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    Cloning and Expression Analysis of MiERF2, an AP2/ERF Transcription Factor in Mango
    WEI Ling, KOU Mingrui, LI Wen
    Chinese Journal of Tropical Crops    2024, 45 (1): 1-9.   DOI: 10.3969/j.issn.1000-2561.2024.01.001
    Abstract53)   HTML4)    PDF(pc) (10265KB)(40)       Save

    Mango (Mangifera indica L.) is one of the major cash crops in the tropics and a typical respiratory leap fruit, whose ripening senescence is associated with ethylenee. AP2/ERF transcription factors are widely present in plants, and it is found that the transcription factors are involved in the signal transduction of endogenous ethylene synthesis in fruits, and are key genes in the ethylene signaling pathway, playing an important role in plant growth and development, response to adversity stress and storage and transportation. To investigate the effect of AP2/ERF transcription factor on post-harvest mango ripening and senescence, a MiERF2 gene of 915 bp in length, encoding 305 amino acids, was cloned by PCR using Guifei mango as the target of this study. The molecular formula of MiERF2 protein was C1449H2259N433O470S11. The molecular weight was 33 618.16 Da, the total atomic number was 4622. The theoretical isoelectric point was 7.66, with 30 positively charged residues and 29 negatively charged residues. The protein was hydrophilic and structurally unstable. MiERF2 didn’t contain a signal peptide, didn’t contain a transmembrane region, and phosphorylation modification was mainly threonine. MiERF2 contained a conserved structural domain of AP2, the secondary structure was dominated by 66.12% of random curl, also contained 24.67% of α-helix, 1.32% of β-fold, 7.89% of the extended chain. Its three-dimensional structure model contained three β-fold and one α-helix, consistent with the characteristics of the AP2 structural domain. The results of motif analysis and multiple sequence matching indicated that MiERF2 protein belonged to the ERF subfamily. Phylogenetic analysis showed that the closest relative to MiERF2 was the pistachio PvERF109-like, which is also a member of the Lacertidae family. Onion subcellular localization results showed that MiERF2 was localized in the nucleus. Quantitative real-time fluorescence analysis showed that the expression of MiERF2 differed after 400 μg/mL ethephon treatment at different harvest maturity. In 60% maturity mango, the expression of MiERF2 in the treatment group peaked at 9 d and then was significantly lower than that in the control group. In 80% maturity mango, the expression of MiERF2 in the control group was significantly higher than that in the treatment group during storage, except for 18 d. It is suspected that this gene would play a negative regulatory role in ethylene regulation of fruit ripening. This study would provide a theoretical basis for revealing the regulatory role of ERF transcription factors in postharvest ripening and senescence of mango.

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    Characterization and Phylogenetic Analysis of the Complete Chloroplast Genome of Paris polyphylla var. alba (Melanthiaceae)
    ZHANG Shudong, LING Lizhen, XIE Dandan, LIU Zhenzhen
    Chinese Journal of Tropical Crops    2023, 44 (8): 1551-1560.   DOI: 10.3969/j.issn.1000-2561.2023.08.004
    Abstract83)   HTML8)    PDF(pc) (3180KB)(156)       Save

    Paris polyphylla var. alba, a medicinal plant of Melanthiaceae, is classed as the national second-grade protected species of China. With the increasing demand for raw materials of Rhizoma paridis, the wild resources of P. polyphylla var. alba have been seriously damaged. In order to protect the genetic resources and clarify the systematic positon of this species, Illumina Hiseq X Ten platform was used to sequence the chloroplast (cp) genome. The structural characteristics of the complete cp genome sequence and phylogenetic relationship of P. polyphylla var. alba in Paris were analyzed. The results showed that the cp genome was 163 944 bp in length with a typical quadripartite structure with a large single-copy (LSC) region of 84 179 bp, a small single-copy (SSC) region of 12 967 bp, and a pair of 33 399 bp inverted repeats (IRs). The genome contained 134 genes, including 88 protein-coding genes (PCGs), 38 tRNA genes and 8 rRNA genes. A total of 645 long repeats and 97 simple sequence repeats (SSRs) loci were detected in the complete cp genome, in which forward and palindromic repeats were the mainly long repeat types, and most of SSRs had A/T base preference. Phylogenetic analysis based on the complete cp genomes showed that Paris formed a monophyletic group, and could be further divided into five major clades corresponding to five sections, respectively. The varieties of P. polyphylla are located in Sect. Euthyra, but are not clustered a monophyletic group, and P. polyphylla var. alba is closely related to P. mairei. This study would provide a scientific basis for studying the phylogeny, species identification and resource conservation of Paris.

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    Cloning and Expression Analysis of MYB61 Genes in Impatiens chlorosepala and Impatiens uliginosa
    XIANG Nanxing, LI Zefeng, LI Xinyi, WEI Chunmei, HUANG Meijuan, HUANG Haiquan
    Chinese Journal of Tropical Crops    2023, 44 (8): 1561-1568.   DOI: 10.3969/j.issn.1000-2561.2023.08.005
    Abstract80)   HTML4)    PDF(pc) (4404KB)(98)       Save

