CTU Journal of Innovation and Sustainable Development

Identification of Exserohilum rostratum causing leaf spot on Dendrobium amabile and Dendrobium clavatum

Huynh Thi Hong Phan — 2026-07-09

Fungal diseases are among the most persistent and underestimated threats to orchid cultivation, often causing severe decline if not detected early. In this study, leaf spot disease was recorded on two native orchid species, Dendrobium amabile and D. clavatum. To identify the causal agent, symptomatic leaves were collected and subjected to fungal isolation, pathogenicity testing, morphological characterization, and multi‑locus sequence analysis. Artificial inoculation reproduced typical leaf spot symptoms, confirming pathogenicity. Morphological traits of colonies and conidia indicated affiliation with the genus Exserohilum. Molecular analyses of the ITS, LSU, TEF1, and ACT gene regions further resolved the isolates as E. rostratum, with high sequence similarity among the representative strains. Minor morphological variation was noted, particularly in conidial dimensions, but overall consistency supported species‑level identification. This study establishes a new host association between E. rostratum and D. amabile and D. clavatum and demonstrates the effectiveness of combining morphological and molecular approaches for precise fungal identification. The generated multilocus dataset provides a useful reference for future studies on orchid pathogens and fungal taxonomy.

Disease-reducing effects of Streptomyces albaduncus ATB 24 on shallot basal rot caused by Fusarium oxysporum under postharvest storage conditions

Tran Viet Quyen — 2026-07-09

Shallot basal rot caused by Fusarium oxysporum severely affects bulb quality and causes significant economic losses during postharvest storage. This study identified antagonistic soil bacteria isolated from shallot fields capable of reducing the disease under postharvest storage conditions of local farmers. The three strongest antagonistic bacterial isolates against the pathogen in dual cultures on petri plates, i.e., ATA 33, ATB 24, and ATB 32, were tested for their disease-reducing effects. Each isolate was tested using three different cell densities (10⁷, 10⁸, and 10⁹ CFU/mL) in a completely randomized experimental design. The 10⁸ CFU/mL suspension of ATB 24 significantly reduced disease incidence (53.33%) as compared to the untreated control (96.67%) after 35 days of storage. ATB 24 was identified as Streptomyces albaduncus using morphological characterization and 16S rRNA gene sequencing. Streptomyces albaduncus ATB 24 could be a biological control agent of shallot basal rot during postharvest storage in practice.

Genome-wide analysis of amino acid transporter genes reveals their potential roles in drought stress and drought-associated disease responses in peanut (Arachis hypogaea)

Ha Duc Chu — 2026-07-09

Amino acid transporters (AATs) are central to nitrogen allocation, amino acid distribution, and metabolic adjustment in plants, but this gene family has not been systematically characterized in cultivated peanut (Arachis hypogaea). In this study, 30 AAT genes were identified from the peanut genome and analyzed for chromosomal distribution, protein properties, gene structure, phylogenetic relationships, and expression profiles. The identified ArahyAAT genes were unevenly distributed across 18 chromosomes and showed marked variation in exon-intron organization, which indicates structural diversification within the family. Transcriptome analysis revealed different expression patterns across vegetative and reproductive tissues, with several genes showing preferential expression in roots, nodules, and reproductive organs. To assess their stress responsiveness, five root low-expression genes were selected for RT-qPCR analysis under drought stress and combined drought stress plus charcoal rot infection. ArahyAAT04, ArahyAAT09, and ArahyAAT21 were induced under drought stress, while ArahyAAT07 showed strong induction under the combined treatment. ArahyAAT23 showed limited transcriptional change across the tested conditions. These results suggest that specific ArahyAAT genes may contribute to stress-associated amino acid transport and metabolic adjustment in peanut roots. This study provides a genome-wide characterization and expression analysis of the peanut AAT gene family and identifies candidate genes for future functional studies on...

Involvement of induced resistance in the disease-reducing effect of antagonistic Serratia nematodiphila CT-78 against rice bacterial leaf blight

Thai Tran Anh Thu — 2026-07-09

Serratia nematodiphila CT-78 was previously shown to be antagonistic against Xanthomonas oryzae pv. oryzae, thus reducing rice bacterial leaf blight. This study examined the changes in activities of the two defense-related enzymes polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) to clarify whether induced resistance contributes to the disease-reducing effect of S. nematodiphila CT-78. Applications of 10⁷ CFU/mL CT-78 suspensions by seed soaking, foliar spraying and their combination significantly induced both PPO and PAL activities at early stages which peaked up at 2 days after pathogen inoculation. The combined application of seed soaking and foliar spraying of CT-78 showed stronger and continuous inductions of the enzyme activities 0-7 days after pathogen inoculation. Detection of hydrogen peroxide (H₂O₂) accumulation in rice leaf tissues supported the involvement of induced resistance in the observed disease reduction. H₂O₂ accumulated in a higher level in leaf tissues of rice plants treated with CT-78 suspensions and inoculated with the pathogen compared to those either treated with CT-78 suspensions or inoculated with the pathogen alone. This indicates enhanced oxidative responses in rice plants against pathogen infection. The results show that the application of S. nematodiphila CT-78 induces resistance at early stages to protect rice plants against bacterial leaf...

