Welcome to Chinese Journal of Tropical Crops,
25 August 2020, Volume 41 Issue 8 Previous Issue   
Screening of Stable Reference Genes for qRT-PCR Analysis in Macadamia integrifolia
YANG Qian,YANG Ziping,ZHOU Yali,CHEN Dongquan,LIU Heng
2020, 41 (8):  1505-1512.  doi: 10.3969/j.issn.1000-2561.2020.08.001
Abstract ( 9 )   HTML ( 1 )   PDF (1710KB) ( 4 )  

Macadamia nut is an important economics crop in subtropical areas of China. The selection of a suitable reference gene is an important prerequisite for successful gene expression analysis by real-time fluorescence quantitative PCR (RT-qPCR). In order to select the appropriate reference genes, we investigated the expression stability of 11 candidate genes (18S rRNA, Actin, CYP, EF1a, EF1b, GAPDH, MDH, TUBa, TUBb, UBQ, UBC) in RT-qPCR experiments in different tissues, including kernel, peel, roots, stem, leaf from Macadamia with geNorm, NormFinder, BestKeeper, ΔCt, RefFinder program software packages. As determined by geNorm, MDH/EF1b were the most stable reference genes, TUBa was the least stable gene. BestKeeper revealed that MDH was the most stables reference gene, and EF1b ranked the second. The rank in BestKeeper was similarly with that in geNorm. The result by NormFinder showed GAPDH was the most stable gene, CYP ranks the second, the least stable gene was TUBa. ΔCt algorithm demonstrated that18S was the most stable gene, GAPDH ranks the second, MDH and EF1b ranked the third and fourth. To obtain a consensus result of the most stable reference genes according to the RefFinder approach, the geometric mean of the four algorithms corresponding rankings for each candidate gene were calculated: MDH>18S>GADPH>EF1b>CYP>UBC>EF1a>Actin>TUBb>UBQ>TUBa. The result showed that MDH was the most suitable reference gene for macadamia in different tissues.

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Transcriptome Analysis of Primary Stem of Chlorophyll Deficient Mutants from Artocarpus heterophyllus
ZHENG Liting,YU Xudong,CAI Zeping,LUO Jiajia,WU Fanhua,DONG Junna,CAO Peina
2020, 41 (8):  1513-1221.  doi: 10.3969/j.issn.1000-2561.2020.08.002
Abstract ( 6 )   HTML ( 1 )   PDF (4376KB) ( 2 )  

To explore the influence of chlorophyll synthesis deficiency on the primary stem development of Artocarpus heterophyllus, the transcriptome of the primary stem of a chlorophyll deficient mutant (CDM) of A. heterophyllus was analyzed. After assembly by de novo, 295 869 Unigenes were obtained. NR, NT, Swissprot, KEGG, KOG, Pfam and GO databases were used for sequence alignment. A total of 174 291 Unigenes were annotated. After filtering the low abundance genes, 22 988 differentially expressed genes were selected. Compared with the control check (CK), there were 379 genes up-regulated in CDM and 22 609 genes down-regulated. GO classification results showed that 3712 genes were annotated and classified into three categories: molecular function, cellular component and biological process, with a total of 48 functional groups. In addition, 2080 Unigenes were involved in 19 KEGG pathways, 30 of which were involved in flavonoids biosynthesis pathways. Through transcriptome sequencing, this paper analyzed the effect of chlorophyll synthesis deficiency on the primary stem development of A. heterophyllus, which would provide data foundation for the study on the stem development of woody plants.

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Single-microspore Microdissection of Hevea brasiliensis
YANG Xingxing,WANG Ying,ZHUANG Nansheng,GAO Heqiong,WANG Yuxiang
2020, 41 (8):  1522-1528.  doi: 10.3969/j.issn.1000-2561.2020.08.003
Abstract ( 5 )   HTML ( 1 )   PDF (1430KB) ( 2 )  

Hevea brasiliensis is an important tropical crop. In this study, the young male flowers of ‘Reyan 7-33-97’ in the meiotic tetrad period were used as the experimental materials to obtain single cells. Four enzymatic solutions, 5% cellulose, 5% pectinase, 5% β-glucanase, 5% cellulase and 4% pectinase mixed enzyme solution, were used in the experiment to explore the best scheme for the degradation of tetrad callose. As a result, under the condition of 1 h and 37℃, 5% cellulase and 4% pectinase mixed enzyme solution had the best enzymatic hydrolysis effect, and the single microspore with good quality could be obtained. Through the continuous exploration and experiment on the fine length of the needle tip, the diameter of the sharpening of the needle and the micro-operation separation system, a set of microdissection technology system suitable for the single microspore of ‘Reyan 7-33-97’ was successfully established. Single-microspores were the direct products of meiosis. The separation and analysis of single cells could accurately resolve gene recombination and exchange during the meiosis of rubber trees, and determine the genomic variation. The study would provide theoretical and technical support for single-cell whole genome sequencing of H. brasiliensis.

