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Welcome to Chinese Journal of Tropical Crops,
25 April 2022, Volume 43 Issue 4 Previous Issue   
Omics & Biotechnology
Genomic Characteristics and Phylogenetic Analysis of Chloroplast of Cordyline fruticosa
LI Weiying, XIN Jing, ZHAO Wenzhi, DONG Zhanghong, MA Luyao, XIA Maotian, GAO Jie, XIN Peiyao
2022, 43 (4):  653-665.  doi: 10.3969/j.issn.1000-2561.2022.04.001
Abstract ( 115 )   HTML ( 20 )   PDF (1754KB) ( 73 )  

Cordyline fruticosa is an common horticultural plant, widely distributed in tropical Asia, Oceania and South America. In order to clarify the characteristics of the chloroplast genome of C. fruticosa and understand its phylogenetic status, the chloroplast genome was sequenced by Illumina sequencing technology, and the relevant data of middle linear plot, ENC-plot, PR2-plot and SSR loci were mined and analyzed. The total length of the complete chloroplast genome was 154 488 bp, and the GC content was 38%. The length of large single copy area was 85 279 bp and the GC content was 36.1%. The small single copy area was 20 325 bp, and the GC content was 32.6%. And bidirectional repetition zones were 24 442 bp, respectively, and the GC content was 43.4%. 131 genes were annotated, including 111 unigenes genes, including 78 protein-coding genes, 4 rRNA genes and 29 tRNA genes. Phylogenetic tree was constructed using the chloroplast genomes of 19 plant species in C. fruticosa and Agavaceae family. C. fruticosa was most closely related to C. indivisa. The content of GC3 in the chloroplast genome of C. fruticosa was 29.47%, GC1 and GC2 were 46.45%, 39.14%, respectively. The base content of GC3 was lower than that of GC1 and GC2, indicating that codon ends preferred to end with A and U. The ENC values ranged from 35.48 to 59.44, indicating that the codon bias was weak. ENC-plot analysis showed that there were 20 ENC frequency ratios between-0.05 to 0.05, indicating that codon preference was mainly affected by natural selection pressure. PR2-plot analysis revealed T>A, G>C, indicating that the chloroplast genome of C. fruticosa was affected by many factors. Codon preference is mainly influenced by selection. Using RSCU and ENC values as references, 17 codons were determined as optimal codons in the chloroplast genome of C. fruticosa. Among the 91 SSR loci detected, there were 3 pentanucleotides and 55 single nucleotides. 76.92% of the SSR loci took A, T (A / T, AT / AT and AAAT / ATTT) as repeat units. It showed that the A and T repeat units were the main SSR sites in the chloroplast genome of C. fruticosa. The results of this study could provide a theoretical basis for the taxonomy and phyletic evolution of C. fruticosa and Cordyline.

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Identification and Analysis of polygalacturonasegenes Family in Pomelo
LIU Ruonan, LIU Linting, ZHOU Qiurong, ZHANG Bei, GAO Zhijian, GE Cong, ZHUANG Mulai, LI Yan, WANG Ping
2022, 43 (4):  666-674.  doi: 10.3969/j.issn.1000-2561.2022.04.002
Abstract ( 54 )   HTML ( 5 )   PDF (2770KB) ( 37 )  

Strawberry, peach, apple and some other fruits gradually soften in the late growth period and during storage, while citrus, especially pomelo, granulated in the later ripening and storage, which seriously affects its economic value. In this study, the members of CgPG gene family in the pomelo genome library and the changes of PG enzyme activity were investigated to reveal the relationship between CgPGs expression and juice sacs granulationin the ripening process of pomelo fruit. The number, location and structure of CgPG gene family members in pomelo genome library were analyzed by bioinformatics, and the expression of CgPG gene family members was identified. The degree of granulation and the activities of PG were determined. 26 CgPG genes from pomelo genome were clustered into 6 subgroups (group A-group F) by phylogenetic tree analysis. Except for class E, all exons and introns and motifs were essentially conservative. GDDC domain of CgPG26 in Group E was mutated to GDDA, and SPNTDGI was mutated to APNTDGI respectively. The CgPG genes were mainly distributed on chromosomes 1, 2, 4, 5, 7 and 9. There were 5-6 tandem duplications of genes on both chromosomes 2 and 5. Group A and group B were related to fruit ripening. CgPG5 in group A and CgPG1, CgPG24 in group B were involved in fruit ripening and juice sacs softening, and CgPG13, CgPG12, CgPG26 were involved in pectin degradation and homeostatic regulation in cell wall during pomelo granulation. By expression analysis, CgPG5 in Group A and CgPG1, CgPG24 in Group B might be involved in softening and final decay during the ripening process of the non-granulated fruits, and the significant expression of the genes indicated the juice sacs were decomposed. CgPG5 in Group A and CgPG1, CgPG24 in Group B might be involved in the temporary degradation of pectin during the ripening process of easily granulated fruits. The high expression of the genes made juice sacs softened, which was the optimal time for consumption. The expressions of the genes were highly decreased during the juice sacs granulation. Therefore, CgPG genes expression showed different trends, indicating that CgPG genes might belong to two different regulatory systems in non-granular fruits and easily granular fruits. Among them, CgPG5, CgPG1, CgPG24 belonged to the pectin degradation system of juice cell softening in pomelo at late maturity, while CgPG13, CgPG12, CgPG26 belonged to the cell wall homeostasis regulation system of pomelo granulation.

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Development and Application of a New Functional Marker of Fragrant Gene in Rice (Oryza sativa L.)
LIU Wenjing, HU Wenbin, ZHOU Zheng, LIU Ye, ZHAO Zhenghong, XU Qingguo
2022, 43 (4):  675-683.  doi: 10.3969/j.issn.1000-2561.2022.04.003
Abstract ( 52 )   HTML ( 4 )   PDF (3113KB) ( 46 )  

Fragrance is an important trait which affects the quality of rice. The mutation of Badh2 is the main contribution of fragrance in rice, and there are mainly several types of exon mutation, such as the second exon, the fourth exon, the fifth exon, the seventh exon and the eighth exon of Badh2, and the mutation of the seventh exon is the most studied one. In order to improve the accuracy, safety and efficiency of rice fragrant detection, the molecular marker with three primers (3-primer marker)was designed based on the mutation of the seventh exon of Badh2 (eight bp deletion and three bp mutation), and three primers were named Fgr-FF, Fgr-NF and Fgr-R respectively. The mutation of the seventh exon of Badh2 could be detected accurately by the three3-primers molecular marker, and the homozygous and heterozygous of fragrant rice were identified. This marker took advantage of the poor conservation of the 5' end of primers in polymerase chain reaction (PCR), added the 31 bp exogenous deoxyribonucleic acid (DNA) to the 5' end of the primer Fgr-NF. This marker enlarged the differences of length between the non-fragrant and fragrant bands of PCR from 8 bp to 41 bp, and the homozygous, heterozygous and non-fragrant genotypes of rice could be accurately, clearly and quickly detected by agarose gel electrophoresis. The results of PCR amplification with the three-primer marker indicated that: 115 bp DNA fragment in the fragrant rice, 156 bp DNA fragment in the non-fragrant rice, both 115 bp and 156 bp DNA fragments in the heterozygous rice. The 30 rice varieties were detected by the 3-primer marker. And the results showed that: there were nine fragrant homozygous genotype varieties and twenty non-fragrant homozygous genotype varieties, which were consistent with the two phenotypic identification methods, KOH method and chewing method. There was one heterozygous genotype variety, and its genotype identification results was inconsistent with the phenotypic identification results, because the fragrant gene of rice was recessive gene, the leaves of heterozygous rice were non-fragrant, while some grains were fragrant. The traditional fragrant identification methods were easy to misjudge the fragrance of heterozygous rice. However, These results of gene detection and phenotypic verification showed that the 3-primer marker designed by this study was accurate and reliable. The 94 individual plants from F2 generation were detected by the 3-primer marker, and the results also showed that there were 23 fragrant homozygous plants, 44 non-fragrant homozygous plants and 27 heterozygous plants, which accorded with the 1∶2∶1 ratio of Mendelian genetic law. This study not only excluded the subjective error of KOH method and chewing method, but also avoided the toxicity and time consuming of polyacrylamide gel electrophoresis, and greatly improved the breeding efficiency of fragrant rice varieties.

