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    25 June 2022, Volume 43 Issue 6 Previous Issue    Next Issue
    Omics & Biotechnology
    Cloning and Expression Analysis of DWF5 Genes Involved in the Sterol Synthesis in Oil Palm
    ZHANG Weisheng, LIU Zhichao, CAO Hongxing, YAN Yan, CHEN Ping, LI Rui
    2022, 43 (6):  1095-1101.  doi: 10.3969/j.issn.1000-2561.2022.06.001
    Abstract ( 198 )   HTML ( 189 )   PDF (2024KB) ( 179 )  

    DWARF5 (DWF5) encodes 7-dehydrocholesterol reductase, which is a key enzyme in the synthesis of sterols and participates in the formation of plant oil bodies (OBS) by regulating the synthesis pathway of sterols. The cultivar, ‘Reyou No. 4’, was taken as the experimental material to explore the effects of DWF5 gene on the development of OBS in the mesocarp of oil palm. After extracting RNA from mesocarp, the reverse transcription cDNA was used as a template to conduct full-length cloning of genes. Two EgDWF5 genes obtained were named EgDWF5-1 and EgDWF5-2. The bioinformatics method was applied to analyze and predict physicochemical properties, structural characteristics, and genetic relationship, etc.. The expression levels of the genes in roots, stems, leaves, flowers, and fruits at different stages after flowering were analyzed by quantitative real-time PCR. The results showed that the number of amino acids encoded by the EgDWF5-1 and EgDWF5-2 gene was 434 and 374, respectively, the relative molecular masse was 49.71 kDa and 42.68 kDa, the isoelectric points was 8.61 and 8.69, the protein instability indexes was 38.60 and 38.13, and the aliphatic index was 98.80 and 96.68. The gravy was 0.347 and 0.313. Both proteins were hydrophobic. EgDWF5 has the most closed genetic relationship with rice and maize, but less related to other species. The qRT-PCR analysis showed that the two EgDWF5 genes were expressed in all organs of oil palm, among which EgDWF5-1 was highly expressed in mesocarp, which was significantly higher than that in roots, leaves, flowers and other parts. The expression trend of EgDWF5-1 gene increased from 12 to 18 weeks after flowering and reached the peak at 20 weeks after flowering, and then gradually decreased, which was consistent with the synthesis trend of the OBS in the oil palm mesocarp. EgDWF5-2 gene was highly expressed in roots and stems, but the expression level of it was low in mesocarp, and its expression trend in mesocarp gradually decreased from 12 to 18 weeks after flowering. Therefore, it is speculated that EgDWF5-1 is involved in the regulation of development of OBS in oil palm, while EgDWF5-2 is not involved in this regulation and may play a role in the growth and development of oil palm. This study would lay a foundation for further exploring the mechanism of EgDWF5 regulating OBS formation in oil palm.

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    Cloning and Expression Analysis of PG Gene in Jackfruit
    CHEN Jie, HUANG Shuyi, LI Zhenqin, LIAO Qianxian, SONG Kanghua, HONG Keqian, WANG Junning
    2022, 43 (6):  1102-1113.  doi: 10.3969/j.issn.1000-2561.2022.06.002
    Abstract ( 144 )   HTML ( 173 )   PDF (3519KB) ( 116 )  

    To clarify the role of PG gene in the process of jackfruit ripening and softening, using ‘Haida 2’ jackfruit as the material, the dynamic changes of the hardness and pectin were studied at room temperature (20℃) during the ripening of the fruits treated with 0.5 mg/L 1-MCP and 1000 mg/L ETH, four polygalacturonase genes from ‘Haida 2’ fruits were cloned, and the bio-informatics and expression were analyzed. The results showed that with the ripening of the fruit, the firmness of the pulp droped rapidly, the soluble pectin and ionic pectin continued to increase, and the covalent pectin decreased. ETH treatment promoted the increase in WSP and ISP content and accelerated the process of fruit softening. 1-MCP treatment inhibited the decrease of pulp firmness in the early stage of fruit storage, delayed the process of fruit softening, but significantly increased the content of three types of pectins. The length of the open reading frames (ORF) of AhePG1~AhePG4 genes were 1221-1434bp, encoding 406-477 amino acids. AhePG1 protein contained four conserved domains (I-IV), AhePG2、AhePG3 only contained domains I and II, and AhePG4 lacked domain III. The relationship among amino acid sequences encoded by AhePG genes and PG genes from peach (AF095577.1), Phaseolus vulgarise (XM_007162208.1), Humulus (MN971583.1), and Phaseolus vulgarise (XM_007151391.1) was close, with similarities of 75.63%, 73.11%, 79.71% and 70.75%, respectively. The results of qRT-PCR analysis showed that the expression level of AhePG1 gene was low in the early stage and high in the later stage of fruit ripening. The expression level of AhePG2/3/4 genes was generally lower. ETH treatment inhibited the expression of AhePG1 gene, while 1-MCP treatment delayed the increase of four AhePGs expression, but increased the expression of AhePG2, AhePG3 and AhePG4 genes in the late stage of maturity. The result of correlation analysis showed that pulp firmness had a significant and very significant negative correlation with water-soluble pectin content and AhePG1 gene expression, and water-soluble pectin content had a significant positive correlation with AhePG1 gene expression. It showed that the softening of jackfruit fruit was related to the degradation of pectin, and AhePG1 maight be one of the key PG genes in jackfruit fruit pectin degradation and fruit softening, which controlling the softening of the fruit at the later stage of maturity.1-MCP treatment could delay the ripening of jackfruit fruit, but did not affect the softening of the fruit during the later ripening period, which meight be affected by AhePG genes.

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    Cloning and Functional Analysis of CpMGT1, a Magnesium Transporter Gene from Carica papaya
    XU Yinggang, ZOU Zhi, GUO Jingyuan, KONG Hua, ZHU Guopeng, GUO Anping
    2022, 43 (6):  1114-1121.  doi: 10.3969/j.issn.1000-2561.2022.06.003
    Abstract ( 123 )   HTML ( 169 )   PDF (6675KB) ( 106 )  

    Magnesium is a macronutrient that plays essential roles in plant growth, development, photosynthesis, stress response as well as other biological processes. In higher plants, it has been established that absorption, transport, distribution, and reallocation of Mg2+ are mainly mediated by MGTs/MRS2s (magnesium transporters/mitochondrial RNA splicing2s) and MHXs (magnesium-proton exchangers). Among them, the family MGT, also known as CorA (cobalt resistance A) that was originally identified in Salmonella typhimurium, was most studied, especially in model plants such as arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa). By contrast, little information is available in papaya (Carica papaya L.), an economically important tropical crop of the Caricaceae family within Brassicales. Based on mining accessible genome and transcriptome data of papaya, in this study, a magnesium transporter gene named CpMGT1, which includes an open reading frame of 1332 bp, was successfully cloned using RT-PCR (reverse transcription polymerase chain reaction). Furthermore, the protein physicochemical properties and conserved motifs were investigated using bioinformatics tools, the gene expression patterns were analyzed using qRT-PCR (quantitative real-time PCR), and functional complementarity was performed through heterologous expression in S. typhimurium mutant MM281 that lacks Mg2+ transporting systems (i.e. CorA, MgtA, and MgtB) and can’t grow on media containing low concentrations of Mg2+. Results showed that CpMGT1 was predicted to encode 443 amino acids with a theoretical molecular weight of 50.43 kDa and an isoelectric point of 5.12; the protein was shown to contain two hydrophobic transmembrane regions (i.e. TM1 and TM2), while TM1 harbored the highly conserved GMN motif; the subcellular localization prediction suggested that the CpMGT1 protein was located in the plasma membrane, whereas the evolutionary analysis revealed that it was closely related to AtMGT1 and AtMGT2, two high affinity Mg2+ transporters in arabidopsis; the expression analysis showed that CpMGT1 was constitutively expressed in tissues examined, with most abundance in roots, stems, and fruits; heterologous expression of CpMGT1 in the MM281 mutant could significantly improve the growth of engineering strain at low Mg2+ concentrations, implying its high Mg2+ transport activity. Taken together, this study presents the molecular cloning and characterization of the first MGT gene in papaya, including sequence features, physicochemical properties, evolutionary relationships, gene expression patterns as well as Mg2+ transport activity. These results could not only lay a solid foundation for further uncovering the accumulation mechanism of Mg2+ in different tissues especially in the fruit, but also provide a valuable resource for genetic improvement in papaya and other species.

