Dioscorea Opposita Research Articles

Regulatory effects of yam (Dioscorea opposita Thunb.) glycoproteins on energy metabolism in C2C12 and 3T3-L1 cells and on crosstalk between these two cells.

Controlling energy and regulating metabolism have been key strategies in the treatment of metabolic disorders such as obesity. Yam glycoprotein (Y-Gly) is a polysaccharide-protein complex extracted from Chinese yam that has beneficial effects on glucose and lipid metabolism. This study aimed to investigate the role of Y-Gly in regulating energy metabolism in C2C12 and 3T3-L1 cells. Y-Gly was subjected to extraction and chemo-profiling. Staining methods, assay kits, Western Blot and transcriptomics were mainly used to determine the role of Y-Gly. Additionally, the study sought to examine the impact of Y-Gly on white adipose browning in 3T3-L1 cells, employing a cell co-culture technique. Y-Gly promoted myotube differentiation in C2C12 myoblasts, increased cellular glucose consumption, promoted ATP synthesis and mitochondrial biogenesis, and played an active role in energy expenditure and glycolipid metabolism related pathways such as AMPK and MAPK. The introduction of Y-Gly inhibited lipid accumulation after lipogenesis in 3T3-L1 cells, facilitated induction of white adipose browning related proteins such as PPARγ and UCP1 expression, and the effect was more significant after cell co-culture. Y-Gly regulates glucose and lipid metabolism by activating the key proteins in the aforementioned pathways, and plays a role in energy metabolism regulation through crosstalk between muscle and adipose tissues. This suggests a possible role of Y-Gly in metabolism-related diseases.

Multi-level fingerprinting and immune activity evaluation for polysaccharides from Dioscorea opposita Thunb.

To establish the quality control method of Dioscorea opposita Thunb., the multi-level fingerprinting of polysaccharides was established and the relationship between fingerprint and immune activity was analyzed. The two molecular weight segments Mw1 (1.38 × 105–1.63 × 106 Da) and Mw2 (3.27 × 103–4.37 × 103 Da), thirteen infrared absorption peaks (3399.26 cm−1, 2929.32 cm−1, 1631.78 cm−1, 1400.39 cm−1, 1351.80 cm−1, 1123.58 cm−1, 1024.76 cm−1, 931.53 cm−1, 854.76 cm−1, 760.43 cm−1, 708.14 cm−1, 616.47 cm−1, and 526.78 cm−1), and four monosaccharides (Man, Rha, GalA, and Glc) were used to evaluate the quality of Dioscorea opposita Thunb. The molecular weight fragments of Mw1, FT-IR absorption peaks of 1631.78 cm−1, and two monosaccharides (Man and Glc) would be used to identify Dioscorea opposita Thunb. polysaccharide (DOP) from different origins. The relationship of spectrum-effect showed that polysaccharides with features such as higher Mw1, a lower peak height of 1631.78 cm−1, higher content of Man, and lower content of Glc exerted stronger immune activity. In conclusion, this study established a polysaccharide-based quality evaluation method for Dioscorea opposita Thunb. and explored the relationship between polysaccharide fingerprints and in vitro immune activity, which provided a basis for further research on Dioscorea opposita Thunb.

The metabolic profiling of Chinese yam fermented by Saccharomyces boulardii and the biological activities of its ethanol extract in vitro

Chinese yam (Dioscorea opposita Thunb.), as one of the medicinal and edible homologous plants, is rich in various nutrients and functional factors. In this study, Chinese yam fermented by Saccharomyces boulardii was performed to investigate its bioactive components and metabolic profile. And then, the main bioactive components and biological activities of fermented Chinese yam ethanol extract (FCYE) were evaluated. Results showed that there were 49 up-regulated metabolites and 52 down-regulated metabolites in fermented Chinese yam compared to unfermented Chinese yam. Besides, corresponding metabolic pathways analysis initially revealed that the distribution of bioactive substances was concentrated on alcohol-soluble small molecular substances. Ulteriorly, the total polyphenol content and the total flavonoid content in FCYE were significantly increased, and the corresponding antioxidant and immunomodulatory activities in vitro were also significantly enhanced. Our study provided a new reference for the comprehensive utilization of Chinese yam and laid a theoretical foundation for the development and application of natural probiotic-fermented products.