    During the evolution from lower plants to higher plants, lignification is the key to adapt to the terrestrial environment, while lignin deposition in the cell wall is an important manifestation of lignification, and MYB61 plays an important role in lignin synthesis pathway. In order to explore the molecular mechanism of MYB61 in lignin synthesis of Impatiens chlorosepala and Impatiens uliginosa, MYB61 genes, named IcMYB61 and IuMYB61 in this study, were cloned by using the RT-PCR method. The full-length cDNA was 1035 bp and 1002 bp, encoding 344 aa and 333 aa, containing an intron of 84 bp and 66 bp, respectively. Physicochemical analysis suggested that IcMYB61 and IuMYB61 were unstable hydrophilic protein. Domain analysis of protein showed that IcMYB61 and IuMYB61 contained two typical SANT conserved domains. The comparison of amino acid sequences of MYB61 with that of other species showed that there were highly conserved R2 and R3 regions at the N-terminal, which was speculated to be R2R3-MYB gene. Based on the phylogenetic analysis, it found that IcMYB61 and IuMYB61 were clustered together with I. glandulifera, confirming that the same genus is more closely related. The qPCR showed that IcMYB61 and IuMYB61 were expressed in three different parts of the two periods, and the expression levels were the lowest in roots. In I. chlorosepala, the highest expression of IcMYB61 was in the leaves at the seedling stage, and the highest expression level was in the stem at the mature stage. In I. uliginosa, the expression of IuMYB61 was the highest in the stems of both periods. By measuring the total lignin content in stems and leaves of the two species, it was found that the lignin content of both species was the highest in stems, which was consistent with the expression trend of MYB61. It is speculated that MYB61 mainly regulates the biosynthesis of lignin in the stems of I. chlorosepala and I. uliginosa. The above-mentioned results would provide some basic data and scientific basis for exploring the regulation mechanism of MYB61 on the lignin synthesis of Impatiens and the culture of new varieties.

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    Evaluation of 141 Excellent Zhongzhe Sugarcane Germplasms Based on Principal Component Analysis and Cluster Analysis
    GUO Qiang, JIANG Qingmei, HE Hongliang, LI Zhengying, LIANG Yongjian, QIN Changxian, TANG Liqiu
    Chinese Journal of Tropical Crops    2024, 45 (1): 49-59.   DOI: 10.3969/j.issn.1000-2561.2024.01.006
    Abstract16)   HTML1)    PDF(pc) (1510KB)(20)       Save

    Scientific evaluation of sugarcane germplasm resources can provide high quality parental materials for sugarcane cross breeding. In this study, seven phenotypic traits of 141 excellent sugarcane germplasm were evaluated for diversity using methods such as principal component analysis and cluster analysis. The variation coefficients of smut rate, cane yield, millable stalks, stalk weight and sucrose content were all greater than 10%, with the variation coefficients of smut rate being the largest at 67.21%. Correlation analysis showed that the cane yield was highly significantly positively correlated with plant height, stalk diameter, millable stalks and stalk weight, and the stalk diameter was highly significantly negatively correlated with millable stalks, and the sucrose content was highly significantly negatively correlated with smut rate. The results of principal component analysis showed that the cumulative contribution rate of 3 principal component factors was 74.725%, among which the first principal component was related to yield traits, the second principal component was related to stems and quality traits, the third principal component was related to disease traits and quality traits. Based on cluster analysis, the 141 sugarcane germplasm resources could be divided into 3 groups, among which group Ⅰ had the taller plants, highest yield and highest sucrose content, highest disease resistance, strong persisrence, and had excellent performance for all traits. Group Ⅱ had the smaller plants, lowest yield and lowest sucrose content, lowest disease resistance, poor persisrence, and had poor performance for all traits. Group Ⅲ had average performance for all traits. 60 germplasm resources were selected with excellent overall performance by principal compoment analysis results and cluster analysis results, among which ZZ153303, ZZ150505, ZZ165201 and ZZ151106 could be used as high sugar content parents, ZZ15710, ZZ160913, ZZ162026, ZZ112819, ZZ1415219, ZZ1510055, ZZ140802 and ZZ151106 could be used as highly resistant smut parents, ZZ134007, ZZ118607, ZZ167010, ZZ144101 and ZZ156615 could be used as high yield parents.

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    Effects of Forchlorfenuron on Yelid, Quality and Storability of Guifei Mango Fruit
    GAO Zhaoyin, WANG Jiabao, LI Min, GONG Deqiang, CHEN Yeyuan, HU Meijiao
    Chinese Journal of Tropical Crops    2024, 45 (1): 162-168.   DOI: 10.3969/j.issn.1000-2561.2024.01.017
    Abstract15)   HTML0)    PDF(pc) (1242KB)(18)       Save