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Tissue Culture Technology for Pedicel Shoots of Dendrobium kingianum Bidwill
CHEN Heming,JIANG Nan,LYU Fubing,XIAO Wenfang,LI Zuo,ZHU Genfa
2020, 41 (8):  1529-1534.  doi: 10.3969/j.issn.1000-2561.2020.08.004
Abstract ( 10 )   HTML ( 1 )   PDF (1654KB) ( 1 )  

The induction and proliferation and rooting tests of Dendrobium kingianum Bidwill were studied using pedicel shoots as the explant. The two induction media of MS+6-BA 2.0 mg/L+NAA 0.5 mg/L+10% CM and MS+6-BA 2.0 mg/L+NAA 0.5 mg/L+AC 1.0 g/L+10% CM could induce buds. 70.6% pedicels died without lateral buds induced or lateral buds too weak, but it provided an effective way for seedling production and germplasm resources protection. In the proliferation culture, the medium of MS+6-BA 3.0 mg/L+AD 3.0 mg/L+10% CM was beneficial to proliferation culture. In the rooting and growth culture, the medium of 1/2 MS+NAA 0.3-0.5 mg/L+10% CM was suitable for the rooting culture of D. kingianum ‘Jinsika’ (DJ).

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A Study to Develop an in Vitro Dual Culture System with Carrot Hairy Roots and Arbuscular Mycorrhizal Fungi
ZHANG Jinlian,LIU Jinhua,BAO Han,LI Dongping,SONG Juan,HUANG Jinghua,CHEN Tingsu
2020, 41 (8):  1535-1542.  doi: 10.3969/j.issn.1000-2561.2020.08.005
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Agrobacterium rhizogenes K599 was used to induce carrot hair roots. An in vitro dual culturing system with Funneliformis mosseae and carrot hairy roots was then developed, and factors including methods to obtain axenic, supersonic processing, chilling treatment and medium pH that might affect both AM fungal spores germination and dual culturing were optimized. It was found that the third axenic method resulted in the highest germination rate (48.88%) and the lowest contamination rate (9.98%) at 15 days. Supersonic processing helped reduce AM fungal spores’ contamination by 11.17% to 14.53%, while a chilling pretreatment at 4℃ for 10 days and 15 days increased the germination rate of AM fungal spores to 70% and 65%, respectively. In water agar, the highest germination rate was achieved at a pH of 6.5 (48.50%), whereas spore germination was inhibited when pH was lower than 5.5 or higher than 8.0, with germination rate decreased to 15.43% at pH 5.5 and 16.06% at pH 8.0. Furthermore, it was found that the success rate of dual culturing was enhanced when sterilized spores were first germinated on agar medium and long hyphae were then selected for inoculation with their extension direction towards the growth direction of the carrot root. The MSR medium was found to be optimal for dual culture. The successful in vitro dual culture of carrot hairy roots and arbuscula mycorrhizal fungi provides an ideal experimental system to obtain pure AM fungal spores and to conduct future studies on the physiological and molecular mechanism of carrot mycorrhiza.

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Evaluation of Aluminum Tolerance of Cynodon dactylon Germplasm Resources
CUI Rongjing,LIU Guodao,HUANG Chunqiong
2020, 41 (8):  1543-1552.  doi: 10.3969/j.issn.1000-2561.2020.08.006
Abstract ( 9 )   HTML ( 2 )   PDF (1240KB) ( 1 )  

In this study, the aluminum tolerance of 66 Cynodon dactylon germplasm materials with different geographical distribution was preliminarily evaluated by five indexes, namely, relative withering rate, relative turf quality, relative shoot mass weight, relative root mass weight and relative total mass weight. The results showed that there were significant (P<0.05) or extremely significant (P<0.01) differences in the growth of C. dactylon germplasm under the treatment of 2500 μmol/L aluminum concentration. The variation coefficient of different indicators was ranged from 19.90% to 36.56%, among which the variation coefficient of relative withering rate was the largest (36.56%), while the variation coefficient of relative turf quality was the smallest (19.90%). There was an extremely significant positive correlation between relative shoot mass weight and relative total mass weight (P<0.01), and the correlation coefficient was 0.942. Through the subordinate function method, 66 samples of C. dactylon germplasm were divided into four grades, among which Grade 1 was extremely resistant to aluminum, including five samples, accounting for 7.57% of the total tested materials. Grade 2 was relatively resistant to aluminum, including four materials, accounting for 6.06% of the materials tested. Grade 3 was intermediately resistant to aluminum, including 47 materials, accounting for 71.21% of the materials tested. Grade 4 was sensitive to aluminum, including 10 materials, accounting for 15.15% of the materials tested. Through the comprehensive evaluation of the aluminum tolerance of the 66 materials, five aluminum resistant germplasms were selected, namely B219, B532, A522, A075 and B509.

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Evaluation and Selection of Bletilla Species Through AHP Method
ZHU Jiao,HUANG Weichang,CAO Jianguo,ZHOU Xiangyu
2020, 41 (8):  1553-1559.  doi: 10.3969/j.issn.1000-2561.2020.08.007
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The research aimed to screen out Bletilla germplasms with good ornamental characteristic, growth potential and suitability for Shanghai to be used for breeding and gardening. Twelve Bletilla germplasms were comprehensively evaluated with the analytic hierarchy process (AHP) for 13 characters in three aspects such as ornamental characteristic, adaption, cultivation and management, and a resource evaluation model was established. Ornamental characteristic was the major factor affecting the comprehensive evaluation of Bletilla. AHP and cluster analysis revealed the 12 germplasms could be divided into two grades. Six were regarded as the excellent germplasms, and the left six were good germplasms. Five Bletilla striata Rchb. germplasms with high ornamental value and good growth were from Shaanxi, Jiangxi, Chongqing, Hubei and Anhui. Bletilla ochracea germplasm from Hubei was also selected.

