Chinese Journal of Tropical Crops
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Welcome to Chinese Journal of Tropical Crops,
2024 Volume 45 Issue 4
Published: 25 April 2024
  
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    Omics & Biotechnology
  • Omics & Biotechnology
    DU Xiaoyu, ZHAO Yijie, ZHANG Shixin, TIAN Weimin, CHAO Jinquan
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    Phytosulfokine (PSK) is a small peptide hormone unique to higher plants, widely involved in biological processes such as plant growth and development, division and differentiation, biotic and abiotic stress. PSK receptor (PSKR) is a direct receptor for PSK and is crucial for PSK signal transduction. In the present study, HbPSKR2 was cloned from rubber tree by RT-PCR (reverse transcription-polymerase chain reaction), and its bioinformatics, gene expression pattern, interacted proteins screening and identification were also analyzed. Results showed that the open reading frame of HbPSKR2 had a total length of 3159 bp and encoded 1052 amino acids with molecular weight 114.84 kDa and theoretical isoelectric point 6.34. Domain analysis showed that HbPSKR2 was a typical trans-membrane protein. The first 640 amino acids were the antenna structures composed of leucine rich repeat (LRR), the 692 to 714 amino acids were transmembrane domains, and the 765 to 1052 amino acids were kinase domains. Multiple comparisons were conducted on the membrane kinase domain of HbPSKR2 and the membrane kinase domain of PSKR homologous proteins in Arabidopsis and rice. The results showed the existence of conserved sites such as ATP binding site, CaM binding site, Activation segment, GC Centre. Expression pattern analysis showed that HbPSKR2 was highly expressed in the cambium region of rubber tree. The expression level of HbPSKR2 was significantly increased at the early stage of coronatine (COR) treatment. Twelve candidate proteins interacted with HbPSKR2 were screened by yeast two hybrid technology, and the interaction between two protein kinases (HbPBL8 and HbPIX13) and HbPSKR2 was further verified by luciferase complementary imaging. The strong fluorescence signal was observed by co-transformation HbPSKR2-nLUC/HbPBL8-cLUC and HbPSKR2-nLUC/HbPIX13-cLUC into tobacco, suggesting the interaction between HbPSKR2-HbPBL8 and HbPSKR2- HbPIX13 in vivo. The cloning of HbPSKR2 and identification of HbPSKR2 interacted protein would provide new insights into the molecular mechanism of laticifer differentiation in rubber tree.

  • Omics & Biotechnology
    XIE Xiuju, XIA Qiyu, LIU Shuai, MAI Xianjun, JIA Ruizong, GUO Anping, XU Zhisheng, LI Feng, KONG Xiangyi, ZHAO Hui
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    The traditional method for detecting the copy numbers of exogenous gene in transgenic plants is Southern hybridization, which is costly and time-consuming, and is difficult to meet the breeding needs of high-throughput detection of the copy numbers of exogenous gene. Therefore, this study aims to establish a fast and high-throughput method for detecting the copy numbers of exogenous gene in transgenic papayas. In this study, two single copy genes, Cpa03g018830 and Cpa03g018770, were selected from the papaya genome. Using the known exogenous gene as a single copy integrated transgenic papaya as a reference, the copy numbers were identified by digital PCR. Further, using them as reference genes, and the commonly used screening marker gene NPTII in papaya transgenic breeding as an exogenous target gene, methods for detecting the copy numbers of exogenous gene in transgenic papaya using digital PCR and fluorescence quantitative PCR were established. The results showed that Cpa03g018830 and Cpa03g018770 were both single copy genes; the established digital PCR method was accurate and reliable in detecting the copy numbers of exogenous gene in transgenic papayas, while fluorescence quantitative PCR had a higher accuracy in detecting single or low copy integration of exogenous genes in transgenic papayas, and a lower accuracy in detecting multiple copy integration of exogenous genes. Therefore, fluorescence quantitative PCR is suitable for initially screening out single or low copy integration plants from a large number of transgenic plants. The single copy Cpa03g018830 and Cpa03g018770 identified in this study can be used as reference genes for detecting the copy numbers of exogenous gene in transgenic papayas. The established methods for detecting the copy numbers of exogenous gene in transgenic papayas using digital PCR and fluorescence quantitative PCR techniques are simple, fast and suitable for batch detection, providing new methods for selecting single or low copy lines in transgenic resistance breeding of papayas.

  • Omics & Biotechnology
    YANG Lin, YANG Fan, ZHANG Hangying, HUANG Bocheng, QIU Qinghua, ZHANG Juncheng
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    To explore the relationship between the expression of psoralen synthase gene (PS) and psoralen synthesis, quantitative real-time PCR (qPCR) and high performance liquid chromatography (HPLC) were used to determine the expression of PS and the content of psoralen in roots, stems, leaves and fruits of Ficus hirta Vahl (FH) from Guangxi and Fujian. PS was expressed in roots, stems, leaves and fruits of Guangxi and Fujian FH, and the expression was tissue-specific. The relative expression level in roots was the highest (expression in branch roots was higher than that in principal roots), followed by leaves (expression in entire margined leaves were higher than that in incised leaves), and the expression levels in stems and fruits were extremely low. The psoralen contents of FH had some differences from the two producing areas. They were accumulated in the principal root, branch root, entire margined leaf, incised leaf, stem and fruit from Guangxi and Fujian provinc FH, and the contents were the highest in branch roots, which was 3.206 mg/g and 2.947 mg/g respectively, followed by principal root (2.136 mg/g and 0.419 mg/g). The content in incised leaves was 0.022 mg/g and 0.028 mg/g respectively, that in entire margined leaves was 0.069 mg/g and 0.035 mg/g. The psoralen content of stem (0.003 mg/g and 0.003 mg/g) and fruit (0.002 mg/g and 0.001 mg/g) was lower than other parts. The psoralen content was correlated with the expression of PS. The study would provide insights into understanding the role of PS in the psoralen metabolic in Ficus hirta Vahl.