    Guifei mango has bright color and sweet taste, which is deeply loved by consumers. However, the yield and economic benefits of this mango had been seriously affected due to a high fruit abortion rate. Forchlorfenuron (CPPU) is a swelling agent used in the mango industry of Hainan which can improve fruit setting rate, promote fruit enlargement and induce parthenocarpy. But, the abuse of CPPU resulted in a higher percentage of abnormal fruit, the decline of quality, stay-green after harvest and flavor change. To find a appropriate dosage, we compared the effects of CPPU spraying with different concentrations on the yield, quality, postharvest storage characteristics and incidence of disease in mango fruit. The experiment was carried out in a demonstration park of mango standardization production, Chinese Academy of Tropical Agricultural Sciences, Dongfang City, Hainan Province. The Guifei mango trees with healthy, consistent size and vigor were selected as the test material. The age of trees is about 12 years. And CPPU aqueous solutions of 10 mg/L, 20 mg/L and 60 mg/L were sprayed on 15, 25 and 35 days after full bloom, respectively. Distilled water was used as a blank treatment. Six trees were selected for each treatment (3 repetitions). The fruits were harvested at 78 days after flowering, then put into corrugated boxes to avoid damage. All the fruits were brought back to the laboratory and stored in a cold storage at (25±1)℃ and 80%-90% relative humidity (RH). Fruit color parameters (L* value, a* value, b* value) and pericarp pigments (contents of total chlorophylls, anthocyanins and carotenoids) were measured during harvest and storage to evaluate the effect of CPPU on the fruit color. Fruit firmness and contents of soluble solid content (TSS), titratable acid (TA), vitamin C were measured to evaluate the effect of CPPU on inner quality, postharvest storage characteristics and fruit ripening of mango fruit. In addition, the effects of CPPU on yield, single fruit weight of parthenocarpic fruit/pollinated and fruit-shape index were also studied. Spraying 10 mg/L CPPU solution could significantly improve the average yield (45.73 kg), 34.03% higher than the control (34.12 kg). Spraying a CPPU solution of higher concentration (20 mg/L, 60 mg/L) had no obvious effect on yield increase, or even reduced the yield. Spraying 10 mg/L CPPU solution had little effect on the number of fruits per tree. But if spraying CPPU solution of 20 mg/L and 60 mg/L could significantly reduce the number of fruits per tree by 46.08% and 60.19% compared with the control. Spraying 60 mg/L CPPU solution had the most obvious effect, the single fruit weight of pollinated and parthenocarpic fruit increased by 28.48% and 117.25% respectively. Spraying CPPU solution could increase the fruit-shape index of mango, but there was no significant difference compared with the control. Spraying CPPU had a significant effect on the contents of chlorophyll, carotenoid and anthocyanin during maturation and ripening of mango. That fruits treated with CPPU had higher chlorophyll and carotenoid content, lower anthocyanin content, and showed a greener color. The chlorophyll content in a mango peel treated with 10 mg/L, 20 mg/L, 60 mg/L CPPU increased by 5.12%, 8.67%, 9.83% and 21.23%, 36.63%, 48.07% respectively during maturation and ripening compared with the control. And the increase of carotenoid content was more obvious treated with 60 mg/L CPPU than that treated with 10 mg/L and 20 mg/L, the carotenoid content increased 22.56% and 18.81% respectively during maturation and ripening compared with the control. Different from chlorophyll and carotenoids, the content of anthocyanins decreased gradually with the increase of CPPU concentration. The content of anthocyanins decreased by 8.94%, 13.62%, 18.30% and 13.83%, 16.19% and 17.58% respectively treated with 10 mg/L, 20 mg/L, 60 mg/L CPPU during maturation and ripening compared with the control. The process of mango fruits from green to yellow was delayed by CPPU spraying during storage. Spraying CPPU solution could increase fruit firmness and titratable acidity (TA) content, reduce soluble solids content (TSS) content and delay fruit ripening. The incidence rate of anthracnose and stem-end rot decreased after CPPU treated. But in all processing, only the fruits treated with CPPU in doses of 10 mg/L were normal during fruits coloring. In addition, spraying CPPU could prolong the storage time of mango fruits, 60 mg/L CPPU treatment could delay the ripening for 4 days. Spraying 10 mg/L CPPU on 15, 25 and 35 days after full bloom stage could increase fruit-shape index, promote fruit enlargement and increase the mango yield. At the same time, the postharvest fruit treated with 10 mg/L CPPU could delay fruit softening and ripening during storage, reduce the occurrence of postharvest diseases, prolong storage time. Nevertheless, the nutritional quality of fruit was also decreased during ripening with the fruit hardness increased and the TSS content decreased. Spraying higher concentration of CPPU solution (20 mg/L, 60mg/L) had no obvious effect on yield increase, or even reduced the yield. Therefore, we suggest that spraying 10 mg/L CPPU solution in mango production, which could improve the yield, prolong the storage time and ensure the postharvest fruit quality.

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    Identification and Expression Analysis of OSCA Gene Family in Tea Plant
    LIU Dandan, WU Qiong, JIAO Xiaoyu, SUN Minghui, WANG Wenjie
    Chinese Journal of Tropical Crops    2024, 45 (1): 10-22.   DOI: 10.3969/j.issn.1000-2561.2024.01.002
    Abstract26)   HTML4)    PDF(pc) (2248KB)(17)       Save

    The hyperosmotic Ca2+ channel protein OSCA is crucial for controlling hyperosmotic stressors in plants. To understand the role of the OSCA gene family in tea plant response to drought stress, this study was conducted to identify the OSCA gene family based on the whole genome data of tea plant and analyze the gene and protein structures and promoter cis-acting element, and analyze the expression patterns of CsOSCAs in different tissues of tea plant, among different drought-resistant varieties and under drought stress. The results showed that the tea plants genome contained 12 members of the OSCA gene family, named CsOSCA1-CsOSCA12. The amino acid sequences encoded by the CsOSCAs were 667-831 bp in length, with protein molecular weight ranging from 76 630.55 kDa to 93 563.99 kDa and isoelectric points ranging from 6.15 to 9.33, containing 9-12 transmembrane structural domains, all containing the characteristic conserved structural domain DUF221, which could be divided into four subfamilies based on phylogenetic relationships. Ten CsOSCAs were localized to seven chromosomes of Camellia sinensis and two CsOSCAs were localized to the contig of unanchored chromosomes. The secondary structure of the CsOSCAs contained 32%-38% transmembrane structure and 60%-68% α-helix. The CsOSCAs were tissue expression specific, and CsOSCA2, CsOSCA3, CsOSCA11, and CsOSCA12 were significantly higher in the drought-sensitive variety CN98 than those in the other two drought-tolerant varieties. Nine genes were responded to PEG stress, among which CsOSCA2, CsOSCA3, CSOSCA5, CsOSCA8, CsOSCA10, and CsOSCA12 were strongly induced by drought stress. Six genes included drought-inducible response elements, and 11 genes contained abscisic acid response elements, according to further examination of the promoter cis-acting elements. It is hypothesized that the OSCA gene family of tea plants play an important role in the response to drought stress, and this study would provide a reference for the functional analysis and stress resistance of OSCA gene in tea plant.