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    Analysis on Agronomic Characters and Heritance for the Rice Semi-dwarf Mutant ‘Shuang-Fu-Ai-Nuo’
    ZHANG Linjin, YUAN Dingyang, LIU Taoli, TAN Ying, YANG Zhen, ZENG Jianguang, WANG Xuehua, TAN Yanning
    2022, 43 (6):  1122-1128.  doi: 10.3969/j.issn.1000-2561.2022.06.004
    Abstract ( 99 )   HTML ( 13 )   PDF (3469KB) ( 85 )  

    Lodging is an important factor affecting the production of rice (Oryza sativa L.). The semi-dwarf materials are ideal germplasms to coordinate the contradiction between yield and lodging resistance. Previously, a semi-dwarf mutant named ‘Shuang-Fu-Ai-Nuo’ was obtained in ‘Xiang-Fu-Nuo No.1’ induced by radiation mutagenesis. Here, this work aims to reveal its characters on stem node configuration, basic agronomic traits and genetic law. It showed that ‘Shuang- Fu-Ai-Nuo’ was 24.88 cm lower than ‘Xiang-Fu-Nuo No.1’ with a plant height of 133.11 cm. In particular, panicle, the first and second stem node was notably shortened by 18.10%, 23.06% and 19.19% respectively. But, the third, fourth and fifth ones were not obviously shortened, indicating the target gene mainly controlls the elongation of panicle and upper stem node. The effective panicle number per plant in ‘Shuang-Fu-Ai-Nuo’ amounted to 10.4, and it was 2.04 times of the level of 5.2 in ‘Xiang-Fu-Nuo No.1’. Such a superiority ensured an increase of 25.26% in yield per plant although a decrease of 20.24% for total grains per panicle and 7.51% for grain weight. Meanwhile, no notable difference was observed in appearance quality including grain length, grain width and length to width ratio between ‘Xiang-Fu- Nuo No.1’ and ‘Shuang-Fu-Ai-Nuo’. Similarly, the two samples remained the same level on the eating quality regarding amylose content and gel consistency, suggesting the semi-dwarfism habit has no adverse effects on rice quality. The detection of genetic background revealed that, ‘Xiang-Fu-Nuo No.1’ and ‘Shuang-Fu-Ai-Nuo’ confered the same genotype for each one of the 48 SSR markers. Due to the genetic similarity of 100.00%, ‘Shuang-Fu-Ai-Nuo’ was confirmed a real sibling that induced from ‘Xiang-Fu-Nuo No.1’. Moreover, the inheritance of the trait of plant height were investigated, by employing two F2 population derived from ‘Shuang-Fu-Ai-Nuo’ reciprocally crossed with ‘Xiang-Fu-Nuo No.1’. The theoretical separation ratio of semi-dwarf plants to wild-type plants was in line with 1:3, that proves the target gene is controlled via a single recessive nuclear gene. This study clarified the phenotype of plant height and genetic pattern of ‘Shuang-Fu-Ai-Nuo’, providing a basis for better mining its usage in rice genetic improvement.

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    Weighted Correlation Network Analysis Reveals Candidate Genes Related to Fruit Color Transition in Pepper (Capsicum annuum L.)
    JIN Weiheng, MUMTAZ Muhammad Ali, HE Chengyao, XIA Yu, HAO Yuanyuan, LI Caichao, WANG Zhiwei
    2022, 43 (6):  1129-1143.  doi: 10.3969/j.issn.1000-2561.2022.06.005
    Abstract ( 90 )   HTML ( 12 )   PDF (5536KB) ( 99 )  

    Pepper belongs to the annual or perennial pepper genus (Capsicum L.) in the Solanaceae. Amid all vegetables grown in China, pepper is ranked first as per its sowing area and output value. Fruit color is one of the most intuitive economic traits of pepper, which directly affects people's purchase choice. Nevertheless, the regulation of pepper fruit color is affected by many factors, especially the key regulatory factors in the process of fruit pigment formation and the regulation of related pigment biosynthesis are not clear. To understand the mechanism of pepper fruit color formation, physiological testing, transcriptome sequencing and weighted gene co-expression network analysis (WGCNA) was performed using Capsicum germplasm HNCA0076 as the experimental material, presenting five colors during fruit development. During the five different color periods of the fruit, the chlorophyll content was significantly different, the carotenoids content showed an increasing trend, the flavonoid content was relatively stable, and the anthocyanin content decreased gradually after purple fruit stage, and increased after orange fruit stage. The quality of the RNA sequencing data met the requirements for further analysis. The number of differentially expressed genes (DEGs) up-regulated and down-regulated in each period was 826 (276), 390 (588), 1248 (1800) and 1528 (2485). As the fruit matures, the number of differential genes in adjacent comparison combinations gradually increased. DEGs were analyzed by gene ontology (GO) enrichment with a main focus on molecular functional such as tetrapyrrole binding, heme binding, transferase activity, oxidoreductase activity, iron ion binding and hydrolase activity. After KEGG enrichment analysis, DEGs were found mainly enriched in carotenoid biosynthesis, flavonoid biosynthesis, starch and sucrose metabolism. Among these, the expression of the three genes from the carotenoid metabolic pathway were up-regulated during the transition from purple to yellow, and the expression of 11 genes from the flavonoid metabolic pathway were down-regulated during the transition from yellow to red. The differentially expressed genes of four comparative combinations were annotated to 8877, 8736, 8689, and 8573 transcription factors (TFs), and together to 8049 TFs, including AP2, F-box, MYB, and UDPGT. We performed a WGCNA using non-redundant DEGs associated with four modules including chlorophyll, carotenoid, coloring, and flavonoid content. Further analysis indicated that 29 TFs such as p450 (LOC107859314), Pkinase (LOC107839192, LOC107875415), F-box (LOC107863894), and zf-MYND (LOC107852593) may be involved in the regulation of pepper fruit color conversion. This study would provide an important data for further exploring the key regulatory factors in the process of pepper fruit coloring and analyzing the regulation of related pigment biosynthesis.

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    Mechanism Study of STE20L4 in Promoting Hypocotyl Elongation of Arabidopsis thaliana
    SHE Yuting, DING Yong
    2022, 43 (6):  1144-1151.  doi: 10.3969/j.issn.1000-2561.2022.06.006
    Abstract ( 112 )   HTML ( 9 )   PDF (7257KB) ( 73 )  

    Hypocotyl elongation assists plants to break through the soil and changes from heterotrophic to self-sustaining, which is the guarantee of normal life activities of higher plants. In this study, a mutant with shorter hypocotyl was identified by observing the hypocotyl of a series of Arabidopsis mutants in our laboratory and the molecular mechanism of regulating hypocotyl elongation was preliminarily explored. STE20L4, as a MAP4K, encodes a mitosis-activated protein kinase homologous to STE20 in yeast and activates downstream MAP3K in the MAPK cascade signaling pathway. Genotyping identification and semi-quantitative results showed that ste20l4-1 and ste20l4-2 were mutants with loss of function. Through phenotype observation, the ste20l4 mutant shows a short hypocotyl either in long daylight (16 h light/8 h dark), short daylight (8 h light/16 h dark) and dark (24 h dark) conditions compared with the wild type. Cytological results showed that short hypocotyl of ste20l4 mutants were due to a shortening of cell length rather than a change in cell number. The plant hormone gibberellin can promote the elongation of the hypocotyl and the sensitivity to its treatment can be used as a method of judging whether to participate in the GA signal transduction pathway. Under different gradient concentrations GA (0, 0.5 µmol/L, 1 µmol/L, 2 µmol/L and 5 µmol/L) treatment, the hypocotyl elongation of ste20l4 mutants were not significant compared with the wild type. Paclobutrazol (PAC) is an inhibitor of endogenous GA synthesis, with gradient concentrations PAC (0, 0.01 µmol/L, 0.02 µmol/L, 0.05 µmol/L, 0.1 µmol/L, 0.2 µmol/L, and 0.5 µmol/L) processing, the inhibition of hypocotyl elongation in mutants were also less pronounced than wild type. The above physiological results show that STE20L4 is involved in regulating the growth and development of hypocotyl in the GA signal transduction pathway. After fusing the protein of STE20L4 with fluorescent tags, we transfected them into tobacco and Arabidopsis protoplasts to observe subcellular localization, the results showed that STE20L4 was expressed in both cell membranes and cytoplasm. A series of RT-qPCR of GA downstream genes associated with hypocotyl elongation were tested in the wild-type and ste20l4 mutants. The results showed that the transcriptional levels of XTH17, EXP2, PRE1, PIF4, YUC2 and SAUR19 genes were significantly downregulated in the ste20l4 mutant, suggesting STE20L4 may participate in hypocotyl elongation by indirectly regulating the expression of these downstream genes. In summary, STE20L4 participates in the GA signal transduction pathway and regulates hypocotyl elongation by promoting the expression of hypocotyl elongation-related genes downstream of the GA. Our study preliminarily elaborated the molecular mechanism of STE20L4 regulating plant hypocotyl elongation, which provides a reference for further study of the interaction between MAPK and GA to regulate plant growth and development.