Molecular Insights into the Defense of Dioscorea opposita Cultivar Tiegun Callus Against Pathogenic and Endophytic Fungal Infection Through Transcriptome Analysis.

Dioscorea opposita cultivar Tiegun is an economically important crop with high nutritional and medicinal value. Plants can activate complex and diverse defense mechanisms after infection by pathogenic fungi. Moreover, endophytic fungi can also trigger the plant immune system to resist pathogen invasion. However, the study of the effects of endophytic fungi on plant infection lags far behind that of pathogenic fungi, and the underlying mechanism is not fully understood. Here, the black spot pathogen Alternaria alternata and the endophytic fungus Penicillium halotolerans of Tiegun were identified and used to infect calli. The results showed that A. alternata could cause more severe membrane lipid peroxidation, whereas P. halotolerans could rapidly increase the activity of the plant antioxidant enzymes superoxide dismutase, peroxidase, and catalase; thus, the degree of damage to the callus caused by P. halotolerans was weaker than that caused by A. alternata. RNA sequencing analysis revealed that various plant defense pathways, such as phenylpropanoid biosynthesis, flavonoid biosynthesis, plant hormone signal transduction, and the mitogen-activated protein kinase signaling pathway, play important roles in triggering the plant immune response during fungal infection. Furthermore, the tryptophan metabolism, betalain biosynthesis, fatty acid degradation, flavonoid biosynthesis, tyrosine metabolism, and isoquinoline alkaloid biosynthesis pathways may accelerate the infection of pathogenic fungi, and the ribosome biogenesis pathway in eukaryotes may retard the damage caused by endophytic fungi. This study lays a foundation for exploring the infection mechanism of yam pathogens and endophytic fungi and provides insight for effective fungal disease control in agriculture.

Effects of Dioscorea opposita mucilage addition on the physicochemical properties, texture, and stability of set-type yogurt

Dioscorea opposita mucilage (DOM), a polysaccharide-protein polymer with antioxidant activity, can be served as a natural ingredient in nutritional yogurts. The effects of DOM addition at different concentrations (2%, 4%, 6%, 8%, 10% and 12% w/w) on the total number of lactic acid bacteria, pH, titratable acidity, syneresis, viscosity, texture, color and sensory evaluations of full-fat yogurts and skimmed yogurts during 21 days storage at 4 °C were investigated. The results suggested that DOM could improve the growth of LAB, strengthen the network and gelation of yogurt, and thicken the dispersion, which led to the significant decrease in pH and cohesiveness, and drastic increase in the syneresis, firmness and adhesiveness. Additionally, sensory evaluation revealed that the overall liking scores of full-fat yogurts (8.1–8.7) were higher than those of skimmed yogurts (7.9–8.3), which exhibited strong correlations with firmness and viscosity of set-type yogurts. Although DOM addition affected the sensory undesirably, such as creaminess, the thickness and overall liking were improved, especially for the skimmed yogurts. In summary, 8% w/w DOM could effectively improve the texture, quality and stability of set-type yogurts. This study provides new applications in functional dairy products and promotes the value of the by-products of D. opposita.

Phytochemical analysis and cardiovascular protective effect of four herbal medicines with functional food properties (Four Huaiqing Chinese Medicine)

Rehmannia glutinosa Libosch, Achyranthes bidentata Bl. (A. bidentata), Dioscorea opposita Thunb, and Chrysanthemum morifolium Ramat (C. morifolium) are known as the ‘Four Huaiqing Chinese Medicine’ in China, which are used as materials for functional foods. In this paper, the constituents of Four Huaiqing Chinese Medicine were identified by UPLC-Q-TOF-MS/MS, and flavones and aromatic compounds are mainly responsible for these herbs. Moreover, C. morifolium exhibited the most significant effect in cobalt chloride-induced HUVECs injury, which could decrease cell apoptosis and the overproduction of ROS, lactic dehydrogenase (LD) and pyruvic acid, and increase the migration capacity of cells. Meanwhile, A. bidentata exhibited the most significant effect in isoproterenol-induced H9C2 cell injury, which could decrease the levels of ROS overproduction, BNP, NO, LD and pyruvic acid. Western blot revealed that C. morifolium and A. bidentata also could decrease the levels of bax/bcl-2 ratio, cleaved caspase-3, cytochrome c, HIF-1ɑ, GLUT1, HKII and PFKFB3, respectively.