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    Distribution and Genome Sequence Analysis of Southern Tomato Virus in Hainan, China
    CHE Haiyan, LIN Yating, LUO Daquan, LONG Haibo
    Chinese Journal of Tropical Crops    2024, 45 (1): 30-40.   DOI: 10.3969/j.issn.1000-2561.2024.01.004
    Abstract17)   HTML1)    PDF(pc) (1700KB)(16)       Save

    Virus disease is one of the most serious diseases in tomato production in Hainan, China. The small RNA deep sequencing data of tomato virome in Hainan revealed the presence of Southern tomato virus (STV) in samples from several regions, and a single STV infected sample was found. RT-PCR screening of 987 field samples with virus-like symptoms collected from 2015 to 2021, was carried out to determine the distribution of STV in Hainan province. Results indicated that STV was detected in 142 samples from nine regions, STV had existed in Hainan tomatoes as early as 2015, STV detection rate increased from 8.82% in 2015 to 22.45% in 2021, showing an upward trend year by year. The complete genome length of four isolates amplified using RT-PCR and RACE was identical, each consisting of 3446 nt. Two partially overlapping open reading frames (ORFs) presented in the positive-sense RNA strand, the 5′-proximal ORF (position 147-1280 nt) encoded a 377 amino acid (aa) peptide representing a potential coat protein (p42), the second ORF (position 1048-3336 nt) contained typical motifs for an RNA-dependent RNA polymerase (762 aa). The length of 5 untranslated region (UTR) and 3 UTR was 146 nt and 110 nt respectively. Paired comparison showed that the nucleotide similarity among four STV isolates was 99.86%-100.00%, the nucleotide similarities with other STV isolates available in GenBank were 98.45%-99.94%. In phylogenetic trees based on the complete genome of STV, eighty STV isolates were obviously divided into two groups (Group Ⅰ and Group Ⅱ). Group Ⅰ included Asian, American, European and African isolates. In group Ⅱ, except for one Asian isolate, the others were European isolates, and four Hainan isolates were divided into group Ⅰ. The grouping of STV isolates was related to geographical location, may not be related to the host. The regions with high genomic sequence variability between Hainan isolates and group Ⅰ isolates were 881-1061 nt and 1521-1721 nt, and the regions with high genomic sequence variability between Hainan isolate and group Ⅱ isolate were 2041-2241 nt and 2761-2921 nt. No recombination events were found between STV isolates. This is the first report of STV in Hainan Province. The findings of this study would provide an important basis for understanding the distribution and occurrence trends of STV in Hainan province and for the development of effective surveillance and control measure.

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    The Interaction Between Cassava Mosaic Virus AC4 Protein and AtPARN
    LIU Linyu, ZHAO Pingjuan, FU Yan, LIU Zhixin, REN Yanli, ZHANG Xiuchun
    Chinese Journal of Tropical Crops    2024, 45 (1): 197-204.   DOI: 10.3969/j.issn.1000-2561.2024.01.021
    Abstract14)   HTML1)    PDF(pc) (4352KB)(15)       Save

    As an important tropical crop, Manihot esculenta Crantz is one of the top six global food crops and provides a staple food for nearly 700 million people worldwide. However, diseases caused by virus infection are a serious threat to the development of the cassava industry worldwide. Cassava mosaic disease (CMD) is one of the most threatening diseases, causing serious economic losses. Sri Lankan cassava mosaic virus (SLCMV) is one of the pathogens causing cassava mosaic disease. SLCMV is a typical two-component geminiviruses, and its genome consists of two circular components, DNA-A and DNA-B. Nonsense-mediated mRNA decay (NMD) is one of the major pathways of mRNA degradation in eukaryotic cells and a prevalent antiviral defense mechanism in eukaryotes. More and more studies have shown that NMD is not only an important mechanism for regulating mRNA quantity and quality in eukaryotes, but also degrades viral RNA as well as post transcriptional gene silencing (PTGS), which is a prevalent antiviral defense mechanism in eukaryotes. The mRNA decay process of NMD includes four processes: recognition of PTC, deadenylation, decapitation and final exonuclease degradation, and UPF1, PARN, DCP2 and XRN4 are the key proteins in these four processes, respectively. Viruses are specialized parasitic organisms that must escape or be resistant to degradation by host cells in order to successfully infect. Poly(A)-specific ribonuclease (PARN) is a key factor in the NMD signaling pathway. At present, the molecular mechanism of SLCMV resistance to host NMD is unclear. In this study, we will demonstrate that the silent suppressor AC4 encoded by SLCMV interacts with Arabidopsis PARN using yeast two-hybrid system and bimolecular fluorescence complementation (BiFC) experiments. It is hypothesized that the SLCMV AC4 protein may help the virus evade or tolerate degradation by the host cell by inhibiting the viral defense function of the host NMD through interaction with AtPARN. The results lay the foundation for elucidating the molecular mechanism by which cassava mosaic virus regulates the antiviral defense function of host NMD.

