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• Biological Characteristics and Biocontrol of Fusarium oxysporumf. sp. cubense Causing PanamaDiseaseon Banana

  Le Thi Loan, Nguyen Tuan Vu, Vu Dang Toan, Nguyen Duc Huy

  Date Received: 10-05-2023 / Date Accepted: 29-06-2023

   Abstract PDF (VIETNAMESE)

  Panamadisease is a letal fungal diasese caused by the soil-born fungus Fusarium oxysporumf. sp. cubense(Foc). This study aimedto identify isolated Focstrainsandexaminetheir biological characteristics and the antagonistic effects of some antagonistic microbial agents against Fusarium oxysporumf. sp. cubenseisolated from collected samples. The morphological characteristic of the fungus Fusarium oxysporumf. sp. cubensetropical race 4(Foc-TR4) cultured on PDA medium varied from white to pale purple, with no spore cluster formed. There were two types of asexual spores: microconidia and macroconidia. Microconidiawereusually without septum, ovoid, oval, and 1.0-2.1 × 2.2-3.0µm in size. Macroconidiawerewith 2-5 septa, mostly with 2-3 septa, crescent-shaped with average size varying from 2.6-3.2 × 9.2-35.5µm. The pathogen Foc-TR4grew at temperatures from 15-35C. The optimum temperature for fungal growth was 25C. The appropriate pH for Foc-TR4fungus to grow and develop well was 6.0-7.0. The diameter of the fungal colony rangedfrom 74.8-77.9mm. The results of evaluating the antagonistic effect against Foc-TR4on PDA medium showed that Trichoderma asperellumgave the highest inhibitory effect (74.52%), followed by the Chaetomium globosumC10 at 67.35% and Bacillus velezensisYB9 at 61.33%. The results of this study provide more information about Foc-TR4strain and the biological controlof banana wiltdisease.

• Screening Streptomyces sp.  Strains for Antagonistic Activity against Phytopathogenic Alternaria alternata

  Dang Thi Thanh Tam, Nguyen Thi Thu, Nguyen Vu Phuong Thao, Nguyen Van Giang

  Date Received: 05-12-2025 / Date Accepted: 04-01-2026 / Date Published: 29-04-2026

   Abstract PDF (VIETNAMESE)

  This study was conducted with the aim of screening and evaluating the antifulgal activity against Alternaria alternata of potential native actinomycete genetic resources. The antagonistic activity of actinomycetes strains against A. alternata was evaluated through methods such as co-cultivation, agar diffusion analysis, and molecular techniques to identify genes involved in the synthesis of bioactive compounds in the selected actinomycete strains. Experimental results showed that, using co-cultivation on PDA medium, nine strains with antagonistic activity against A. alternata were screened from 56 actinimycete strains. Notably, Streptomyces sp. VNUA24 showed the strongest antifungal effect, with an inhibition percentage of 77.62 ± 2.63% after 12 days of  co-cultivation. The 7-day culture filtrate of the strain VNUA24 grown in Gause I medium did not display any antagonistic activity against A. alternata. Interestingly, evaluation of the volatile organic compounds produced by Streptomyces sp. VNUA24 revealed inhibitory effects, resulting in an antagonistic activity of 23.13% after 7 days of incubation. The PCR analysis detected the presence of 5 out of 8 biosynthetic genes associated with the production of bioactive metabolites belonging to the PKS-I, PKS-II, and NRPS gene clusters. Overall, the findings indicate that Streptomyces sp. VNUA24 is a promising candidate for the development of biocontrol products in managing crop diseases caused by A. alternata. 