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Ornamental Evaluation of Endemic Orchids from Guangdong Province
SU Ziying,LI Lan,ZHANG Xiying,CHEN Meixuan,CHEN Lijun,LI Yuling
2020, 41 (8):  1560-1565.  doi: 10.3969/j.issn.1000-2561.2020.08.008
Abstract ( 13 )   HTML ( 2 )   PDF (1150KB) ( 3 )  

The analytic hierarchy process (AHP) was applied to construct the ornamental value evaluation system for sixteen endemic orchids from Guangdong based on literature review and field investigation. Twelve indexes, including characteristics of flower, foliage and fruit were studied to choose the species that could be applied to horticulture and landscaping. The results showed that the weight of flower diameter reached the highest. The sixteen endemic orchids from Guangdong could be divided into three grades. Grade I (2.8-3.0), including three species, had the highest ornamental value; Grade II (2.5-2.8), including eight species, had medium ornamental value; Grade III (<2.5), including five species, had lower ornamental value. Due to the high ornamental value and excellent biological characters, three species in Grade I, Vanilla shenzhenica, Platanthera zijinensis and Dendrobium jiaolingense, could be introduced and further explored in horticulture and landscape application.

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Establishment of Genetic Transformation System for Zoysia matrella
WANG Kai,WANG Yi,QU Aiai,WANG Rui,GUO Hailin,LI Xiaohui,SHE Jianming,ZONG Junqin,LI Jianjian,LIU Jianxiu
2020, 41 (8):  1566-1573.  doi: 10.3969/j.issn.1000-2561.2020.08.009
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Zoysia matrella is a perennial warm-season turfgrass, one of halophytes with the salt-tolerantce, and is widely used in temperate zone and subtropical regions. However, its complete genetic transformation system have not been reported. In this study, the callus from Z. matrella was used as receptor material and the genetic transformation of the salt-tolerant gene ZmPDI was carried out by Agrobacterium-mediated method to study a series of conditions for transformation efficiency including the co-culture time, concentration of the infection, and infection time. The results showed that the optimal genetic transformation was supposed to be: agrobacterium concentration OD600 = 0.4, infected for 30 minutes, co-cultured for 3 days and then followed by selective culture. During the whole process, the optimum concentration of timentin in the postponed culture medium was 250 mg/L. As for hygromycin, the optimal selection pressure for callus was 40 mg/L, while the best concentration for rooting screening was 15 mg/L. The histochemical analysis of β-glucuronidase (GUS) activities and PCR identification indicated that the ZmPDI gene was transferred into the genome by hygromycin resistance selection.

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Character Analysis of Hybrid Offspring of Dendrobium officinale and Dendrobium huoshanense
JIANG Jinlan
2020, 41 (8):  1574-1581.  doi: 10.3969/j.issn.1000-2561.2020.08.010
Abstract ( 5 )   HTML ( 2 )   PDF (2152KB) ( 2 )  

To select the best hybrid lines, the growth, phenotypic traits and polysaccharide content of Dendrobium officinale, Dendrobium huoshanense and their F1 hybrid lines were determined and analyzed. The growth of tissue culture was significantly different in each line, in the range 0.15-0.69 g, superior to their parental strains accounting for 75.00%. The growth of the transplanting seedlings was ranged for 0.03-0.44 g, superior to their parental strains, accounting for 75.00%. Eight phenotypic traits of the tissue culture seedlings showed superior to their parents, accounting for 88.89% of the total investigation. In the transplanting seedlings, four phenotypic traits of the cultivated seedlings showed superior to their parents, accounting for 44.44% of the total investigation. The content of polysaccharides in each line was significantly different from that of their parents. The content of polysaccharides in seven lines was superior to their parents, accounting for 87.50% of the total lines studied. In summary, interspecific hybridization is one of the effective ways to improve the output and quality of Dendrobium.

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Flowering and Fruiting Characteristics of Cassava Diploid and Its Autotetraploid
LI Hengrui,CHEN Huixian,YANG Haixia,ZHANG Xiufen,HE Wen,LIANG Zhenhua,GUO Suyun,LIU Lianjun,LI Ping,CHEN Haisheng,YAN Huabing
2020, 41 (8):  1582-1588.  doi: 10.3969/j.issn.1000-2561.2020.08.011
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In this study, the diploid and its autotetraploid of ‘Xinxuan 048’ and ‘SC205’ were used as the test variety, and the differences of flowering and fruiting characteristics in the diploid and autotetraploid were compared using the method of fixed-plant observation to explore the effect of cassava chromosome doubling on flowering and fruiting characteristics, and provide scientific reference for the creation and identification of cassava polyploid material. The flowering and fruiting phenotypes of the tetraploids of the two cassava varieties were later than that of the diploid, and the size of the male and female flowers, anthers, fruits and seeds of the tetraploid was larger than that of the diploid. There were differences in anther distribution between different ploidy varieties of the two cassava varieties, and there were significant differences in the color of different ploidy female flowers in ‘Xinxuan 048’. Bisexual flowers appeared in the tetraploids of ‘Xinxuan 048’. There were also differences in the number of flowering and fruit setting between different ploidy cassava. The total single flower mass and total number of female or male flowers of the tetraploid of ‘Xinxuan 048’ were significantly larger than those of the diploid, but the difference of ‘SC205’ was not significant. Therefore, doubling the chromosome of cassava can delay the flowering time, increase the size of the reproductive organs, change the flower morphological characteristics and the number of male and female flowers and the total amount of flowers, but the change is different due to variety difference.