Effect of electrohydrodynamic (EHD) drying on active ingredients, textural properties and moisture distribution of yam (Dioscorea opposita)

This paper systematically investigates the changes in material properties during electrohydrodynamic (EHD) drying, the discharge characteristics of the EHD system as well as the active ingredients, textural properties (hardness, adhesiveness, etc.) and moisture distribution of yam under EHD, air drying and hot air drying were investigated. The results showed that the active particles and the ionized wind generated during the discharge process of the electrohydrodynamic drying device had a significant effect on the drying. Compared to thermal drying, 21 kV drying resulted in the most complete cellular structure, the best internal bound water content as well as textural properties of yam. It played a positive role in the retention of internal nutrients in yam, and the total phenol and allantoin contents were increased by 25.74% and 81.99%, respectively. These results elucidate the advantages of electrohydrodynamic drying in yam drying and provide a reference for the application of EHD in drying.

α-pyrone derivatives from the endophytic Fusarium sp. L33 isolated from Dioscorea opposita

Two new α-pyrone derivatives, fusaripyrones C and D (1 and 2), along with six known compounds, namely phomapyrone C (3), fusarilactone A (4), pleospyrone D (5), 5-hydroxy-7-(2′-hydroxypropyl)-2-methyl-chromone (6), phenylacetic acid (7), and p-hydroxyphenylacetic acid (8) were isolated from Fusarium sp. L33, an endophytic fungus isolated from the leaves of Dioscorea opposita. Their structures were elucidated by NMR spectra, HRESIMS, optical rotation experiments and single-crystal X-ray diffraction analysis. Compounds 2, 3, and 6 were evaluated for their cytotoxic activity against five selected human tumor cell lines.

A Frontier Review of Nutraceutical Chinese Yam.

Yams are the edible subterranean rhizomes, or tubers, of plants from the genus Dioscorea. There are approximately 600 species of yam plants in the world, with more than 90 of these growing in East Asia. One particular species, Dioscorea opposita Thunb., is highly praised as "the Chinese yam". This distinction arises from millennia of storied history, both as a nutritional food source and as a principal ingredient in traditional Chinese medicine. Among the many cultivars of Dioscorea opposita Thunb., Huai Shanyao has been widely regarded as the best. This review surveyed the historical background, physiochemical composition, applications as food and medicine, and research prospects for the Chinese yam. Modern science is finally beginning to confirm the remarkable health benefits of this yam plant, long-known to the Chinese people. Chinese yam promises anti-diabetic, anti-oxidative, anti-inflammatory, immunomodulatory, anti-hyperlipidemic, anti-hypertensive, anti-cancer, and combination treatment applications, both as a functional food and as medicine.

Response of the Symbiotic Microbial Community of Dioscorea opposita Cultivar Tiegun to Root-Knot Nematode Infection.

Yam is an important medicinal and edible dual-purpose plant with high economic value. However, nematode damage severely affects its yield and quality. One of the major effects of nematode infestations is the secondary infection of pathogenic bacteria or fungi through entry wounds made by the nematodes. Understanding the response of the symbiotic microbial community of yam plants to nematodes is crucial for controlling such a disease. In this study, we investigated the rhizosphere and how endophytic microbiomes shift after nematode infection during the tuber expansion stage in the Dioscorea opposita Thunb. cultivar Tiegun. Our results revealed that soil depth affected the abundance of nematodes, and the relative number of Meloidogyne incognita was higher in the diseased soil at a depth of 16 to 40 cm than those at a depth of 0 to 15 and 41 to 70 cm. The abundance of and interactions among soil microbiota members were significantly correlated with root-knot nematode (RKN) parasitism at various soil depths. However, the comparison of the microbial α-diversity and composition between healthy and diseased rhizosphere soil showed no difference. Compared with healthy soils, the co-occurrence networks of M. incognita-infested soils included a higher ratio of positive correlations linked to plant health. In addition, we detected a higher abundance of certain taxonomic groups belonging to Chitinophagaceae and Xanthobacteraceae in the rhizosphere of RKN-infested plants. The nematodes, besides causing direct damage to plants, also possess the ability to act synergistically with other pathogens, especially Ramicandelaber and Fusarium, leading to the development of disease complexes. In contrast to soil samples, RKN parasitism specifically had a significant effect on the composition and assembly of the root endophytic microbiota. The RKN colonization impacted a wide variety of endophytic microbiomes, including Pseudomonas, Sphingomonas, Rhizobium, Neocosmospora, and Fusarium. This study revealed the relationship between RKN disease and changes in the rhizosphere and endophytic microbial community, which may provide novel insights that help improve biological management of yam RKNs.

