Chinese Journal of Tropical Crops
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Welcome to Chinese Journal of Tropical Crops,
2024 Volume 45 Issue 6
Published: 25 June 2024
  
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    Omics & Biotechnology
  • Omics & Biotechnology
    ZOU Zhi, ZHENG Yujiao, QIAO Xueying
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    Plasma membrane intrinsic proteins (PIPs), which belong to the aquaporin (AQP) family within the major intrinsic protein (MIP) superfamily, are known for the high water transport activity at the cell membrane. The subfamily is highly conservative and only includes two phylogenetic groups named PIP1 and PIP2. Natural rubber, an important industrial raw material and strategic material, is mainly derived from Para rubber tree (Hevea brasiliensis Muell. Arg.), a big tree originated in the Amazon basin of South America. As a special tissue for rubber synthesis and storage, the laticiferous cells possess no plasmodesmata with neighboring parenchyma cells, and the water balance is mainly mediated by PIP aquaporins. In previous studies, a highly abundant PIP gene denoted HbPIP1;4 was identified, however, no detectable water transport activity was found when heterologously expressed in Xenopus laevis oocytes, which may be due to its inability to localize to the cell membrane. To uncover the acting site and multimerization features of HbPIP1;4 in vivo, recombinant plasmids pNC-Cam1304-SubN-HbPIP1;4, pNC-BiFC-ECN-HbPIP1;4, and pNC-BiFC-ENN- HbPIP1;4 for subcellular localization and bimolecular fluorescence complementation (BiFC) were successfully constructed. Agrobacterium tumefaciens transformed with above recombinant plasmids were used to infiltrate tobacco (Nicotiana benthamiana), and transiently transformed leaves were subsequently checked using laser confocal microscopy. Compared with wide distribution of fluorescence signals throughout the cell for the control pNC-Cam1304-SubN, signals of pNC-Cam1304-GFP-HbPIP1;4 were restricted to the cell membrane, supporting the plasma membrane localization of HbPIP1;4, which is consistent with the bioinformatics prediction. The result was further supported by the BiFC analysis, which also implied that HbPIP1;4 could form homomultimer, in accordance with the 3D prediction via homology modeling. The results would lay a solid foundation for further uncovering the mechanism of water balance of the laticifer. Nevertheless, PIP aquaporins that could interact with HbPIP1;4 in rubber tree remain to be further characterized.

  • Omics & Biotechnology
    WANG Zhiyuan, LIANG Hongcui, CAI Jianhe, CHEN Baoshan, XU Xiongbiao
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    Sporisorium scitamineum, the pathogen of destructive disease smut, usually causes abnormal growth of meristematic tissue and forms a “black whip” in meristem tissues. In some cases, it induces formation of flowering structures in some sugarcane cultivars (genotypes), but the exact mechanism remains unclear. In order to explore flowering related genes and the expression patterns in sugarcane in response to infection by S. scitamineum, the healthy and S. scitamineum infected ‘guitang42’ sugarcane cultivar samples were analyzed by transcriptome sequencing. A total of 3276 differentially expressed genes (DEGs) were identified, of which 1677 genes were up-regulated (P<0.05) and 1599 genes down-regulated (P<0.05). The DEGs were mostly enriched in the biosynthesis process, ribosome, ribonucleoprotein complex, ribosome structural components, etc. according to GO enrichment analysis. The KEGG analysis showed that the DEGs were mostly enriched in amino acid biosynthesis, purine metabolism, carbon metabolism, phagocytosis, and other metabolic pathways. Also, out of 30 DEGs were identified to be associated with flowering, and the representative genes such as FT1, PIE1, GID1, GA20ox-1, GA20ox-2 were validated by qRT-PCR. The qRT-PCR results were consistent with the transcriptomic data, confirming the dependability of the transcriptome sequencing results. The findings would present essential candidate genes for revealing the mechanism of early flowering of sugarcane plants caused by S. scitamineum, and lay the foundation for disease resistance breeding.

  • Omics & Biotechnology
    YANG Weihai, GUO Shanxiang, XU Ting, XIAO Yi, LEI Wenjun
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    Leaf photosynthesis is the energy source of plant life activities. However, some macadamia varieties (Macadamia integrifolia) planted in southern China are prone to generate the etiolated leaves under the continuous high temperature in summer, which seriously affects the shoot growth and fruit production of macadamia trees. In order to explore the mechanism of photosynthetic energy generation in the etiolated leaves of macadamia, the genes related to photosynthetic energy metabolism were identified and screened in this study, based on the previously obtained transcriptome sequencing data from the leaves of HAES344 macadamia at different yellowing stages, and the expression changes of the key genes in photosynthetic energy metabolism were analyzed during leaf yellowing of HAES344 macadamia by qRT-PCR. 96 genes with differential expression in the etiolated leaves of HAES344 macadamia were identified to be related to energy metabolism according to KEGG functional annotation and enrichment analysis, and the number of the differentially expressed genes enriched in the oxidative phosphorylation pathway was the highest, followed by carbon fixation pathway, and the least genes were enriched in the antenna proteins. After screening (RPKM>0.5), a total of 43 genes related to photosynthetic energy metabolism were obtained. Among these genes, the expression level of 27 genes decreased significantly in the yellowed leaves, while the remaining 16 genes did the opposite. Through the qRT-PCR analysis of the relative expression level of key functional genes in the photosynthetic energy metabolism, the CAP10A gene encoding photosystem Ⅱ (PSⅡ) antenna protein, the ATPC and ATPF genes encoding ATPase subunit protein, the enzyme genes related to carbon assimilation (GAPA, GPD, At4g2652 and rbcL), the Os05g0200100 and CXXS1 genes encoding thioredoxin, and the TIC32 gene associated with plastid protein transmembrane transport showed a significant lower transcription level in the etiolated leaves of HAES344 macadamia compared with the normal leaves, while the SIR and APR3 genes related to sulfur metabolism and the PGR5, ndhB and ndhD genes mediating cyclic electron transfer did the opposite, which suggested that the greatly changed expression patterns of genes related to photosynthetic energy metabolism affected the production of photosynthetic energy in the macadamia yellowing leaves. The results of this study would provide a reference for further exploring the mechanism of photosynthetic energy metabolism-related genes in the etiolated leaves of macadamia.