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Purification of the Potyviral Helper Component-proteinase Using Agroinfection-compatible Twin-Strep-tagged Infectious cDNA Clone of Papaya Leaf Distortion Virus
YANG Xiukun, SHEN Wentao, TUO Decai, WANG He, YAN Pu, LI Xiaoying, ZHU Guopeng, ZHOU Peng
2022, 43 (4):  684-692.  doi: 10.3969/j.issn.1000-2561.2022.04.004
Abstract ( 45 )   HTML ( 5 )   PDF (5555KB) ( 32 )  

Papaya leaf distortion mosaic virus (PLDMV, genus Potyvirus) is an emerging threat to papaya production. The helper component proteinase (HC-Pro) encoded by potyvirus is a multifunctional protein involved in different steps of the viral cycle including aphid-vector transmission, virus replication and movement, cleavage of the polyprotein and suppression of RNA silencing. To enable the study of HC-Pro functions, high quantities of protein are required. Here we describe the construction of a PLDMV infectious clone that produces HC-Pro protein with a Twin-Strep-tag fused at the N-terminus, and the development of an efficient method to purify large amounts of PLDMV HC-Pro protein for the virus-infected papaya plants. To construct an agroinfection-compatible Twin-Strep-tagged PLDMV infectious cDNA clone designated pPLDMV-Strep, the previously constructed pPLDMV-WT plasmid that contained the full-length cDNA of the wild-type PLDMV genome was used as the template to amplify two DNA fragments containing all PLDMV viral sequences, the backbone of binary vector pGreenII-35S and Twin-Strep-tag by PCR with specific two primer pairs. Then, both PCR amplified fragments were assembled to produce the pPLDMV-Strep vector using one-step In-Fusion Cloning. Based on the Escherichia coli Cell-Free method, the pPLDMV-Strep were directly transformed into Agrobacterium tumefaciens to prevent potential problems such as plasmid instability during propagation in E. coli. Sequencing of the PCR products from A. tumefaciens transformants confirmed that the full-length viral sequences in pPLDMV-Strep was identical to that of the wild-type PLDMV isolate and the Twin-Strep-tag was introduced correctly into N-terminus of the PLDMV HC-Pro. The agroinoculated papaya seedlings with A. tumefaciens transformant harboring the plasmid pPLDMV-Strep developed systemic mosaic symptoms on leaves at 20 days post inoculation (dpi) which were similar to those caused by wild-type PLDMV. The results suggested that the PLDMV-Strep was infectious and insertion of Twin-Strep-tag into PLDMV genome did not affect the viral infectivity. Furthermore, a protocol for purifying rapidly the PLDMV HC-Pro from PLDMV-Strep-infected papaya leaves based on the Strep-tag-Tactin@XT affinity chromatography was developed. the N- and C-terminal peptides from the purified Twin-Strep-tagged HC-Pro were identified by liquid chromatography electrospray ionization tandem mass spectrometric (LC/ESI-MS/MS) analysis. Compared to previous several potyviral HC-Pro heterologous expression systems in baculovirus, yeast or E. coli, a major advantage of the expression system based on the agroinfection-compatible strep-tagged infectious cDNA clone was capable of producing more authentic HC-Pro proteins because purified PLDMV HC-Pro was from the virus-infected host plants. The results would provide a rapid and low-cost alternative method to obtain biologically active PLDMV HC-Pro protein and will facilitate to further study the structure and multifunction of PLDMV HC-Pro.

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Fecal Metabolomics of Polysaccharide from Jackfruit Pulp in Mice Based on UPLC-Q-TOF-MS/MS
MA Zhiyuan, CEHN Yuzi, TAN Lehe, ZHANG Yanjun, WU Gang, ZHU Kexue
2022, 43 (4):  693-702.  doi: 10.3969/j.issn.1000-2561.2022.04.005
Abstract ( 47 )   HTML ( 6 )   PDF (3485KB) ( 45 )  

Artocarpus heterophyllus Lam. is rich in nutrients, including carbohydrate, protein, amino acid, polyphenol, fatty acid, vitamin and minerals, which can be used as good sources for some important nutrients. Nowadays, A. heterophyllus Lam. trees are widely distributed in Hainan, Guangdong, Guangxi, Yunnan, Fujian, and Taiwan provinces. Polysaccharide, as an important biological molecule, participates in cell activities. Recently, a water-soluble polysaccharide named JFP-Ps was isolated from A. heterophyllus Lam. pulp, which consisted of rhamnose, arabinose, galactose, glucose, xylose and galacturonic acid, with an average molecular weight of 1668 kDa. JFP-Ps exerted immunomodulatory effect by inducing lymphocyte proliferation, enhancing antioxidant activity and increasing the secretion of TNF-α, IFN-γ and IL-1β. Moreover, JFP-Ps can be fermented into short-chain fatty acids, including acetate, propionate, butyrate and valerate acid by gut microbiota. However, there was little research about the the metabolism of JFP-Ps during gastrointestinal digestion. Based on our previous research, the present study was aim to investigate the fecal metabolomics of JFP-Ps on fecal metabolites from mice. Healthy Kunming mice were divided into four groups, including 50 mg/kg mouse body weight (low dose group), 100 mg/kg mouse body weight (medium dose group), and 200 mg/kg mouse body weight (high dose group) and the same volume of distilled water (blank control group). After experimental treatment for 2 weeks, fresh fecal samples were collected for metabolomics analysis. A metabolomics method based on Agilent 1290 series UPLC and with 6530B series Q-TOF mass spectrometer (UPLC-Q-TOF-MS/MS) was developed to identify the fecal metabolites. Then related metabolic pathways were analyzed by matching KEGG and Wiki pathways. Our results showed that 30 potential biomarkers were authenticated using principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA), including 22 types in the negative ion mode and 8 characteristic metabolites in the positive ion mode. The results of metabolomics pathway analysis showed that the metabolites were related to the biological pathways and processes, including metabolism of phenylalanine, alanine, aspartic acid, tryptophan, cholesterol, 2-oxocarboxylic acid and nucleotide. They also have been proven to be related to the tricarboxylic acid cycle activity, PPAR signaling pathway, activation pathways in class A GPCRs, degradation of benzoic acid and derivatization of amino acids, nuclear receptors, glutathione and one-carbon cycle, urea cycle and amino metabolism pathways. The results indicated that JFP-Ps could regulate the metabolism of cholesterol, biosynthesis of fatty acid and triglycerides, omega-3 and omega-6 fatty acids metabolism and the secondary metabolites in mice. The results could provide theoretical basis for elucidating the bioactive substances and its mechanism of JFP-Ps.