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    Cloning and Expression Analysis of LWD Genes in Impatiens uliginosa
    LI Xinyi, LI Yang, LUO Chao, WEI Chunmei, HUANG Meijuan, QU Suping, HUANG Haiquan
    2022, 43 (6):  1152-1159.  doi: 10.3969/j.issn.1000-2561.2022.06.007
    Abstract ( 95 )   HTML ( 6 )   PDF (2476KB) ( 93 )  

    WD40 is a large transcription factors family, which has the functions of regulating anthocyanin biosynthesis, plant growth and development, abiotic stress response and so on. LWD (LIGHT-REGULATED WD) gene is a known biological clock regulator in this family, but there are few reports about plant LWD gene at present, and its function needs further study. In order to investigate the influence of LWD gene on the flower color of Impatiens uliginosa, two LWD genes of I. uliginosa were cloned by RT-PCR and other techniques, named IuLWD1 and IuLWD2 respectively. The full-length cDNA were 1041 bp and 1032 bp, encoding 347 amino acid and 344 amino acid respectively. The analysis of basic physical and chemical properties showed that the GC content of IuLWD1 and IuLWD2 was 46% and 50%, respectively; the relative molecular weight of IuLWD1 and IuLWD2 was 38 838.47 kDa and 39 029.65 kDa respectively; the theoretical isoelectric point of IuLWD1 and IuLWD2 was 4.71 and 4.70 respectively. The unstable index of IuLWD1 and IuLWD2 was 53.60 and 52.58, respectively, indicating that both proteins were unstable proteins. The total average hydrophilic index of IuLWD1 and IuLWD2 was -0.388 and -0.366, respectively, indicating that both proteins hydrophilic proteins. The analysis of domains showed that both IuLWD1 and IuLWD2 contained six typical WD40-repeat conserved domains, indicating that IuLWD1 and IuLWD2 belonged to WD40 superfamily. Sequence alignment showed that the amino acid sequence of IuLWD1 and IuLWD2 was similar to those of Paeonia suffuticosa, Vitis vinifera and Morella rubra. Based on the phylogenetic analysis, it showed that IuLWD1 was clustered with Vitis vinifera and Paeonia suffruticosa, and the homology reached 85%; the IuLWD2 and Morella rubra were clustered into one branch with 90% homology, and then they clustered together. It was inferred that the two genes were collateral relatives. According to the analysis of qRT-PCR, IuLWD1 and IuLWD2 were expressed in four different flower colors and four different development stages of I. uliginosa, the highest expression level was in the deep-red flower, and the lowest expression level was in the white-flower among all tested different colors. The expression level of both genes was positively correlated with flower color, and the expression level of IuLWD1 was higher than that of IuLWD2, which indicated that both IuLWD1 and IuLWD2 played an important role in the anthocyanins biosynthesis of I. uliginosa, and IuLWD1 played a stronger role in regulating the flower color formation of I. uliginosa. The above results established a foundation for further exploring the formation and variation mechanism of the flower color of I. uliginosa, improving the flower color of Impatiens and cultivating new species.

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    Plant Cultivation, Physiology & Biochemistry
    Effects of Extraneous Salicylic Acid on Physiological Index of Brazil Banana Seedling under NaCl Stress
    ZENG Liping, WANG Nanqi, LI Xinguo
    2022, 43 (6):  1160-1165.  doi: 10.3969/j.issn.1000-2561.2022.06.008
    Abstract ( 101 )   HTML ( 17 )   PDF (1193KB) ( 121 )  

    Banana (Musa spp.) is one of the most important economic fruits in the world and staple food in African. Salinity stress is a major factor that affects banana fruit production and quality. Brazil banana seedling (M. AAA Cavendish var. Brazil) is a major banana cultivar in South China. The plant phenolic salicylic acid (SA) plays a regulatory role in plant physiology and metabolism. Effects of extraneous SA on physiological index of Brazil banana seedling under NaCl stress is still unknown. In this paper, we focused on the need for analyzing the effect of physiological properties of Brazil banana seedling by means of spraying exogenous concentration (0.5, 1.0, 2.0, mmol/L) SA under 70 mol/L of NaCl salt stress, the effect of physiological indexes including relative water content (RWC), and proline content of leaves, were studied. The result indicated that under salt stress the relative water content on leaves and total chlorophyll content of the seedling decreased significantly, the content of prolinet, soluble sugars, soluble proteint and malondialdehyde (MDA) on leaves increased significantly. After further treatment with SA 0.5, 1.0 mmol/L, compared to only dealt with NaCl, the relative water content on leaves, the content of total chlorophyll, proline, soluble sugars and soluble proteins of the seedling increased significantly, while the content of MDA decreased. However, after further treatment with SA 2.0 mmol/L, compared to only dealt with NaCl, the relative water content on leaves, the content of proline, soluble sugars and soluble proteins had no significant difference. The symptom of salinity stress could be alleviated by the treatment of exogenous salicylic acid of adequate concentration (0.5, 1.0 mmol/L), with the optimum concentration of 1.0 mmol/L. However, high concentration of exogenous salicylic acid mitigation effect is not obvious.

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    Effect of Supplementary Fertigation on Pineapple Growth, Yield and Fertigation Production
    AN Dongsheng, LIU Yanan, YAN Chengming, ZHAO Baoshan, LIU Yang, LI Haoru, DOU Meian
    2022, 43 (6):  1166-1173.  doi: 10.3969/j.issn.1000-2561.2022.06.009
    Abstract ( 107 )   HTML ( 11 )   PDF (1305KB) ( 123 )  

    Intensified seasonal drought turns into a crucial factor affecting tropic agricultural production only to pest and disease. From the autumn of 2014 to the spring of 2020, continuous days without effective precipitation exceeding 90 days and 120 days occurred in 4 years and 2 years, respectively. CAM-Cycling pathway makes pineapple a strong drought tolerance crop, but drought stress still restricts the growth and yield of pineapple even if it can live on. Heavy fertilization at the early growth stage without irrigation adopts in the production of pineapple due to the benefit limitation, which results in the decrease of yield and quality, low fertilizer utilization efficiency and farmland pollution. A major objective of this study is to investigate the effect of the supplementary fertigation on pineapple ‘MD-2’ at field condition. Two irrigation levels including W1 (-15~-35 kPa), W2 (-35~-55 kPa) and three fertilize levels including F1 (100%), F2 (75%), F3 (50%) were conducted as F1W1, F2W1, F3W1, F1W2, F2W2, F3W2 and traditional fertilizer without irrigation to explore the effect on photosynthetic area, PSII quantum use efficiency (ΦPSII), dry matter production, economic characters and fertigation production, taking non-fertigation as the contrast. The results showed that supplementary fertigation significantly improved the plant height, leaf length, leaf width, leaf number and dry matter production of pineapple. The decrease of leaf number and leaf length was the main factor that reduced the single plant leaf area under fertigation and photosynthetic area reduction resulted in the decrease of dry matter production. The significant difference of single plant leaf area and the aerial part dry matter production represented among the fertilizer levels rather than irrigation levels, confirmed that the adverse effects of pineapple growth under fertigation originated from the fertilizer reduction and limitation of fertilizer usage in drought. The PSII quantum use efficiency (ΦPSII) of pineapple D-leaf without irrigation remained relatively high, which declined only 15% compared with irrigation treatment. Then it recovered after drought stress relieved in rainy season accompanied the reverse of the yellow leaf back to green. This phenomenon inferred that pineapple is insensitive to non-severe drought, the drought damage to pineapple leaf originate from the photoinhibition and photoreaction center regeneration might be the crucial assistance of the ΦPSII recovery. But the irreversible reduction of photosynthetic area determined the decrease of fruit dry matter production and yield at harvest. Partial factor productivity showed F3>F2>F1 while the yield and Brix showed F3<F2≈F1, which made F2 the best fertilizer level. Irrigation water productivity represented W2>W1, between which no significant difference in yield and Brix was shown under F2. Therefore, F2W2 is the appropriate supplementary fertigation pattern for pineapple production. In summary, pineapple is insensitive to non serve drought stress, maintaining the 20 cm depth soil water potential above -60 kPa guarantees the water requirement of pineapple, meanwhile, saves 25% of fertilizer consumption.