  • Omics & Biotechnology
    LIN Zhaowei, MENG Xiuli, TANG Qinghua, NIU Xiaoqing, SONG Weiwei
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    Areca palm is an important tropical economic crop in Hainan Province. Areca palm yellow leaf disease (YLD) caused by phytoplasma infection is a devastating disease in the production of areca in China. In order to establish an accurate and efficient detection method for areca palm yellow leaf phytoplasma, this study designed and synthesized specific primers AMf/AMr and AM-Prode based on the 16S rDNA gene of areca palm yellow leaf phytoplasma. The method was used to test the accuracy, sensitivity, specificity and repeatability, and to detect phytoplasma diseases in other plants. The method could accurately detect the positive samples, and the healthy samples had no amplification curve. In the sensitivity test, the method could detect the sample concentration level of 1.16×101 copies/μL, and the standard curve equation was y=-3.4185x+43.624, the amplification efficiency was 96.12%, and the correlation coefficient R2=0.9833. In the specificity test, the method had good specificity for the detection of YLD, and the genomes of areca, other disease pathogens and the endophytes did not interfere with the method. In the repeatability test, the method had good repeatability for the detection of YLD. The detection method could be used to detect 8 phytoplasma diseases such as chinaberry yellow leaf disease, ‘Pericampylus glaucus’ witches' broom disease and pepper yellow leaf disease and the detection of phytoplasma has certain universality. The establishment of detection method is conducive to providing reliable technical means for the accurate diagnosis of YLD, pathogen monitoring and vector insect detection.

  • Omics & Biotechnology
    WANG Dan, XU Bingqiang, SUN Yong, PENG Cunzhi, CHANG Lili, TONG Zheng
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    Hevea brasiliensis is an important natural rubber-producing plant. Rubber particles (RP) in latex are important organelles for the synthesis of natural rubber, which can be divided into large rubber particles (LRP) and small rubber particles (SRP) according to the diameter. Although the specific mechanism of its regulation of natural rubber synthesis in response to exogenous ethylene stimulation has been studied. However, the specific regulatory mechanism of LRP and SRP in regulating natural rubber synthesis in response to ethylene stimulation is still unclear. In order to clarify the role of RP with different diameters in the synthesis of natural rubber, LRP and SRP stimulated by ethylene were isolated and the proteins of corresponding samples were extracted for differential protein analysis. 37 differential proteins in response to ethylene stimulation were identified in the LRP, which were involved in natural rubber biosynthesis, glycolysis/gluconeogenesis, carbon metabolism and amino acid biosynthesis, and some other metabolic pathways, including four members of the REF/SRPP family. 56 differential proteins were identified in SRP, which were involved in protein processing, endocytosis, splicing in endoplasmic reticulum, and some other metabolic pathways, including five members of the REF/SRPP family. The key differential accumulation protein REF138 had many isoforms with different isoelectric points (pI) and molecular weights (MW). REF138 isoforms below the standard pI (4.80) on LRP were down-regulated in response to ethylene stimulation, while isoforms above the standard pI were up-regulated to ethylene stimulation. Different from LRP, more isoforms of REF138 on SRP changed in response to ethylene stimulation, and isoforms with standard MW (14.7 kDa) were up-regulated in response to ethylene stimulation, while isoforms with higher than standard MW were down-regulated in response to ethylene stimulation. The function analysis of key differential proteins showed that there were interactions among the members of the REF/SRPP family. REF138, REF175, REF258, SRPP117 and SRPP204 may form protein complexes and bind to RP. In addition to the members of the REF/SRPP family, 20 proteins interacting with REF138 were mainly involved in the spliceosome and endocytic metabolic pathways, and 50 proteins interacting with REF258 were involved in the regulation of lipid metabolism and the synthesis of secondary metabolites. In conclusion, functional analysis of differential proteins and the interaction proteins responsive to ethylene stimulation on LRP and SRP might preliminarily reveal the metabolic regulatory mechanism of LRP and SRP in regulating natural rubber synthesis in response to exogenous ethylene stimulation.