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Germplasm Resources, Genetics & Breeding
Two New Records of the Genus Micropsalliota from China
LIU Wei, CHEN Yanliu, ZHANG Linping, LIANG Junfeng
2022, 43 (4):  703-709.  doi: 10.3969/j.issn.1000-2561.2022.04.006
Abstract ( 38 )   HTML ( 5 )   PDF (1906KB) ( 27 )  

In this paper, two samples of Micropsalliota collected from Guangdong Province were classified and identified. A method of combining morphological comparison and gene sequence was used. Finally, the two specimens were identified as Micropsalliota bifida R.L. Zhao, Desjardin, Soytong & K.D. Hyde and Micropsalliota subalba Heinem. & Little Flower, both of them are new record species in China. M. bifida is characterized in its small fruiting body, pure white pileus when mature, free and crowded lamellae, white when young, then brown when mature, white annulus, oval to almond-shaped and smooth basidiospores, hyaline and smooth cheilocystidia, sometimes bifid with two toe-like lobes, 17.6~32.0 µm×4.6~7.4 µm, absent pleurocystidia, and pileipellis composed of creeping hyphae. M. subalba is characterized in its small fruiting body, pileus surface with radial cilia, free and crowded lamellae, white and superior annulus, oval and smooth basidiospores, 25.6~56.5 µm×7.1~12.6 µm, clustered, hyaline, and smooth cheilocystidia, absent pleurocystidia, and pileipellis composed of creeping hyphae. Furthermore, the detail description, illustrations and phylogenetic tree are provided, and the differences in morphology with similar species are analyzed in this paper. To this end, the species and geographical regions of this genus in China are added.

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Five Newly Recorded Species of Orchidaceae in Tibet
ZHAO Jiamin, LI Mengkai, PANG Shenshen, ZHENG Weilie, XING Zhen, ZHOU Peng, WANG Wei
2022, 43 (4):  710-713.  doi: 10.3969/j.issn.1000-2561.2022.04.007
Abstract ( 77 )   HTML ( 3 )   PDF (1397KB) ( 39 )  

The characteristics of regional background plant species are of great significance to the study of flora and plant species evolution. Orchids are the most evolved group of angiosperms, and the distribution and population characteristics have been focused for a long time. Tibet is a hot area of orchids distribution in China, especially in Yarlung Zangbo Grand Canyon, the world’s largest grand Canyon and where the background information of orchids is still unclear. As a result, many investigations have been carried out and lots of studies about newly records and new species of Orchidaceae have been reported in recent years. In order to understand Orchidaceae in Yarlung Zangbo Grand Canyon, the member of forestry Innovation Team of Xizang Agriculture and Animal Husbandry University have investigated the resources of orchids in the Grand Canyon for many times in recent years. After identification, 5 newly records species of orchidaceae were observed in Tibet, which were Dendrobium praecintum, Dendrobium sulcatum, Dendrobium thyrsiflorum, Odontochilus lanceolatus, and Rhomboda tokioi. All of the five newly Tibetan records of orchids were founded in Modog County, Tibet Autonomous Region. In additon, D. praecintum, D. sulcatum, D. thyrsiflorum and D. tokioi are widely distributed in the southern of the Himalayas, but this study was the first report that the four species were existed in Tibet. Moreover, our results indicated that the four orchids maybe continuously distributed from Sikkim to Yunnan in the southern of the Himalayas to some extent. Additionally, the distribution area of A. lanceolatus is a newly distributed site in China (previously reported in Guangdong, Taiwan, and so on). Therefore, our results have values for the diversity and floristic characteristics of orchids in Yarlung Zangbo Grand Canyon.

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Diversity Analysis of Fruit Quality in Germplasm Resources of Mango in Baise, Guangxi, China
LI Xi, WANG Yerong, HUANG Huili, ZHONG Yong, YANG Jinying, JIANG Qiang, CHEN Qianfu
2022, 43 (4):  714-721.  doi: 10.3969/j.issn.1000-2561.2022.04.008
Abstract ( 52 )   HTML ( 8 )   PDF (2767KB) ( 45 )  

Mango (Mangifea indica L.) is an important fruit crop cultivated along Youjiang River dry-hot valley area in Baise. Now, with the increasing in mango new producing areas, new varieties are widely cultivated. However, traditional varieties are still widely cultivated in Baise. In order to enhance the competitiveness of ‘Baise mango’, it is urgent to breed new varieties which are suitable for Youjiang River dry-hot valley. At present, many studies have been carried out on the evaluation of different mango traits outside Guangxi, but there are few reports on the diversity of mango germplasm in Baise. 17 mango germplasm resources cultivated in Baise were used to identify 23 qualitative and quantitative traits. Correlation analysis, principal component analysis and cluster analysis were used to analyze the diversity. The diversity of 16 mass traits (fruit shape index, fruit weight, edible rate, total soluble solid, total acid, sugar-acid ratio, polyphenols, vitamin C, ferrum, calcium, magnesium, lutein, zeaxanthin, lycopene, α-carotene, β-carotene) in mango fruits was studied. The results showed that the variation of qualitative and quantitative traits was very rich in different mango varieties. The genetic diversity index ranged from 0.65 to 1.50, which was the smallest genetic diversity index in stickness between peel and pulp and the largest genetic diversity index in peel color. The variation coefficient of quantitative traits ranged from 12% to 96%, which was the smallest variation in edible rate and the largest variation in ferrum. Edible rate was positively correlated with fruit weight, was negatively correlated with β-carotene. Ferrum was positively correlated with fruit shape index, negatively correlated with edible rate. Vitamin C was positively correlated with lutein and lycopene. Sugar-acid ratio was negatively correlated with total acid. Magnesium was negatively correlated with fruit shape index. Principal component analysis showed that fruit weight, soluble solids, vitamin C, sugar-acid ratio, ferrum, calcium, α-carotene, lutein and lycopene were the main quantitative traits. Cluster analysis showed that the germplasm resources were divided into three groups. In the first group, the shape of fruit cross section was ovate oblique, with pine flavor, high content of soluble solid, lutein and α-carotene. In the second group, the shape of fruit cross section was ovate oblique, with pine flavor, relatively low content of solid-acid ratio, polyphenol and lycopene. In the third group, peel color was dark, without pine flavor, lower content of sugar-acid ratio and polyphenols, ferrum, lycopene and α-carotene. This study would provide a theoretical basis for genetic improvement, germplasm innovation and application of mango breeding in Baise.