  • Omics & Biotechnology
    CHEN Jianfen, CAO Zhenmu, QIN Yuling, SHEN Longbin, LIU Weixia, ZHU Dan, WU Yiting, LIU Ziji, WANG Xu
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    Pepper mild mottle virus (PMMoV) is one of the most serious pathogens worldwide. Currently, five pathogenic types of PMMoV have been reported, including P0, P1, P1,2, P1,2,3 and P1,2,3,4. The wide host range and strong pathogenicity of PMMoV seriously affect the yield and quality of pepper, and breeding for disease resistance is the most economical and effective means to control this virus. Our previous study determined that PMMoV infected with Danzhou pepper germplasm nursery in Hainan is the P1,2 pathogenic type. In order to screen PMMoV-resistant pepper germplasm resources, 110 germplasms were tested for PMMoV resistance using the reported L3-linked molecular markers. 46 pepper germplasms containing molecular markers of resistance were inoculated with PMMoV P1,2 pathogenic type by inoculation at seeding stage. Local symptoms were investigated 5 d after inoculation, and systemic symptoms were investigated 20 d after inoculation, and disease indices were calculated. The results showed that there were significant differences in disease resistance among different pepper germplasms, and the disease indexes of various germplasms ranged from 8.86-60.00. The germplasms showing high resistance (HR) to PMMoV P1,2 pathogenic type were CF19-34m and 19FB6-1. The germplasms showing resistance (R) wasCCJ93-1. The germplasms showing medium-resistance (MR) included 17YB32, 17SCa28m, 15SM39-2, 14SM555×14SM1, 14SM567-2, 14SM526-1, 14SM565-1, 14SM502-1, 14SM519-1, 14SM504m, 14SM503m, 14SM519-3, 14SM518-2, 14SM519-2, CCJ52-1, etc. The presenting susceptible (S) germplasms were 14SM514m, CCJ22-1, CCJ113-2, CCJ135-1, CCJ157-1, L537-1m, L545, CCJ87-2 and CCJ133-1, and the obtained disease-resistant germplasms accounted for 80.43% of the total identified materials. The results of this study would lay the foundation for creating germplasm resources resistant to pepper mild mottle virus and breeding resistant varieties.

  • Germplasm Resources, Genetics & Breeding
  • Germplasm Resources, Genetics & Breeding
    LIU Huizhuan, CAO Min, TANG Li, SONG Jiming, LI Junyi, FENG Yating, LUO Kai, CHEN Yinhua
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    Cassava (Manihot esculenta Crantz) is the third largest food crop in the tropics and is the food ration of nearly 600 million people in the world. Cassava is mainly cultivated in tropical regions, where often damaged by waterlogging in rainy season, which leads to serious decline in yield and quality. Therefore, it is important for selecting cassava germplasm resources with high waterlogging-resistance. In this study, a pot experiment was carried out, and plant height increment, relative chlorophyll content (SPAD), relative conductivity, superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) of 28 cassava germplasm resources were measured under waterlogging stress treatment after 6 days. Variance, correlation analysis, principal component analysis and subordinate function analysis were used to evaluate waterlogging resistance and screen the waterlogging tolerant germplasms at the seedlings stage. The waterlogging tolerance of 28 cassava germplasms had great difference and the response mechanism of different cassava germplasms to waterlogging stress showed huge difference among the 28 germplasm resources. There were significant positive correlation between plant height increment and relative chlorophyll content (P<0.01), and the correlation coefficient was 0.253. There were negative correlation coefficient between the relative chlorophyll content with relative conductivity of 0.266 (P<0.01). Principal component analysis using 6 indexes indicated that the 4 principal components accounted for 82.85% of accumulative contribution rates among the germplasms. The main factors were CAT, plant height increment, SOD, and relative chlorophyll content, respectively. According to subordinate function analysis, waterlogging tolerance of the germplasms from high to low was Qiongzhong 1, SC6068, SC201, ME191, M-F532, GR891, C222, GR3, F2000, Luoyong 80, 46-12, GR5, KU58, H660, SC5, F03P, M-GR911, CH20, M-F671, COL713, Boss 2, JG1301, GR911, E407, F274, SC8, M-SC5, Thailand. The results of this study would provide basic materials for the breeding of new varieties of cassava with high waterlogging-tolerance and for the future research of cassava waterlogging tolerance mechanism.

  • Germplasm Resources, Genetics & Breeding
    ZHOU Haiqi, XIA Ling, LYU Shun, ZENG Lisha, WANG Fang, HUANG Xiaoyan, CHEN Dongyi, LIU Wenqing, LIANG Shaoli, LIU liqin
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    Banana classification is a difficult problem, using morphological features to classify is unable to meet the needs. Molecular marker technology has been gradually applied to population identification and classification, genetic relationship analysis and genetic diversity research of banana varieties (lines). In this paper, SRAP molecular marker technology was used to analyze the genetic relationship of 89 banana germplasm resources. Using 10 pairs of positive and negative primers to form 100 pairs of primer combinations, and 13 pairs of SRAP primers with easy identification, clear band type and high polymorphism were screened out. 170 identifiable bands were amplified by the 13 pairs of primers, with an average of 13.08 bands per pair of primers, of which 140 bands showed polymorphism, with a polymorphism ratio of 79.00%. The similarity coefficient of 89 banana germplasm resources varied from 0.241 to 1.000, and the genetic diversity was very rich. The similarity coefficient of the same type of wild banana from the same place or different places was high. When the similarity coefficient was 0.49, the 89 banana resources could be divided into six groups. The first major category were AAA group Xiangyajiao, AA group Gongjiao, AAB group Longyajiao and AA group wild banana (AAA, AA, AAB). The second major category were ABB group Fenjiao, ABB group Fendajiao and BB group wild banana (ABB, BB). The third major category were Dajiao and a banana wild relative Musa itinerans. M coccinea, Musella lasiocarpa, Heliconia belonged respectively to the fourth, fifth and sixth category. The results are basically consistent with the current classical classification conclusion. Only some banana germplasm have different classification status, indicating that it is feasible to use SRAP markers to classify banana germplasm resources. At the same time, the cultivated Xiangya banana, Gongya banana and Longya banana have the same ancestry, and are close to the wild banana of AA genotype, while the wild banana of BB genotype is close to the pink banana, the pink banana and the wild banana of BB genotype, and the banana germplasm resources of different genomes are gathered together, which showing that the origin of banana germplasm resources affects the genetic relationship of offspring, and a single classification method cannot completely distinguish the banana germplasm resources. In addition, the genetic relationship between plantain and plantain is relatively close, but it is impossible to distinguish whether plantain contains A and B genomes, so the genotype and genetic background of plantain need further study.