  • Omics & Biotechnology
    FU Lanping, XIN Shuli, LIU Yonghua, ZHU Guopeng
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    Grey mold is a common disease in tomato production caused by Botrytis cinerea, a necrotrophic pathogen, which often leads to dramatic reduction of tomato yield. Sucrose catabolism plays an important role in plant defense against pathogen infection by providing carbon skeleton and energy for plant defense responses and/or regulating the expression of defense-related genes through signaling pathway. Previous studies have shown that cell wall invertase (CWIN), a kind of sucrose-degrading enzyme, can enhance plant resistance to several necrotrophic pathogens. However, no research has been conducted to study the role of CWIN in tomato resistance to B. cinerea. In this study, wild type tomato (W) and its transgenic line (R) with elevated CWIN activity were used as materials to study the effect of CWIN on tomato resistance to B. cinerea (Bc) via in vitro inoculation. In addition, inoculated leaves were sampled 12 h and 60 h post inoculation (hpi) for RNA-Seq to elucidate possible molecular mechanisms underlying the regulation of CWIN to tomato resistance against B. cinerea. The results are as follows: (1) Elevated CWIN activity enhanced tomato resistance to B. cinerea; (2) KEGG annotation showed that DEGs (W-Bc-12 h-vs-R-Bc-12 h) from 12 hpi were significantly enriched in five pathways, including biosynthesis of secondary metabolites, metabolic pathways, DNA replication, starch and sucrose metabolism, and steroid biosynthesis; No significant enrichment pathway was found for DEGs (W-Bc-60 h-vs-R-Bc-60 h) from 60 hpi. (3) By mapping DEGs to plant-pathogen interaction pathway, it was revealed that the LRR-receptor serine/threonine-like kinase gene FLS2 and heat shock protein gene HSP90 involved in hypersensitive response and defense-related gene induction were up-regulated in RNAi leaves after inoculation, indicating the two genes may participate in the regulation of CWIN to tomato resistance to B. cinerea. (4) The analysis of plant hormone signal transduction pathways and MapMan mapping showed that the signal pathway of jasmonic acid (JA) and ethylene (ET) was enhanced in RNAi leaves after inoculation, while the signal pathway of salicylic acid (SA) was weakened, indicating that the hormones might work together to improve the resistance of RNAi tomato to B. cinerea. In addition, the signal transduction of growth-promoting hormone auxin (IAA) and cytokinin (CTK) was also enhanced in RNAi leaves after inoculation, but that of senescence-promoting hormone abscisic acid (ABA) was weakened. The changes in signal pathways of IAA, CTK and ABA could inhibit the cell death in host during bacterial infection, thus preventing the necrotrophic pathogen B. cinerea from obtaining necessary nutrients from the dead host cells for its infection. In addition, MapMan mapping also revealed that cell wall thickening, proteolysis, reactive oxygen species (redox state and peroxidases) and secondary metabolites were also greatly enhanced in RNAi leaves after inoculation, which all contribute to improving the disease resistance of tomato. In conclusion, this study showed that elevated CWIN activity enhanced tomato resistance to B. cinerea. Transcriptome analysis not only verified the existing molecular mechanisms underlying the regulation of CWIN to plant resistance to microbial pathogens, such as cell wall thickening, accumulation of reactive oxygen species (ROS) and hypersensitive response (HR), accumulation of resistance hormones (SA and JA/ET), biosynthesis of pathogenesis-related protein (e.g. PR and HSP proteins) and secondary metabolites (such as phytotoxins and phenolics), but also revealed several possible new mechanisms including the signal transduction of growth-promoting hormone (IAA and CTK) and senescence-promoting hormone (ABA) and proteolysis. This study can provide theoretical guidance for the improvement of tomato resistance to B. cinerea by using modern biotechnologies such as genetic engineering and molecular breeding.

  • Germplasm Resources, Genetics & Breeding
  • Germplasm Resources, Genetics & Breeding
    ZHANG Yingping, JI Xunzhi, YU Shaohong, SU Fan, QIN Xiaowei, HAO Chaoyun, WU Lianzhang, XU Fei, HE Juncai, HE Weidong, YOU Shengjun
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    The germplasm resources of Amomum tsao-ko (AT) at different altitudes in Nujiang, Yunnan were used as the materials to explore the genetic diversity of the agronomic phenotypic traits of AT germplasm resources at different areas. The genetic diversity of the agronomic phenotypic traits of AT was analyzed by measuring 8 agronomic phenotypic traits, using coefficient of variation, genetic diversity index, variance analysis, correlation analysis, cluster analysis, principal component analysis and comprehensive evaluation. The results showed that there were large variations in the agronomic phenotypic traits, and the variation coefficient was 7.63%-32.51%, among which the variation coefficient of tiller number was the largest. The traits showed good diversity, H' (diversity index) was 1.933-2.355, with an average of 2.024. There were significant differences in the agronomic phenotypic traits among different germplasms. There was a significant positive correlation between fruit longitudinal diameter and fruit shape index and fruit weight. There was a significant positive correlation between fruit transverse diameter and fruit weight. There was a significant negative correlation between fruit shape index and leaf width. Cluster analysis divided the AT germplasm resources at different areas into two groups, among which the AT germplasm resources from the areas of Lushui and from Fugong were clustered into one group. Three principal components were extracted from eight agronomic phenotypic traits, and the cumulative contribution rate reached 76.940%, which could comprehensively reflect most of the information of agronomic phenotypic traits of AT. The comprehensive evaluation results showed that SD12, SD20, SD7, SD17, SD18 and SD5 were ranked in the top six, and the comprehensive performance was better. The genetic diversity of the agronomic phenotypic traits of 24 AT germplasm resources in different areas of Nujiang, Yunnan is relatively rich, and the variability of AT germplasm resources in different areas is obvious. Among them, the agronomic phenotypic traits of SD12, SD20, SD7, SD17, SD18 and SD5 AT are better, which are more suitable for breeding.