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Yield and Economic Benefit of Potato in Winter under Different Release Periods of Controlled Slow Release Compound Fertilizers and Ratio of Nitrogen, Phosphorus and Potassium
LUO Qifeng,ZHANG Xinming,CHEN Lin,XU Pengju,PAN Song,HE Chunxi,CAO Xianwei
2020, 41 (8):  1589-1595.  doi: 10.3969/j.issn.1000-2561.2020.08.012
Abstract ( 4 )   HTML ( 1 )   PDF (1453KB) ( 0 )  

The study was aimed to solve the problems of excessive fertilizer supply in early stage of winter potato growing, short of fertilizer in late stage and imbalance between supply and demand of fertilizer nutrients in Guangdong. A random complete block design was used with potato ‘Favorita’ as the test variety. The effects of controlled slow release compound fertilizers with different release periods on the yield and economic benefits of winter potato were studied under different NPK ratios. When the ratio of nitrogen, phosphorus and potassium was N∶P2O5∶K2O= 1.0∶0.5∶2.0, the total yield, relative yield increase, economic benefit and relative economic-benefit increase for CRF60d was the highest, being 56 550 kg/hm 2, 68.24%, 92 575 yuan/hm 2 and 69.12%, respectively, and that for CRF90d with N∶P2O5∶K2O=1.0∶0.5∶2.0 was 55 034 kg/hm 2, 63.73%, 88 186 yuan/hm 2 and 61.10%, respectively. Considering the factors such as yield and economic benefits, the suitable fertilization scheme for the main potato producing areas in winter in Guangdong is the controlled slow release compound fertilizer with 60-90 d release period, and the total NPK should reach N 240 kg/hm 2, P2O5 120 kg/hm 2 and K2O 480 kg/hm 2.

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Application of Two Soil Conditioners in Alluvial Sandy Soil of Meizhou Tobacco-growing Area
LI Jiqin,YANG Shaohai,HUANG Zhenrui,LU Yusheng,GU Wenjie,LI Shuling
2020, 41 (8):  1596-1601.  doi: 10.3969/j.issn.1000-2561.2020.08.013
Abstract ( 5 )   HTML ( 1 )   PDF (1141KB) ( 0 )  

The field application effect of tobacco yield, quality and physical and chemical properties of soil conditioners in the alluvial sandy soil in Meizhou tobacco area was studied. Both conditioner I and conditioner II significantly increased yield, output value, ratio of high quality tobacco and average price. The yield and output value of conditioner I was 30.42% and 57.56% higher than that of the control, and conditioner I significantly reduced the incidence of tobacco bacterial wilt and tobacco mosaic virus. Conditioner I increased soil pH by 1.42 compared with the control, and the content of available potassium, exchangeable magnesium and exchangeable calcium in conditioner I treatment was 13.21%, 63.21% and 4.9 times higher than that of the control. Both conditioners increased the number of bacteria and actinomycetes in the soil. Conditioner I significantly increased the activity of soil invertase, phosphatase, urease and dehydrogenase.

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Variation and Correlation Analysis of Mineral Elements Contents for Core Collection of Landrace Rice in Guangxi
XIA Xiuzhong,ZHANG Zongqiong,NONG Baoxuan,YANG Xinghai,ZENG Yu,ZHUANG Jie,LIU Kaiqiang,LI Danting
2020, 41 (8):  1602-1609.  doi: 10.3969/j.issn.1000-2561.2020.08.014
Abstract ( 4 )   HTML ( 1 )   PDF (1584KB) ( 11 )  

The content of Ca, Fe, Zn and Se in brown rice of 419 core collection accessions of Guangxi landrace was analyzed in 2014 and 2015. A total of 34 SSR markers were used to identify the content of four mineral elements by Pearson correlation analysis in the two years. The content of the four mineral elements in the two years was significantly different and positively correlated. The content of Ca and Se in indica was higher than that in japonica with significant difference. The content of Fe and Zn in japonica was higher than that in indica with significant difference. The content of mineral elements was associated with longitude, latitude and altitude of the rice cropping regions. The content of Fe was the highest in southern Guangxi, that of Zn was the highest in central Guangxi, that of Ca, Fe, Zn was the highest in black rice, that of Se was the highest in red rice, that of Ca and Zn of black rice was significantly higher than that of red and white rice, and that of Fe was not significantly among three pericarp colors. The range of correlation coefficient of the content of the four mineral elements between the two years from 0.159 to 0.557, 2014 was significantly positively associated with 2015. There was no obvious difference among the content of the four elements in 2014. In 2015, the content of Se was significantly positively correlated with that of Fe and Zn (P<0.05), the content of Zn was significantly positively associated with that of Fe (P<0.01) and Ca (P<0.001). A total of 167 alleles were detected by SSR markers, with genetic diversity index 0.574 and genetic information 0.522. Pearson correlation analysis showed that 18 loci were associated to the content of the four mineral elements, among them, eight loci weree different from the previous studies. The study would provide a theoretical basis and material foundation for related gene mining and rice breeding with high mineral element content.