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Comprehensive Evaluation of Quality Characteristics of Fruit from Different Avocado Strains
XU Dan, LIU Yuanzheng, ZHANG He, LI Yanxia, MA Weihong, LIU Xinyi, WANG Jiashui, LIU Jinping
2022, 43 (4):  722-728.  doi: 10.3969/j.issn.1000-2561.2022.04.009
Abstract ( 51 )   HTML ( 5 )   PDF (1405KB) ( 47 )  

In this study, 9 avocado lines from Danzhou and Baisha, Hainan, China were selected as the research objects, namely DL-F, FR-1, LY-C, LY-L; RK-1, RK-2, RK-3, RK-4, RK-5. 31 important fruit quality traits, including mineral elements, fatty acid composition, vitamin C, total phenols, and flavonoids, of 9 varieties of avocados were determined. Graphite furnace atomic absorption spectrophotometer was used to determine the mineral content in the fruit. Soxhlet extraction was used to extract the oil in the avocado pulp. The relative contents of fatty acids in the oils and fats were determined by gas chromatography-mass spectrometry, the physicochemical properties of avocado oil were determined according to national standards, vitamin C was determined by high performance liquid chromatography, and important fruit quality indexes such as flavonoids and total phenolics were determined by NaNO2-AlNO3-NaOH method and ferrous tartrate method. Results showed that most of the fruit quality traits of different avocado lines were different. The oils of the nine lines had no significant differences in density and refractive index. The different avocado lines were rich in vitamin C, but there was no difference in its content. The fruits had a relatively high content of mineral elements. Compared with other fruits, the contents of potassium, phosphorus and oleic acid were relatively high, which is an important index for evaluating the nutritional content of avocado fruits. Cluster analysis results showed that when the Euclidean distance was 5, the varieties could be clustered into 4 categories. The first category included RK-2 and RK-3, which had high iodine value and low saponification value. The second category included DL-F, LY-L, FR-1, RK-1 and RK-4, which had higher palmitic acid, saponification value, water content and vitamin C content. The third category was LY-C, which performs well in all indicators. The fourth category was only RK-5, which had poor fruit quality. In summary, in this study, a comprehensive analysis of various quality traits of avocado was conducted in different lines from native Hainan, and several analytical methods may provide references for the systematic evaluation and variety improvement of avocado in Hainan. At the same time, the improvement and breeding of superior avocado cultivars should not only be evaluated for fruit quality, but also be combined with a wide range of indicators including disease resistance, fitness, and abundance of fruit, so that avocado cultivars with strong adaptability and suitable promotion can be screened.

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Comparative Analysis of Phenotypic Traits of Yellow Skin Pepper and Green Skin Pepper
HE Runming, GUO Hanquan, LIU Hongbiao, HUANG Zhiwen, WANG Kai, SHEN Ying, TIAN Yonghong
2022, 43 (4):  729-741.  doi: 10.3969/j.issn.1000-2561.2022.04.010
Abstract ( 55 )   HTML ( 4 )   PDF (1889KB) ( 34 )  

China is the largest pepper producer and consumer country in the world. Green skin pepper and yellow skin pepper are the main vegetable pepper varieties in the market. It is particularly important to understand the characteristics and differences in the phenotypic traits and genetic diversity of mainstream yellow skin pepper and green skin pepper varieties in the market. Therefore, we conducted a comparative analysis of the coefficient of variation, genetic diversity index, correlation, main component and clustering of 25 field phenotypic traits of 36 yellow skin peppers and 38 green skin peppers that are currently the mainstream in the market. The results showed that in addition to the difference in fruit color, there are also certain differences in traits such as plant height, single fruit weight, fruit surface texture and fruit surface shrinkage between yellow skin pepper and green skin pepper, the average plant height of yellow pepper is about 16% higher than that of green pepper, the average weight of a single fruit of yellow skin pepper is about 41.4% heavier than that of green skin pepper, the overall surface of the green pepper is weaker and the texture is smoother, while the yellow pepper is more wrinkled. In the genetic diversity index, the variation range of yellow skin pepper is 0.1268-0.9915, and that of green skin pepper is 0.2762-1.3697,and the diversity of green skin peppers is higher than that of yellow skin peppers. There are differences in the correlation between plant height and fruit shape index, plant height and fruit longitudinal diameter, and leaf length and fruit transverse diameter, single fruit weight and fruit shape index, and leaf width and fruit transverse diameter, single fruit weight and fruit shape index, and longitudinal diameter and transverse diameter in yellow skin pepper and green skin pepper. Fruit factor is a comprehensive index that dominates the characteristics of yellow skin pepper, and growth factor is a comprehensive index that affects the characteristics of green pepper. The results of cluster analysis were categorized by the traits with higher principal component loading values, and echoes the results of the principal component analysis, and contains similar yellow pepper and green pepper varieties, and contrasts with the separate clustering results. After cluster analysis, 36 yellow skin pepper varieties were divided into 7 groups, among which the first group had 19 varieties, accounting for 52.7% of all yellow skin pepper,38 green pepper varieties were divided into 7 groups, among which there were 9 varieties in the fifth group and the sixth group, accounting for 23.6% of the total, this shows that the homogeneity among pepper varieties is relatively serious.

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Phenotypic Genetic Diversity and Utilization Evaluation of Wild Cymbidium goeringii Germplasms from Leye County, Guangxi, China
ZENG Yanhua, LONG Qiangyu, HE Jingzhou, LI Xiuling, FAN Jizheng, BU Zhaoyang
2022, 43 (4):  742-753.  doi: 10.3969/j.issn.1000-2561.2022.04.011
Abstract ( 38 )   HTML ( 2 )   PDF (2192KB) ( 45 )  

To understand the relationship among Cymbidium goeringii germplasms from Leye County, and to improve the utilization efficiency, genetic diversity and characteristic relativity analysis were conducted based on 43 phenotypic traits, including 13 qualitative characters and 30 quantitative characters of 66 C. goeringii germplasms. The resources were cluster-analyzed and comprehensively evaluated based on the principal component analysis of the phenotypic traits. The results showed that the phenotypic diversity of C. goeringii germplasms was rich and the trait variation was high. The coefficient of variation (CV) of quantitative characters ranged from 11.62% to 41.56%, and the highest value of CV was detected in peduncle height. The CV of qualitative traits ranged from 9.26% to 55.7%, and the value of flowering habit, lip main color and petal shape were relatively high. The results indicated that the growing peduncle height, the increasing number of flowers, the stamen petalization lip main color and petal shape were the key breeding directions of spring orchid ornamental traits. Correlation analysis indicated that there was strong positive correlation between side sepal width (SSW) and medium sepal width (MSW), side sepal length (SSL) and medium sepal length (MSL), side sepal shape (SSS) and medium sepal shape (MSS), petal inner main color (PIMC) and sepal main colour (SMC). The correlation coefficient was 0.7951, 0.7648, 0.771 and 0.741, respectively. By contrary, there was strong negative correlation between side sepal angle (SSA) and side sepal preend shape (SSPS), lip shape (LS) and medium sepal preend shape (MSPS), lip spot number (LSN) and leaf color (LC), and the correlation coefficient was -0.4557, -0.4316, -0.4181, respectively. Five and eleven principal components with 10 factors were extracted using the principal component analysis (PCA) of both quantitative and qualitative traits, and the cumulative contribution rate was 78.193% and 73.023% respectively. The phenotypic factors contained in the principal components could be used as the main character indexes for germplasm innovation and parent selection for breeding ornamental spring orchid. Based on cluster analysis, The 66 spring orchid accessions were classified into four major groups when the euclidean distance was about 18.77. There was only one accession, C18019-3 in Class Ⅰ, and there were 9 accessions, mainly of the same origin, in Class Ⅱ. There were 28 accessions in Class Ⅲ and most of them were red flowers. There were 28 accessions in Class Ⅳ, and most of them had larger flowers. 19138-38, 19138-40, 18011, 18007 and 19134-1 were selected after comprehensive evaluation. The research would provide theoretical references for understanding the relationship between wild spring orchid germplasms in Guangxi and provide scientific basis for the evaluation and full utilization of resources.