  • Germplasm Resources, Genetics & Breeding
    LIN Fei, KANG Yong, MUHAMMAD Dawood, ZHOU Chenran, LI Yamei, GUO Yuhua, YIN Junmei
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    Bombax ceiba is a deciduous tree belonging to the Genus Bombax in the Malvaceae family. It holds significant importance as an ornamental plant of economic, medicinal and edible value in southern China. It is the city flower of Guangzhou and Panzhihua. The traditional propagation methods for B. ceiba are seed sowing and grafting. However, the seeds are difficult to preserve and easily deteriorate, leading to decreased germination rates. Grafting results in even lower survival rates. Therefore, this experiment aimed to study the tissue culture techniques for the rapid propagation of B. ceiba. In this study, B. ceiba seeds were used as the experimental materials, and different disinfection methods were tested to determine the most suitable method for seed disinfection, aiming to obtain sterile seedlings. Using the sterile seedlings as the explants, various basic culture media, combinations of shoot-inducing hormones, induction and proliferation media for apical and adventitious buds, as well as rooting media, were tested and optimized. Additionally, seedling acclimatization experiments were conducted to explore the optimal basic culture medium, hormone combination, induction and proliferation medium, rooting medium, and seedling acclimatization methods. The results showed that the optimal basic culture medium for B. ceiba tissue culture was MS medium supplemented with 30 g/L sucrose and 7.5 g/L agar. The best disinfection method for B. ceiba seeds was 75% ethanol treatment for 1 min, followed by five rinses with sterile water, 4-hour sterilization with a 50% H2O2 solution prepared from 30% H2O2, and another five rinses with sterile water. The optimal plant growth regulators for inducing differentiation of apical buds into young shoots were a combination of 6-benzylaminopurine (6-BA) and naphthaleneacetic acid (NAA). The best induction and proliferation medium was MS medium supplemented with 0.5 mg/L 6-BA, 0.5 mg/L indole-3-butyric acid (IBA), 30 g/L sucrose, and 7.5 g/L agar. The optimal rooting medium was half-strength MS medium supplemented with 0.5 mg/L IBA, 30 g/L sucrose, 7.5 g/L agar, and 0.2 g/L activated charcoal. The recommended substrate for seedling acclimatization was a mixture of sand, peat soil, and vermiculite in a ratio of 1∶1∶1. Through the optimization of seed disinfection methods, culture media selection, hormone combinations, and seedling acclimatization experiments, an efficient tissue culture system for B. ceiba was established. This would provide technical support for the in vitro preservation of B. ceiba seedlings, propagation of superior individuals, healthy seedling breeding, and the industrialized production of seedlings, and lay a foundation for the genetic transformation system of B. ceiba.

  • Germplasm Resources, Genetics & Breeding
    LI Zhiqing, LI Yamei, LI Chonghui, YIN Junmei
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    Phalaenopsis-hybrid Dendrobium is an important ornamental plant in tropical area and has high market values, with beautiful flower appearance and abundant flower colors. In this study, the protocorms and young seedling’s stem segments of commercial varieties, Den. Yaya Victoria, Den. Swirl and Den. Sonia Hiasakul, were used as the explants. The effects of different phytohormone combination on embryogenic callus induction, adventitious bud differentiation and plantlet regeneration were investigated. During the embryogenic callus (EC) induction stage, the best induction explants were protocorms and 2-month-old seedling stem segments and EC could be obtained after 30 days culture in dark condition. The best medium for EC induction of was MSD (MS+30 g/L glucose+1 g/L Hyponex+8 g/L agar) as the basic medium with 0.5 mg/L KT and 0.2-0.5 mg/L 2,4-D. The highest average induction rate of EC was 31.11%, 22.78%, and 50% for Den. Yaya Victoria, Den. Swirl and Den. Sonia Hiasakul, and the induction time for Den. Yaya Victoria was only 15 days from explants to EC. The best proliferation medium was MSD+0.5 mg/L IBA+0.5 mg/L KT, which maintaining EC in good condition without differentiation and the multiplication rate was 0.9. The best medium for differentiation was 1/2 MS+0.5 mg/L IBA+0.15 mg/L KT under light condition of 16 h one day, EC quickly differentiating and forming 2-3 leaf adventitious buds within 30 days, and finally regenerating into plantlet after 60 days in the same medium. The best rooting medium was 1/2 MS+30 g/L sugar+0.5 mg/L NAA+8 g/L agar, with rooting rate 100% and five roots in length 1.3 cm per plantlet. In this research, the EC induction, proliferation and differentiation media have a wide-spectrum and the EC regeneration pathway could lay a solid foundation for further molecular breeding of Phalaenopsis-hybrid Dendrobium.

  • Germplasm Resources, Genetics & Breeding
    JIANG Jinlan
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    Fenjiaren is a new Dendrobium variety bred by Sanming Academy of Agricultural Sciences for both ornamental and edible purposes. In factory seedling cultivation, it was found that Fenjiaren had slow cluster bud proliferation, low proliferation coefficient, underdeveloped root system of tissue culture seedlings and other problems, which affecting the large-scale production of this variety. To improve the efficiency of factory seedling cultivation of the variety, the sterile seedlings were used as the explants, the effects of plant growth regulators including 6-BA, NAA, and additives such as banana puree and AC on the proliferation of stem segments and the rooting of seedlings were studied using L9(33) orthogonal experiments. The suitable culture medium for the proliferation of stem segments of Fenjiaren was 1/2 MS+6-BA 3 mg/L, banana puree 100 g/L, white sugar 30 g/L, activated carbon AC 1 g/L, and agar powder 5.6 g/L. After 4 months of cultivation, the proliferation coefficient of the stem segment was 5.08. Range analysis indicated that the primary and secondary relationship of the factors was 6-BA>NAA>banana puree. The inter subject effect test showed that 6-BA had a significant impact on the growth rate coefficient (P<0.05). The most suitable culture medium for rooting was 1/2 MS+NAA 1 mg/L+banana puree 100 g/L+white sugar 15 g/L+agar powder 5.6 g/L. After 2 months of cultivation, the growth rate coefficient of the rooting was 12.82, the average plant height of the seedling was 12.66 cm, the average leaf length was 4.02 cm, the average number of roots was 11.80, and the average plant weight was 1.67 g. Range analysis indicated that the primary and secondary relationship of the factors was NAA>AC>banana puree. This study optimized the proliferation and rooting conditions of a new variety of Fenjiaren, which could provide technical reference for the seedling breeding of new varieties of Dendrobium and other Orchid plants.