  • Germplasm Resources, Genetics & Breeding
    HUANG Yulan, LI Yanying, ZHOU Jia, LAO Chengying, ZHOU Lingzhi, WEI Benhui, LI Suping, SHEN Zhangyou
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    Eight main agronomic traits were statistically analyzed using cassava germplasm resources. The result showed that the data for the eight agronomic traits were normally distributed, with the coefficients of variation ranging from 7.2% to 46.9%. The coefficient of variation for starch yield was 46.9% and the coefficient of variation for the dry matter rate was 7.2%. Correlation analysis showed that there was a degree of significant positive correlation between the different traits, with a highly significant positive correlation between weight of fresh tuberous root per plant and stem diameter. Principal component analysis combined eight traits into three main components. The cumulative contribution rates in each year amounted to 92.55% and 93.67%, respectively. The first principal components were weight of fresh tuberous root per plant, fresh tuberous root yield, starch yield and dry tuberous root yield. The second principal components were starch content and dry matter. Cluster analysis suggested that the resources could be divided into four groups in each year at the Euclidean distance of 6.0. Group Ⅱ had excellent performances in weight of fresh tuberous root per plant, fresh tuberous root yield, starch yield and dry tuberous root yield, which could be preferred as parental materials for new cassava varieties selection and breeding of high yield and good quality.

  • Germplasm Resources, Genetics & Breeding
    YANG Sixia, HUANG Xuguang, LU Yansong, HUANG Ailing, HUANG Yuhan, HUO Xing, LIAO Tanggui
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    Phenotypic traits are the basis of breeding, which can reflect the genetic variation of species to a certain extent. Exploring the phenotypic diversity of Hibiscus rosa-sinensis cultivar can provide reference for the utilization of germplasm resources and the breeding of new varieties. In this study, 39 H. rosa-sinensis cultivar resources were selected as the research object. Data of 25 phenotypic traits were collected and measured, including 9 quantitative traits and 16 qualitative traits. Diversity analysis, correlation analysis, cluster analysis, principal component analysis and comprehensive evaluation were carried out. The results of diversity analysis showed that there was abundant variation in the 39 H. rosa-sinensis cultivar resources resources, and the coefficient of variation of 9 quantitative traits ranged from 9.49 to 31.05, among which, the coefficient of variation of pedicel length was the largest, and the coefficient of variation of leaf length/width was the smallest; the index of diversity was 1.7592 to 2.0299, among which the index of style length was the highest, and edicel length diversity index was the lowest. The diversity index of 16 quality traits ranged from 0.3898 to 1.3203, among which the diversity index of flower heart and eye area was the highest, and the diversity index of flower pattern was the lowest. Correlation analysis showed that there were significant positive correlations between flower diameter and petal length, outermost petal morphology and petal secondary color, leaf length and leaf width, petal length and style length, flower diameter and style length, petal length and width, and flower diameter and petal width. There was a significant negative correlation between petal width and pattern, style length and pattern, leaf width and leaf length-width ratio, and petal length and pattern. The cluster analysis showed that the 39 species could be divided into four groups at Euclidean distance of 20. The Ⅰ group contained 33 species resources, which were mainly characterized by the flower diameter between 11 cm and 17 cm, and could be further divided into two subgroups. The Ⅱ group contained two species, which were mainly characterized by double petals and small flower diameter between 10 cm and 11 cm. The Ⅲ group contained three species, which were characterized by single petals and large flower diameter, with the flower diameter between 18 cm and 20 cm. The Ⅳ group contained only one species. Principal component analysis showed that 9 principal components were extracted, the cumulative variance contribution rate of 79.85%. Through the calculation of main component of the 39 specie, the comprehensive score of Huo fenghuang was the highest, followed by Valentine's day, Moorea Hanging Garden and Fei jiangjun, while that of Yueyecaihong and Chocolate Cake was the lowest.

  • Germplasm Resources, Genetics & Breeding
    FAN Qiuyun, YUN Yingying, LIANG Weihong, SHI Youhai
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    Spontaneous plants have strong growth adaptability, can self-multiply and form a good natural landscape, which are important materials for the construction of conservation-oriented landscape. The typical-sampling method was used to investigate the spontaneous plants in 16 city parks of Haikou, so as to comprehensively understand the diversity level of spontaneous plants and provide reference for the construction of conservation-oriented gardens. The results showed that 220 spontaneous plant species belonged to 59 families and 176 genera were recorded in this research. Among them, 154 plants were native plants (accounting for 70%) and 66 plants were exotic species (accounting for 30%), meanwhile, 48 plants were invasive alien species (accounting for 22.27%). Asteraceae, Poaceae and Fabaceae, the largest families, played a major role in the quadrats with 75 species from 64 genera, accounting for 36.36% and 34.09% of the total genera and species of Spontaneous plants. Perennial herbs and annual/biennial herbs were the main life forms, accounting for 51.36% (113 species) and 44.09% (97 species), respectively. Spontaneous plants have strong ecological adaptability and high potential for landscape application. In the future construction of urban landscape, the existing spontaneous plants in the parks should be reasonably planned and utilized, increasing the proportion of native plants and constructing the spontaneous plants landscape with regional characteristics according to different environments.