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    Liang Jixing
    Chinese Journal of Tropical Crops    1988, 9 (1): 53-72.  
    Abstract4103)      PDF(pc) (1638KB)(1471)       Save
    The major soil types of Hainan Island may be divided into the following seven orders and twenty great groups.(1) The order of ferrallitic soil contains the great groups of 1aterite (latosol) ,1ateritic soil, 1ateritic red soil and yellow soil,(2) The order of semi-eluvial soil contains the great groups of dfy red soil and limestone red soil (terrarossa).(3) The order of initially developed soil contains the great groups of purple soil (purplish soil), b1ack limestone soil (rendzina or rendizine) ,volcanic ash soil, new alluvial soil, coastal sandy soil, young soil, lithosol (litho-soil) and skeleton soil,(4) The order of semi-bydromorphic soil contains the great igroups of Chao soil and mountain scrubby-meadow soil.(5) The order of hydromorphic soil contains the great groups of bog soil and peat soil.(6) The order of alkali-saline soil only . contains the great group of solonchak.(7) The order of anthropic soil (man-made soil) only contains. the great group of paddy soil (rice paddy soil).The geographical distribution, the profile morphology, and the physical and chemical properties of these major soil types are exp1ained briefly.
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    Screening of Pasture for the Red Soil Regions in Fujian and Ecologica Effect of Pasture Intercropping in Mountainous Orchards
    Weng Boqi Luo Tao Ying Zhaoyang Hu Yibin Zheng Zhongdeng
    Chinese Journal of Tropical Crops    2004, 25 (2): 95-101.  
    Abstract117)      PDF(pc) (691KB)(201)       Save
    Cultural adaptability of 128 accessions of leguminous and graminaceous pastures introduced to the red soil regions in Fujian Province was studied. Many accessions (Cassia rotundifolia; Arachis pintoi; Digitaria smutsii;Dactyls glomerate; Triticale) adapted for production were screened. The experimental results indicated that intercropping pastures reasonably in orchards could not only efficaciously prevent soil erosion(for instance, the frequency and amount of runoff were reduced by11.4%and98.7% respectively), but also improve smae ecological environment to some extent, which were favourable to the growth of the fruit trees. Great economic and ecological benefits were achieved.
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    Advances in the Mechanism,Artificial Agarwood-induction Techniques and Chemical Constituents of Artificial Agarwood Production
    EI Wenli ZUO Wenjian YANG Delan DONG Wenhua DAI Haofu
    Chinese Journal of Tropical Crops    2013, 34 (12): 2513-2520.  
    Abstract246)      PDF(pc) (343KB)(904)       Save
    Agarwood is a highly valuable product which can be used in fragrances and as traditional medicines, and its supply from wild sources is far less than market demand. The fact of over-harvesting the wild tree of Aquilaria and agarwood formation occuring naturally for ten or hundred years, agarwood has led to the depletion of wild trees. The artificial agarwood-induction technology becomes an inevitable course. The paper reviewed the advances in mechanism,artificial agarwood-induction technology and the chemical constituents produced by different artificial garwood-induction technology to provide scientific basis for efficient artificial agarwood-induction.
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    Seed Dormancy Characteristics and Breaking Technique of Manihot esculenta
    GUO Changlin, SONG Jiming, LUO Kai, TANG Li, FU Xiumei, CHEN Yinhua, ZHANG Rui
    Chinese Journal of Tropical Crops    2023, 44 (8): 1624-1634.   DOI: 10.3969/j.issn.1000-2561.2023.08.012
    Abstract75)   HTML1)    PDF(pc) (2991KB)(73)       Save

    Cassava (Manihot esculenta Crantz) is an important food and bioenergy crop globally. One of the most significant methods for germplasm development and variety selection is hybridization. However, a series of problems including difficulty in seed germination hinder severely the development of new cultivars. Thus, in present study, seed dormancy characteristics as well as dormancy breaking methods were investigated with freshly harvested natural hybrid seeds of SC124. The cassava seeds are oval and contain a seed coat, endosperm and embryo according to the observation of anatomy and scanning electron microscopy. The outer epidermis is smooth and contains epidermal layer, spongy parenchma and densely arranged palisade parenchma from outside to the inside. The seed coat and seed caruncle slow down the water absorption of cassava seeds, while the primary reason for inducing seed dormancy is the mechanical hindrance of seed coat and the existence of the inhibitor, which could be classified as physiological dormancy. Treatments by scarified seed micropyle, removing seed coat and scarified seed micropyle + two alternating cycles of moist cold temperature (0 ℃) for 2 h followed by moist warm temperature (30 ℃) for 2 h could effectively break seed dormancy and improve seed germination percentage. Treatment by scarified seed micropyle was the most effective methods, which promoted seed germination from 2% to 88% and germination rate was also the fastest. The optimum temperature for germination of cassava seeds was 35 ℃, and the germination percentage and germination index was 88% and 36.6, respectively. The research could provide scientific basis for understanding seed structure, seed dormancy characteristics and the best broken method for cassava seeds in production practice, and also provide a theoretical reference for the expression of excellent traits of cassava hybrid offspring.

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    Effects of Plastic Film Mulching Treatments on Photosynthetic Characteristics and Yield of Amorphophallus muelleri Intercropped in Rubber Plantations
    YUAN Huifang, YAN Xiangshuai, LI Jinwei, TIAN Yaohua
    Chinese Journal of Tropical Crops    2024, 45 (1): 134-143.   DOI: 10.3969/j.issn.1000-2561.2024.01.014
    Abstract16)   HTML1)    PDF(pc) (1125KB)(14)       Save

    The aim of the study is to estimate the effects of different mulching treatments on the photosynthetic characteristics of leaves, soil physical properties and yield of Amorphophallus muelleri intercropped in rubber plantations. Seven treatments (silver film, black film, white film, straw mat, thickened black film, microporous black film and no mulch (CK) were set up in this experiment. Photosynthetic characteristics of A. muelleri leaves at the three stages of head changing, corm and maturity were measured and analyzed. Net photosynthetic rate (Pn), stomatal conductance(Gs), transpiration rate(Tr), intercellular CO2 concentration(Ci), electron transfer rate(ETR), physiological characteristics parameters including soluble protein(SP) content, soluble sugar(SS) content, chlorophyll(Chl) content, chlorophyll a/b(Chl a/b). soil in situ physical properties including soil moisture comtent (SMC), soil conductivity(SC), soil temperature (ST), and underground corm yield of A. muelleri were assayed. The photosynthetic parameters (Pn, Gs, Tr and ETR) of A. muelleri leaves increased by different plastic film mulching treatments at the same period. Pn, Gs and Tr of straw mat treatment at the head changing stage and expansion stage were significantly higher than those of the other treatments (P<0.05), the amplitude of the other treatments fluctuated irregularly and there were significant differences among them. At the mature stage, SP and Chl of A. muelleri leaves under different treatments were significantly higher than those under the control in the same period, and there was no significant difference among all treatments. In the same period, the SS and Chl a/b of A. muelleri leaves under different treatments were slightly different. The SS of each treatment at the maturity stage was significantly higher than that of the control, and the SS of the control at the three stages was the lowest, while the Chl a/b of e plastic film treatment at the maturity stage was not significantly different from that of the control. In the same period, SMC and SC by different plastic films were higher than those of the control. The water retention effect of thickened black film treatment was the best, the SC of microporous black film treatment in the expansion stage and straw mat treatment in the maturity stage were significantly the highest, but there was no significant difference in SMC and SC among other treatments. Pn, Gs, Tr, ETR, SP, and Chl of the same mulch treatment at different stages were all in the following order: head changing stage>expansion stage>maturity stage, while the SS and Chl a/b of each treatment were in the following order: maturity stage>expansion stage>head changing stage. According to the results of correlation analysis between all indexes and yield, except ST and yield were negatively correlated, other indexes were positively correlated with yield. Compared with the control, different plastic film mulches increased the yield of A. muelleri. Black mulching, straw mat and thickened black mulching treatments significantly increased the yield, while white mulching and microporous black mulching treatments did not significantly increased the yield. Therefore, silver plastic film, black plastic film, straw mat and thickened black plastic film are suitable choices for A. muelleri to increase the production and efficiency in practical production.