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Plant Cultivation, Physiology & Biochemistry
Research Progress on Mechanism and Regulation of Latex Flow in Hevea brasiliensis Muell. Arg.
GUO Bingbing, DAI Longjun, YANG Hong, ZHAO Xizhu, WANG Lifeng
2022, 43 (4):  754-768.  doi: 10.3969/j.issn.1000-2561.2022.04.012
Abstract ( 39 )   HTML ( 7 )   PDF (1080KB) ( 37 )  

Latex flow, one of the most important parts in the latex harvesting from laticifer cells of rubber tree’s bark, is related to natural rubber biosynthesis, latex regeneration, rubber tapping technology, phloem turgor pressure and many other factors, accounting for 60% of production costs. In recent years, important progress has been made in the synthesis and regulation mechanism of natural rubber (isoprene) biosynthesis pathway, latex diagnostic indexes, laticifer wound plugs mechanism and tapping panel dryness (TPD) occurrence and repair mechanism caused by excessive tapping. In this paper, we summarized the current situations including natural rubber biosynthesis and latex regeneration, laticifer wound plugs, factors influenced latex flow as well as physiological and molecular biological mechanisms of latex flow. Furthermore, combining with the continuous introduction of new technologies into the research field of rubber latex flow, the development trend and application of rubber tree latex flow mechanism were prospected, which provided theoretical basis for rubber tree latex flow mechanism research and guidance for the development of new efficient and safe stimulation technology.

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Advances in Flowering Regulation of Paphiopedilum
YIN Yuying, FANG Lin, LI Lin, CHEN Xian, FU Wenqun, WU Kunlin, ZENG Songjun
2022, 43 (4):  769-778.  doi: 10.3969/j.issn.1000-2561.2022.04.013
Abstract ( 34 )   HTML ( 4 )   PDF (589KB) ( 34 )  

Paphiopedilum species, popularly known as slipper orchids because of the resemblance of the pouch-shaped lip to a lady’s slipper, gorgeous flower color and long-lasting flowering, have captured the interest of many orchid growers and hobbyists and are one of the most popular and rare orchid genera being sold and exhibited today. Wild populations are under the threat of extinction as a result of over-collection, loss of suitable habitats, and all species are listed in the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) Appendix I and the trade is prohibited. At present, most of the popular Paphiopedilum species on the market are hybrids or a small number of native species obtained by asymbiotic seed germination in Taiwan and other places. Due to its long growth cycle, large differences among species and diverse flowering habits, it is difficult to achieve effective flowering regulation. Paphiopedilum has a sympodial habit of growth. After blooming, the plant will resume growth at the base of the previous shoot. The apical meristem of each new growing shoot continually differentiates its leaves until it initiates flower buds under proper environmental conditions. The Paphiopedilum is a raceme with polyfloral primordia. The dominant flower and lateral flower (s) of polyfloral species or varieties develope simultaneously or successively. However, the single flower species or varieties are caused by the cessation of development of lateral flower buds after differentiation. Flowering time and flowering abundance are two very important horticultural traits. Light, temperature, plant growth regulators and fertilizers are the main factors affecting plant flowering. For the Paphiopedilum species mainly distributed in tropical regions, the photoperiod has no significant effect on the flowering period. Temperature is a key factor to promote the growth of spring-flowered Paphiopedilum from vegetative growth to reproductive growth. Gibberellin (GA3) and 6-benzylpurine (6-BA) alone or in combination can effectively control the flowering period. The use of plant growth regulators in some monofloral species could promote the development of lateral flowers to form double or multiple flowers. Regular spraying of low-concentration water-soluble fertilizers containing high phosphorus and high potassium before flowering can also effectively advance the flowering period. This article reviews the related researches on the growth habit, flower bud differentiation and flowering regulation technology of Paphiopedilum. With reference to other methods of orchid flowering period regulation, suggestions for Paphiopedilum flowering regulation are put forward in order to provide reference for the research on the flowering regulation technology and the commercial production of Paphiopedilum.

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Effects of Arecanut and Pandan Intercropping on Photosynthetic Characteristics and Aroma Components of Pandan Plants
YU Huan, ZHONG Yiming, JI Xunzhi, ZHANG Ang, TANG Jinxuan, LI Jinshuang, DENG Wenming, ZONG Ying, QIN Xiaowei
2022, 43 (4):  779-787.  doi: 10.3969/j.issn.1000-2561.2022.04.014
Abstract ( 38 )   HTML ( 4 )   PDF (1150KB) ( 34 )  

The paper was aimed to study the effects of arecanut and pandan intercropping on photosynthetic characteristics and aroma components of pandan leaves. In this study, a arecanut orchard in Xinglong area, Wanning City, Hainan Province was selected as the test plot. Field experiments were used to determine the photosynthetic characteristics and aroma components of pandan leaves under the pandan monoculture and arecanut and pandan intercropping planting patterns.The net photosynthetic rate of the leaves of pandan after intercropped with arecanut significantly increased, the temperature of the leaves significantly decreased, and the net photosynthetic rate significantly negatively correlated with leaf temperature. In the two planting patterns, it was identified that pandan leaves contained 31 aroma components of 9 types, including pyrroles, alcohols, phenols, furans, furanones, hydrocarbons, acids, ketones and esters. The contents of 17 common aroma components including squalene, phytol, neophytadiene, 2,3-dihydrobenzofuran, 3-methyl-2-(5H)-furanone, acetol, 2-acetyl-1-pyrroline and so on of intercropping pattern were significantly higher than that of pandan monoculture. The contents of methyl pyruvate and furanone were significantly lower than that of monoculture. The contents of squalene and 3-methyl-2-(5H)-furanone of pandan leaves were significantly positively correlated with the net photosynthetic rate. 2-acetyl-1-pyrroline, squalene, and chlorophyll. The contents of 2-acetyl-1-pyrroline, squalene, phytol, neophytadiene, 2,3-dihydrobenzofuran, 3-methyl-2-(5H)-furanone, and acetol were all negatively correlated with leaf temperature. It can be seen that the arecanut and pandan intercropping can increase the net photosynthetic rate of pandan leaves and reduce the temperature of the leaves, thereby increase the contents of main aroma components and improve the quality of pandan leaves. This would provide theoretical support for arecanut and pandan intercropping efficient cultivation pattern.