  • Plant Cultivation, Physiology & Biochemistry
  • Plant Cultivation, Physiology & Biochemistry
    RAO Xibing, QIAN Zhenfeng, ZENG Dan, ZHANG Rongqiong, LYU Shaozhi, SHEN Qingqing, WU Huaying, HE Lilian, LI Fusheng
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    Low temperature is one of the main environmental factors affecting the growth, yield and distribution of sugarcane. It is of great significance to explore the physiological response characteristics of sugarcane under low temperature stress and screen strong cold-tolerant sugarcane parent materials for guiding sugarcane breeding and promoting the development of sugarcane industry. In this study, eight different sugarcane varieties and one sugarcane wild species (Erianthus fulvus 99-1 clone) were used as the experimental materials to study the physiological index response after low temperature stress treatment, and the cold tolerance of the nine materials was comprehensively evaluated by principal component analysis, fuzzy membership function method and cluster analysis. The contents of malondialdehyde (MDA), chlorophyll (Chl), soluble sugar (SS) and soluble protein (SP) in most materials were higher than those of CK after low temperature stress (3 ℃, 3 days). The content of proline (Pro) in all materials was higher than that of CK, while the activity of superoxide dismutase (SOD) was lower. The activities of peroxidase (POD) and catalase (CAT) in most materials were higher than those of CK. According to the comprehensive evaluation value (D) and cluster analysis, the nine materials were divided into three groups: strong cold resistance type (E. fulvus 99-1, Yacheng 89-9, ROC10), moderate cold resistance type (ROC20, Yuetang 93-159, Huangjiali, ROC16) and weak cold resistance type (Dianzhe 01-58, ROC22). The results indicate that different sugarcane varieties have different adaptability to low temperature. Strong cold-tolerant sugarcane varieties can quickly adjust themselves under adversity, reasonably increase the content of osmotic adjustment substances and the activity of antioxidant enzymes, further remove harmful substances such as reactive oxygen species (ROS) in the body, and balance cell metabolism process, so as to better adapt to low temperature environment. This study would lay a foundation for exploring the regulation mechanism of sugarcane response to low temperature stress and breeding new sugarcane varieties with strong cold tolerance.

  • Plant Cultivation, Physiology & Biochemistry
    CHEN Wenyi, CHEN Huiping
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    Seed germination is a key link for plants to enter the vegetative growth stage. During the germination of rice (Oryza sativa L.) seeds, the aleurone layers synthesize and secrete a series of acid hydrolases (such as α-amylase, protease) to degrade the storage substances in the endosperm and provide nutrition for the growth of rice seedlings. The degradation of storage proteins is inseparable from the role of proteasome and protease in rice seeds. In order to explore the involvement of 26S proteasome, 20S proteasome and its subunit PBA1 in the regulation of GA on the storage proteins in the aleurone layers of germinated rice seeds, the rice hybrid Teyou 128 was used as the experimental material. The activity of 26S proteasome, 20S proteasome and PBA1, the transcription level of OsPBA1 and the change of total protein content were detected by enzyme-linked immunosorbent assay and real-time fluorescence quantitative PCR. GA significantly promoted the degradation of storage proteins in aleurone cells and accelerated the germination of rice seeds. When GA synthesis was blocked, the degradation process of storage protein in aleurone layer cells was delayed, thus delaying the germination of rice seeds. Under normal culture conditions, the peak values of 26S proteasome activity and 20S proteasome activity in the aleurone layers of rice seeds appeared at 6 d and 7 d, respectively, while the OsPBA1 expression level and PBA1 activity showed peaks at 5 d and 8 d. Further studies showed that GA could induce the activity of PBA1, 20S proteasome and 26S proteasome, thereby accelerating the process of seed germination. The 26S proteasome activity inhibitor MG132 inhibited the growth of germinated rice seeds, but increased the activity of 20S proteasome and PBA1. The above studies preliminarily revealed the role of 26S proteasome in GA regulating the degradation of storage proteins in rice aleurone layers and its effect on the germination of rice seeds.

  • Plant Cultivation, Physiology & Biochemistry
    CHEN Yue, LIANG Qinggan, WANG Mengzhao, CHEN Yanli, ZHU Guopeng
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    In order to explore the effects of nitrogen fertilizer application rate and planting density on the source-sink relationship and yield of sweet potato during ridge-sealing period, and to improve the cultivation techniques of sweet potato in Hainan, a field experiment was carried out from 2019 to 2020. The fresh-eating sweet potato variety Gaoxi14 was used as the test material, and three planting densities were set up, namely 47 600 plants/hm2 (D1), 71, 400 plants/hm2 (D2) and 142 900 plants/hm2 (D3). Four nitrogen application rates (0 kg/hm2 (N0), 60 kg/hm2 (N1), 120 kg/hm2 (N2), 180 kg/hm2 (N3) were designed in a double-factor split plot design with planting density as the main plot and nitrogen application rate as the subplot to study the effects of different planting densities and nitrogen application rates on photosynthetic characteristics, the relative chlorophyll content (SPAD), stem and leaf growth, dry matter accumulation and distribution in source and sink, tuber characteristics in ridge-sealing period, yield and its components and commodity in harvest period of Gaoxi14. Under the same planting density, the net photosynthetic rate (Pn), fresh weight of stem and leaf, number of branches, longest vine length, number of tubers per plant and single tuber weight of commercial sweet potato increased first and then decreased with the increase of nitrogen application rate, and reached the maximum at N1 treatment. The yield of sweet potato increased first and then decreased with the increase of nitrogen application rate, and reached the maximum under N2 treatment, which was 32.0% higher than that under N0 treatment, but there was no significant difference between N2 and N1 treatments. Under the same nitrogen application rate, the dry matter distribution ratio of sweet potato roots increased first and then decreased with the increase of planting density. The D2 treatment reached the maximum but there was no significant difference between D2 and D3 treatments. The root shoot ratio and yield increased significantly with the increase of planting density, and reached the maximum at D3 treatment. The yield of D3 was 30.9% and 24.1% higher than that of D1 and D2, respectively. The results of correlation analysis showed that the nitrogen application rate and planting density had significant effects on the dry matter accumulation and distribution of root tubers, while the planting density had a significant positive correlation with the yield of sweet potato at harvest stage, and the correlation coefficient was 0.704. Based on the results of this experiment, when the nitrogen application rate was 60 kg/hm2 and the planting density was 142 900 plants/hm2 (D3N1), the yield of Gaoxi 14 was the highest, reaching 30.1 t/hm2, and the corresponding potato commodity rate was 94.3%, which was the best among all treatments.