Identification of WRKY gene family in Dioscorea opposita Thunb. reveals that DoWRKY71 enhanced the tolerance to cold and ABA stress.

WRKY transcription factors constitute one of the largest plant-specific gene families, regulating various aspects of plant growth, development, physiological processes, and responses to abiotic stresses. This study aimed to comprehensively analyze the WRKY gene family of yam (Dioscorea opposita Thunb.), to understand their expression patterns during the growth and development process and their response to different treatments of yam and analyze the function of DoWRKY71 in detail. A total of 25 DoWRKY genes were identified from the transcriptome of yam, which were divided into six clades (I, IIa, IIc, IId, IIe, III) based on phylogenetic analysis. The analysis of conserved motifs revealed 10 motifs, varying in length from 16 to 50 amino acids. Based on real-time quantitative PCR (qRT-PCR) analysis, DoWRKY genes were expressed at different stages of growth and development and responded differentially to various abiotic stresses. The expression level of DoWRKY71 genes was up-regulated in the early stage and then down-regulated in tuber enlargement. This gene showed responsiveness to cold and abiotic stresses, such as abscisic acid (ABA) and methyl jasmonate (MeJA). Therefore, further study was conducted on this gene. Subcellular localization analysis revealed that the DoWRKY71 protein was localized in the nucleus. Moreover, the overexpression of DoWRKY71 enhanced the cold tolerance of transgenic tobacco and promoted ABA mediated stomatal closure. This study presents the first systematic analysis of the WRKY gene family in yam, offering new insights for studying WRKY transcription factors in yam. The functional study of DoWRKY71 lays theoretical foundation for further exploring the regulatory function of the DoWRKY71 gene in the growth and development related signaling pathway of yam.

Structural characterization and immunomodulatory activity of a polysaccharide from Dioscotea opposita

The purified polysaccharides fraction, DOP-2, was prepared from Dioscorea opposita Thunb (D. opposita). This study combined in vitro and in vivo experiments to comprehensively investigate the index changes in RAW264.7 cells and immunocompromised mice under DOP-2 intervention, aiming to elucidate the potential mechanisms of immunomodulatory effects of DOP-2. DOP-2 (10 ∼ 500 μg/mL) significantly elevated the levels of NO, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) factors secreted by RAW264.7 cells, and restored the body weight of immunosuppressed mice and improve the degree of injury to the immune organ index, resulting in significant immunomodulatory effects. Notably, DOP-2 promoted the production of short-chain fatty acids (SCFAs) in immunosuppressed mice and modulated the composition of their gut microflora. These findings highlight the potential benefits of DOP-2 therapy in improving immune function and gut health, and will provide a theoretical basis for the application of D. opposita polysaccharides as an immunomodulatory adjuvant.

Unveiling the impact of harvest time on Dioscorea opposita Thunb. cv. Tiegun maturity by NMR-based metabolomics and LC-MS/MS analysis.