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Response of Banana to Low pH and Aluminum Toxicity Stress
ZHANG Jiangzhou, LI Baoshen, WU Liangquan
2022, 43 (4):  788-797.  doi: 10.3969/j.issn.1000-2561.2022.04.015
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Banana (Musa spp.) is an important fruit in tropical and subtropical regions of the world. It plays a crucial role in the development of tropical economy. China is one of the world’s main banana planting countries, with the second highest total production in the world after India. Low pH and Al toxicity are the main limiting factors in banana production and seriously decrease the banana yield and quality. Therefore, identifying the effects of low pH and Al toxicity stress on banana growth and nutrient uptake can provide theoretical basis for regulating the soil health of acid soils. In this study, pot and hydroponic experiments were conducted. The pot experiments were set under soil pH of 3.7 and 6.5, with the banana varieties of ‘Williams B6’ (Musa AAA Cavendish cv. Williams B6), ‘Brazil’ (Musa AAA Cavendish cv. Brazil) and ‘Nantianhuang’ (Musa AAA Cavendish cv. Nantianhuang), to study the differences in the response of banana varieties to low pH. The results showed that low pH significantly inhibited banana growth and nutrient uptake. The three banana varieties grown at high pH 6.5 soils had significantly higher biomass and nutrient contents (N, P, K, Ca and Mg) of different parts (roots, pseudostems and leaves) than those on low pH 3.7 soils. Compared to high pH soils, bananas grown at pH 3.7 showed an average decrease of 77% in biomass and 73%-604% in nutrient uptake of N, P, K, Ca and Mg, while no significant differences were observed among banana varieties. In the hydroponic experiments, four Al concentrations of 0, 25, 50, 100 μmol/L were applied to explore the response to Al stress. The results of hematoxylin staining of banana root tips showed that the colors of banana root tips gradually deepened with the increase of Al concentrations, and the Al toxicity appeared obviously. The above-ground biomass and nutrient contents (N, P, Ca and Mg) of banana showed a decreasing trend with increasing Al concentrations. Banana grown in Al concentrations of 100 μmol/L showed a significant decrease of root growth rates, shoot biomass, SPAD values of leaf margin and leaf center, and Ca and Mg uptake. This study showed that low soil pH and Al toxicity significantly inhibited the growth and nutrient uptake of banana, with the same trend shown among different varieties. This research provides an important reference for acid soil management in banana orchards, and will contribute to the banana quality, nutrient efficiency and green development of banana industry in China.

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Growth and Antioxidant Physiology Effects of Nymphaea minuta under Different Light Conditions
WANG Hongyan, BU Zhaoyang, LI Xianmin, LU Jiashi, LI Chunniu, HUANG Zhanwen, SU Qun
2022, 43 (4):  798-806.  doi: 10.3969/j.issn.1000-2561.2022.04.016
Abstract ( 40 )   HTML ( 3 )   PDF (1038KB) ( 55 )  

Water lilies have high ornamental value and are world-famous aquatic flowers with various varieties and rich colors, known as the “pond palette”. The play an important role in garden waterscape construction and water purification. Miniature water lilies are small in size, suitable for family planting and ornamental. Nymphaea minuta is a typical miniature water lily, which is an excellent breeding material for new cultivar of miniature water lily. In order to promote the application of miniature water lily in home gardening, understand the light demand and adaptation rules of miniature water lilies, the growth characteristics and physiological parameters of miniature water lily (Nymphaea Minuta) were studied under shading rates of 0 (CK), 30%, 50% and 70%, respectively using artificail shading. The results showed that with increasing shading rate, the flower number, diameter of flower, pedicel emergence height, pedicel diameter, leaf area, leaf number, stem length, root number, root length, leaf dry weight, stem dry weight, root dry weight, total dry weight, growth vigor and survival rate of N. minuta decreased to a certain extent with significantly difference (P<0.05) and all of them being at the highest level under the full light condition. In the shading treatment for 120 days, the difference of flower number increased between different shading rate treatment (P<0.05), but the difference of flower dry weight was not significant, and the survival rate was the lowest under shading rate 70%. With the same shading time treatment, the MDA content in leaves decreased with the increase of shading rate. There was significant difference in MDA content between 30 days and 60 days of shading treatment (P<0.05), but no significant difference between 90 days and 120 days of shading treatment. In the shading treatment for 30 days and 60 days, the FAA content, POD and SOD activities in leaves did not show consistent change. In the shading treatment for 120 days between different shading rate treatment, the FAA content, POD and SOD activities in leaves increased then decreased, POD activities showed significantly difference (P<0.05), while MDA and FAA contents showed no significantly difference. Therefore, N. minuta adapts to different light environments by changing its morphological characteristics and adjusting its antioxidant physiology, which has strong antioxidant enzyme systems and shade tolerance. It grew best under full light condition with largest amount of flowers and grew well under medium shade treatment, while grew bad under lack of light treatment. This study provides a a theoretical basis for the application of Nymphaea minuta in indoor cultivation and home gardening.

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Effects of GA3 on the Growth and Main Quality of Double-flower Lily ‘Carolina’
ZHANG Ying, ZHANG Qin, LIU Jie, LI Wenxiang, LIU Song, HUANG Haiquan, HUANG Meijuan
2022, 43 (4):  807-815.  doi: 10.3969/j.issn.1000-2561.2022.04.017
Abstract ( 24 )   HTML ( 1 )   PDF (3490KB) ( 29 )  

Lilium sp. is a perennial bulbous flower in the genus Lilium of Liliaceae, is a popular bulbous flower in the flower market. It is beautiful in shape, elegant in color and charming in fragrance among which double lily is favored by consumers due to its advantages such as stamen degeneration, no pollen, beautiful flower shape and long ornamental period. Gibberellin is an important endogenous hormone and plays a crucial role in the normal growth and development of plants. It is widely used in crops, vegetables, fruits and flowers. In this study, double-flower lily ‘Carolina’ was used, six different concentrations of GA3 (50, 100, 200, 400, 600, 800 mg/L) were applied during the lily growth by spraying the leaves while water was used as the control. The plant height, stem diameter and postharvest quality were investigated in order to study the effect of GA3 on the growth of double-flower lily ‘Carolina’. The results showed that the cultivation experiment 400 mg/L GA3 had the best promotion effect on improving ‘Carolina’ plant height, flower bud length and flower opening rate, which was 10.40%, 9.13% and 17.78% higher than those of the control, respectively, reaching extremely significant differences. 800 mg/L GA3 could promote the accumulation of ‘Carolina’ to chlorophyll relative content. 100 mg/L GA3 had the best effect on prolonging flowering time of ‘Carolina’, 10.64% longer than that of the control. In terms of tubers, 800 mg/L GA3 had better promoting effect on single fresh weight, total weight and average root number of tubers. During its vase storage, 100 mg/L GA3 had the best effect on delaying fresh weight of flower branch, increasing bud opening rate, prolonging single and whole flowering period. 600 mg/L GA3 had the best effect on delaying the accumulation of chlorophyll relative content and MDA, and improving the activities of SOD and POD enzyme, with extremely significant difference. In a comprehensive comparison 600 mg/L GA3 had the best promotion effect on double lily ‘Carolina’, followed by 400 mg/L. In conclusion, application of GA3 has different effects on the growth and postharbital quality of ‘Carolina’. Appropriate concentration of GA3 can effectively promote the growth of ‘Carolina’ plant height, bud and bulb, increase chlorophyll relative content, SOD and POD enzyme activities, delay the accumulation of MDA, so as to prolong the ornamental period of lily and improve flower quality. This study provided some basic data and theoretical basis for the better application of gibberellin in the cultivation and post-harvest preservation of double lily.