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    Absorption and Accumulation Characteristics of Nitrogen, Phosphorus and Potassium in Field Propagation of Disease-free Sugarcane Original Seedlings
    JIANG Shuting, PENG Lishun, YANG Benpeng, CAO Zhengying, YANG Xue
    Chinese Journal of Tropical Crops    2024, 45 (1): 68-76.   DOI: 10.3969/j.issn.1000-2561.2024.01.008
    Abstract15)   HTML0)    PDF(pc) (1140KB)(14)       Save

    This study was conducted to explore the cumulative demand of nitrogen, phosphorus and potassium in disease-free sugarcane original seedlings, and provide reference for the nutrient management in the process of field propagation of disease-free sugarcane original seedlings. The growth of the disease-free sugarcane original seedlings of Zhongtang No. 1 in 2020 and 2021 was investigated, and the biomass and contents of nitrogen, phosphorus and potassium in roots, stems and leaves at various growth stages were determined for further analysis of the accumulation, phase absorption and daily absorption rate of nitrogen, phosphorus and potassium. It took 6 to 7 months for disease-free sugarcane original seedlings to reach 15 stem nodes from temporary planting of seedlings to the best harvest of seed canes. From July, August to late September (stem 1 to 2), the growth of sugarcane stems was the fastest. The cumulative increase of dry matter was the fastest in stem 4 (late October to late November), and this is the key stage of biomass accumulation. During the whole growth period of the disease-free sugarcane original seedlings, the content and accumulation of each element from high to low were potassium > nitrogen > phosphorus. Among the organs of roots, stems and leaves, leaves and stems always had higher nitrogen, phosphorus and potassium contents. The accumulation of nitrogen, phosphorus and potassium was mainly stored in the leaves before the stem elongation stage 1, and then mainly stored in the stems. The nutrient uptake rates of nitrogen, phosphorus and potassium at the seedling stage and tillering stage was 24.84%, 26.18% and 27.74%, respectively, and it was 55.54%, 58.61% and 52.30% at the stem 1 to 3 (late July to late October), while 19.62%, 15.20% and 19.96% during stem 4 and 5 (late October to late December). Reasonable fertilization can be carried out according to the phase absorption of each element, thereby improving the quality and economic benefits of disease-free sugarcane seedlings production. The demands of nitrogen, phosphorus and potassium in the breeding process of disease-free sugarcane original seedlings were clarified, which would provide a reference for the scientific and reasonable fertilization in large-scale field propagation of disease-free sugarcane original seedlings in the future, and improving the efficiency of the propagation and nutrient utilization of disease-free original seedlings.

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    Correlation Between the Expression Level of Natural Rubber Biosynthesis Genes and Rubber Yield
    YANG Shuguang,CHEN Yueyi,LI Yan,ZHANG Shixin,ZHANG Xiaofei,ZENG Xia,CHAO Jinquan,TIAN Weimin
    Chinese Journal of Tropical Crops    2019, 40 (3): 475-482.   DOI: 10.3969/j.issn.1000-2561.2019.03.009
    Abstract552)   HTML13)    PDF(pc) (796KB)(403)       Save

    Latex is thought to be a protective substance associated with injury response in rubber trees. Tapping can significantly promote rubber production, which should be closely related to the expression of genes involved in rubber biosynthesis in the laticifer cells of rubber trees. However, the exact relationship between the expression of the rubber biosynthesis genes and the dry rubber yield is yet to be elucidated. In the present study, qPCR was used to analyze the expression of six rubber biosynthesis genes, HbHRT2, HbSRPP, HbREF, HbHMGR1, HbHRT1 and HbGAPDH, in the laticifer cells of five Wichham germplasms and five 1981°IRRDB germplasms following tapping them with S/2 d/3 tapping system. The results showed that the expression of these genes was significantly higher in most Wichham germplasms than in 1981°IRRDB germplasms, as shown by fold increases of 1.05-14.62, 0.97-4.26, 1.46-12.56, 0.83-2.99, 0.43-7.54, 1.92-11.31, respectively, for HbHRT2, HbSRPP, HbREF, HbHMGR1, HbHRT1 and HbGAPDH. Correspondingly, the average fold change was 7.54, 2.55, 5.69, 1.71, 2.71, 4.91. Correlation analysis showed that the expression level of these genes was positively related to dry rubber yield. Two of the genes, HbREF and HbGAPDH, could be exploited as the molecular markers in high rubber yield breeding programs for both genes showed a highest correlation between their expression level and the corresponding rubber yield.