  • Plant Cultivation, Physiology & Biochemistry
  • Plant Cultivation, Physiology & Biochemistry
    LI Chengzhen, YUAN Bingchen, WANG Yanru, LAN Jun, LUO Lijuan, YU Daogeng
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    The study was aimed to investigate the effects of litchi orchard intercropping Stylosanthes guianensis on soil physicochemical properties and soil bacterial community structure, and to provide theoretical basis for litchi orchard intercropping S. guianensis. Soil samples from litchi orchard intercropped with S. guianensis and litchi monocropping modes were used to determine soil physicochemical properties and analyzed by bacterial amplicon sequencing. After intercropping S. guianensis in litchi orchard, in the soil layer depth of 0-20 cm, nitrate nitrogen content significantly increased by 47.52%, available phosphorus content highly significantly increased by 141.53% and available potassium content highly significantly reduced by 125.59%; in the soil layer depth of 20-40 cm, nitrate nitrogen content highly significantly increased by 76.02%, available phosphorus content highly significantly increased by 48.52%, and available potassium content highly significantly reduced by 188.57%. In terms of alpha bacterial diversity, there were no significant changes in Chao1 index, AEC index, Simpson index and Shannon index in 0-20 cm soil layer and 20-40 cm soil layer after intercropping S. guianensis in litchi orchard. In terms of soil bacterial community structure, the main dominant phyla in the soil samples were all Acidobacteriota, Proteobacteria, Firmicutes, Chloroflexi, Bacteroidota, Verrucomicrobiota, Actinobacteriota, Gemmatimonadota, Myxococcota, Crenarchaeota, and Crenarchaeota were soil-specific relative abundances greater than 1% of the phyla after intercropping S. guianensis at 0-20 cm soil depth; at the genus level, in the 0-20 cm soil layer, Candidatus_Nitrosotalea was the genus with soil-specific relative abundance greater than 1% after intercropping S. guianensis, and at the 0-40 cm soil level, Nitrospira was the genus with soil-specific relative abundance greater than 1% after intercropping S. guianensis, Proteobacteria, Verrucomicrobiota, and Gemmatimonadota increased at all soil depths after intercropping S. guianensis; the results of the redundancy analysis showed that the soil bacterial community was mainly affected by effective phosphorus, nitrate nitrogen, and organic matter. In summary, intercropping litchi orchard with S. guianensis would improve the physicochemical properties and change the structure of soil bacterial community in litchi orchard soil, and play a certain role in optimizing the environmental conditions of litchi orchard soil.

  • Plant Cultivation, Physiology & Biochemistry
    WANG Lulu, LIU Xinyi, WANG Hui, WANG Jun
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    The wood of most tree species of DalbergiaL. f. is well-known in the world. The research on wood anatomy mainly focus on tree species, while the research on vine or climbing plant species is rare. This paper discussed the macroscopic and microscopic wood structures of seven species of vines or climbing plants of DalbergiaL. f., and summarized systematically, and compared with the tree species of D. odorifera, so as to provide a scientific basis for wood identification, species identification, protection, breeding, development and utilization of this genus. The macrostructure showed that the difference between heartwood and sapwood was not obvious, and had little glossy, aromatic and oily when rich in gum. The growth ring was not obvious. The pores were obvious and common rich in gum, which were smaller and sparsely distributed in primary xylem, larger and densely distributed in secondary xylem. Included phloem was round. The microstructures indicated that they were all diffuse-porous wood, single pores, radial multiple pores, pores arrangement dispersed, single perforation, inter-vessel pitting alternate, vestured pitting, elliptical to nearly round, and obvious on the tangential section. Axial parenchyma was abundant and overlapped, paratubular banded, annular tubular. The wood rays were non overlapping, more fine and dense. D. odorifera was diffuse-porous wood to near semi-ring-porous wood, included phloem was absent, pith was smaller, axial parenchyma was mainly winged and polymerized-winged (paratubular banded type) or minimal banding (off tube type), low pores density. To sum up, there are many similarities in the wood anatomical structures of the seven vines or climbing plants of DalbergiaL. f., but there are also significant differences mainly in wood rays, wood rays width and pith core inclusions. Wood rays were mainly homotypic multiple columns, occasionally homotypic uniseriate of D. tsoi and D. yunnanensis. D. pinnataand D. benthamiiwere similar with homotypic single or multiple columns, while the former also had heterogeneous Ⅲ type rarely. D. hanceiand D. peishaensis were similar with mainly heterogeneous uniseriate, occasionally heterogeneousⅠ type, while the former also had heterogeneous Ⅲ type rarely. D. candenatensis was mainly heterogeneous Ⅱ type, followed by heterogeneousⅠtype and heterogeneous uniseriate. The wood rays width of D. haneiand D. peishaensis was 1-2 cells, that of D. pinnata, D. benthamiiand D. candenatensiswas 1-3 cells, that of D. yunnanensiswas 1-4 (mostly 2-3) cells. that of D. tsoiwas 1-5 (mostly 3-4) cells. The pith core inclusions was mainly golden yellow, but that of D. tsoiwas silver white, and that of D. pinnatawas absent or not obvious.