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    Effect of Irrigation on Yield, Quality and Sugar and Acid Accumulation of ‘MD-2’ Pineapple in Dry Season
    LIU Siru, MA Haiyang, LIU Yanan, XIAN Aimin, XU Minggang, SHI Weiqi
    2022, 43 (6):  1174-1182.  doi: 10.3969/j.issn.1000-2561.2022.06.010
    Abstract ( 88 )   HTML ( 11 )   PDF (3287KB) ( 108 )  

    Water is an important controllable factor that affects the growth and development of fruits, and the formation of fruit quality can be directly or indirectly controlled by affecting plant growth. However, the seasonal dry period severely restricts the growth and development of pineapple plants, especially the effect of irrigation in the dry season on the yield and quality of pineapples is still unclear. The aim of this study was to probe the response characteristics of pineapple yield and quality to water input during seasonal drought. In this experiment, ‘MD-2’ was used as the research object. Based on the monitoring of the actual rainfall in the dry season, four gradient levels (W1 20 mm, W2 50 mm, W3 100 mm, W4 150 mm) were designed to increase the irrigation volume, and the non-increasing irrigation was used as CK. And the yield, quality, sugar and acid content of pineapple were analyzed and determined. The results showed that increasing irrigation in the dry season could significantly increase ‘MD-2’ pineapple fruit yield, average single fruit weight and commercial fruit rate, and the highest and lowest gradient levels of pineapple yield were W4 and CK respectively (W4 was 45.56% more than CK). With the increase of irrigation in the dry season, vitamin C, the total soluble solids and titratable acidity of ‘MD-2’ pineapple fruit gradually decreased, and the total soluble sugar and sugar-acid ratio showed a trend of first increasing and then decreasing, the overall performance was W2>W1>CK>W3>W4. The ratio of total soluble sugar to sugar and acid in W2 was the highest at 12.94% and 26.95, which was significantly greater than that in CK, with an increase of 87.26% and 64.6%, respectively. The sucrose content of ‘MD-2’ pineapple fruit increased with the increase of the irrigation amount in the dry season, showing a one-variable quadratic curve function (P<0.05), and its proportion increased from 38.8% of CK to 65.1% of W4, and the overall performance was W4>W3> W1>W2>CK; While the contents of fructose and glucose decreased linearly with the increase of irrigation amount in the dry season (P<0.01), and the overall performance of the two ratios was: CK>W2>W1>W3>W4. It can be seen that irrigation in the dry season promoted ‘MD-2’ pineapple fruit. Fructose and glucose were converted into sucrose, and the proportion of sugar types was changed, which in turn changed the flavor quality of pineapple fruit. The content of citric acid and quinic acid showed a significant first increase and then decrease with the increase of irrigation volume in a one-variable quadratic function relationship (P<0.05). The content of malic acid increased in a very significant linear function with the increase of irrigation in the dry season (P<0.001). In the dry season, the proportion of citric acid was relatively stable and reached 50%, while the proportion of malic acid only increased significantly in the treatment of W4, and the proportion of quinic acid decreased significantly in the treatment of W4. Irrigation in the dry season is very necessary for yield, fruit quality and fruit flavor quality improvement. According to the actual amount of natural rainfall, proper adjustment of irrigation to keep the total water supply at about 300 mm can achieve high-quality and high-yield pineapple fruits in the Leizhou Peninsula.

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    Comparative Analysis of Nitrogen Uptake and Use Efficiency for Sugarcane Variety ‘Yunzhe 05-51’ and ‘Yunzhe 081609’ at Seedling Stage
    ZHAN Jian, DENG Ke, ZHANG Di, MENG Bo, ZHOU Yifan, DENG Yan
    2022, 43 (6):  1183-1190.  doi: 10.3969/j.issn.1000-2561.2022.06.011
    Abstract ( 150 )   HTML ( 12 )   PDF (1495KB) ( 105 )  

    As an important crop for sugar production, sugarcane (Saccharum spp. hybrid) production in China faces a big problem of high nitrogen (N) fertilizer application but low N use efficiency. Besides optimizing nutrient managing, selecting and planting N-efficient sugarcane variety is also an important strategy to reduce N input without yield loss. In the present study, two sugarcane varieties from Yunnan, i.e ‘Yunzhe 05-51’ and ‘Yunzhe 081609’ were grown under six N supply levels (0, 0.1, 0.5, 1, 5, and 10 mmol/L) in solution culture, and plant biomass, root morphology, plant N concentration and accumulation, N uptake efficiency and physiological utilization efficiency of seedlings were measured. The results showed that: (1) As N supply level increased, shoot, root and whole plant biomass of the two varieties first increased and then decreased, and the root biomass of ‘Yunzhe 081609’ reached the peak at lower N supply level than that of shoot, while that of ‘Yunzhe 05-51’ showed opposite. ‘Yunzhe 05-51’ and ‘Yunzhe 081609’ reached the best growth at 0.5 and 1 mmol/L, respectively, and ‘Yunzhe 081609’ had higher biomass than ‘Yunzhe 05-51’ at the same N supply level. (2) Total root length and average diameter first rose and then stabilized with increasing N supply, while the root surface area kept increasing and specific root length increased at first and then decreased in the two varieties. Under the same N supply ‘Yunzhe 081609’ showed higher total root length, average diameter and surface area, but lower specific root length than ‘Yunzhe 05-51’. (3) Plant N concentration and accumulation went up and then kept stable with increasing N supply for both varieties, and ‘Yunzhe 081609’ showed higher N accumulation than ‘Yunzhe 05-51’. (4) With the increase of N supply, both varieties showed an increasing and then stabilizing trend in N uptake per unit root length, while an increasing and then decreasing trend in N uptake per unit root surface area. The N physiological utilization efficiency decreased significantly with the increase of N supply level for both varieties. ‘Yunze 081609’ showed higher N uptake per unit root length than ‘Yunzhe 05-51’ in the range of 0.1-10 mmol/L N supply, but there was no consistent trend in N uptake per unit root surface area for the two varieties. Both varieties had no significant difference in N physiological utilization efficiency under the same N level. These results indicated that ‘Yunzhe 081609’ had higher N uptake than ‘Yunze 05-51’ mainly due to better root growth, which led to lower N requirement for optimal growth at seedling stage in ‘Yunzhe 081609’.

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    Comparative Estimation of Potassium Contents in Guanxi Honey Pomelo Leaves by Multiple Regression Models
    LI Fangliang, KONG Qingbo, ZHANG Qing
    2022, 43 (6):  1191-1199.  doi: 10.3969/j.issn.1000-2561.2022.06.012
    Abstract ( 93 )   HTML ( 8 )   PDF (1187KB) ( 97 )  

    Potassium (K) is one of the three nutrient elements of honey pomelo, which is an important index for accurate diagnosis and quantitative evaluation of growth status. The hyperspectral estimation model of K contents in honey pomelo leaves was established to provide basis for rapid, non-destructive and accurate estimation of K contents. Based on the hyperspectral data of pomelo leaves and the measured data of K contents, this study first analyzed the correlation between the K contents of pomelo leaves and the original and first-order differential spectra, then analyzed the correlation between sensitive band vegetation index and the K contents of pomelo leaves, and found out the spectral parameters with good correlation with the K contents of pomelo leaves, then the partial least squares regression model (PLS), BP neural network regression model (BPNN), random forest regression model (RF) and support vector machine regression model (SVM) of pomelo leaves K contents were established, and the best estimation model of K contents in pomelo leaves was determined. In the measured band of 350-1050 nm, the spectral reflectance of pomelo leaves decreased with the increase of K contents. In 513-598 nm and 699-735 nm, it reached a significant negative correlation level, the maximum negative correlation coefficient was -0.47 (554 nm) and -0.45 (715 nm), respectively. In 507-552 nm and 691-711 nm, potassium in pomelo leaves reached a significant negative correlation level with the first-order spectral reflectance, the maximum negative correlation coefficient was -0.54 (528 nm) and -0.53 (702 nm). In 557-655 nm, it reached a significant positive correlation level, and the maximum positive correlation coefficient was 0.58 (579 nm). 554, 715, 528, 579, 702 nm were selected to construct the spectral parameters and establish the difference vegetation index (DVIλ1, λ2), ratio vegetation index (RVI λ1, λ2) and normalized difference vegetation index (NDVI)λ1, λ2). NDVI°579,702, RVI554,715, RVI°528,579, R°579 were the spectral parameters that had good correlations with the K contents of pomelo leaves. Four regression models such as PLS, BPNN, RF and SVM were established to estimate K content in pomelo leaves and verified. R2, RMSE and RE of the estimation model of pomelo leaves K contents established by RF method was 0.84, 1.49 and 7.84%, respectively. R2, RMSE and RE of the estimation model by SVM method were 0.81, 1.61 and 8.01% respectively. While R2, RMSE and RE of the estimation model by BPNN method were 0.74, 2.28 and 9.01% respectively; R2, RMSE and RE of the estimation model by PLS method were 0.72, 2.44 and 9.95% respectively. R2 of the validation model of PLS, BPNN, RF and SVM methods were 0.79, 0.84, 0.85 and 0.82 respectively. Compared with PLS, BPNN and SVM, RF had higher R2, lower RMSE and lower RE, indicating that the accuracy of RF based K contents estimation model was higher than that of PLS, BPNN and SVM. Through the comparison of four hyperspectral estimation models for K contents in Guanxi honey pomelo leaves, the accuracy of random forest estimation model was higher than that of PLS, BPNN and SVM.

