than 1% were detected in this study, including 2 aldehydes, 19 hydrocarbons, 16 esters, 5 ketones, 4 alcohols, 5 amines and acids, and 5 other compounds. There were no common aroma components, and the aromatic components of F. nilgerrensis Schlecht were mainly esters and hydrocarbons, but they did not reach 50%. The aromatic components were mainly esters and hydrocarbons. The variety of aroma components of F. nilgerrensis Schlecht in Lijiang Yulong Snow Mountain was the most abundant, while that in Qinba Mountain of Wanyuan was the least. Among the aroma components measured, the first three with higher relative content were as follows: erythro-9,10-dibromopentacosane, dibutyl phthalate, benzeneethanamine. Cluster analysis and PCA analysis showed that the aroma components of F. nilgerrensis Schlecht in Yulong Snow Mountain of Lijiang were divided into a single cluster. Although they were both F. nilgerrensis Schlecht varieties, the aroma components were quite different due to geographical location and environmental characteristics. The influence of environment on the volatile compounds of strawberry needs further study.

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Agricultural Ecology & Environmental Protection
Temporal and Spatial Variation of Tropical Fruit Planting Structure in Hainan Island
YE Lu, LI Yuping, LIANG Weihong, LIU Yanqun, QIN Xiaoli, DENG Chunmei, JIN Yan
2022, 43 (12):  2586-2596.  doi: 10.3969/j.issn.1000-2561.2022.12.021
Abstract ( 8 )   HTML ( 2 )   PDF (3353KB) ( 4 )  

As tropical fruit industry is the pillar industry for peasants in Hainan province to increase income, the analysis of the evolution course and driving factors of tropical fruit planting structure since the establishment of Hainan province is conducive to putting forward corresponding adjustment and optimization strategies and promoting the optimization and upgrading of tropical fruit industry in Hainan Island. In this paper, the methods of gravity center analysis, regression analysis and spatial analysis were used to study the structural type evolution, planting proportion trend, gravity center migration and driving factors of tropical fruit planting structure in Hainan Island and its inner cities and counties from 1988 to 2020. The area of tropical fruits in Hainan Island fluctuated and increased, mainly mango, banana, litchi, pineapple, citrus, orange and grapefruit, longan, etc.. In which, the moving distance of the gravity center of longan production was the largest, while the pineapple was the smallest. The total planting structure of tropical fruits in Hainan Island was composed of mango, banana, litchi and pineapple, and the proportion of single fruit, combination of two fruits and combination of three fruits was 48 : 0 : 52. The planting structure of tropical fruits in cities and counties was composed of banana, mango, litchi, pineapple, longan, citrus, orange and grapefruit. The proportion of single fruit, combination of two fruits and combination of three fruits was 78 : 9 : 13. The spatial aggregation characteristics of tropical fruit planting structure in all cities and counties were obvious, and experienced the process of aggregation, dispersion and re-aggregation. Most cities and counties formed a stable dominant planting structure, and a few were still adjusting and exploring the dominant planting structure suitable for local. The regional aggregation characteristic which the change trends of main fruits planting proportion were the same became more obvious. The driving factors for the evolution of tropical fruit planting structure in Hainan Island mainly included the natural environment, policy support, social demand, market situation and Nongken reform. This paper concludes that to promote Hainan tropical fruit industry to stable, high quality development as a whole, it ought to follow the natural resource conditions, take the market demand as the guidance, comprehensively consider the economic and social development, ecological protection and other factors, regulate the industrial scale reasonably, and promote the formation of local advantages and characteristics of fruit planting structure on the basis of fully understanding of the evolution of local fruit planting structure and its driving factors.

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Effects of Precipitation Pattern Change on the Growth Carbon and Nitrogen Metabolism of Alpinia oxyphylla During Dry Season
HU Wen, ZHOU Xiaohui, LI Qinfen, CHENG Hanting
2022, 43 (12):  2597-2605.  doi: 10.3969/j.issn.1000-2561.2022.12.022
Abstract ( 7 )   HTML ( 1 )   PDF (1142KB) ( 1 )  