Antagonistic Bacillus sp. strains against Phytophthora sp. in jackfruit: Isolation, identification, and enzyme production

Nguyen Phu Dung — 2026-07-09

Jackfruit (Artocarpus heterophyllus) is an important economic crop in tropical and subtropical regions, especially in South and Southeast Asia. In recent years, trunk canker disease caused by Phytophthora palmivora has emerged as a major threat to jackfruit production. To explore sustainable alternatives to chemical control, this study investigated the antagonistic potential of Bacillus rhizobacteria. Four Bacillus sp. strains (CT1, CT2, CT3, and CT4) were isolated from 12 jackfruit rhizosphere soil samples from jackfruit fields in Chau Thanh commune, An Giang province, Viet Nam. Morphological characterization was performed, followed by in vitro antagonism assays against Phytophthora sp. One strain exhibiting the highest inhibition activity was selected for ITS gene sequencing and enzymatic profiling. The results showed that all were gram-positive, catalase-positive, KOH-negative, and showed antifungal activity. Among them, the strain identified as Bacillus velezensis CT4 exhibited the most stable antagonistic effect (17.8–73.7%) and the strongest production of cellulase (33.4–64.2 mm), β-glucanase (40.7–68.8 mm), and protease (45.5–65.7 mm) from 3 to 9 days after the test. Bacillus velezensis CT4 was considered a promising biocontrol agent for managing trunk canker disease, with the potential for commercial applications or scalability in jackfruit.

Host range and reservoirs of Lasiodiplodia theobromae causing longan fruit rot in Ba Ria–Vung Tau, Viet Nam

Chu Trung Kien — 2026-07-09

Fruit rot caused by Lasiodiplodia theobromae is one of the major diseases of longan. This study investigated the host range and reservoirs of the pathogen in longan farms of Ba Ria–Vung Tau, Viet Nam. A total of 32 fruits were identified as the hosts of L. theobromae. Among those, 20 fruits showed rot symptoms after pathogen inoculation. Besides the longan cultivars Xuong com vang, Long, Hung Yen, Edor and Tieu da bo, An Phuoc plum was highly susceptible to L. theobromae. Avocado, guava, rough orange, mandarin, rambutan, jackfruit, banana and sapodilla were moderately susceptible to the pathogen. Solanaceae and Cucurbitaceae fruits did not show clear symptoms after pathogen inoculation. Mycelia and pycnidia of L. theobromae could survive in inflorescence peduncles, fruit pedicels and dried fruit tissues which help the pathogen persist in longan farms through different cropping seasons. The pycnidia in these reservoirs release L. theobromae conidia, thus fostering continuous infection of fruit rot in longan farms.

Molecular characterization of Gilbertella persicaria, the causal agent of postharvest soft rot in Barbados cherry (Malpighia glabra L.), and evaluation of chitosan and selected plant extracts under in vitro and in vivo conditions

Nguyen Quoc Thai — 2026-07-09

Postharvest soft rot is one of the most destructive diseases affecting Barbados cherry (Malpighia glabra L.), causing substantial losses in fruit quality and marketability in Dong Thap Province, Viet Nam. This study identified Gilbertella persicaria as the causal agent of postharvest soft rot through morphological characterization and ITS rDNA sequence analysis, and evaluated the inhibitory efficacy of chitosan and selected plant extracts under both in vitro and in vivo conditions. In vitro assays demonstrated that chitosan at concentrations of 0.6–1.0% completely inhibited mycelial growth and markedly suppressed spore production, whereas garlic extract (6–8%) exhibited strong but short-lived antifungal activity. Under in vivo conditions, chitosan at 0.8–1.0% significantly reduced disease incidence (32.5–37.5%) and lesion area (8.9–16.6%) compared with untreated controls. These findings demonstrate the potential of chitosan as an eco-friendly and effective alternative for managing postharvest soft rot in Barbados cherry.