  • Plant Cultivation, Physiology & Biochemistry
    ZHAO Tian, XIN Shuli, HUANG Zherui, LIU Yonghua, ZHU Guopeng
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    The yield and quality of sweetpotato root tubers can be significantly improved by applying paclobutrazol (PBZ), and sucrose-degrading enzymes play important roles in the development of storage roots of sweetpotato. However, the physiological and biochemical mechanisms underlying PBZ-regulated storage root development is still unclear, and especially it remains to be investigated whether sucrose metabolism is involved in the PBZ-regulated development of storage roots. In this paper, sweetpotato cultivar Kokei 14 was used, a predominant cultivar planting in Hainan. After applying PBZ treatment in the early stage of cultivation (20-30 d after planting, dap), the following phenotypic parameters were investigated at 120 dap including the fresh weight of storage root per plant, fresh weight per storage root and storage root number per plant. To elucidate the physiological and biochemical mechanisms relevant to sucrose metabolism underlying PBZ-regulated storage root development, the following physiological and molecular parameters were also examined in storage roots at different development stages (30, 60, 90 and 120 dap) including the content of starch and soluble sugars (glucose, fructose and sucrose), the activities of sucrose-degrading enzymes and expression levels of the gene families. PBZ increased the yield of sweetpotato by increasing the fresh weight per storage root, but without affecting storage root number per plant. PBZ increased the content of soluble sugar and starch in storage root. However, the effect of PBZ on the yield and quality of storage roots only occurred in the early stage (30-60 d after planting) after treatment, and in the late stage (90-120 d), PBZ treatment had no significant effect on yield and quality. PBZ treatment significantly increased the activities of sucrose synthase (Sus), cell wall invertase (CWIN) and cytoplasmic invertase (CIN). However, PBZ had no significant effects on vacuolar invertase (VIN). As compared to CWIN and CIN, Sus activity was induced by PBZ treatment much earlier and more dramatic. Sus activity was significantly induced at 30 dap, whereas the activity of CWIN and CIN were significantly induced at late stage i.e. 60 dap. In other periods (especially 90-120 d), PBZ treatment had no significant effect on the activities of Sus, CWIN and CIN. The determination of the expression level of Sus, CWIN and CIN genes showed that IbSus2, IbSus5-7 and IbSus9 highly expressed in storage tuber were all significantly induced by PBZ at 30 dap. IbCIN3, IbCIN7 and IbCIN8 expressed in storage roots, and IbCWIN2 and IbCWIN4 expressed in storage roots were significantly induced by PBZ at 60 dap. However, in other periods (especially 90-120 d), PBZ treatment had no significant effect on the expression level of the relevant genes. It is speculated that the increase of Sus expression and activity under PBZ treatment is earlier and more dramatic, which can promote the rapid and biosynthesis and accumulation of starch and the rapid expansion of storage roots, while the subsequent increase of CWIN and CIN expression and activity can increase the content of soluble sugar in root tubers thus improving the quality of storage roots, and can also provide energy supply for starch biosynthesis and storage root expansion. The specific members of Sus, CWIN and CIN genes induced by PBZ had also been identified. Notably, the effects of PBZ on the yield and quality of storage roots, and activities and gene expression levels of sucros-degarding enzymes in storage roots mainly occurred in the short period after PBZ treatment. With the extension of time, the effects of PBZ on the above indicators gradually disappeared. Therefore, in order to improve the yield of sweetpotato in production, it is necessary to conduct PBZ treatment throughout the entire growth period of sweetpotato. The above results can provide a theoretical basis for achieving high-quality and high-yield sweetpotato production by variety breeding or cultivation measures.

  • Plant Cultivation, Physiology & Biochemistry
    YU Ruoyun, YANG Weibo, FENG Yuanjiao, LUO Zifei, CHEN Siting
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    The intercropping of Mallotus peltatus under the forest helps to break the bottleneck of land use. It is of great significance to apply green nanotechnology to improve the benefits of its compound planting. In order to clarify the regulatory role of nano-iron in the intercropping of M. peltatus under the coconut forest, the annual seedling of M. peltatus was taken as the research object to carry out the cultivation experiment. We investigated the comprehensive effects of five concentrations of nano-iron treatments (CK: 0 mg/L, T1: 25 mg/L, T2: 50 mg/L, T3: 75 mg/L, T4: 100 mg/L) on the leaf growth, photosynthetic and chemical characteristics of M. peltatus. After the first nano-iron treatment, the leaf length, width and dry weight of M. peltatus in T3 treatment were significantly higher than those in CK, while the leaf number in each treatment was significantly more than that in CK. Compared with CK, the chlorophyll content of M. peltatus treated with four nano-iron concentrations increased significantly by 14.96% (T1), 16.18% (T2), 17.91% (T3) and 20.58% (T4). As the concentration of nano-iron increased, the leaf net photosynthetic rate, transpiration rate, stomatal conductance, efficiency of primary conversion of light energy of PSⅡ, actual photochemical efficiency of PSⅡ and electron transport rate of M. peltatus overall increased. After the second nano-iron treatment, leaf length, width, dry weight and number of M. peltatus treated with T1, T3 and T4 were significantly higher than those of CK. Compared with CK, the chlorophyll content of M. peltatus in each treatment significantly increased by 10.28% (T1), 7.53% (T2), 11.13% (T3) and 11.41% (T4). With the increase of nano-iron concentration, the leaf net photosynthetic rate, transpiration rate and stomatal conductance of M. peltatus increased significantly, but decreased when the concentration reached T3 treatment. The potential activity of PSⅡ and efficiency of primary conversion of light energy of PSⅡ of M. peltatus also decreased significantly in T3 treatment. After two treatments, the contents of flavone, fat and ash of M. peltatus increased significantly in T1 treatment compared with CK. The contents of fat and ash decreased with the increase of nano-iron concentration. To sum up, nano-iron has a positive regulatory effect on the growth of M. peltatus under the coconut forest, but high concentration will inhibit its photosynthesis and growth. We recommend that the appropriate concentration is 25‒50 mg/L. This study could provide theoretical reference for the application of nano-iron in intercropping M. peltatus under the coconut forest.

