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• 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

  Received: 04-05-2022 / 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.

• Isolation and Characterization of Sclerotium rolfsiiStrains Causing Stem Rot Disease in Peanut

  Nguyen Xuan Truong, Tran Thi Dao, Ta Ha Trang, Nguyen Thanh Huyen, Ngo Thi Van Anh, Nguyen Xuan Canh

  Received: 04-08-2022 / Accepted: 20-12-2022

   Abstract PDF (VIETNAMESE)

  Peanut production has been facing many difficulties due to the increasing incidence of Sclerotinia stem rot disease caused by Sclerotium rolfsiibut there is still no effective solution to deal with this disease. Therefore, this study was conducted to determine the biological characteristics of S. rolfsii, thereby orienting measures tocontrol the disease more effectively. From 10 peanut samples showing stem rot symptoms collected from Thai Binh and Nam Dinh provinces, by inoculating method on PDA medium combined with artificial infection method on peanut plant, 6 fungal strains were determined capable of causing disease, in which LT1 and LN1 expressed the strongest pathogenicity. They were identified as S. rolfsiiisolate LT1 and S. rolfsiistrain LN1, respectively. Two isolates were in the same mycelial compatibility group. Specifically, they grew and formed sclerotia well in PDA medium at 30oC and pH: 5,0-6,0. Simultaneously, on the PDA medium, the colonies of LT1 and LN1 showed maximum growth (>90 mm) after 3 days of culture. Their aerial mycelium was white and abundant. Their sclerotia were formed after 4-5 days of culture and turned brown after 6-7 days with 921 sclerotia (LT1) and 420 sclerotia (LN1). Both of them produced acid to reduce pH of the culture medium sharply and produced extracellular enzymes.