  • Plant Cultivation, Physiology & Biochemistry
    PENG Suna, XU Zhengwei, $\boxed{\hbox{HUA Yuwei}}$, GU Xiaochuan, CHENG Jing, HUANG Huasun, HUANG Tiandai
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    Natural rubber is an important strategic material and industrial raw material in China, which mainly originates from rubber tree. The growth cycle of rubber tree is long, and the quality of rubber seedling directly affects the development of rubber industry. The somatic embryo plantlet of rubber tree shows good consistency in the previous studies, and has the advantages of rapid growth and high yield. Hainan Innovation Base for production of Natural Rubber New Planting Material is the base of the current large-scale production of rubber tree somatic embryo plantlets of Reyan 73397 and Reyan 917. In this paper, in order to clarify the large-scale production of the somatic embryo plantlets of rubber tree, the plant height, stem diameter, leaves number and taproot length of Reyan 73397 somatic embryo plantlets from 2018 to 2020 were studied, the differences in each index of the two varieties in 2020 were, compared, and the classification of different varieties in different years were done. The proportions of plant height, stem diameter, leaf number and taproot length of Reyan 73397 were similar in each region from 2018 to 2020. There were no significant differences in plant height, leaf number and taproot length in three years. There were significant differences in stem diameter between 2018 and 2019, and the mean value of the three years was above 2.00 mm, and the difference between the maximum and minimum value was only 0.09 mm. The plant height of Reyan 73397 and Reyan 917 was the same, and the mean value of plant height of both varieties was 8.0 cm. The plant height of the two varieties was mainly 5.0‒10.0 cm, accounting for 66.13% and 66.91%, respectively. The stem diameter range of Reyan 73397 and Reyan 917 was 0.80‒4.23 mm and 1.13‒3.73 mm, respectively. The mean value of the two varieties was 2.11 mm and 2.18 mm, respectively. The stem diameter of the two varieties was highly concentrated between 1.50‒3.00 mm, 85.94% and 83.82%, respectively. The leaf number of Reyan 73397 and Reyan 917 was ranged from 0 to 6 and 1 to 4, respectively. The number of leaves of the two varieties was mostly 1 to 3, accounting for 88.82% and 96.32%, respectively. The rate of 2 leaves in Reyan 917 was as high as 52.94%. The average taproot length of Reyan 73397 was 9.5 cm, while that of Reyan 917 was 9.1 cm. The taproot length of both varieties concentrated in the range of 8.0‒12.0 cm, accounting for 74.12% and 79.41%, respectively. There were no significant differences in plant height, stem diameter and leaves number between the two varieties in 2020, while there was significant differences in taproot length (P<0.05). The proportion of first-grade plantlets and second-grade plantlets of different varieties in different years (2018—2020) was 19%‒22% and 56%‒62%. It is concluded that the mass production of rubber tree somatic embryo plantlet is stable, which could provide reference for the popularization of the production technology of rubber tree somatic embryo plantlet.

  • Post-harvest Treatment & Quality Safety
  • Post-harvest Treatment & Quality Safety
    QIN Huaide, ZHANG Anyang, NIE Zhiyi, KANG Guijuan, WEI Mingming, ZENG Rizhong, LUO Wei, ZHAN Ruifang
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    The quality and performance of natural rubber (NR) are closely related to Hevea brasiliensis (rubber tree) varieties, tapping systems, seasonal variation and phenology etc. In order to uncover the annual change rules from April to December of NR qualities among different rubber tree varieties, we investigated the NR qualities from five clones including PR 107, RRIM 600, Reyan 917, Reyan 73397 and Reyan 879 cultivated in Danzhon of Hainan, China, and analysed the vulcanization characteristics and the mechanical properties of the vulcanized NR prepared from the latex harvested in May. The results showed that the mooney viscosity, protein percentage, volatile percentage, Wallace plasticity (P0) and plasticity retention index (PRI) presented a downward or upward trend in an annual tapping cycle from April to December, which indicates that the NR quality parameters are affected by both genotypes and environmental factors such as weather and sunshine etc. The protein percentage in NR from the latex of the four rubber tree clones was more than 3.0% in December. The cure characteristics of NR from Reyan 917 were totally different from those of the other four rubber trees. Under the same tapping system of S/2 d/3, the tensile strength and the elongation at break of the vulcanized rubber from Reyan 879 was the smallest compared with the other four clones. The results would contribute to instructing the new variety breeding and rubber production on the one hand, and to providing scientific supports for high-performance NR manufacturing on the other hand.

  • Post-harvest Treatment & Quality Safety
    PAN Xiaowei, ZHAO Zhifang, ZHAN Guoyan, LIANG Yaohui, PAN Zheng, CHEN Shuxian, YE Jianzhi
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    KOH was used as the activator combined with ultrasonic treatment to treat rubber seed shell to prepare activated carbon, and the best preparation conditions were optimized. The surface structure of the chemical carbon was regulated by controlling the preparation and processing conditions. The physical and chemical properties of the active carbon were characterized by specific surface area voidness analyzer, FT-IR, SEM, element analyzer, and TGA. The adsorption capacity of methylene blue and iodine was investigated. The optimal preparation conditions were reagent∶material ratio 1∶1, ultrasonic action for 60 minutes, activation time for 60 minutes, and activation temperature of 700 ℃. Activation temperature had the greatest impact on the adsorption capacity of activated carbon, followed by the reagent to material ratio and ultrasonic time, with the activation time having the smallest impact. The absorption of methylene blue was 400 mg/g, and iodine was 1340.2 mg/g, respectively. The yield was 25.9%, the specific surface area was 1034.5009 m2/g, and the total pore volume was 0.9511 cm3/g with ultrasonic pretreatment (UAC). The adsorption value of methylene blue was 300 mg/g, iodine adsorption value was 894.0 mg/g, yield was 20.8%, specific surface area was 690.2461 m2/g, total pore volume was 0.6830 cm3/g without ultrasoni pretreatment (NAC). Both contained hydroxyl, alcohol hydroxyl and carbonyl functional groups. This is conducive to the enhancement of adsorption performance, and the characteristics of cellulose, hemicellulose and lignin were obvious. The nitrogen adsorption isotherm of the rubber seed shell activated carbon was type Ⅰ. Activated carbon contained a large number of microporous structures with uniform distribution. There was no pore structure on the surface of the rubber seed shell, and there were a large number of pore structures on the activated carbon surface after KOH activation. The surface of UAC activated carbon was smooth and flat, with many rich and regular pore structures. In contrast, the pore surface of NAC had many small pores, and the surface was rough. The carbon (C) content in the rubber seed shells was rich. After KOH activation, the C content of the activated carbon prepared by ultrasonic treatment and activated carbon prepared without ultrasonic treatment increased from 56.81% to 75.97% and 64.89%, respectively. However, the content of hydrogen (H) and nitrogen (N) decreased, making it an excellent raw material for activated carbon. The TGA results indicate that the sample activated by KOH was more stable than the rubber seed shell, and the total weight of UAC and NAC samples tended to stabilize after losing 62% and 68%, respectively. In conclusion, the better performance of the samples prepared by ultrasonic pretreatment indicates that the cavitation effect of ultrasonic wave acts on the structural surface of the activated carbon, causing it to undergo structural changes, thus, the adsorption capability of the active carbon, the specific surface area, etc. are enhanced.