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Physiological and Biochemical Analysis of Oncidium in Response to Stress of Soft Rot Pathogen
WU Qiuzhen,LIN Zhengchun,NI Shanshan,LAI Zhongxiong
2020, 41 (8):  1610-1615.  doi: 10.3969/j.issn.1000-2561.2020.08.015
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The pseudobulb of Sherry Baby, Oncidium was infected by bacterial soft rot bacteria infection. The first leaf on the pseudobulb was sampled 0, 8, 16, 24, 32 h, after infection to determine the chlorophyll fluorescence properties [Fv/Fm, Y(Ⅱ), Y(NPQ), Y(NO)], superoxide dismutase(SOD), peroxidase(POD), catalase(CAT), polyphenol oxidase(PPO) activity, malondialdehyde (MDA), lignin, and the change of soluble sugar content. The results showed that with the extension of infection time, Fv/Fm, Y(Ⅱ), Y(NPQ) gradually decline, Y(NO) increased, and the photosynthetic system was damaged. PPO activity and lignin content decreased gradually; SOD and POD activity increased gradually; CAT activity and soluble sugar content first increased and then decreased; MDA content decreased gradually from 0 to 24 h and then leveled off after 24 h. The study would heip to explore the resistance mechanism and establish the physiological method of resistance identification.

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Identification and Etiology of a New Dangerous Neopestalotiopsis Leaf Fall Disease of Rubber Tree (Hevea brasiliensis) in China
LI Boxun,LIU Xianbao,SHI Tao,CAI Jimiao,ZHENG Xiaolan,FENG Yanli,XU Chunhua,HUANG Guixiu
2020, 41 (8):  1616-1624.  doi: 10.3969/j.issn.1000-2561.2020.08.016
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Based on the current outbreak and epidemic situation of a novel Neopestalotiopsis leaf fall disease of rubber trees (Hevea brasiliensis) in major rubber planting countries abroad and its great impact on natural rubber industry economy, the authors conducted a preliminary inspection on 13 farms and rubber plantations in main rubber producing areas in Hainan, Yunnan and Guangdong provinces, and found suspected disease samples in Baoxian Farm, Zhizhong Town, Ledong County, Hainan. In this study, the pathogens of the suspected disease samples were isolated, purified and the pathogenicity was determined. Through morphological and molecular phylogenetic analysis, the pathogen was identified as Neopestalotiopsis aotearoa Maharachch., K.D. Hyde & Crous. The basic biological characteristics showed that the suitable temperature for the mycelial growth and spore germination was 28℃, the lethal temperature of spores was 50℃. The optimum pH value was 6.5, the optimum carbon sources were sucrose and D-glucose, the optimum nitrogen sources were potassium nitrate and soybean peptone, and the optimum medium was PDA, which could produce spores after eight days. The pathogen and its basic biological characteristics were preliminarily identified, which would provide theoretical basis for the reserve of related technical measures for the prevention and control of the disease in advance.

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Synergistic Effect of Fungicides and Bacillus subtilis Czk1 Against Rubber Root Diseases
XIE Li,HE Chunping,LIANG Yanqiong,LI Rui,ZHAI Chunxin,WU Weihuai,ZHENG Jinlong,YI Kexian
2020, 41 (8):  1625-1633.  doi: 10.3969/j.issn.1000-2561.2020.08.017
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This study aimed to explore the potential of the synergistic control of rubber root diseases by Bacillus subtilis and chemical fungicides, and provide a basis for the sustainable prevention and control of rubber root diseases. The efficacy of seven fungicides and Czk1 strain against rubber red root disease and rubber brown root disease and the bio-compatibility of fungicides with Czk1 were determined by the inhibition zone and plate colony counting methods, while the combined effect was determined by the Horsfall method. The half-maximal inhibitor concentration (EC50) of "Gen Kang" on rubber red root disease and rubber brown root disease was 0.6253 μg/mL and 0.0522 μg/mL, respectively, which represented the lowest EC50 and showed good bio-compatibility with Czk1. "Gen Kang" (EC50=0.6253 μg/mL) was mixed with Czk1 (EC50=6.46×10 7 CFU/mL) in the volume ratio of 3∶7, respectively, against rubber red root disease and yielded IR value of 1.60, which was higher than the IR value of 1.51 that was obtained when "Gen Kang" (EC50=0.0522 μg/mL) was mixed with bio-control bacteria Czk1 (EC50=2.33×10 8 CFU/mL) in the same volume ratio. The results showed that "Gen Kang" could be used in combination with B. subtilis Czk1 to control rubber root disease as demonstrated by the significantly higher inhibitory effect obtained from their combined performance than when both "Gen Kang" and B. subtilis Czk1 strain were used independently. The use of "Gen Kang" in the mixture was only one-third (1/3) of that of single agent, which greatly reduced the use of chemical agents.