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Physiological and Biochemical Responses of Eight Hydrangea Cultivars to High Temperature Stress
LU Aixian, LING Rui, CHENG Shengyu, ZHAI Junwen, ZHENG Zexin, WU Shasha
2022, 43 (4):  816-828.  doi: 10.3969/j.issn.1000-2561.2022.04.018
Abstract ( 103 )   HTML ( 4 )   PDF (1484KB) ( 50 )  

High temperature in summer is one of the important factors restricting the introduction and planting of Hydrangea in Southern China. The study of the physiological and biochemical response mechanism of Hydrangea under high temperature stress has important reference significance for the application of Hydrangea under special site conditions. In this experiment, eight cultivars of Hydrangea were used as materials to determine the physiological and biochemical changes of eight indexes under high temperature stress of 44℃/33℃ (day/night) in an artificial climate box. The results showed that under high temperature stress, the heat damage index of the eight cultivars of Hydrangea showed a rising trend, and the order from high to low was ‘Inspiration’> ‘Tricolor’ > ‘Shakespeare’ > ‘Komachi’ > ‘Essar’ > ‘Elbtal’> ‘Stockings’ > ‘Corsage’. The relative electrical conductivity and malondialdehyde contents of the eight Hydrangea cultivars increased continuously. The contents of relative electrical conductivity and malondialdehyde in leaves of ‘Shakespeare’, ‘Tricolor’ and ‘Komachi’ increased the most, and the contents of relative electrical conductivity and malondialdehyde in leaves of ‘Essar’, ‘Corsage’ and ‘Elbtal’ increased the least. The activities of superoxide dismutase, peroxidase and catalase in the leaves of eight cultivars of Hydrangea were significantly affected by moderate high temperature. The content of soluble sugar changed little in the early stage of high temperature stress, but showed an overall increasing trend. The content of soluble protein increased, and the protein synthesis rates of ‘Tricolor’ and ‘Inspiration’ were the lowest, and the protein synthesis rates of ‘Corsage’ and ‘Elbtal’ were the highest. The content of proline increased, the osmotic regulation ability of ‘Stockings’ and ‘Corsage’ through free proline was significantly stronger than that of other cultivars, and the osmotic regulation ability of ‘Tricolor’ and ‘Inspiration’ through free proline was significantly weaker than that of other cultivars. The contents of soluble sugar, soluble protein and proline of osmotic regulation substances in eight cultivars of Hydrangea were all increased by high temperature stress to adapt to high temperature stress of 43℃/33℃. The fuzzy membership function was used to analyze the comprehensive order of high temperature resistance of 8 Hydrangea cultivars from high to low: ‘Shakespeare’ was the most high temperature resistant variety, followed by ‘Elbtal’, ‘Komachi’, ‘Stockings’, ‘Corsage’, ‘Inspiration’, ‘Essar’, and ‘Tricolor’ was the least high temperature resistant variety. This study provided a theoretical basis for the physiological and biochemical response mechanism of Hydrangea cultivars under high temperature stress and provided reference value for the application of Hydrangea cultivars under special site conditions.

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Differences in Ovary Development Between Nymphaea ‘Bull’s Eye’ and Nymphaea ‘King of Siam’ after Pollination
TANG Yuwei, LI Jiahui, MAO Liyan, HUANG Qiuwei, LONG Lingyun, YU Yanping, SU Qun
2022, 43 (4):  829-839.  doi: 10.3969/j.issn.1000-2561.2022.04.019
Abstract ( 31 )   HTML ( 3 )   PDF (2700KB) ( 28 )  

Nymphaea (water lily) is an aquatic flower that has been introduced in recent years in our country. In particular, double petal water lily are very popular and full of love and attention by water lily lovers and breeders. And it has been increasingly widely used in the field of aquatic garden landscapes. But in the process of breeding, breeders often encounter the situation of failed hybridization. This makes it hard for breeders to breed double flower. In order to study on the reason that double petal water lily is difficult to set fruit, we selected the more representative cultivar Nymphaea ‘King of Siam’ from double petal water lily as the experimental group, and the better fertile cultivar Nymphaea ‘Bull’s Eye’ as the control group. Firstly, the microstructure of ovaries at different stages after pollination was compared by paraffin section technique. Secondly, the stigmas and ovules were further observed by scanning electron microscope. Finally, the differences of gene expression between developing and abortive ovary were analyzed by RNA-Seq. The results showed that multicellular uniserial papillae were distributed on the stigma surface of the two water lily varieties, and a circle of grooves were formed at the junction between single cells. The number of papillae was large and closely arranged. We think this structure can more easily capture foreign pollen. Meanwhile, after 7 days of N. ‘Bull’s Eye’ pollination, most of the ovules developed into red seeds, 10 days later, the ovary expanded into fruit, and the seed coat changed from red to black to form mature seeds. On the other hand, after 7 days of pollination, no seeds were formed in N. ‘King of Siam’. However, some ovules in its ovary develop, and its epidermis turns red. The morphological characteristics are similar to the red ovules after 4 days of N. ‘Bull’s Eye’ pollination. Therefore, we speculate that a small number of ovules may have completed fertilization, but can not develop further. Than, the ovary was completely aborted after 10 days. Microstructural observation showed that there were significant differences in ovule development between the two varieties after 7 days of pollination. The ovules of N. ‘Bull’s Eye’ increased significantly, and the zygotes began to form embryos, while the nucellus in the ovules of N. ‘King of Siam’ shrank and the ovules gradually disappeared. After 10 days of pollination, the embryo of N. ‘Bull’s Eye’ began to develop and further changed to seed morphology. In additional, the enrichment analysis of differential genes showed that photosynthesis antenna protein, photosynthesis, porphyrin and chlorophyll metabolism, ribosome, starch and sucrose metabolism may be the key pathways affecting the development of waterlily ovary. Consequently, we speculate that the abortion of the ovary of N. ‘King of Siam’ may be due to the inhibition of its own photosynthesis, which affects the production of nutrients such as sucrose and starch.

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Plant Protection & Bio-safety
Effect of Rotation of Banana Varieties with Different Genetic Backgrounds on Controlling Fusarium Wilt
WANG Fang, ZENG Lisha, ZHOU Haiqi, CHEN Kangli, LYU Shun, XIA Ling, LIU Wenqing, ZHANG Keheng, TANG Qilu, LIU Jianping
2022, 43 (4):  840-852.  doi: 10.3969/j.issn.1000-2561.2022.04.020
Abstract ( 40 )   HTML ( 2 )   PDF (2355KB) ( 30 )  