  • Post-harvest Treatment & Quality Safety
    CHEN Yuanjie, XU Jing, LIU Changtao, HUANG Jinghua, CEN Juren
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    The antioxidant activity, total polyphenol and total flavonoid content differences of local Hainan specialty teas (Moringa Tea, Kuding Tea, Wuzhishan Green Tea, Baisha Green Tea, Wuzhishan Black Tea, Languiren and Partridge Tea) were evaluated. Results revealed significant variations in antioxidant activity among the teas. The antioxidant activity of the tea extract exhibited a dose-dependent relationship with sample concentration and demonstrated excellent thermal stability. The total polyphenol and total flavonoid content of the teas was ranged from 9.80% to 22.84% and 0.90% to 4.67%, respectively, and the total polyphenol content of Wuzhishan Green Tea was the highest, which was 2.33 times that of Moringa Tea. The difference in total polyphenol content of Kuding Tea, Wuzhishan Black Tea, Languiren, and Partridge Tea was not significant, while the total flavonoid content of Wuzhishan Green Tea was the highest, and the total flavonoid content of Wuzhishan Green Tea was 5.18 times that of Moringa Tea. The difference in total flavonoid content of Wuzhishan Black Tea, Languiren, and Partridge Tea was not significant, and the total polyphenol and total flavonoid content of Wuzhishan Green Tea were the highest among the teas. The seven tea extracts had antioxidant reduction ability, and the tea polyphenol content and total flavonoid content showed a good quantitative relationship with the scavenging ability of free radicals. Moringa Tea had the strongest ability to scavenge ABTS, Wuzhishan Black Tea had the strongest ability to scavenge superoxide radicals, and Baisha Green Tea had the best antioxidant effect overall, with the reduction ability, DPPH scavenging ability, hydroxyl radical scavenging ability were the strongest. The antioxidant properties of the seven tea extracts did not change significantly when incubated at different temperature conditions and boiling water, indicating that the seven tea extracts had better thermal stability. This study shows that Hainan specialty teas are rich in total polyphenols and total flavonoids and exhibit strong antioxidant abilities, providing a theoretical foundation for further development and utilization of Hainan specialty teas.

  • Post-harvest Treatment & Quality Safety
    SUN Yuan, WANG Danyang, SUN Jing, BAI Yajuan, FAN Bei, SONG Hongbo, JI Jianbang, LU Cong, WANG Fengzhong
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    The aim of this study was to explore the protective effect of arecoline on the cell model of H2O2-induced oxidative stress damaged model in SH-SY5Y cells and elucidate its mechanism. Cell viability was detected by CCK-8 assay. Spectrophotometry was used to detect LDH release, MDA, SOD, and CAT contents. Flow cytometry was used to detect cell apoptosis and mitochondrial membrane potential. Western blot was used to detect the expressions of Nrf2, HO-1, Keap1, Bcl-2, Bax and Caspase-3. Arecoline could reduce cell apoptosis and significantly increase mitochondrial membrane potential. The level of SOD elucidateand CAT increased while the level of MDA decreased. Arecoline 140 μmol/L group could significantly up-regulate the protein expression of Nrf2, HO-1 and Bcl-2 (P<0.001, P<0.0001), and down-regulate the protein expression of Keap1, Bax and Caspase-3 (P<0.001, P<0.0001). Conclusions: arecoline can effectively improve H2O2-induced oxidative stress injury in SH-SY5Y cell by activating the Nrf2/HO-1 signaling pathway, enhancing the activities of antioxidant enzymes and regulating the oxidation reduction system of cells, as well as regulating the Bcl-2/Bax/Caspase-3 signaling pathway and inhibiting cell apoptosis.

  • Post-harvest Treatment & Quality Safety
    SONG Shuhui, YANG Shuang, WANG Chao, LI Puwang, JIAO Jing, LIU Siru, HE Zuyu, LIU Yunhao, ZHOU Chuang, YANG Ziming
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    Biochar was modified with different concentrations of hydrogen peroxide, and the differences in its structural characteristics were analyzed to study the modification effect of hydrogen peroxide on biochar obtained from banana stem and the effect of modified biochar on Cr absorption of maize under Cr stress. The effects of modified biochar on the growth, Cr uptake and accumulation of maize under Cr stress were studied. With the increase of hydrogen peroxide concentration, the number of oxygen-containing functional groups on the surface of biochar increased, while the aromatics decreased and the polarity increased. After the modification, the surface of biochar was smooth, the pore diameter increased, and the specific surface area and pore volume decreased with the increase of hydrogen peroxide concentration. Modified biochar by 20% and 30% hydrogen peroxide mainly fixed heavy metals through the adsorption of functional groups, reduced its biological activity, and reduced the Cr absorption and accumulation by corn. The study showed that 20% and 30% hydrogen peroxide significantly changed the surface structure of biochar, which was conducive to alleviating the toxicity of heavy metal Cr to corn plants. 30% hydrogen peroxide modified biochar promoted the growth of corn under Cr stress.