  • Post-harvest Treatment & Quality Safety
  • Post-harvest Treatment & Quality Safety
    CHEN Linyi, GUO Hao, CHEN Hongmei, ZHANG Geye, LIAO Lulu, ZHOU Wanting, ZHANG Mengxue, YI Zhigang
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    Tea quality is closely related to the growth and ecological environment of tea plant (Camellia sinensis). The difference between day and night temperature (DIF) affects the synthesis and accumulation of tea plant metabolites, which in turn affects the quality of tea. In this study, Fuyun No. 6 was selected as the research object, and four DIF treatments (0 ℃, 5 ℃, 10 ℃ and 15 ℃) were simulated to explore the effects of DIF on photosynthesis and volatile and non-volatilequality components of tea fresh leaves. The results showed that the net photosynthetic rate (Pn), stomata conductance (Gs) and transpiration rate (Tr) of tea plants increased significantly with the increase of DIF (P<0.05). Increasing DIF significantly increased the contents of chlorophyll a (Chl a), chlorophyll b (Chl b), chlorophyll (a+b) [Chl (a+b)] and carotenoids (Car), and reached the maximum when DIF was 10 ℃. In addition, the change of DIF had an effect on the volatile components and relative contents of main components in fresh tea leaves, and the relative contents of alcohols and aldehydes were the largest in the volatile components of fresh tea leaves. The increase of DIF could significantly enhance the relative contents of aldehydes, and the relative contents of volatile components and main aroma components in fresh tea leaves were different with the change of DIF. The content of hexanal increased with the increase of DIF, with the highest value of 39.94% at DIF=15 ℃, while the relative content of cis-3-hexenol decreased with DIF increasing. The change of DIF significantly affected the activities of β-glucosidase, β-primeverosidase and lipoxygenase. The activities of β-glucosidase and β-primeverosidase first increased and then decreased with the increase of DIF, and reached the maximum when the DIF was 5 ℃, while the activity of lipoxygenase was opposite. Furthermore, the contents of free amino acids and caffeine increased significantly with the increase of DIF, which were 2.44 and 2.55 times at DIF=15 ℃ than those at DIF=0 ℃, respectively. The total flavonoids content and ratio of tea polyphenols to amino acids decreased significantly with the increase of DIF (P<0.05), with the lowest value of 2.84% and 3.24 at DIF=15 ℃. The contents of free amino acids in fresh tea leaves were significantly positively correlated with Pn, while the ratio of tea polyphenols to amino acids showed significantly negatively correlated with Pn (P<0.01). This study indicated that the increase of DIF could significantly affect the volatile aroma substances of fresh tea leaves and improve the taste and quality of tea, which could provide a certain theoretical basis for tea plantation site selection and tea planting.

  • Post-harvest Treatment & Quality Safety
    LIN Yuzhao, FENG Mengfei, CHEN Hongbin, JIANG Xuanjing, ZHENG Jinshui, WU Jinwen
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    Wampee [Clausena lansium (Lour.) Skeels] is a species of Rutaceae family and native to Southern China, which contains a large number of bioactive compounds that are beneficial to human health. However, because of the thin pericarp and soft pulp, wampee fruit is susceptible to the mechanical damage and the quality deterioration symptoms of fruit rot, pericarp browning and storage characteristic loss, and thus reducing the commercial value and edible value of harvested wampee fruit. Therefore, it is necessary to develop a safe and environmentally friendly postharvest storage technology for enhancing the storage behavior and quality, and prolonging storage time of harvested wampee fruit. Oxyresveratrol (OXY) is a naturally active product, with the efficacies of anti-browning, anti-oxidation, antibacterial, anti-inflammatory and antiviral. OXY has been studied more in the field of medicinal health care, but less in the field of food preservation. However, there are no reports on increasing the storage behavior and postharvest quality of wampee fruit by the usage of exogenous OXY. The study was aimed to study the effects of exogenous OXY treatment on the preservation of harvested wampee fruit. The fruit of wampee cv. Jixin was used as the experiment material, and the wampee fruit was treated by OXY solution with concentration of 0.2 g/L and distilled water (CK) for 30 min, separately. Then, the fruit was air-dried and packaged (50 fruits per bag), and stored at relative humidity 85% and temperature (25±1)℃ for 10 days. The changes of related indices of the storage behavior and postharvest quality in wampee fruit were observed and measured every two days. Compared to CK, OXY treatment could delay the increments of pericarp cell membrane permeability, browning degree and browning index, and maintain a higher commercially acceptable fruit rate but a lower weight loss percentage of harvested wampee fruit. Furthermore, OXY treatment might keep the higher values of L* and hue angle, a higher total phenolics content, but the lower activities of phenolases such as peroxidase and polyphenol oxidase in pericarp of harvested wampee fruit. Moreover, OXY treatment could retain the higher contents of total soluble solids, vitamin C, titratable acidity, sucrose and total soluble sugar in pulp of harvested wampee fruit. Therefore, the treatment of exogenous OXY could effectively enhance the storage behavior, and retain the pericarp appearance quality and pulp nutritional quality, and thus prolong the storage time in harvested wampee fruit.