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    Influence of Dissolved Organic Matter on Determination of Iron in Solution and its Mechanism
    WU Dongming,LI Yi,CHEN Yaohua,DENG Xiao,WU Chunyuan
    Chinese Journal of Tropical Crops    2019, 40 (7): 1441-1448.   DOI: 10.3969/j.issn.1000-2561.2019.07.028
    Abstract1316)   HTML8619)    PDF(pc) (1439KB)(1224)       Save

    Quantitative detection is a crucial technique for investigating the geochemical processes of ferric ion (Fe). However, due to the ubiquity of dissolved organic matter (DOM) in environmental medium, the combination of Fe with DOM may affect the determination of Fe in solution. Therefore, the effect of DOM between atomic absorption spectrometry (AAS) and colorimetry for Fe determination was tested. Precision of AAS was as good as colorimetry, both of them were less than 5%. However, AAS was more accurate with a recovery rate of 86.4%-97.8% and its detection limit was as low as 0.012 mg/L. DOM had a significant effect on colorimetry. The presence of DOM increased testing time and relative standard deviation of 11.5 h, 1.2%-22.2%, respectively. Moreover, the accuracy was also decreased by 28.3%-44.4%. As the concentration of DOM increasing, the accuracy was decreased in the tendency of exponential function, and the trend of the veracity fitted well with unary quadratic model. Moreover, the effect of DOM was greater with the decreasing concentration of iron. On the contrary, the presence of DOM had no significant influence on AAS. The results of EEMs and FTIR indicated that existed hydrogen bonding or π-π interaction occurred between DOM and Fe/phen that affected the interaction of Fe and colorimetry in a drive to influence the testing results.

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    Identification, Bioinformatics and Expression Analysis of Taro Starch Branching Enzyme Genes
    DONG Weiqing, LIU Lili, JIANG Huiping, QIU Zuyang, HE Fanglian
    Chinese Journal of Tropical Crops    2023, 44 (7): 1373-1382.   DOI: 10.3969/j.issn.1000-2561.2023.07.007
    Abstract68)   HTML4)    PDF(pc) (2446KB)(85)       Save

    Starch branching enzyme (SBE) play a key role in amylopectin biosynthesis and directly influence the content and structure of starch. Taro is a major tuber crop, widely cultivated in tropical and subtropical regions of the world. At present, there are few studies on SBE in taro, and the number, molecular structural characteristics and expression patterns of SBE genes in taro are not clear. In this study, a comprehensive analysis of taro SBE genes was conducted for the first time, and three SBE genes (CeSBE1, CeSBE2 and CeSBE3) were identified. The amino acid numbers of CeSBE1, CeSBE2 and CeSBE3 proteins was 828, 845 and 598, respectively, with molecular mass of 92 956.71 Da, 95 625.13 Da and 69 169.16 Da, and isoelectric point of 5.22, 5.41 and 7.36, respectively. Phylogenetic analysis showed that the three CeSBE proteins were divided into three different subgroups. Gene structure analysis showed that the number of CeSBE1, CeSBE2 and CeSBE3 exons was 16, 22 and 10, respectively. Conservative structural domain analysis showed that both CeSBE1 and CeSBE2 proteins had α-amylase_C and α-amylase structural domains and 7 motifs, while CeSBE3 protein had α-amylase and CBM_48 structural domains and 3 motifs. Analysis of cis-acting elements in the promoter region of CeSBE gene showed that a total of 55 cis-acting elements were predicted, 29 of which were functionally annotated, involving elements related to light response, hormone response, plant growth and development, and environmental stress. The three CeSBE genes were expressed in all tissues, with CeSBE2 being significantly expressed in corms and leaves (P<0.05). At different developmental stages of the corm, CeSBE2 had high expression at all developmental stages, showing a trend of increasing and then decreasing expression, with peak expression at 120 d of corm development. The increase in total starch and amylopectin content at different developmental stages of the corm was consistent with the trend of CeSBE2 expression, suggesting that CeSBE2 may be a key gene for amylopectin biosynthesis in taro. The study would enhance the understanding of CeSBE gene family members and provide the basis for genetic improvement of yield, quality and nutritional traits in taro.

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    Research Review, Current Progress and Future Outlook on Cassava Diseases in China
    SHI Tao, LI Chaoping, WANG Guofen, HUANG Guixiu
    Chinese Journal of Tropical Crops    2023, 44 (12): 2355-2368.   DOI: 10.3969/j.issn.1000-2561.2023.12.001
    Abstract80)   HTML15)    PDF(pc) (887KB)(46)       Save

    Cassava is the sixth-important grain crop in the world and the major cash crop in Southern China. Now cassava related industries play an important role in the local agricultural economy. Various kinds of diseases often happen and cause serious economic losses in the field, which become an important issue. This paper briefly reviewed the progress of cassava disease research, including the slow development stage from the founding of the P. R China to the 1980s, the fast development stage from the 1990s to the 2010s, and the rapid development stage after the 2010s. The latest research progress is the core part of this paper. Currently, there are four categories and eleven kinds of diseases that harm cassava in China. Cassava bacterial blight (CBB) is the most serious disease, and brown leaf spot occures in the largest area. Cassava mosaic disease (CMD) is the worst disease in the world, which has invaded mainland China. Chinese Academy of Tropical Agricultural Sciences and other institutions have launched the research of disease database construction and intelligent monitoring technology. The researcher had estimated the risk of five kinds of dangerous disease to cassava planting industry of China. For CMD and cassava brown streak disease, the research on the resistance evaluation of the main varieties, damage mechanism of virus, and detection methods were studied. As far as CBB, monitoring technology, genome sequencing of pathogen, pathogenic and copper resistant mechanisms, genetic variation of pathogen populations, selection of resistant germplasm and its function mechanism were investigated. The effective bactericide for CBB was screened, the efficient spraying and biological control technology were formed, along with the stem disinfection method was popularized in the field. In term of CMD, the occurrence area, virus identification, key factors for long range diffusion were confirmed in China, and significant advance was achieved in virus damage and propagation mechanism. The advance of monitoring and control technology on another seven kinds of common diseases was also expounded in this paper. With the development of the national economy, there have been new trends in China’s cassava planting industry, such as food consumption and scaling planting. The authors further look forward to the number of participating institutions, the speed of scientific research progress, the boosting role of multidisciplinary integration, and new research hotspots will emerge in the future. This article would help relevant practitioners to better understand the current situation and research progress of cassava diseases in China, and also provide a reference for the research and application of monitoring technologies of other crop diseases in tropical areas.