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Biological Characteristics of Alternaria Leaf Blight of Scaevola taccada and Screening of Fungicides in vitro
WANG Yi,HU Meijiao,LI Min,GAO Zhaoyin,HONG Xiaoyu,ZHANG Shaogang,ZHAO Chao
2020, 41 (8):  1634-1641.  doi: 10.3969/j.issn.1000-2561.2020.08.018
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Alternaria leaf blight of Scaevola taccada is a common and serious disease in Xisha Island. The pathogen of the disease was identified as Alternaria longipes. To further clarify the biological characteristics of the pathogen and its sensitivity to fungicides. Therefore, in this study, the biological characteristics of A. longipes were preliminarily studied by the mycelium growth rate method, and the toxicological test of 13 fungicides such as difenoconazole to this pathogen was determined. The optimum growth medium was potato dextrose agar medium (PDA), followed by potato sugar agar medium (PSA). The suitable growth temperature was 25 to 30℃, and the optimum growth temperature was 28℃. The suitable pH value was 5.0 to 7.0, and the optimum pH value was 6.0. The optimal carbon source was sucrose, while fructose was not conducive to colony growth. The optimal nitrogen source was glycine, while urea was not conducive to colony growth. Light time had no significant effect on colony growth. Laboratory toxicity test showed that the best inhibition effect was found in difenoconazole water-dispersible granular with EC50 value of 0.15 μg/mL, followed by flusilazole emulsion, hexazolium suspension agent and penconazole emulsion, with EC50 values of 0.37, 0.44 and 0.51 μg/mL, respectively, while azoxystrobin suspension agent and carbendazol wettable powder had the worst inhibitory effect, with an EC50 value of more than 3000 μg/mL.

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Community of Predatory Arthropods in Rice Fields in Off-Season Breeding Region
ZHOU Xia,XIE Xiang,TAN Yanhua,YI Xiaoping,XIA Qiyu,ZHANG Lili,GUO Anping
2020, 41 (8):  1642-1647.  doi: 10.3969/j.issn.1000-2561.2020.08.019
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Off-season breeding regions of Hainan province are located in the tropical area. 60% of Off-season breeding regions were planted for rice. To study the community of predatory arthropods in the Off-season breeding region rice fields for biological control and monitoring purpose, field insect sampling by the suction method in different rice developmental stages were conducted in Sanya in 2013. The results showed that there were 40 species predatory arthropods of 9 orders, and the population dynamics of the dominant predators Micraspis discolor and Tetragnatha maxillosa in rice fields were studied. The study would provide a foundation for the biological control in tropical areas and monitoring purpose in Off-season breeding regions.

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Parasitic Capacity of Five Trichogramma Species to Eggs of Tirathaba rufivena
LIN Yuying,JIN Tao,MA Guangchang,WEN Haibo,GONG Zhi,PENG Zhengqiang
2020, 41 (8):  1648-1653.  doi: 10.3969/j.issn.1000-2561.2020.08.020
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Tirathaba rufivena Walker (Lepidoptera: Pyralidae) is a destructive pest of areca palm, Areca catechu L. (Arecaceae), in China. In order to screen out dominant Trichogramma species for their effectiveness in controlling this pest, the parasitism capacity of T. japonicum Ashmead, T. dendrolimi Matsumura, T. embryophagum Harti, T. chilonis Ishii, and T. ostriniae Pang et Chen, on T. rufivena eggs at different densities was investigated in this study. The number of parasitized eggs by T. japonicum, T. dendrolimi, and T. embryophagum increased with the increasing density of the T. rufivena eggs within a certain density levels. At a host density of 35, 30 and 25 eggs/tube (Volume=84.8 cm 3) for T. japonicum, T. dendrolimi and T. embryophagum, respectively, the number of parasitized eggs and parasitism rate was the highest. The number of parasitized eggs was 16.2, 8.8 and 10.6, respectively, parasitism rate was 46.3%, 29.3% and 42.4%, respectively. Trichogramma species less than 12 h old were provided with adequate eggs of T. rufivena within 72 h, most of host eggs were parasitized by T. japonicum, T. dendrolimi and T. embryophagum during the period of 0 to 24 h. The parasitism proportion was 84.8%, 48.6% and 60.7% respectively. The number of offspring was 48.5, 50.8 and 53.8 individuals, respectively. Percentage of female progeny was 68.2%, 74.4% and 55.1%, respectively. It indicated that T. japonicum have a strong parasitic ability to the eggs of T. rufivena. T. japonicum, T. dendrolimi and T. embryophagum could be used as the dominant Trichogramma species for controlling T. rufivena.

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Weed Species, Distribution and Damage on Sisal Plantation and Its Strategy of Control
FAN Zhiwei,LI Xiaoxia,LIU Yan,XI Jingeng,WANG Ya,SHEN Yide,HUANG Qiaoqiao,YI Kexian
2020, 41 (8):  1654-1664.  doi: 10.3969/j.issn.1000-2561.2020.08.021
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Weed species, distribution and damage on sisal (Agave sisalana) plantation in China were investigated. There were 200 weed species, belonging to 144 genus and 49 families, on sisal plantation, of which 40 species in Poaceae, 24 species in Asteraceae, 20 species in Fabaceae, 10 species in Rubiaceae and in Cyperaceae. There were 79 species in annual weed, 1 species in biennial weed, 100 species in perennial and 20 others. 143 species reproduced with seed reproduction, 57 species with seed, stem, stolon and rhizome reproduction. 68 species were alien invasive weed and 132 species were native weed. Three species (Imperata cylindrica var. major, Panicum repens, Cyperus rotundus) caused damage in 5 degree and 7 species (Eleusine indica, Digitaria setigera, Praxelis clematidea, Spermacoce alata, Erigeron canadensis, Bidens pilosa, Mikania microrantha) in 4 degree. A new viewpoint is proposed that sisal plantation with good cover plants is an ecological plantation and without cover plants cannot be an ecological plantation. Sod culture in sisal plantation can fertilize soil, raise sisal growth, feed animal and control pest.