Dioscorea opposita Thunb. cv. Tiegun maturity (DM) is an important factor influencing its quality. However, there are few studies on the impact of harvest time on its maturation. In the present study, a NMR-based metabolomics approach was applied to investigate the dynamic metabolic changes of D. opposita Thunb. cv. Tiegun at six different harvest stages: stage 1 (S1), stage 2 (S2), Stage 3 (S3), stage 4 (S4), stage 5 (S5) and stage 6 (S6). Principal component analysis showed distinct segregation of samples obtained from S1, S2 and S3 compared to those derived from S4, S5 and S6. Interestingly, these samples from the two periods were obtained before and after frost, indicating that frost descent might be important for DM. Eight differential metabolites responsible for good separation of different groups were identified by the principal component analysis loading plot and partial least squares-discriminant analysis. In addition, quantitative analysis of these metabolites using liquid chromatography-tandem mass spectrometry determined the effects of harvest time on these metabolite contents, two of which, sucrose and allantoin, were considered as potential biomarkers to determine DM. The present study demonstrated that NMR-based metabolomics approach could serve as a powerful tool to identify differential metabolites during harvesting processes, also offering a fresh insight into understanding the DM and the potential mechanism of quality formation. © 2024 Society of Chemical Industry.

Comparison of water mobility and distribution in Dioscorea opposita Thunb. cv. Tiegun during hot‐air and microwave drying processes

SummaryLow‐field nuclear magnetic resonance (LF‐NMR) was employed to investigate changes in mobility as well as distribution of water in yam slices in the course of hot‐air drying (HAD) and microwave drying (MD) processes. Moisture content, effective moisture diffusivity, and water activity were also analysed. According to the results, a total of three water fractions with various T2 relaxation times were observed in fresh yam slices: T21 (0.9–2.6 ms), T22 (30–130 ms), and T23 (130–1245 ms). With the increment in drying temperature and the rise of microwave power in the course of drying, there was a significant decline in the transverse relaxation time and peak amplitude of T23. The overall moisture content exhibited a good correlation with Atotal during both HAD and MD processes, with coefficients equivalent to 0.9194 and 0.9024, respectively. With rising drying temperature and microwave power, there was a corresponding rise in effective moisture diffusivity. In comparison with HAD, the rate of water diffusion and evaporation in yam slices dried by MD was higher. Taking into account the drying efficiency and moisture state, MD was suggested as a preferable drying technology for dehydrating yam slices.

Identification and pathogenicity of Colletotrichum truncatum causing yam anthracnose – A new record in China

Yam (Dioscorea spp.) is a significant tuber crop. In October 2022, yam (Dioscorea opposita Thunb.) leaves exhibiting typical anthracnose symptoms were observed at the Yam Germplasm Resource Nursery of Wen County, Jiaozuo City, Henan Province, China. The disease incidence was recorded at 92.05%. The symptoms manifested as brown to dark brown circular or irregular large spots on the leaves, some of which displayed noticeable irregular concentric rings. A total of 23 isolates were obtained, with JCHN023-1 and JCHN003 isolates being the representative. The pathogen was successfully re-isolated from lesions of inoculated leaves, fulfilling Koch's postulates. Morphologically, the conidia appeared colorless, crescent-shaped, circular blunt at both ends, and measured (15.2-) 18.2–30 (−34.1) × (2.1-) 2.3–3.9 (−4.2) μm in length (average = 24.1 × 3.1 μm) without septa. The setae were black-brown and exhibited 1-4 septa. Subsequently, a multigene phylogenetic analysis, involving internal transcribed spacer (ITS), partial actin (ACT), chitin synthase 1 (CHS-1) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), identified the fungus as Colletotrichum truncatum. Inoculation of detached leaves from 10 varieties of D. opposita confirmed their broad-spectrum pathogenicity to yam. This represents the first report of yam anthracnose caused by C. truncatum in China and provides a theoretical foundation for yam anthracnose prevention and control.