  • Post-harvest Treatment & Quality Safety
    ZHANG Yingping, XU Fei, MU Mingxing, YOU Shengjun, HE Juncai, SU Fan, JI Xunzhi, WANG Can, HAO Chaoyun, QIN Xiaowei, GU Fenglin, WU Guiping
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    The study was aimed to explore the differences in physical and chemical indexes and volatile components of different types of Amomum tsaoko powder. The physicochemical indexes of A. tsaoko powder such as color difference, essential oil content, moisture content, particle size and surface microstructure were investigated. The volatile components of A. tsaoko powder were analyzed by headspace solid-phase microextraction and gas chromatography-mass spectrometry. The color difference ∆E of seven different fruit types of A. tsaoko powder was from 19.17±0.29 to 25.15±0.17, L* value was from 72.50±0.23 to 76.87±0.07, a* value was from 5.17±0.05 to 6.97±0.15, b*value was from 12.35±0.43 to 16.91±0.43. The content of volatile oil was from (0.76±0.01)mL/100 g to (1.30±0.26)mL/100 g. The moisture content was from 11.13%±0.12% to 15.05%±0.23%. In terms of particle size, NL5 and NL6 fruit powder particles had the largest difference. A total of 31 volatile components were detected in the seven fruit powder, and 17 common components were detected, mainly aldehydes and alcohols, including 2-decenal, (E)-, eucalyptol, citral, geraniol, geranyl acetate, etc. Among them, 28 volatile components were detected in NL2 fruit types, and the relative content of 2-decenal, (E)- was the highest (22.24%±2.29%). The relative content of eucalyptol in NL5 fruit type was the highest (17.52%±2.16%). Therefore, there are some differences in color difference, essential oil content, moisture content, particle size and surface microstructure of the powder of different fruit types. The volatile components of different fruit types of A. tsaoko fruit powder have both common characteristics and differences. The research could provide theoretical guidance for the production and application of high-quality pure natural A. tsaoko powder.

  • Post-harvest Treatment & Quality Safety
    ZHANG Yajiao, YU Fulai, YUAN Chao, CHEN Xiaolu, XIE Xiaoli, WANG Kai, HUANG Mei, CHEN Zhenxia, GUAN Lingliang, CHEN Songbi
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    The study was aimed to analyze the genetic diversity of the phenotypic traits and chemotypes of different Ocimum basilicum germplasm resources, to provide theoretical reference for the innovative utilization of basil germplasm resources and variety selection. The botanical traits of 15 basil germplasm resources and the volatile components of the leaves investigated and determined using gas chromatography-mass spectrometry (GC-MS), together with the relative odour activity values (ROAV). At the same time, principal component analysis and cluster analysis were carried out on the tested germplasms. The 15 basil germplasms differed significantly in plant height, plant width, leaf length, leaf width and stem thickness, except for the number of branches. 104 volatile compounds were identified, including 37 alkanes, 32 terpenes, 8 esters, 5 phenols, 4 alcohols, 3 aldehydes, 1 ether, and 14 other compounds, of which there are two types of common components, 2,4-di-tert-butylphenol and heptadecane. According to the ROAV values obtained from the enquiries and calculations, the key aroma substances were found to be eugenol, linalool, eucalyptol, cis-citral, methyl cinnamate, 4-allyl anisole, etc. The principal component analysis and cluster analysis of the volatile substances the germplasms could be classified into five groups, namely, Thai basil, Anise basil, Siam queen basil and Sweet basil were grouped together, Jiu Cengta basil, Genovese basil, Red rubin basil, Purple dark opal basil and Purple ruffles basil were grouped together, Clove basil and Lemon basil were grouped together, Tuscany basil, Pluto basil and Italian large leaf basil were grouped together, Cinnamon basil was grouped one category. The phenotypic trait cluster analysis also classified basil into five groups, with Pluto basil into a group, Clove basil, Anise basil and Purple dark opal basil into a group, Thai basil into a group, Italian large leaf basill and Cinnamon basil into a group. The remaining eight germplasm were clustered into a group. The 15 germplasms have significant differences in botanical characters and volatile components, and are rich in genetic diversity, which could be targeted for breeding of basil-specific germplasms.

  • Plant Protection & Bio-safety
  • Plant Protection & Bio-safety
    WU Qinghua, JIA Ruizong, GUO Jingyuan, YANG Muzhi, HU Yujuan, HAO Zhigang, ZHAO Hui, GUO Anping
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    Papaya is an economically important tropical fruit. Papaya ringspot virus (PRSV) is an important virus disease of papaya, often causing significant yield losses and quality deterioration. Since the introduction of the first transgenic papaya in 1998, PDR-based breeding strategies for disease resistance have been successfully applied. The contradiction between disease resistance based on sequence homology and increased virus genetic diversity became a new challenge for papaya breeding. In this study, we propose to use RNAi strategies aim at nuclear inclusion b gene (Nib) to obtain broad-spectrum resistance to PRSV papaya. With optimized embryo callus generation-Agrobatium meidated transformation-shoot regeneration, 52 shoots were obtained after resistance screening and a total of 24 transgenic positive shoots were obtained by specific PCR screening for the T0 generation. In the T0 generation field natural disease test, the transgenic papaya strains were significantly more resistant to disease than the non-transgenic control, with NibB5-2 having the best resistance in the field. Molecular charaterization of the insertion site of Nib5-2 was located at position 1976766 on chromosome 2 supercontig_30 by hiTAIL-PCR method. Green house inoculation test of NibB5-2 T1 generation, there was no virus accumulation and no disease symptoms, confirmed the resistance. Our resulst reveal that RNAi silcencing the Nib gene enhance the papaya virus resistance, meanwhile enriched the candidated genes for virus resistance breeding.

  • Plant Protection & Bio-safety
    AN Xuanxian, SANG Weijun, ZHANG Deping, LI Haoxi, YANG Jiangmin, LEI Xuemei, WANG Wuquan, YANG Maofa
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    Tobacco is an important economic crop, and its leaves have great economic value. In recent years, with the increase of tobacco planting areas, the varieties of leaf diseases are on the rise. Two strains of tobacco leaf spot disease pathogenic bacteria were isolated from the tobacco leaf disease samples in Hezhou, Guangxi. Through polygenic phylogenetic analysis, they were identified as Cumuliphoma indica, which is the first report on the tobacco leaf spot disease caused by C. indica in China. To clarify the biological characteristics of the pathogen and screen the control agents, this study used the mycelial growth rate method to study the lethal temperature of the mycelia of the strain, and its growth in different media, temperatures, pH, carbon sources, nitrogen sources, light cycles and to determine the sensitivity of the pathogen to nine chemical agents. The biological characteristics showed that the temperature range of C. indica mycelium growth was wide, and the optimum temperature was 28 ℃. Weak acid environment was more favorable for mycelium growth, and the optimal pH was 5. It grew fastest on CMA and CDA. The optimum nitrogen source was peptone. The optimum carbon sources was soluble starch. The lethal temperature of mycelium was 49 ℃, and the water bath was 10 min. Light had a significant effect on the growth of the mycelia, and 24 h full light was the most favorable. The results of laboratory screening showed that the nine tested fungicides had different inhibition on the growth of C. indica mycelia, among which boscalid 50% WG had the best inhibitory effect, EC50 was 0.025 mg/L. The second was fludioxonil 50% FS (0.084 mg/L), iprodione 500 g/L SC (0.217 mg/L), prochloraz 450 g/L EW (1.354 mg/L), mancozeb 80% WP (6.565 mg/L), difenoxazole 10% ME (9.576 mg/L), pyraclostrobin 25% SC (34.237 mg/L) and myclobutanil 40% SC (38.804 mg/L). The inhibitory effect of tebuconazole 430 g/L SC was the weakest, EC50 was 42.574 mg/L. The study revealed the biological characteristics of C. indica for the first time, and recommended 50% acetanilide WG as a candidate fungicide for the prevention and control. The results could provide a reference for the effective prevention and control of tobacco leaf spot disease caused by C. indica.