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    Plant Protection & Bio-safety
    Evaluation of Field Resistance of Rubber Tree Germplasms to Powdery Mildew and Anthracnose
    LI Peichun, LI Zengping, LIANG Xiaoyu, MA Zhan, LIN Chunhua, HE Junjun, LI Wenxiu, ZHANG Hualin, ZHANG Yu, LUO Ping
    2022, 43 (6):  1200-1213.  doi: 10.3969/j.issn.1000-2561.2022.06.013
    Abstract ( 84 )   HTML ( 13 )   PDF (3019KB) ( 105 )  

    Powdery mildew and anthracnose are the main diseases of rubber trees in China, which seriously affect the yield of latex and cause great economic losses to natural rubber industry. It is the most economical and effective measures to cultivate resistant germplasm resources. According to the field statistics of natural incidence of powdery mildew and anthracnose in 2018, 2019 and 2021, the disease resistance of 192 germplasms of rubber trees was identified, providing supportive data for resistance breeding of rubber trees. The results showed that powdery mildew was severe in 2019, with a mean disease index of 34.37 and a maximum disease index of 94.07 for the germplasm population, while it was less severe in 2018 and 2021, with mean disease indices of 10.68 and 9.70, respectively. Anthracnose was severe in 2021, with a mean disease index of 29.12 and a maximum disease index of 65.31 for the germplasm population, while it was less severe in 2018 and 2019, with mean disease indices of 18.64 and 18.15, respectively. The data of severe disease years were used to identify 24 highly-resistant varieties and 9 moderately-resistant varieties against powdery mildew and 35 resistant varieties against anthracnose. The germplasms reached resistance levels to powdery mildew and anthracnose in the three years, accounting for 22% and 19% of the germplasms tested. Membership function analysis and cluster analysis were used to rank the resistance levels of the candidate germplasms. The mean value of the membership function of the top 10 germplasms ranked for powdery mildew resistance ranged from 0.86 to 1.00, with standard deviation values ranging from 0.003 to 0.073. At the genetic distance 2.5 of the powdery mildew resistant clustering tree, ‘Zhanshi 5025’ in the first rank was clustered into a separate class. The germplasms from the second to sixth rank were clustered into a class, which was significantly distinguished from other classes. The mean value of the membership function of the top 10 germplasms ranked for anthracnose resistance ranged from 0.83 to 0.90, with standard deviation values ranging from 0.020 to 0.102. At the genetic distance 2.5 of the anthracnose resistance clustering tree, the germplasms from the first to fifth rank were clustered into a separate class, which was remarkably distinguished from other classes. ‘Zhanshi 5025’ ‘Zhanshi 12-3’ ‘Zhanshi 5005’ ‘Tianren 31-45’ and ‘Zhanshi 5026’ showed excellent resistance to powdery mildew. ‘Zhanshi 477-6’ ‘Zhanshi 366-2’ ‘Zhanshi 485-114’ ‘Zhanshi 41-3’ and ‘RO42’ showed excellent resistance to anthracnose. The resistance identification method combined with membership function and cluster analysis would provide an important technical reference for comprehensive evaluation of germplasm resistance.

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    Biological Characteristics and Pharmacological Experiments of Eotetranychus sexmaculatus on Seven Rubber Tree Clones
    SU Xuefang, SUN Jing, WEI Mingming, LI Weiguo, HUANG Xiao
    2022, 43 (6):  1214-1220.  doi: 10.3969/j.issn.1000-2561.2022.06.014
    Abstract ( 84 )   HTML ( 6 )   PDF (1055KB) ( 89 )  

    As important pest mites of rubber trees, Eotetranychus sexmaculatuss causes great harm to the growth and development of rubber trees and affects rubber production. To further clarify the development and reproduction of E. sexmaculatus on different rubber tree clones, and the sensitivity of different mite states to acaricides. In this study, the leaves of seven new clones of rubber trees were used as the hosts of E. sexmaculatus, and the morphological characteristics, developmental duration, and reproductive ability of each mite state were analyzed. At the same time, the activity of the four insecticides against the mites of E. sexmaculatus was determined by the method of soaking leaf butterfly, the method of leaf residual toxicity, and the method of glass dipping. The results showed that under the conditions of (28±1)℃, RH (75±5)%, and light [16(L)∶8(D)], the development time of E. sexmaculatus on each of the above 7 rubber tree clones. From long to short: adult mite stage > later nymph → adult mites> front nymph → later nymphs> egg → front nymphs. The developmental period of each mite state of E. sexmaculatus on the RRIM strain was the shortest. The development period of ‘Reyan 87-6-62’ and ‘Reyan 87-6-47’ clones was relatively long, and the number of single female eggs laid by E. sexmaculatus on the 7 rubber tree clones was as follows: ‘PR107’>‘RRIM600’>‘Reyan 89-4-19’>‘Reyan 93-59’>‘Reyan 89-4-51’>‘Reyan 87-6-47’>‘Reyan 87-6-62’. ‘PR107’ had the most single female yield, and the average number of eggs laid by females was 12.17. In ‘Reyan 87-6-62’, the number of eggs laid by a single female was the least, and the average number of eggs laid by a single female was 7.33. Different chemical agents were screened for the control of E. sexmaculatus. The results showed that the control effects of the four agents were all above 80% at 15 days after the treatment, among which 15% pyridaben EC and 1.8% abamectin·cypermethrin EC had good quick-acting effect, and the control effect can reach more than 80% after 3 days of application.

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    Effects of Spraying Parameters of Four-rotor Plant Protection UAV on Droplets Distribution in Rubber Plantations
    HUANG Xize, LIANG Xiaoyu, REN Saihao, TIAN Fang, ZHANG Yu, WANG Meng
    2022, 43 (6):  1221-1230.  doi: 10.3969/j.issn.1000-2561.2022.06.015
    Abstract ( 82 )   HTML ( 8 )   PDF (1302KB) ( 74 )  

    Droplet distribution characteristics affect the effectiveness of spray on crops, and spraying parameters are one of the important factors affecting the droplet distribution characteristics of plant protection unmanned aerial vehicles. The purpose of this study was to reveal the effects of spraying parameters such as dosage and droplet size on droplet distribution of electric quadrotor plant protection unmanned aerial vehicles in tall trees such as rubber forest. The target of this study was the mature rubber plantation of ‘Reyan 7-20-59’. The dosage of 18.75, 37.50, 75.00, 90.00, 105.00 L/hm2 and particle sizes of 70, 100, 150, 250 μm were set respectively. The main operational quality technical index data include droplet spectrum width, droplet coverage density and droplet distribution uniformity in horizontal and vertical directions. The data of main operation quality technical indexes were collected by water sensitive paper at six heights using the five-point sampling method. The optimal spraying parameters of the quadrotor unmanned aerial vehicles were selected and the field flight test was carried out in the optimal control period of powdery mildew. The results showed that the droplet spectrum width decreased with the increase of dosage, and the droplet coverage density increased significantly. When the dosage was 75 L/hm2 and above, the minimum droplet coverage density requirement was met. With the increase of droplet size, the droplet spectrum width of quadrotor unmanned aerial vehicles showed an increasing trend, and the droplet coverage density had no significant difference. The horizontal distribution uniformity of droplet size 100 μm was the best. The distribution uniformity of fog droplets produced by quadrotor unmanned aerial vehicles with different dosage and droplet size was consistent in the vertical direction of rubber forest, and the penetration of quadrotor unmanned aerial vehicles was good in rubber forest. In this study, the optimal spraying parameters of 75 L/hm2 and 100 μm spray particle size of quadrotor unmanned aerial vehicles were selected in rubber forest. In the optimal control period of rubber tree powdery mildew, prochloraz (EW) and tebuconazole (SC) agent were used for field flight control test, and the average control effect was 65.7% and 82.9%. This study would provide a group of application parameters of quadrotor unmanned aerial vehicles for the control of powdery mildew of rubber trees, which could provide reference for the operation of quadrotor unmanned aerial vehicles for the control of pests and diseases in rubber forest.