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Effects of Different Concentrations of Chitosan Treatment on Storability and Storage Quality of Passion Fruit Postharvest
GUO Xin,LIN Yuzhao,ZENG Lingzhen,LIN Jingying,YU Xingxing,LIN Hetong
2020, 41 (8):  1665-1673.  doi: 10.3969/j.issn.1000-2561.2020.08.022
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The effects of different concentrations of chitosan treatment on the storability and storage quality of harvested passion (Passiflora caerulea L.) fruit were investigated in this study. The harvested passion (Passiflora caerulea L. cv. Fujian passion No.1) fruit were immersed in different concentrations of Kadozan (chitosan) solution with dilutions of 1∶50, 1∶100, 1∶150, 1∶200, and 1∶250 (VKadozan∶VKadozan + Water) for 5 min, while the passion fruit dipped in distilled water for 5 min as the control. The treated-passion fruits were air-dried for 0.5 h after dipped, then the passion fruits were packaged in polyethylene film bags with a thickness of 0.015 mm (10 passion fruits per bag), and stored at 28℃ and 80% relative humidity for 15 days. During storage, three bags of passion fruits (30 passion fruits) from each group were sampled at 3-day interval and measured the indices of the storability and quality attributes of passion fruits. Compared with the control, Kadozan (chitosan) treatment could effectively reduce the respiration rate of the fruit, retard the increment of pericarp cell membrane permeability, decrease the weight loss percentage from fruit, but keep higher commercially acceptable fruit rate. Additionally, higher chromaticity values of L *, a * and b * of the fruit surface, higher amounts of pericarp anthocyanin, flavonoid, and total phenolics, higher contents of pulp total soluble solid, titratable acidity, total soluble sugars, sucrose, vitamin C, and carotenoid were found in the Kadozan (chitosan) treated-passion fruit. Therefore, chitosan treatment could enhance the storability and retain higher storage quality of the passion fruits during postharvest storage. Among different concentrations of Kadozan (chitosan), the dilution of 1:200 (VKadozan∶VKadozan + Water) revealed the best storability and quality attributes of the passion fruit, which could be a novel approach for increasing storability and extending the shelf-life of passion fruits during postharvest storage.

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Processing Parameters of Extracting Pepper Oleoresin by Three Phase Partitioning
CHEN Xingxing,SONG Li,GU Fenglin,WU Guiping,TAO Rui
2020, 41 (8):  1674-1682.  doi: 10.3969/j.issn.1000-2561.2020.08.023
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In this study, three phase partitioning (TPP) was employed to extract the pepper oleoresin from black pepper powder. The effects of the addition amount of pepper powder, ammonium sulphate concentration, ratio of crude extract to t-butanol, pH and temperature on the yield of pepper oleoresin and piperine content were studied. In addition, the extraction process of pepper oleoresin was optimized by a response surface test. The optimal condition obtained was as follow: the addition amount of pepper powder 5%, ammonium sulphate concentration 10%, ratio of crude extract to t-butanol 1∶0.5, pH 4 and temperature 20℃. Under the optimal conditions, the yield of black pepper oleoresin and piperine content was 12.90% and 30.46%, respectively. The results provide a reference for the industrial extraction of pepper oleoresin.

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Aroma Components of Essential Oil of White Pepper from Six Hybrid Germplasms by GC-MS
FAN Rui,ZHOU Liping,WU Baoduo,CHEN Dongmei,TENG Dingwei,QIN Yonglan,ZHENG Qiaoran,HAO Chaoyun
2020, 41 (8):  1683-1693.  doi: 10.3969/j.issn.1000-2561.2020.08.024
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The aroma components of six hybrids, ‘PC003’, ‘PC008’, ‘PC009’, ‘PC011’, ‘PC033’, ‘PC036’, of Panniyu and Reyin-1 were assayed with GC/MS analysis in the study. The constituents of high content of white pepper essential oil were caryophyllene [(30.93±0.00)%-(53.81±0.01)%], cocaene [(0.83±0.00)%-(10.09±0.00)%], δ-citronene [(0.08±0.00)%- (7.64±0.01)%], caryophyllene oxide [(0.10±0.00)%-(5.86±0.00)%], α-erythro-alcohol [(0.18±0.00)%-(5.51±0.01)%], hopsene [(0.55±0.01)%-(6.64±0.00)%] and isopropyl glycol [(2.56±0.00)%-(4.12±0.00)%] and other compounds. A total of 77 kinds of compounds such as alkenes, alcohols, esters, phenols, etc. were detected. The volatile components and total percentage detected in different white pepper essential oils were different. The component and content of the white pepper essential oil for the six hybrids were relatively different. The results would provide references for breeding of new verities and exploiting of outstanding black pepper germplasm in the future.

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Inhibitory Activity of Extracts of Antidesma montanum on the Proliferation of Breast Cancer Cells MDA-MB-231
MA Funing,HUANG Dongmei,SONG Shun,WU Bin,GUO Gang,WANG Daxin,TAN Lin
2020, 41 (8):  1693-1699.  doi: 10.3969/j.issn.1000-2561.2020.08.025
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In order to understand the health function and active components of tropical wild plants in Hainan Island the ethanol extract of the fruits and leaves of Antidesma montanum inhibiting the proliferation of breast cancer cells MDA-MB-231 by the CCK-8 method was studied in this research. The IC50 were 483 μg/mL and 306 μg/mL after 72 h treatment. The ethanol extract of the leaves of A. montanum was separated by petroleum ether, ethyl acetate, n-butanol and water respect. The ethyl acetate phase showed higher inhibitory activity than other phases, and the inhibition proliferation IC50 was 150.5 μg/mL after 72 h treatment. Through the wound healing and transwell test, the ethyl acetate phase showed inhibition in migration and invasion activity of MDA-MB-231 cells. The active components could make the S phase in cell division delayed by flow cytometry detection. One of the components was identified as amentoflavone analyzed by UPLC-MS/MS. The IC50 of amentoflavone inhibition proliferation of MDA-MB-231 cells was 192.6 μg/mL after 72 h treatment, which showed it’s one of the active ingredients in the leaves of A.montanum.