  DOI: https://doi.org/10.31817/tckhnnvn.2026.24.4.07

• Evaluating the Potential of Using Antagonistic Fungus Trichoderma asperellum to Control Root-Knot Nematode (Meloidogyne incognita) in Tomatoes

  Nguyen Thi Thanh Hong, Nguyen Duc Huy

  Date Received: 08-02-2025 / Date Published: 21-02-2025

   Abstract PDF (VIETNAMESE)

  The root-knot nematode Meloidogyne incognita is a common pest on tomato plants. This study aimed to evaluate the efficacy of Trichoderma asperellum in controlling root-knot nematodes (M. incognita) under laboratory and pot conditions. The experiment was designed with five treatments, including four concentrations of T. asperellum spore suspension (10⁴, 10⁵, 10⁶, and 10⁷ spores/ml) and a control treatment (0 spores/ml). Results showed that the concentration of 10⁷ spores/ml was the most effective, reducing the hatching rate of nematode eggs (113 eggs/152 eggs, equivalent to 25.65%) compared to the control after 24 hours of treatment. At this concentration, T. asperellum also killed second-stage juveniles (M. incognita) with a mortality rate of 88% after 72 hours. Additionally, the 10⁷ spores/ml concentration increased tomato plant height (55.7 cm) and weight (46 g), compared to the control (48.27 cm and 36.43 g). This concentration also significantly reduced the number of galls per root (118.67) and the number of eggs per egg mass (154), compared to the control values of 218.33 galls and 241.67 eggs per egg mass - These are indicators of the nematode's reproductive ability. This study provides valuable insights into the potential use of the biocontrol fungus T. asperellum in managing root-knot nematodes on tomato plants.

  DOI: https://doi.org/10.1234/1gph0n30

• Isolation of Broad-Spectrum Antifungal Bacteria against Phytopathogenic Fungi

  Pham Hong Hien, Tran Thi Bao Yen, Dang Thi Thanh Tam

  Date Received: 07-02-2025 / Date Published: 21-02-2025

   Abstract PDF (VIETNAMESE)

  The research aimed to identify potential antifungal bacteria against phytopathogenic fungi. From rhizosphere soil samples, 43 bacterial isolates were collected and screened. The results indicated that there were three strains with strong antifungal activity against fungal phytopathogens, including Fusarium solani, Fusarium oxysporum, and Alternaria alternata. In addition, the biological characteristics of three potential bacterial strains were evaluated. Based on analysis of 16S rRNA sequence and specific genes, all three bacterial strains were identified and named as Bacillus sp. TV1.1, B. amyloliquefaciens TV2.5, and B. subtilis TV2.12. The results indicate that all three antagonistic bacterial strains could be potential biocontrol agents to control fungal diseases in plants.

  DOI: https://doi.org/10.1234/s7345s51

• Studies on Damping-off Diseases Caused by Rhizoctonia solani Kühnof Some Crops in Hanoi, 2011-2012

  Do Tan Dung

  Date Received: 29-05-2013 / Date Accepted: 15-08-2013 / Date Published: 13-06-2025

   Abstract PDF (VIETNAMESE)

  Rhizoctonia solani Kühnis a soil-borne fungus that causes root rot disease on a wide range solanaceous, cucurbitaceous and fabaceous plants such as tomato, soybean, cucumber, yard long bean and groundnut. Field surveys conducted during 2011-2012 in Hanoi showed that the damping-off disease occurred on all host plants in the Hanoi region. However, the disease incidences varied from crop to crop, ranging from 2.8% on tomato, 4.55% on groundnut, 7.6% on cucumber to 7.46% on yard long bean. The morphological, biological studies and particularly pathogenicity tests of five R. solani isolates from five above-mentioned diseased plants showed that all isolates were identical in morphological, biological and pathogenic features. Bio-tests of the R.solani isolates on artificial medium showed that the antagonistic fungus (Trichoderma viride) is effective in controllingl R. solani. In the dual culture test (Petri disks test), the inhibition efficacies of T. viride to two isolates of R. solani isolated from tomato and cucumber were 79.1% and 79.8%, respectively. Potting test, in which plants were grown in sterilized soil in the greenhouse showed that the control efficacies of T. viride to these two R. solani isolates were 73.2% on tomato and 76.2% on cucumber..