Allantoin Derived From Dioscorea opposita Thunb Ameliorates Cyclophosphamide-Induced Premature Ovarian Failure in Female Rats by Attenuating Apoptosis, Autophagy and Pyroptosis

Allantoin Derived From Dioscorea opposita Thunb Ameliorates Cyclophosphamide-Induced Premature Ovarian Failure in Female Rats by Attenuating Apoptosis, Autophagy and Pyroptosis

Preparation, structure characterization, and in vitro bioactivity of yam starch-polyphenol complex

Abstract Background Chinese yam (Dioscorea opposita Thunb.), with medicinal and edible properties, holds a significant position in both traditional medicine and food in China. It is rich in resistant starch (RS), which imparts various beneficial effects, including anticonstipation, regulation of blood lipids, and prevention of gastric ulcers. However, the resistance of native yam starch to digestion diminishes during cooking, necessitating suitable modifications. Objective In this article, yam starch was complexed with five different polyphenols to create RS5. The goal was to explore how these diverse polyphenols influence the physicochemical characteristics and bioactivities associated with yam RS. Method Yam starch-polyphenol complexes, involving five different polyphenols, namely, magnolol (MAG), ferulic acid (FA), resveratrol (RES), apple polyphenols (APs), and green tea polyphenols (GTPs), were prepared. The investigation encompassed the assessment of physicochemical properties, structural traits, in vitro cholate binding capacity, and in vitro antidigestive effects of these complexes. Results The results highlight the pronounced affinity of MAG for yam starch, followed by FA. Fourier transform infrared spectroscopy reveals that starch-polyphenol binding primarily involves noncovalent interactions. X-ray diffraction analysis discloses V-type crystal structures in YS-MAG, YS-APs, and YS-GTPs complexes. The incorporation of polyphenols reduces the thermal stability of starch while enhancing its in vitro cholate binding capacity, restraining starch digestion, and elevating RS content. Notably, YS-FA exhibits an impressive RS content of up to 54.15%. In addition, YS-MAG and YS-FA significantly enhance the production of short-chain fatty acids. These findings deepen our comprehension of the interplay between yam starch and polyphenols, offering valuable insights for the development of novel food products with enhanced health benefits.

Exogenously applied abscisic acid accelerates wound healing of Chinese yam tubers (Dioscorea opposita) through promoting suberin polyphenolics biosynthesis

Water loss, nutrient elution and pathogen attacks caused by mechanical wounding are the primary sources of postharvest loss of fruit and vegetables. Continuously increasing information has unraveled that abscisic acid (ABA) can accelerate wound healing of fruit and vegetables via stimulating suberin polyphenolics (SPP) biosynthesis, whereas the effect of ABA in wound healing of Chinese yam tubers remains unclear. The treatment of ABA and fluridone (FLD, an inhibitor of ABA biosynthesis) on postharvest wound healing of yam tubers was investigated in this study. The results showed that ABA treatment facilitated wound healing process of yam tubers, representing by the reduced weight loss and relative electrolyte leakage (REL). ABA enhanced the expression levels of phenylalanine ammonialyase (PAL), cinnamic acid 4-hydroxylase (C4H) and 4-coumarate-CoA ligase (4CL), as well as the corresponding enzyme contents and activities. Correspondingly, the contents of major monomers such as ferulic acid, caffeic acid and p-coumaric acid also increased. Simultaneously, ABA could improve the expression of peroxidase (POD), the enzyme content and activity, as well as hydrogen peroxide (H2O2) production, which might contribute to the polymerization of SPP and lignin. Inversely, inhibition of ABA production by FLD application displayed an opposite effect to ABA treatment. These results demonstrate that application of ABA stimulated wound healing of Chinese yam tubers via improving the gene expressions of relevant enzymes, their contents and activities, so that maintain high quality of postharvest yam tubers.

Antifatigue effects and antioxidant activity in polysaccharide fractions from Chinese yam bulbils.

Polysaccharides are the principal component in Chinese yam (Dioscorea opposita Thunb.) bulbils. The properties and antifatigue of polysaccharides from yam bulbils (PYB) were identified and compared. Their molecular weights (PYB-1 and PYB-2) were approximately 145 and 11 kDa, respectively, with active β-configurations. Meanwhile, the antifatigue activities of PYBs were tested in mice via exhaustive swimming tests (EST). The EST results indicated that PYB-1 and PYB-2 significantly prolonged swimming time in mice (p < .05). Associated with this increase was a rise in hepatic glycogen content and antioxidant enzyme (superoxide dismutase (SOD), glutathione peroxidase (GSH-Px)) activity, along with a decline in blood urea nitrogen, lactic acid, and malondialdehyde levels. The results showed that molecular weight might contribute to the antifatigue effects of PYBs. Additionally, antioxidant tests showed that PYB-1 had stronger free-radical scavenging activity than PYB-2. Taken together, the findings indicated that PYBs exhibited effective antifatigue and antioxidant activities providing additional evidence supporting the use of PYBs as functional food ingredients for relieving fatigue.