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Screening of Antioxidant Sites of Dendrobium aurantiacum Rchb. f. var. denneanum (Kerr.) Z. H. Tsi. Leaves Based on Grey Relational Degree Analysis
RUAN Peihua,DENG Hong,FU Yongmei,ZHANG Shu,GUO Cai’e,HUANG Shubin,LI Zhichao
2020, 41 (8):  1700-1707.  doi: 10.3969/j.issn.1000-2561.2020.08.026
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The leaves of Dendrobium aurantiacum Rchb. var. f. denneanum (Kerr.) Z. H. Tsi. were coarse-extracted with different concentrations of ethanol. And then with different polar solvents, the petroleum ether layer, dichloromethane layer, ethyl acetate layer, n-butanol layer and water layer were obtained from 60% ethanol crude extract, whose antioxidant activity was higher. Those layer obtained were assayed with the ultra performance liquid chromatography (UPLC) and UV-spectrophotometric method. With DPPH antioxidant activity as an index, the grey correlation degree correlation analysis was used to screen the main antioxidant activity. The highest amount of flavonoids, 24.89%, was in the n-butyl alcohol layer, and the highest amount of polysaccharide, 0.23%, layer was in the water layer. Each extraction layer had antioxidant activity, and the free radical clearance ability in order from strong to weak was water layer, n-butanol layer, ethyl acetate layer, dichloromethane layer, petroleum ether layer. Besides, the n-butanol layer and water layer were selected as the main antioxidant active parts. And the antioxidant activity was the result of the synergistic action of flavonoids and polysaccharides, which could provide some guidance for further extraction of antioxidant active compounds and development of natural antioxidants.

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Allelopathy of Root Exudates and Aqueous Extracts from Soil of Cassava to Rigidoprus lignosu and Corynespora cassiicola of Hevea brasiliensis
YUAN Fei,LIU Zifan,YAN Wenjing,LIU Peipei
2020, 41 (8):  1708-1713.  doi: 10.3969/j.issn.1000-2561.2020.08.027
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In order to study the allelopathic effect of the root exudates and aqueous extracts from the soil of cassava on the Rigidoporus lignosus and Corynespora cassiicola of rubber tree, the growth of the C. cassiicola and R. lignosus of rubber tree were measured using the mycelial growth rate method. The root exudates of cassava could promote the growth of the C. cassiicola and R. lignosus of Hevea brasiliensis. The effect on C. cassiicola of four concentrations was not obvious at any treatment times, while the effect on R. lignosus was more obvious with the concentration increase. When the concentration was 40 mg/mL, the effect on R. lignosus was significant. The allelopathic effect of the four concentration root exudates on C. cassiicola and R. lignosu was not obvious at any treatment days. The allelopathic effect of the aqueous extracts from the soil on C. cassiicola and R. lignosus showed promotion. With the concentration increased, the promotion effect increased gradually. On the 2nd day after treatment, there was a significant effect on R. lignosus when the concentration was 40 mg/mL, while there was a significant effect when the concentration was 8 mg/mL on the 3rd and 4th day after treatment. There was a significant effect on C. cassiicola when the concentration was 200 mg/mL at any treatment days. When the concentration of the aqueous extracts from the soil was less than 8 mg/mL, the effect on R. lignosuof on the 3rd day was not obvious. When the concentration was more than 40 mg/mL, the allelopathic effect on R. lignosu on the 2nd day after treatment was significantly higher than that on the 3rd day and 4th day after treatment. The effect of the four concentration aqueous extracts from the soil on C. cassiicola was not obvious. Intercropping cassava in the rubber plantation could promote the occurrence of Corynespora leaf falling disease and white root disease of H. brasiliensis to a certain extent.

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Investigation and Analysis of Vascular Plant Resources in Yongle Islands
DUAN Ruijun,HUANG Shengzhuo,WANG Jun,ZENG Jun,WANG Hao,DONG Wenhua,LI Wei,MEI Wenli,DAI Haofu
2020, 41 (8):  1714-1722.  doi: 10.3969/j.issn.1000-2561.2020.08.028
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We have investigated the plant resources of eight islands and reefs in the Xisha Yongle Islands. 158 species of higher plants were recorded, which belonging to 53 families and 132 genera,Including 90 species of wild plants and 68 species of cultivated plants. There were large differences in plant species among the eight islands and reefs. There were 124, 56, 1, 24, 29, 12, 39, 0 species in Jinqing island, Ganquan island, Shiyu, Antelope Reef, Guangjin Island, Yagong Island, Yinyu respectively. But, there was no specie found in Quanfu Island. In the survey areas, 34 species were common plants, including 24 wild plants and 10 hemerophyte. The study would lay a good foundation for the conservation, introduction, development and utilization of island and reef plants.

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