  DOI: https://doi.org/10.31817/tckhnnvn.2013.11.4.

• ISOLATION AND IDENTIFICATION OF ANACTINOMYCETESTRAINWITH BIOCONTROL EFFECT AGAINST Xanthomonasoryzaepv. oryzaeCAUSINGBACTERIAL BLIGHT DISEASE IN RICE

  Nguyen Xuan Canh, PhanThiTrang, TranThiThuHien

  Date Received: 05-08-2016 / Date Accepted: 20-11-2016 / Date Published: 13-06-2025

   Abstract PDF (VIETNAMESE)

  In this study,we performed experiments to screen and identify actinomycetestrains that are antagonisticto Xanthomonas oryzae pv. oryzaecausing rice bacterial blight disease. Among of 98 strainsisolated, we obtained two strains capable of antagonizing X.oryzae pv. oryzaeusingagar diffusion plate method. The strain numbered43 hada strong activity with a diameter of 22 mm clear zone of bacteria. The strain 43showedwhite colonies after threedays of incubation.Sevendays of incubation the white colonies hadgrey borders, produced soluble pigmentsonthe medium, grew well at 30°Candneutral pH, and adapted wellto high salt concentration medium. The strain 43was able toutilize different sources of carbon and nitrogen. Sequence analysis of 16S rRNA showed that strain 43 hada similarity of 100% comparedto Streptomyces diastaticus subsp.ardesiacus. Based on morphology, culture, physiologicalandbiochemical characteristics and molecular biological analyses the strain 43 was identified asS.diastaticus subsp.ardesiacus.

  DOI: https://doi.org/10.31817/tckhnnvn.2016.14.10.

• Phân lập, nhận diện và đặc tính sinh học của xạ khuẩn sinh enzyme chitinase ở vườn quốc gia Yok Đôn

  Dinh Minh Tran, To Uyen Huynh, Anh Dzung Nguyen

  Date Received: 15-08-2020 / Date Accepted: 25-12-2023

   Abstract PDF (VIETNAMESE)

  Việc tạo ra phân bón sinh học mới là lĩnh vực rất được quan tâm trong nông nghiệp hiện đại. Nghiên cứu này tập trung vào xạ khuẩn có hoạt tính chitinase cao, tạo màng sinh học, thúc đẩy sinh trưởng và kháng nấm bệnh hại cây trồng. Trong nghiên cứu này, hai chủng xạ khuẩn YSS-3.3 và YWS-5.1 được phân lập từ các mẫu đất và giá thể chitin thu tại vườn quốc gia Yok Đôn ở Tây Nguyên. Các chủng này có hoạt tính chitinase cao và tạo màng sinh học. Phân tích trình tự gen 16S rRNA cho thấy chúng có quan hệ di truyền gần gũi nhất với loài Luteimicrobium album, với độ tương đồng trình tự 99,41% và độ phủ trình tự 100%. Phương pháp nuôi cấy trên đĩa thạch chỉ ra rằng các chủng xạ khuẩn sở hữu hoạt tính thủy phân cellulose và tinh bột; hòa tan kẽm, kali và phosphate khó tan; và tổng hợp siderophores. Phân tích bằng UV-HPLC cho thấy các chủng này cũng sản xuất hormone tăng trưởng cây trồng như IAA, GA3 và zeatin. Kỹ thuật nuôi cấy kép chỉ ra rằng các các chủng xạ khuẩn có hoạt tính đối kháng nấm Fusarium oxysporum. Từ những cơ sở trên, L. albumYSS-3.3 và L. albumYWS-5.1 là các ứng cử viên tốt cho các nghiên cứu tiếp theo liên quan đến ứng dụng trong nông nghiệp. Các chủng này cũng là nguồn nguyên liệu tiềm năng để thực hiện các nghiên cứu sâu về trình tự bộ gen, hệ thống chitinase, cellulase và amylase của chúng.