  • Plant Protection & Bio-safety
    ZOU Haiping, ZHANG Jinghong, LI Weiguang, CHEN Xiaomin, BAI Rui, LYU Run
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    Using the meteorological data and disaster information of 18 meteorological stations in Hainan Island in winter (from December to February of the next year) of 1971 to 2020, this paper constructed the meteorological index of chilling injury to winter vegetables with biological characteristics which not only considered the influence of overcast rain and few sunlight, but also could quantify the influence of previous cold injury processes. Combining Mann-Kendall trend test method and ArcGIS techniques, the spatiotemporal change law of chilling injury to winter vegetables in Hainan Island was obtained. The areas with high probability of chilling injury to vegetables in December, January and February and the areas with high probability of light, medium and severe chilling injury to vegetables in each month were mainly distributed in the northwest and middle of Hainan Island, while the areas with low probability were mainly distributed in the west-south-east coastal regions. The chilling injury to vegetables in each month was mainly light and moderate grade, accounting for about 88.3%. Among the three months, chilling injury to vegetables occurred most frequently in January (48.6%), and chilling injury of all grades to vegetables also occurred most frequently in January (50.2%, 43.4% and 40.2% respectively). In the recent 50 years, the annual occurrence times of cold injury to vegetables in each month of winter in Hainan Island were not significantly decreasing in most stations (83.3%, 94.4% and 72.2% respectively). Among the different grades of cold injury to vegetables in 3 months, only the annual occurrence times of severe cold injury to vegetables in February showed an increasing trend in many stations (38.9%), the annual occurrence times of other grades of cold injury were also not significantly decreasing in most stations (61.1%-88.9%). The influence scope of different grades of cold injury to vegetables in each month all decreased significantly in the order of light to severe chilling injury. Compared with each other in three months, the influence scope of cold injury to vegetables in Hainan Island were close to each other in December and February and were significantly smaller than that in January, the influence scope of light and moderate cold injury to vegetables also showed similar rules between months, while the influence scope of severe cold injury to vegetables were close to each other in December and January and were significantly larger than that in February. In the recent 50 years, the influence scope of chilling injury to vegetables in Hainan Island in December, January and February and the influence scope of different grades of chilling injury to vegetables in each month were all non-significant shrinking. In general, in the recent 50 years, the annual occurrence times of cold injury to winter vegetables was decreasing and the influence scope was shrinking, which was generally beneficial to the cultivation of winter vegetables in Hainan Island. However, in February, the annual occurrence times of severe cold injury to vegetables in eastern, central and western regions were increasing, which should be paid attention to.

  • Plant Protection & Bio-safety
    LIN Zhaowei, NIU Xiaoqing, TANG Qinghua, WANG Yenan, MENG Xiuli, SONG Weiwei
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    In August 2022, we found Phyllanthus urinaria with yellows and witches’-broom symptoms, respectively, in areca yellows disease garden in Wenchang city, Hainan province, which were phytoplasma infection. In order to clarify the taxonomic status of the phytoplasma strain in the yellows leaves and witches’-broom of P. urinaria. In this study, we cloned the 16S rDNA gene and ribosomal protein (rp) gene, and analyzed the gene sequence consistency, phylogenetic tree and virtual RFLP. The results showed that the 16S rDNA fragment 1246 bp and rp gene 1212 bp were cloned of P. urinaria yellows phytoplasma, the 16S rDNA fragment 1827 bp and rp gene 1240 bp were cloned of P. urinaria witches’-broom phytoplasma. The gene sequence consistency showed that the 16S rDNA gene sequence of the P. urinaria yellows phytoplasma and the P. urinaria witches’-broom phytoplasma was more than 98% consistent with the phytoplasma of 16SrⅠ group, and 100% consistent with the 16S rDNA sequence of areca yellows phytoplasma Hainan strain; the consistency of them in rp gene sequences was more than 99% to those of the rpⅠ group. The phylogenetic tree analysis showed that the 16S rDNA genes of P. urinaria yellows phytoplasma and P. urinaria witches’-broom phytoplasma were clustered in a large branch with those of aster yellows phytoplasma group (16SrⅠ), and clustered in the same small branch with those of areca yellows phytoplasma of 16SrⅠ-B subgroup, with the close genetic relationship; in the phylogenetic tree of rp gene, they were clustered in a large branch with the aster yellows phytoplasma group (rpⅠ), and clustered in the same small branch with those of aster yellows phytoplasma of rpⅠ-B subgroup, with the close genetic relationship. The virtual RFLP analysis showed that the RFLP map obtained by the 16S rDNA gene of the P. urinaria yellows phytoplasma and P. urinaria witches’-broom phytoplasma was the same as the reference map of the onion yellows phytoplasma of 16SrⅠ-B, and the similarity coefficient was 1.00. In summary, the P. urinaria yellows phytoplasma and the P. urinaria witches’-broom phytoplasma belong to 16SrⅠ-B subgroup in classification. The results of this study could provide a theoretical basis for the prevention and control of areca palm yellow disease by eradicating its intermediate host.