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    Identification of Host Proteins Interacting with RNA Silencing Suppressor of Sugarcane Streak Mosaic Virus
    FENG Xiaoyan, WANG Jungang, WANG Wenzhi, SHEN Linbo, ZHAO Tingting, FENG Cuilian, ZHANG Shuzhen
    2022, 43 (6):  1231-1239.  doi: 10.3969/j.issn.1000-2561.2022.06.016
    Abstract ( 88 )   HTML ( 8 )   PDF (4156KB) ( 97 )  

    Sugarcane streak mosaic virus (SCSMV) is a major pathogen of sugarcane mosaic disease. P1 protein encoded by SCSMV is an RNA silencing suppressor, which plays a key role in suppressing the host’s RNA silencing defense. However, its mechanism is not yet clear. Interaction with host proteins is one of the main pathways for RNA silencing suppressors to exert the suppression functions. Therefore, identifying host proteins that interact with viral RNA silencing suppressors is an important method to study the mechanism of suppressors. In order to explore the mechanism of SCSMV P1 suppressing the host RNA silencing, in this study, SCSMV P1 was ligated to the plasmid pGBKT7 to construct the bait plasmid pGBKT7-P1, then pGBKT7-P1 was tested for toxicity and self-activation, and finally pGBKT7- P1 was used as a bait to screen the host proteins that interact with P1 from the sugarcane cDNA library by yeast two-hybrid technology. The results showed that the bait plasmid pGBKT7-P1 was successfully constructed. After the pGBKT7-P1 bait plasmid was transferred into the Y2H Gold yeast strain, the yeast strain grew well in the SD/-Trp plate and liquid medium, indicating that the pGBKT7-P1 bait plasmid was non-toxic to the Y2H Gold yeast strain. The yeast strain containing the pGBKT7-P1 bait plasmid grew white rather than blue colonies on the SD/-Trp/X-α-Gal plate, and did not grow on the SD/-Trp/X-α-Gal/AbA and SD/-Trp/-Leu/X-α-Gal/AbA plates, indicating that the pGBKT7-P1 bait plasmid had no self-activation activity. The sugarcane cDNA library was screened with pGBKT7-P1 bait plasmid. After screening on SD/-Trp/-Leu/X-α-Gal/AbA plate once and SD/-Trp/-Leu/-His/-Ade/X-α-Gal/AbA plate three times, 42 positive yeast clones were obtained. The positive yeast plasmids were extracted and introduced into Escherichia coli for amplification. After sequencing and blastx comparison analysis, a total of 13 host sugarcane proteins that may interact with SCSMV P1 were obtained, namely auxin-responsive proteins IAA1, IAA15, transcription factors NAC, GATA4, OFP4, eukaryotic translation initiation factor eIF5A, chaperone DnaJ, co-chaperone SBA1, heavy metal-associated isoprenylated plant protein HIPP35, suppressor of mec-8 and unc-52 protein homolog SMU2, outer envelope pore protein OEP24, and two uncharacterized proteins. Based on the functions of the proteins, it was speculated that P1 may interact with host proteins to regulate the expression of host defense response-related genes, and/or interact with host proteins to affect the synthesis, processing, or transport of host RNA silencing-related proteins, thereby exerting the RNA silencing suppressor function of P1. The research results would lay an important foundation for the subsequent in-depth analysis of the RNA silencing suppression mechanism of P1.

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    Isolation and Identification of Symbiotic Actinomycetes from Termites in Hainan and Their Activity Against Tropical Plants Pathogenic Fungi
    WU Weicheng, CHEN Biting, ZHANG Shiqing, GUO Zhikai, LI Jitao
    2022, 43 (6):  1240-1247.  doi: 10.3969/j.issn.1000-2561.2022.06.017
    Abstract ( 114 )   HTML ( 10 )   PDF (2948KB) ( 118 )  

    The nesting and foraging activities of termites are mainly carried out in soil and rotting wood, where many pathogenic microorganisms live. However, termites are extremely vulnerable to these environmental pathogenic microorganisms. Therefore, termites need to rely on their mutualistic symbiotic microflora to form a defense system. Species of actinomycetes are one of the important groups in termite’s symbiotic microflora, which can produce diverse structures of secondary metabolites with antibacterial and antifungal activity. Whether the actinomycetes in termites can inhibit the pathogenic fungi of tropical crops remains to be studied. In order to explore the characteristic actinomycetes with potential application in the healthy development of tropical agriculture in Hainan, the actinomycetes were isolated and purified by the plate separation method from the healthy termites collected in the tropical plants garden of Chinese Academy of Tropical Agricultural Sciences in Haikou. Biocontrol strains were screened against 16 species of plant pathogenic fungi including Colletotrichum gloeosporioides Penz., Colletotrichum musae, Colletotrichum australianum, Phyllosticta capitalensis, Neopestalotiopsis clavispora, Gilbertella persicaria, Lasiodiplodia theobromae, Phomopsis caricae-papayae Fetrak & Cif., Phomopsis asparagi, Thielaviopsis paradoxa, Corynespora cassiicola, Corynespora sp., Pythium aphanidermatum (Edson) Fitzp and Peronophythora litchi by the growth plate-confrontation method. Identification of bioactive strain was based on the phylogenetic tree analysis constructed with 16S rRNA gene sequence. Growth plate-confrontation was directly used to investigate the antimicrobial stability, persistence and bacteriostatic spectrum for the strain and the filtering paper method was used to study the heat stability of antimicrobial substances for the crude extract of the bioactive strain. As a result, one strain of actinomycete (W7) with the best biocontrol activity was isolated from termites. Phylogenetic tree analysis showed that the strain W7 was closely related to Streptomyces genus. Most importantly, the bioactivity tests showed that the strain W7 had strong antifungal persistence and antifungal stability, even after cultivating for 30 d, it still had better antifungal against the tested plant pathogenic fungi. The strain W7 had inhibitory activity against 16 pathogenic fungi. It had strong inhibitory activity against plant pathogenic fungi C. musae, C. cassiicola, P. aphanidermatum (Edson) Fitzp, with strong antibacterial persistence and antibacterial stability. The strain also displayed weak antibacterial activity on plant pathogenic fungi P. asparagi, P. litchi. The fermentation extract showed good heat stability towards the mango pathogenic fungi C. gloeosporioides Penz., but the inhibition rate would decrease with the increase of water bath temperature. This is the first paper to investigate the termite-associated actinomycetes in Hainan. Bioactivity evaluation revealed termite-associated actinomycetes could be good resources for discovering biocontrol agent to control crop disease.