Alpinia oxyphylla is one of the four southern medicines in China, and its cultivation under rubber forest has become the most important agroforestry mode in rubber plantation. The study previously found that insufficient precipitation is the main limiting factor for the growth and photosynthesis of A. oxyphylla during the dry season. However, our knowledge is still limited in understanding the response of A. oxyphylla to precipitation pattern change during the dry season. Three precipitation gradients including decreased precipitation (W-)10 mm/ month, natural precipitation (W) 25 mm/ month and increased precipitation (W+) 40 mm/ month, and set 5 days (5 d) and 10 days (10 d) of interval between precipitation were simulated in the study. The leaf water content in W- plant of 10 d was significantly increased by 3.63% compared with 5 d. In addition, we analyzed plant growth parameters, carbohydrate and N compound levels and the activity of key enzymes related to C and N metabolism through two factors experiment of precipitation and precipitation interval. The aboveground biomass and underground biomass of A. oxyphylla decreased with the decrease of precipitation. The total biomass of 5 d was significantly higher than that of 10 d at all precipitation levels (P<0.05). The plant growth was further inhibited by precipitation and extended precipitation interval. The decreased precipitation changed the activity of carbon metabolism enzymes, inhibited the AMY and INV activity, and promoted the SPS activity. However, this promoting effect became trivial with extended precipitation interval. The accumulation of non-structural carbohydrates (soluble sugar and starch) was promoted by decreased precipitation and activity change of C metabolic enzymes. The decreased precipitation lowered the total N content of A. oxyphylla leaves, and the total N content of W+ and W- in 5 d was significantly increased by 8.33% and 9.81% compared with that of 10 d. The N metabolic components changed in plant leaves with decreased precipitation. Meanwhile, the GS/GOGAT, NR and NiR activity increased with the decreased precipitation, which accelerated nitrate nitrogen (NO3-) reduction and ammonium (NH4+) assimilation. The NO3- and NH4+ in W plant in 5 d were significantly decreased by 57.54% and 152.98 compared with that of 10 d. Therefore, the change of precipitation pattern could affect the change of biomass carbon and nitrogen compounds and metabolic enzymes of the plant during the dry season. In summary, drought stress was adapted to ensure normal growth of A. oxyphylla through biomass allocation and C and N metabolism regulation.

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Interspecific Association of Woody Plants in Michelia shiluensis Community, Diaoluoshan Nature Reserve, Hainan Province
WEI Yaqing, SONG Xiqiang, ZHAO Ying, SHI Youhai
2022, 43 (12):  2606-2613.  doi: 10.3969/j.issn.1000-2561.2022.12.023
Abstract ( 6 )   HTML ( 1 )   PDF (8600KB) ( 1 )  

Michelia shiluensis is one of the endemic plants and national class II endangered protected species in Hainan Island. It has a sporadic distribution in central and southern mountains of Hainan Island, including Diaoluoshan Mountain, Yinggeling Mountainand, Wuzhi Mountain, etc. Diaoluoshan Nature Reserve is the most concentrated distribution area of M. Shiluensis. Study on the interspecific association of woody plants in M. shiluensis community in Diaoluoshan Nature Reserve and analysis of its status in the community is of great significance to in-situ conservation of the species. On the basis of a 2×2 contingency table, χ2-test, Pearson correlation coefficient test and Spearman rank correlation coefficient test were used to analyze the interspecific relationship between M. shiluensis and other plants in the community. There were more positive correlations in the shrub layer than in the tree layer. There was no significant interspecific association between M. shiluensis and most other plants in the community, the interspecific relationship showed a relatively loose trend in general, and the trend of mutual independence among populations was obvious. The tree layer and shrub layer were generally more positively associated with M. shiluensis, indicating that the development of the community was beneficial to the development of the M. shiluensis population.

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Niche of Dominant Plant Populations of Acacia confusa Community in Pingtan Island
MA Xiaodi, JIANG Degang, LIU Zilin, WANG Fang, WEN Ruilong, DENG Chuanyuan
2022, 43 (12):  2614-2625.  doi: 10.3969/j.issn.1000-2561.2022.12.024
Abstract ( 8 )   HTML ( 3 )   PDF (1122KB) ( 6 )  

Acacia confusa is the main construction species of Acacia forest, it’s an excellent afforestation broad-leaved tree species in Pingtan Island. Understanding the niche characteristics of the main woody and herbaceous plants population is helpful to understand the coexistence and competition mechanism of species in island community. We investigated A. confusa communities in Pingtan of its inner and subsidiary islands, Levins and Shannon niche breadth and Pianka niche overlap indexes were used to analyze the ecological niche of the main species in the woody layers and herb layers of A. confusa communities in Pingtan Island. A total of 144 species of vascular plants belonging to 123 genera and 63 families were found, mainly Gramineae and Compositae, significantly different from continental vegetation types. 14 species of invasive plants include Praxelis clematidea, Bidens Pilosa and Erigeron bonariensi were found in the community, which occupied a large niche in the community and may cause some ecological disturbance to the symbiotic population. A. confusa and Casuarina equisetifolia in the tree layer, Sageretia thea and A. confusa in the shrub layer, and Miscanthus sinensis and Praxelis clematidea in the herb layer had higher niche breadth than other species. Species with niche breadth less than 0.5 accounted for 96.67% of the total. The niche breadth of species with higher importance values were generally larger, but not entirely consistent. The niche overlap of dominant population was herb layer (0.253) > shrub layer (0.231) > tree layer (0.149), all smaller than 0.3. The niche overlap between the main species in the community was generally lower, niche differentiation weakened interspecific competition. The strong environmental filterability in the Island led to different degrees of habitat differentiation of the population. The population concentrated in local habitats by narrowing niche breadth, thus promoting the coexistence of species in the island community. The A. confusa community on Pingtan Island was the top zonal community with stable interspecific relationship and slow population regeneration.

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