Banana is rich in germplasm resources. Different banana varieties have different tolerance to each physiological race of Fusarium wilt. Using banana varieties with large differences in genetic background and different resistance for rotation may achieve the effect of preventing and controlling banana Fusarium wilt. In this study, the common cultivated banana types in South China were selected as the research materials, including Cavendish (AAA), Pisang Awak (ABB), Silk (AAB), Gongjiao (AA). Combined with production application, the varieties with different genetic backgrounds and Fusarium wilt resistance were screened through the analysis of genetic diversity of 24 banana varieties. Then, the control effect of rotation modes with different genetic background and Fusarium wilt resistance was studied, and the high-efficiency cultivation mode was selected. 29 primer pairs, which could produce distinct and polymorphic bands, were chosen for SRAP analysis. The results showed that its similarity coefficients ranged from 0.1 to 1.0 and thus a bigger genetic distance, and 24 varieties were clustered into 6 groups at the similarity coefficient of 0.8, which indicated that SRAP technique could be used as a good tool to study bananas’ genetic relationships, and the analysis results showed that there was a certain genetic differentiation in cavendish (AAA), especially the disease-resistant varieties. Then, five resistant cultivars belonging to different genetic branches, ‘Fenza 1’ (group 1), ‘Haigong’ (group 2), ‘Nongke 1’ (group 5), ‘Kangku 1’ (group 5) and ‘Nantianhuang’ (group 5) were screened out to study the pattern of banana rotation by investigating the number of F. oxysporum in rhizosphere soil and the incidence rate. The statistical results showed that rotated ‘Fenza 1’ ‘Haigong’ ‘Kangku 1’ and ‘Nantianhuang’ on the banana field of continuous cropping ‘Nongke 1’ for one year, the number of F. oxysporum in rhizosphere soil of ‘Fenza 1’ and ‘Haigong’ decreased significantly, while the number of F. oxysporum in rhizosphere soil of ‘Kangku 1’ and ‘Nantianhuang’ decreased but the difference was not significant. The incidence of Fusarium wilt of ‘Nongke 1’ in the rotation treatment group was reduced relative to continuous cropping, and the Fusarium wilt incidence rate of two rotation mode, ‘Nongke 1’ - ‘Fenza 1’ one year - ‘Nongke 1’ one year and ‘Nongke 1’ - ‘Haigong’ one year - ‘Nongke 1’ one year decreased significantly. So reasonable rotation of resistant varieties with different genetic backgrounds can effectively reduce the number of F. oxysporum in soil and the incidence rate of Fusarium wilt of banana, which can achieve the effect of disease prevention.

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Resistance Mechanism of Cassava Cultivars to Tetranychus urticae Based on Gene Expression Characteristics of Cyanogenic Glycoside Degradation Pathway
WU Mufeng, LIANG Xiao, CHEN Qing, WU Chunling, LIU Ying, LIU Xiaoqiang, HAN Zhiling
2022, 43 (4):  853-861.  doi: 10.3969/j.issn.1000-2561.2022.04.021
Abstract ( 25 )   HTML ( 1 )   PDF (1508KB) ( 26 )  

In order to explore the resistance mechanism of cassava varieties based on the gene expression characteristics of cyanogen glycoside degradation pathway to Tetranychus urticae, this study used mite-resistant cassava cultivars ‘C1115’ ‘Myanmar’ ‘SC9’ and mite-susceptible cassava cultivars ‘SC205’ ‘Mianbao’ ‘BRA900’ as materials to analyze the cyanogen glycoside degradation pathway genes related to plant insect resistance and the biochemical enzymes changes in the leaves of different parts (top, middle and bottom) when those mites fed for 1 d and 4 d, respectively. The results showed that the expression of α-HNL in the top and middle leaves of mite-susceptible cassava varieties decreased significantly with the extension of the mite infestation time. In the leaves of different parts of mite-resistant cassava varieties, the expression level of α-HNL increased significantly with the extension of the mite infestation time, and the increasing trend was more significant in the middle and bottom leaves. The expression of β-glu in the leaves of different parts of the mite-resistant cassava varieties was very low. It is difficult to compare the changes in the expression level of this gene after different cassava varieties and different parts of the leaves are damaged by mites, but it is not detectable. Among a small number of samples, the proportion of mite-resistant cassava varieties was more than that of mite-susceptible cassava varieties. The results of further enzyme activity analysis showed that after the mite-resistant cassava varieties were infested by mites, as time passed, the enzyme activity of α-HNL encoded by the degradation pathway gene α-HNL showed a tendency to gradually increase or remain unchanged, and the rising trend of the middle and bottom blades was more significant. In the mite-susceptible cassava varieties, with the extension of the mite infestation time, the enzyme activity of α-HNL showed a trend of gradual decrease or first increase and then decrease. The β-GLU enzyme activity encoded by the β-glu gene showed low levels in different cassava varieties, which may be related to the low expression of the corresponding encoded gene. But overall, the degrading enzymes α-HNL and β-GLU encoded by the two genes of the degradation pathway in different leaf tissues of mite-resistant cassava were also significantly higher than that of mite-susceptible cassava. This study initially revealed that cyanogenic glycoside degradation genes and enzymes may be related to the resistance of cassava to Tetranychus urticae after different cassava varieties were infested by mites for different periods of time.

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Comparison of Damage Grades in Laboratory and Population Fitness of Spodoptera frugiperda (Lepidoptera: Noctuidae) on Different Maize Varieties
ZHOU Xiaojuan, LYU Baoqian, LU Hui, TANG Jihong, LIN Nanfang
2022, 43 (4):  862-869.  doi: 10.3969/j.issn.1000-2561.2022.04.022
Abstract ( 51 )   HTML ( 4 )   PDF (1088KB) ( 33 )  

Spodoptera frugiperda (J. E. Smith) is a migratory agricultural pest that happened in China in 2019 migrated from Myanmar. It has the characteristics of wide feeding range and strong migration, adaptability and reproductive ability. Breeding of resistant varieties is an important agricultural control measure, evaluating the damage grades of different maize varieties has a guiding effect on the subsequent use of multi-omics analysis to screen out specific resistance genes and cultivate resistant varieties. In this paper, waxy corn ‘Sunuo No.6’, dent corn ‘Xianyu 335’, sweet corn ‘Huangguan’, and 2 semident corns ‘LP259’ and ‘Zhengdan 958’ were selected to evaluate the damage grades of S. frugiperda under indoor conditions, and establish a population life table of the S. frugiperda. The damage grade of newly hatched S. frugiperda larvae to the five maize varieties ranged from high to low was ‘Huangguan’ (3.55±0.41) > ‘LP259’ (2.88±0.29) > ‘Xianyu 335’ (2.39±0.25) > ‘Zhengdan 958’ (2.15±0.25) > ‘Sunuo No.6’ (1.79±0.19). The adult preoviposition period of ‘Huangguan’ was the longest, which was (2.90±0.55) d. Larval duration was significantly different (P<0.05), the larval duration of ‘Xianyu 335’ was the shortest, which was (12.45±0.13) d. The weight of pupa of ‘LP259’ was the heaviest, which was (169.83±3.20) mg, both female and male adult fed on ‘LP259’ had the longest longevity, which was (10.36±0.58) d and (8.52±0.47) d, respectively. The survival rate of larval duration was not significantly different. The pupation rate and ratio of female of ‘Sunuo No.6’ were the highest, which was (83.10±3.29)% and (64.66±0.25)%, respectively. The eclosion rate of ‘LP259’, which was (95.24±1.99)%. According to the life table, the mean generation time of ‘Xianyu 335’ was the longest, which was (28.21±0.58) d. The net reproductive rate, intrinsic rate of increase and finite rate of increase of ‘Zhengdan 958’ were the lowest, which were 144.50±16.73, 0.1823±0.0023 and 1.1999±0.0028. The newly hatched S. frugiperda larvae prefered to feed on sweet corn ‘Huangguan’, and the comprehensive population life table to S. frugiperda in the population fitness of ‘Zhengdan 958’ was the lowest. It showed that ‘Zhengdan 958’ had the best tolerance to the S. frugiperda. The results of this study would provide a reference for the control of S. frugiperda and identification of potentially resistant species in Hainan.

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