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    Post-harvest Treatment & Quality Safety
    Extraction and Characterization of Root Exudates of Different Cassava Varieties
    HAN Xiao, YANG Weixian, QIN Fengyan, FAN Xiaosu, LI Liangwu, HUANG Kai, YANG Taiyi, SHEN Zhangyou, WEI Maogui
    2022, 43 (6):  1248-1258.  doi: 10.3969/j.issn.1000-2561.2022.06.018
    Abstract ( 98 )   HTML ( 9 )   PDF (1239KB) ( 96 )  

    Autotoxicity caused by the auto-toxicity of root exudates has been proved as one of the most important reasons for continuous cropping obstacle. Root exudates of many plant types have been characterized. However, specific components of cassava root exudates have not been explored. The current study focused on the comparative effects for using different materials and eluants during the extraction and the separation processes of cassava root exudates. Then the best approach for extraction and characterization of the compounds of cassava root exudates were applied for analysing the root exudates of cassava varieties ‘XX048’ ‘NZ199’ and ‘SC205’. The optimal protocol for extraction of water-soluble substances of cassava root exudates can be described as follows: the agar medium was extracted within distilled water for 30 minutes using ultrasonic waves, after the solid-liquid separation process, the compounds in the filtrate was adsorpted with XAD-2, then eluted by ethanol, and analyzed by the gas chromatography-mass spectrometry (GC-MS). In total, twenty-six water-soluble substances were identified. Meanwhile, the optimal protocol for extraction of ethanol-soluble substances of cassava root exudates were as follows: the agar medium was extracted within 50% ethanol for 30 minutes using ultrasonic waves, the compounds in the filtrate were adsorpted with XAD-4 and then eluted also by ethanol. Fifteen compounds were identified by GC-MS. Furthermore, the dominating water-soluble substances in root exudates of cassava variety ‘NZ199’ were methyl hydroxyacetate (the relative content was 3.72%), hydroxyacetone (2.40%) and methylhydrazine (1.79%), and the main alcohol-soluble substances of ‘NZ199’ were ethanol aldehyde (18.89%), hydroxyacetone (2.47%) and formic acid (2.25%). For ‘XX048’, the main water-soluble substances were formic acid (2.68%), 1,5-pentanediol (2.39%) and hydroxyethyl acrylate (2.01%), while the main alcohol-soluble substances were ethanol aldehyde (17.00%), formic acid (2.62%) and hydroxyacetone (2.46%). For ‘SC205’, the main water-soluble substances were formic acid (2.23%), hydroxyacetone (1.80%) and methyl hydroxyethylate (1.43%), while the main alcohol-soluble substances were ethanol aldehyde (16.58%), formic acid (3.06%) and octafluoropentanol (2.98%). Thus, the chemical substances and the relative contents of root exudates varied with genotypes, leading to different resistant abilities of cassava varieties for continuous cropping obstacle.

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    Effects of Postharvest Melatonin Treatment on Fruit Quality and Storability of Phyllanthus emblica Fruit
    JIANG Xuanjing, JIANG Xue, CHEN Hongbin, ZENG Yaqi, ZHENG Jinshui, WU Shaohui, CAI Yingqing
    2022, 43 (6):  1259-1266.  doi: 10.3969/j.issn.1000-2561.2022.06.019
    Abstract ( 90 )   HTML ( 7 )   PDF (1354KB) ( 87 )  

    Phyllanthus emblica L. is one of the three health plants designated by the World Health Organization to be cultivated worldwide. In China, P. emblica has also been listed as a kind of fruit that can be used as medicine and food, with rich nutrition and outstanding health care value. However, harvested P. emblica is prone to suffer problems such as water loss, shrinkage, decay and deterioration, which greatly affects the commercial value of P. emblica. Melatonin is a ubiquitous bioactive molecule with diverse functions in plants and animals. Melatonin has an effective scavenging effect on free radicals in plants, and also plays an important regulatory role on plant resistance to diseases. Treating fruits and vegetables with appropriate concentration of melatonin is beneficial for the preservation, delaying fruit and vegetables spoilage effectively, and improving postharvest storability. In order to improve the storability of harvested P. emblica fruit stored at room temperature, the effects of melatonin treatment on the storability of ‘Lanfeng’ P. emblica fruit were investigated in this research. The selected P. emblica fruits without mechanical damage, diseases and insect damage, with similar size and color, were randomly divided into two groups. The two groups of fruits were respectively dipped in 0.3 mmol/L melatonin solution and deionized water (control) for 20 min. After the dipping treatment and dried for 1 h, the treated fruits were packed in low density polyethylene film bag and stored at room temperature (25±1)℃and 85%-90% relative humidity for 21 days. The marketable fruit commercial rate, disease index, respiratory intensity and other related indexes of fruit quality and storability were determined every three days. The results showed that the postharvest melatonin treatment increased the marketable fruit commercial rate of P. emblica by 22% at the end of storage, significantly reduced the disease index, respiration rate and weight loss of P. emblica fruit. In addition, the contents of total soluble solids, titratable acidity and vitamin C in melatonin treated P. emblica fruits were higher than those of the control fruits, and the deterioration of skin color and flesh texture was slower than that of the control fruits. In conclusion, melatonin treatment could delay the occurrence of postharvest diseases and improve the quality and storability of P. emblica fruits. The results of this research would provide a theoretical foundation for the application of melatonin in preservation of harvested P. emblica fruits, and enrich the theoretical basis on the application of melatonin in preservation of fruits and vegetables.

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    Preparation and Fresh-Keeping Effect of Tea Polyphenol-Chitosan Composite Film
    LIANG Jie, ZHAO Xiaoxu, LIU Tao, WANG Libin, LIN Qinghuo, CAI Lifeng
    2022, 43 (6):  1267-1279.  doi: 10.3969/j.issn.1000-2561.2022.06.020
    Abstract ( 60 )   HTML ( 5 )   PDF (7784KB) ( 69 )  

    Taking polyvinyl alcohol (PVA) and chitosan (CTS) as the substrates, glycerol as the plasticizer, tea polyphenols (TP) as the functional additives, a pollution-free, biodegradable packaging TP-CTS/PVA composite film with antioxidant activity was prepared, and the effects of the concentration of tea polyphenols on the mechanical properities, antioxidant capacity, antibacterical ability, such as the influence of the physical and chemical properties, packaging film related performance were studied. The film was applied to the fresh cherry tomatoes, and the physical and chemical indexes, including sensory quality, totting rate, weightlessness, soluble sugar, titratable acid and microbial indexes during storage were analysed. The results showed that the TP-CTS/PVA composite film had both antioxidant and antibacterial effects. With the increase of TP concentration, the color of the composite film gradually darkened, when the TP concentration was 1.50%, the water solubility of the composite film was the lowest (19.85±0.64)%, and TS of the composite film was at the maximum (13.19±0.77)MPa. When the concentration of TP increase, its antibacterial ability to Escherichia coli and Staphylococcus aureus also continued to increase, it could effectively inhibit bacterial growth. When the TP concentration was 2.0%, the scavenging rate of DPPH free radicals by the composite film reached the maximum (38.53±0.91)%. The composite film coating had a good preservation effect on cherry tomatoes, effectively delaying the rot and water loss of the cherry tomatoes, and improving the shelf life and commodity value of the fruits and vegetables. In addition, during the same storage time, when a composite film with a TP concentration of 1.5% was applied to cherry tomatoes, the sensory evaluation score, weight loss rate, decay rate, titratable acid content, soluble sugar content and other indicators of cherry tomatoes were more effective than other TP concentration tests.This study showed that when TP concentration was 1.5%~2.0%, the TP-CTS/PVA composite film had balanced indicators such as bacteriostasis, water resistance, oxidation resistance and preservation performance, and the TP concentration could be adjusted according to the needs when it is applied in production. The purpose of this study was to explore the possibility of developing antibacterial and antioxidant functional composite packing films for plastic films.

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    Optimize the Formula of a New Amomum tsao-ko Lozenges Using the Quadric Rotatable Design Union Design
    HU Yifan, GAO Xiaoyu, LIU Lei, ZHAO Cunchao, TIAN Yang, FAN Yuanhong
    2022, 43 (6):  1280-1287.  doi: 10.3969/j.issn.1000-2561.2022.06.021
    Abstract ( 69 )   HTML ( 7 )   PDF (1209KB) ( 66 )  

    Amomum tsao-ko is one of the Chinese medicinal materials and spice plants used for both medicine and food. It is rich in a variety of biologically active substances and has various pharmacological effects such as effective regulation of gastrointestinal and laxative. However, there are few reports on the research and development of new functional products of A. tsao-ko, and they are also extremely rare in the market. Because lozenges are easy to carry and eat, in this study, A. tsao-ko was used as the main raw material to make water extracts, and certain auxiliary materials were added after spray drying. Based on sensory scores, the process formula was optimized by the single factor and secondary universal rotation design, and its microbial and physical and chemical indicators were measured. A new Amomum tsao-ko lozenges with unique flavor was developed. The optimized process for the lozenge with the following steps, Amomum tsao-ko powder mixed in boiling water and cooked for 3 min (powder∶water =1∶10), nylon mesh filtration (repeated three times), concentrated the filtrate, filtrate spray dried to obtain aqueous extract, raw and auxiliary materials mixed, granulated, dried, granulated, screened (100 mesh screen), magnesium stearate added, molded. The results showed that the optimal formula of the new A. tsao-ko lozenges was A. tsao-ko aqueous extract 25 g, honey powder 100 g, passion fruit powder 150 g, β-cyclodextrin 15 g, maltodextrin 50 g, magnesium stearate 10 g, white sugar powder 200 g. The A. tsao-ko lozenges prepared under this condition not only retained the unique flavor of A. tsao-ko, but also had a delicate, slightly sweet taste and convenient eating. It has health benefits and is a new product with great research value for the development and utilization of A. tsao-ko. In the future, the health effects and specific effective ingredients of A. tsao-ko Lozenges can be further explored. Research on A. tsao-ko’s efficacy, ingredients and new products is of great significance to the intensive processing and industrial development of A. tsao-ko.