First Report of Anthracnose on Dioscorea opposita Caused by Colletotrichum siamense in Guangdong province in China.

Yam is the world's fourth most important tuber crop, after cassava, potato, and sweet potato in the world, the cultivation area of yam from the Food and Agriculture Organization of the United Nations Statistics Division database (FAOSTAT) is about 8,831,037 ha in 2020. Chinese yam (Dioscorea opposita Thunb.) is an economically important root crop throughout China due to its high economic and medicinal value. South China including Guangdong and Guangxi provinces is one of the important production districts of Chinese yam with economic value. A disease affecting the leaves was observed on yam leaves in August 2021 with an incidence of 20 to 90% in Guangdong and Guangxi provinces. Symptoms start as pinpoint lesions on yam leaves which enlarged to oval spots and large irregular spots. The spots were brown and surrounded by a chlorotic halo with sunken cavities, which are typical symptoms of anthracnose. To identify the causal agent, 9 symptomatic leaves from 3 different districts were collected in Guangdong and Guangxi provinces. Leaf samples were disinfested with 1% NaOCl for 3 min, and cultured on potato dextrose agar (PDA) at 28 °C for 3 days week. 9 single-spore isolates were recovered from each PDA medium. Colonies on PDA were grayish white with bright orange conidial spore masses. Fungal mycelia were hyaline, septate, and branched. Conidia were born on a long conidiogenous cell, straight, hyaline and cylindrical with rounded ends, 5.3 to 6.8×15.2 to 21.3μm (n = 50). Appressoria were dark, smooth-walled, oval in shape. The isolates were morphologically identified as Colletotrichum sp. (Weir et al. 2012). 3 strains were used for the pathogenicity test, 5 plants at creeping stage were inoculated with each isolate separately and 3-5 leaves of each plant were inoculated. Fresh wounds were made with a sterile needle on the healthy surface of yam leaves and each leaf was covered with a piece of cotton drenched with conidial suspension (106 conidia/mL) from each isolate. Control seedlings were inoculated identically except sterile water was used. Inoculated plants were placed in a moisturizing light incubator at 25℃ and 80% humidity under a 12-h light/dark cycle for 7 days and examined daily to monitor disease symptom development. Small round brown spots were observed at the inoculation sites 3 days after the inoculation and eventually became large brown lesions. No symptoms wre observed in the water-inoculated plants. A Colletotrichum sp. strain based on morphology was reisolated from inoculated leaves, fulfilling Koch's postulates. For molecular identification, the direct colony PCR method (Lu et al. 2012) was used to amplify the internal transcribed spacer (ITS) region of ribosomal DNA, calmodulin (Cal), tubulin (Tub) and Apmat loci of three isolates using primer pairs of ITS4/ITS5, CL1C/CL2C, T1/T2 and AM-F/AM-R (Sharma et al. 2015). A phylogenetic tree derived from a maximum likelihood analysis of a concatenated alignment of ITS, Cal, Tub and ApMAT sequences was created. The accession numbers of the three isolates YamZJCS, YamSXCS and YamYLCS used in this study were OP128056-OP128058 for ITS, OP128059-OP128061 for ApMAT，OP128062-OP128064 for Cal and OP128065-OP128067 for Tub. The sequences of the 3 isolates were aligned with related species of Colletotrichum (Sharma et al. 2015). Analyses based on concatenated data sets of 4 genes showed that the sequences had high levels of identity to that of the C. siamense strains. According to both morphological and sequence analyses, the pathogen was identified as C. siamense. There were reports of anthracnose on yam caused by Colletotrichum sp. in Guangxi (Zhu et al. 2007), Hainan (Lin et al. 2018) and Jiangsu (Han et al. 2020) provinces in China. To our knowledge, this is the first report of anthracnose on D. opposita caused by C. siamense in Guangdong province in China.