• Selection of Potential Bacterial Strain for Controlling Gummosis Disease in Citrus (Citrus sinensis)

  Pham Hong Hien, Bach Thi Diep, Nguyen Thi Chuc Quynh, Phung Quang Tung, Dang Thi Thanh Tam

  Date Received: 02-04-2022 / Date Accepted: 05-07-2022

   Abstract PDF (VIETNAMESE)

  The research aimed to identify potential biocontrol agents in controlling Phytophthora spp. that causes gummosis disease of citrus (C. sinensis). Out of 38 strains isolated from the soil samples collected from Hoa Binh and Tien Giang provinces, the strain LHB15 showed strong antagonistic activity against P. citrophthora 18PMS and P. palmivora 17PMS. Analysis of morphological characteristics and 16S rRNA sequence, the strain LHB15 was identified as B. siamensis. The optimal condition for the growth of B. siamensis LHB15 was determined in LB at 37C and pH 7. Testing the antagonistic activity against P. citrophthora18PMS in greenhouse conditions showed a strong reduction in the presence of fungi on soil and citrus roots after 45 days of treatment. The study indicated that the B. siamensisLHB15 is a potential strain for controlling gummosis in citrus.

• Biological Characterization of Streptomycessp. VNUA30 Strain with Antagonistic Activity Against Pathogenic Fungi CausingDisease on some Plants

  Nguyen Thi Thanh Mai, Nguyen Thanh Hai, Nguyen Thi Thu, Tran Thi Dao, Nguyen Xuan Canh

  Date Received: 04-05-2022 / Date Accepted: 05-07-2022

   Abstract PDF (VIETNAMESE)

  Diseases caused by pathogenic fungi account for 80% of plant diseases resulting in a global crop yieldreduction. The use of chemical fungicides for the control of fungal diseases causes environmental pollution and affects human health. Biocontrol using actinomycetes having antifungal activity was reported to be effective and biosafe. This studyfound that actinomycete strain VNUA30 exhibited a broad-spectrum antifungal activity against five plant pathogenic fungi, i.e. Colletotrichum gloeosporioides, Fusarium oxysporumf.sp. cubense(FocTR4), Corynespora casiicola, Sclerotium rolfsii, and Diaporthe sp. with inhibition rate of 62.50%; 52.58%; 72.22%; 57.77%; and 95.37%, respectively. Biological studies showed that strain VNUA30 was able to produce melanoid pigment, siderophore, H2S and IAA, assimilate citrate, reduce nitrate, liquefy gelatin, degrade urea and produce extracellular enzymes chitinase, cellulase, xylanase, protease, and pectinase. Combining the morphological and biochemical characteristics with the 16S rRNA sequence analysis, this strain was identified as Streptomyces deccanensis VNUA30. The results confirmed that actinomycete strain VNUA30 is a potential strain as bio-control agent for fungal diseases on plants with high efficiency.

• Selection of Streptomycesspp. Isolates with Antifungal Activity against Rice Blast Fungus, Pyricularia grisea

  Nguyen Thi Phong Lan, Vo Thi Thu Ngan, Tran Phuoc Loc, Tran Ha Anh

  Date Received: 11-05-2015 / Date Accepted: 29-11-2015

   Abstract PDF (VIETNAMESE)

  Biological control of plant diseases including fungal pathogens has been considered as viable alternative to chemical control. A total of 395 isolates of Streptomyces were evaluated as antagonist agents to Pyricularia grisea. Of these, 50 isolates of Streptomyces showed high antagonistic ability to four races of P. grisea. Six Streptomyces isolates were identified as Streptomyces cavourensis S27, Streptomyces xiamenensis S257, Streptomyces viriabilis S28, Streptomyces iakyrus S233, Streptomyces scopuliridis S136, and Streptomyces fulvissimus S30, that were highly antagonistic to P. grisea. These isolates grew well on medium at high temperature (30oC) and fairly high salt concentration and produced high level of IAA.