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    Analysis and Evaluation of Phenotypic Characters of F 1 Segregation Populations of Date Palm
    WANG Yi, FU Haiquan, ZHANG Ning, GAO Zhaoyin, HU Meijiao, HONG Xiaoyu, LI Dongxia, XU Zhongliang
    Chinese Journal of Tropical Crops    2023, 44 (12): 2485-2497.   DOI: 10.3969/j.issn.1000-2561.2023.12.014
    Abstract17)   HTML3)    PDF(pc) (1943KB)(26)       Save

    In order to understand the diversity of phenotypic traits in F1 segregation populations of date palm, this study used 143 F1 segregation populations of date palms as test materials to analyze the diversity, correlation, principal component and cluster analysis of 17 phenotypic traits, including plant height, crown breadth, stem girth, number of branches and leaf spot incidence. The results showed that there was a high degree of phenotypic variation and rich diversity in F1 segregation population of date palms. The variation degree of quantitative characters was high, the coefficient of variation ranged from 10.927% to 43.350%, and the coefficient of variation of stem girth was the largest. The coefficients of variation of quality traits ranged from 31.447% to 44.619%, among which the coefficients of variation of tiller leaf color and leaf hardness were 44.619% and 42.571%, respectively. The correlation analysis showed that plant height, crown breadth, stem girth, number of branches, the third branch of long, the thorn area length, the total number of tiller leaves, tiller leaves length, tiller leaves width, tiller leaf thickness and leaf color were positively correlated with each other. The incidence of leaf spot was negatively correlated with the other 16 traits. The principal component analysis showed that the cumulative contribution rate of the six principal components reached 87.51%, of which the characteristic value of the first principal component was 10.0836, and the contribution rate was 59.32%. It is mainly affected by the five indicators of plant height, third branch length, crown breadth, stem girth and branch number. The characteristic value of plant height is the largest, which is 0.2948, which mainly reflects the height and growth trend of date palm. The cluster analysis showed that the 143 F1 generation dates could be divided into five groups: Group Ⅰ included 33 dates with the smallest crown, the least number of branches, the shortest tiller leaves length, and the highest incidence of leaf spot disease. Group Ⅱ included 39 dates resources with the shortest plant height, the smallest stem girth, the shortest third branch length, and the heaviest incidence of leaf spot disease. Group Ⅲ included 23 dates resources with longer tiller leaves, darker tiller leaves, erect plant type and mild incidence of leaf spot disease. Group Ⅳ included 33 dates resources with excellent phenotypic traits such as large ratio of leaf length to width of tiller leaves, stiffer tiller leaves and the least incidence of leaf spot disease. Group Ⅴ included 14 dates resources with small ratio of tiller leaves length to width ratio and open plant type. The results of this study can provide a theoretical basis for the breeding of superior parental traits in later stage of date palm.

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    Response of Source-sink Development and Yield and Quality of Sweetpotato to Nitrogen Source and Nitrogen Application Rate
    WANG Ning, MENG Yayi, YAO Jianfeng, WANG Xueyu, LI Yupeng, DENG Baoni, LI Yongzhong, SI Chengcheng
    Chinese Journal of Tropical Crops    2024, 45 (1): 77-86.   DOI: 10.3969/j.issn.1000-2561.2024.01.009
    Abstract19)   HTML0)    PDF(pc) (1258KB)(13)       Save

    Field experiments were conducted to study the relationship between nitrogen source, nitrogen application rate and the interaction on the source-sink development during the whole growth period of sweetpotato Mingmenjinshi and its relationship with yield and quality. The results showed that nitrogen application increased the chlorophyll content and net-photosynthetic rate of sweetpotato at 70 to 110 days after planting, the number of storage root per plant, average storage root weight and yield, the content of soluble sugar, sucrose, soluble protein, polyphenols and vitamin C, and significantly decreased the content of starch. Under the same nitrogen source, at 30 to 120 days after planting, the fresh weight of stems and leaves increased significantly with the increase of nitrogen application; the average number of storage root per plant, the average weight of storage root and the average weight of storage root per plant increased first and decreased then with nitrogen application, and were the highest when the nitrogen application rate was 120 kg/hm2; T/R first decreased and then increased with the increase of nitrogen application rate, and was the lowest when the nitrogen application rate was 120 kg/hm2; and the number of storage root per plant and yield was the highest with nitrogen application of 120 kg/hm2. Under the high-yield nitrogen application rate of 120 kg/hm2, compared with amide nitrogen and nitrate nitrogen, ammonium nitrogen significantly increased chlorophyll content and net-photosynthetic rate at 70 to 110 days after planting; significantly increased the fresh weight of leaves and stems at 30 days after planting; significantly increased the number of storage root per plant at 30 to 120 days after planting; significantly increased the weight of storage root per plant at 60 to 120 days after planting. At harvest, ammonium nitrogen significantly increased the yield of commercial storage root by significantly increasing the number of storage root per plant, also significantly increased the content of soluble sugar, sucrose, soluble protein and vitamin C, and improved flavor quality.

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