  • Plant Protection & Bio-safety
  • Plant Protection & Bio-safety
    LI Xuejun, REN Yuan, CHEN Hongmei, QU Peng, DU Huabo, HE Pengbo, TAN Wanzhong
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    The present work was conducted to identify the pathogen causing anthracnose of Liberica coffee (Coffea liberica) plants and to screen fungicides against the disease pathogen. The leaves of C. liberica with anthracnose symptoms were sampled from fields for fungal isolation and purification. Four pure fungal isolates were obtained and only KFTJ01 was verified pathogenic to the coffee leaves by tests following Koch’s Postulates. The rDNA-ITS sequence (554 bp), beta-tubulin gene (tub2) and calmodulin gene (CAL) were successfully amplified via PCR from genomic DNA of KFTJ01 and sequenced. Blastn analysis of the the three DNA sequences showed that KFTJ01 was identical to the strain WZ-135 (99.62%, MN856281), CREADC-ER2212 (100%, MT409131) and YMTJ4 (100%, MK569149) of Colletotrichum kahawae. KFTJ01 was also clustered with C. kahawae WZ-135 strain on the same end-branch of the phylogenic tree (bootstrap confidence is 98%). Therefore, the pathogen of Liberica coffee was identified as C. kahawae which is a quarantine species and has never been recorded in China. Fungicide selection experiments showed that among the 10 chemicals, methionine-acetazolyl and methyl thiobacillam almost completely (100%) suppressed the colony growth of KFTJ01. The median effective concentration calculated from the functions was 0.0607 mg/mL and 0.0809 mg/mL, respectively, indicating that both the chemicals were very effective against the anthracnose pathogen. The results are important references for the field diagnosis of the coffee plant anthracnose and for controlling the disease epidemics.

  • Plant Protection & Bio-safety
    LIU Zhuofan, SUN Shiwei, MENG Yang, GOU Yafeng, SONG Guomin, TIAN Tian, WEN Siwei
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    Hypothenemus hampei is a new invasive pest in China. It is a main coffee pest and poses a great threat to the coffee industry. The purpose of this study is to clarify the biological characteristics and field occurrence rules of the insect, and to provide a theoretical basis for later monitoring and forecasting and comprehensive management of the insect. In this study, the morphological characteristics, developmental duration and fecundity of various developmental stages of H. hampei were observed at each stage in the indoor feeding conditions. The annual life cycle of H. hampei was observed in the field. The population dynamics and spatial distribution patterns of H. hampei in Wanning city, Hainan province were measured through systematic field investigation from 2021 to 2022 to clarify the biological characteristics and field occurrence of H. hampei, and provide a theoretical basis for the subsequent integrated pest management of H. hampei. The results showed that the developmental duration of egg, larval, pupal and adult stage of H. hampei was (6.75±0.65) d, (17.41±1.63) d, (6.45±1.15) d, (42.74±9.55) d, respectively. The average generation duration was (73.35±11.26) d. The main morphological characteristics of each stage were as follows: egg, elliptic, milky white, with smooth and shiny surface; larval, usually “C” shaped, milky white, slightly transparent, with brown head and no feet; pupal, milky white at the initial stage, and later turn brown, the head hidden under the pronotum; adult body, cylindrical, dark brown to black, shiny; male smaller than the female. Female adults usually laid eggs under dark conditions, the number of eggs laid by a single female was 11.85±1.69, and the ratio of male to female was 10.25∶0.95. The results of indoor and field observations showed that H. hampei had seven generations a year in Hainan, and there was no phenomenon of overwintering. The results of the field survey in 2021—2022 showed that the population of H. hampei began to increase slowly from January, and the incidence of H. hampei increased sharply from April to May, reached a maximum of 60.15% and peak in May, and then declined rapidly. In October, it remained at a relatively stable level. The population increased again in November, with another small peak, reaching 19.87%. In December, it decreased, but it showed a slow increase until March of the following year related to the number of fruits. The survey results on space and orientation showed that during the fruit development period, H. hampei preferred the middle layer (0.5-1.0 m) fruit spatially, and preferred the east and north directions in orientation, which may be related to light and temperature. The results of the four aggregation parameters showed that H. hampei belonged to the aggregation distribution in both horizontal and vertical directions.

  • Plant Protection & Bio-safety
    XIANG Jiayin, SHANG Sang, TIAN Libo
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    Potted bitter melon was treated with Bacillus velezensis N46 to explore the mechanism of preventing powdery mildew of bitter melon. The prevention mechanism of N46 was studied by detecting the spore germination rate of powdery mildew pathogen (Podosphaera xanthii), changes in leaf defense enzyme activity, accumulation of reactive oxygen species, cell allergic necrosis, lignin accumulation, changes in the expression of disease-resistance related genes and disease-resistance pathways. The control effect of high concentration (6×108 CFU/mL) of B. velezensis N46 on powdery mildew of bitter melon reached 59.05%. In the N46 treatment group, the range and peak value of the activity of defense enzymes POD, CAT and SOD increased significantly, the accumulation of reactive oxygen species (ROS) increased significantly, the rate of anaphylactic necrosis increased significantly, and the rate of lignin accumulation in cell wall was significantly enhanced. N46 had a significant inhibitory effect on the conidial germination of pathogen powdery mildew. The expression levels of JA reactive marker lipoxygenase gene (LOC111018837), SA reactive marker gene (LOC111017362) and peroxidase gene (LOC111021192) associated with allergic reaction and cell wall strengthening were detected in the N46 treated bitter melon. Compared with the control group, the expression levels of the genes increased significantly when bitter melon was infected with the powdery mildew bacteria, and the expression levels of JA reactive marker genes in the treatment group were also higher than those in the control group when there was no contact with pathogenic bacteria. The results indicated that N46 treated bitter melon maintained a certain level of “preactivation” of resistance genes when it was not exposed to pathogenic bacteria, but showed a higher expression level when it was exposed to pathogenic bacteria. Finally, the JA response pathway was inhibited by ibuprofen (IBU), and the control effect of B. velesiensis N46 on powdery mildew of bitter melon was almost disappeared, suggesting that the generation of N46 induced powdery mildew resistance of bitter melon depended on JA pathway. In conclusion, B. velezensis N46 has a good control effect on powdery mildew of bitter melon by inhibiting the conidium germination of megalomycesfoliata and inducing JA pathway dependent resistance of bitter melon. This study would provide a new method for the biological control of powdery mildew of bitter melon and a theoretical basis for the effect of B. velezensis on the control of powdery mildew of bitter melon.