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    Agricultural Ecology & Environmental Protection
    Phenological Characteristics of Net Ecosystem Carbon Exchange in Hainan Rubber Forest Ecosystem
    YANG Siqi, YANG Chuan, GONG Yuan, ZHANG Jie, SONG Bo, WU Zhixiang
    2022, 43 (6):  1288-1296.  doi: 10.3969/j.issn.1000-2561.2022.06.022
    Abstract ( 102 )   HTML ( 8 )   PDF (1477KB) ( 86 )  

    Rubber (Hevea brasiliensis) plantation is an important forest ecosystem in the tropical region of China, plays an important role in the regional carbon cycle, and the carbon sink function cannot be ignored. In this study, we take the rubber plantation located in Danzhou, Hainan as the experiment subject, using the 50-meter micro-meteorological observation system which located in the third team of the Chinese Academy of Tropical Agricultural Sciences experimental farm. The data from 2018 to 2020 combined with the phenological model were used to analyze the dynamic characteristics of net ecosystem carbon exchange (NEE), ecosystem respiration (Re), gross primarily productivity (GPP), environmental control factors and phenological characteristics. The rubber plantation played the role of carbon sink and had obvious diurnal characteristics, showing a tendency of “U” shape. NEE was negative during the daytime and positive during the night, the maximum peak for NEE appeared at 11:00—13:00 at noon. When taking the annual as a unit, obvious convergent phenological changes would be found. During the rubber growing season (March to November), Re and GPP were significantly larger than those in the non-growing season, while NEE (negative value) is lower than the non-growing season, showing a single peak, all peaked during the rubber growth period from August to September. The phenological characteristics of the rubber plantation ecosystem showed, GPP increased during the second phase, peaked in the third phase, began to decline in the fourth phase, and continued to decrease during the deciduous period from the fifth phase to the next year first phase. The rubber plantation had a long growing season. Both NEE and Re reach the maximum during the growing season. During the period of the first and second rubber leaves, the rubber plantation net ecosystem exchange increased rapidly due to the heavy rainfall and high heat occurred at the same period. The relationship between NEE and environmental factors in different phenological periods was different. The environmental factors of rubber plantations in Danzhou, Hainan affected the phenology, and the phenology affected the changes of NEE. Study the relationship between phenology and carbon net ecosystem exchange, combined with a comprehensive discussion of environmental factors, would provided theoretical support for subsequent research on rubber plantation carbon cycle and lay a foundation for further research on response of rubber plantation to climate change, and provide more information and reference for rubber plantation ecosystem evaluation and sustainable economic and social development planning.

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    Microbial Immobilization Remediation of Soil Contaminated by Primary Rubber Processing Effluent
    ZHU Dayu, WANG Jun, SUN Hongfei, GE Chengjun, LIU Yingjie
    2022, 43 (6):  1297-1304.  doi: 10.3969/j.issn.1000-2561.2022.06.023
    Abstract ( 70 )   HTML ( 10 )   PDF (2330KB) ( 77 )  

    The effluent from the initial natural rubber processing produces a large amount of high organic matter and has the characteristics of high viscosity, acidity, and high organic matter. Due to its high treatment cost, and the frequent failure of anaerobic treatment, the back-end wastewater treatment does not meet the standard, and even more, wastewater is directly discharged into the surrounding soil to pollute the surrounding soil. However, researchers and environmental protection departments have not paid enough attention to the harm of primary rubber processing wastewater to soil and bioremediation methods. In the early stage of this study, a highly efficient degrading bacterial community with Bacillus as the dominant genus was domesticated and isolated from the contaminated soil near the natural rubber processing plant and named WR-2. WR-2 shows excellent performance in the degradation of wastewater from the initial natural rubber processing, but WR-2 microbial community requires a certain period of preparation and environmental adaptation in the application of soil remediation. Therefore, this article adopts the embedding method to carry out the immobilized pellet preparation experiment with sodium alginate-cassava residue biomass charcoal, bagasse, coconut bran, and two material concentrations of 1.5% and 2%. The immobilized pellet simulation remediation experiment of typical colloid wastewater in the processing wastewater contaminated soil was carried out to study the basic performance of WR-2 embedding and immobilization and its bioremediation ability. After comparing 6 groups of immobilized microspheres in terms of mechanical properties and remediation effects on contaminated soil, it was found that the 2% coconut bran modified immobilized microspheres not only had better mechanical properties but also had better mechanical properties on the organic matter (TOC) of contaminated soil in simulated remediation experiments. The degradation rate was as high as (96.7%), the soil tetramethyl thiuram disulfide (TMTD) was completely degraded on the 14th day, and the soil pH was adjusted from 4.42 to neutral, the total number of soil anions and cations was reduced, and the soil had outstanding microbial activity. What’s more, the 2% coconut bran immobilized pellets greatly improved the microstructure of the soil, decomposing the aggregates wrapped in the soil surface, and thereby improving the aeration and drainage of the soil. Therefore, the choice of sodium alginate 2% coconut bran as the preparation method of immobilized pellets for WR-2, as a method for optimizing the bioremediation of soil contaminated by wastewater from the initial rubber processing, would provide a theoretical basis for the rapid application of WR-2 microbial community.

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    Effects of Different Environmental Factors on Degradation of Paclobutrazol in Mango Plantation Soil in Hainan
    WU Dongming, YIN Wenfang, SONG Yike, LI Qinfen, WU Chunyuan
    2022, 43 (6):  1305-1312.  doi: 10.3969/j.issn.1000-2561.2022.06.024
    Abstract ( 139 )   HTML ( 8 )   PDF (1271KB) ( 119 )  

    Paclobutrazol, as a triazole plant growth regulator, is largely used in mango plantation soil in Hainan province and has high environmental risk in soil. However, the degradation of paclobutrazol in Hainan mango plantation soil is still unclear. This becomes the barriers to predict the bioavailability, toxicity and environmental risk of paclobutrazol in soil. Therefore, three typical soils were chosen in Hainan mango orchard, including Ledong soil, Dongfang soil, and Changjiang soil. Moreover, the degradation characteristics of patrabutrazol in the background soil and the effects of environmental factor were investigated by a microcosm experiment combined with chemometrics modeling. Three environmental factors were explored in this study, including indigenous soil microorganisms, the addition of iron-reducing bacteria, and soil humidity. Results showed that the degradation half-life (t1/2) of paclobutrazol in the soil of Hainan mango plantation ranged from 51 d to 114 d, which indicated that paclobutrazol was a refractory or moderately refractory pesticide in Hainan mango plantation soil. In which, the t1/2 value was largest in Ledong soil, implying the highest residual risk. The effects of environmental factors on paclobutrazol degradation in Hainan Mango plantation soil were closely related to the soil types. The effects of extermination of indigenous microorganisms and the addition of exogenous iron-reducing bacteria on paclobutrazol degradation in Ledong soil were negligible. However, for the Dongfang soil and Changjiang soil, the degradation rate of paclobutrazol decreased by 67.47% and 69.12% respectively, without autochthonous bacteria, and its t1/2 values were extended by 2.4 and 3.0 times, respectively. These results indicated that the degradation of paclobutrazol in two soils was mainly through a biochemical process by microorganisms. Similarly, the addition of iron-reducing bacteria inhibited the degradation of paclobutrazol in both two soils, and prolonged the t1/2 by 2 and 4 times, respectively. This result suggested that the extracellular electron transport not only could not degrade paclobutrazol through oxidoreduction in soil, but also affected the activity of indigenous soil microorganism. The t1/2 values of paclobutrazol under different soil humidity were in the order of 60% > 30% > 100%. This indicated that soil with moderate humidity was beneficial for the degradation of paclobutrazol in Hainan mango plantation soil. Principal component analysis showed that the effects of soil properties on paclobutrazole degradation were greater than that of external environmental factors. In which, cation exchange capacity (CEC) and pH were the two key factors. The soil with high pH value and large CEC were more conducive to the degradation of paclobutrazol in Hainan mango plantation soil. The findings will provide a scientific basis for the prevention and control of the residual risk of paclobutrazol in mango orchard soil in Hainan.

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