Potentially biological control of Bacillus spp. against Fusarium keratoplasticum Geiser et al. 2013 causing wilt in pico chrysanthemum

Nguyen Thi Lien — 2026-07-09

Fusarium wilt, caused by Fusarium spp., is considered one of the most serious diseases affecting pico chrysanthemum (Chrysanthemum spp.), leading to significant yield and quality losses. This study was conducted to identify the fungal pathogen causing wilt disease in pico chrysanthemum and to assess the antifungal potential of Bacillus spp. under in vitro conditions. The fungal isolate FC1 was recovered from infected plants and identified as Fusarium keratoplasticum through analysis of internal transcribed spacer (ITS) gene sequences together with morphological characteristics. Its pathogenicity was confirmed in accordance with Koch’s postulates. All 41 Bacillus isolates exhibited antifungal activity against F. keratoplasticum in dual culture assays, with mycelial growth inhibition ranging from 20.0% to 52.2%. Volatile organic compounds (VOCs) and cell-free supernatants (CFS) produced by six promising isolates (CB3, CB10, CB31, CB32, CB35, and CB36) markedly suppressed both mycelial growth and spore germination of fungal isolate FC1. These findings suggest that the selected Bacillus isolates have strong potential as biological control agents for managing F. keratoplasticum-induced wilt in pico chrysanthemum.

An efficient and lightweight YOLOv8-based model with multi-scale texture representation for durian leaf disease classification

Van Quyet Nguyen — 2026-07-09

Durian (Durio zibethinus) is a high-value fruit crop in Viet Nam, with rapidly increasing production, which underscores the need for accurate leaf condition recognition in real orchards. Field images are challenging because symptoms vary in scale and are captured under uncontrolled illumination and complex backgrounds, while many deep models improve accuracy at the cost of higher computation. This study proposes an efficient YOLOv8-based classifier for durian leaf images. The method removes the deepest downsampling stage to preserve higher-resolution features and introduces PartialTriDW, a lightweight tri-branch depthwise block with adaptive softmax fusion and low-cost channel mixing, to enhance multi-scale texture representation in the early and mid-backbone stages. Experiments on a five-class dataset of 4,437 field images, trained from scratch, show that the YOLOv8 baseline achieves 0.918 accuracy, the CutP5 variant achieves 0.927 accuracy, and the proposed model reaches 0.949 accuracy with 0.56 million parameters and 3.3 GFLOPs, while maintaining comparable latency. The results indicate that preserving spatial detail and strengthening multi-scale texture modeling improve practical durian leaf classification with controlled computational cost.

Genome-wide analysis of pathogenesis-related 5 gene family involved in pathogenesis in sugar beet (Beta vulgaris)

Vu Xuan Duong — 2026-07-09

Thaumatin-like proteins (TLPs), classified as pathogenesis-related protein 5 (PR-5), constitute an important component of plant defense systems. However, systematic information on the TLP family in sugar beet (Beta vulgaris) remains limited. In this study, a genome-wide investigation of TLP genes was conducted to clarify their genomic features, evolutionary relationships, and expression behavior under biotic stress. A total of 21 TLPs were identified in the sugar beet genome. These genes showed uneven chromosomal distribution and displayed marked variation in gene length, exon-intron organization, and protein physicochemical properties. Phylogenetic analysis of Arabidopsis PR-5 proteins classified the sugar beet members into multiple conserved groups, with consistent gene structure patterns within each group. Expression profiling under Sclerotinia sclerotiorum infection revealed that BvTLP09, BvTLP10, BvTLP12, BvTLP04, and BvTLP01 were strongly induced, whereas other PR-5 genes showed weak, unchanged, or reduced transcriptional responses. Reanalysis of RNA-seq data from beet cyst nematode infection further demonstrated distinct expression patterns between resistant and susceptible varieties at early and late infection stages, indicating dynamic and genotype-dependent regulation of PR-5 genes. This study expands current knowledge of the PR-5 gene family in sugar beet and provides a basis for future functional studies on their roles in pathogen-responsive pathways.

Combinations of seed soaking and foliar spraying of methanol Kalanchoe pinnata leaf extracts induce rice resistance against bacterial leaf blight

Pham Thiet Trinh — 2026-07-09

Bacterial leaf blight (Xanthomonas oryzae pv. oryzae) is an important rice disease. This study tested disease-reducing effects of methanol Kalanchoe pinnata leaf extracts prepared by the liquid-liquid extraction method and investigated the mechanism involved in the observed disease reduction. Three extract concentrations (1, 1.5, and 2%) were tested under net house conditions using three application methods [seed soaking combined with foliar spraying at (1) 14 days before inoculation (DBI), (2) 7 DBI and (3) both 14 and 7 DBI]. The disease was assessed through lesion lengths at 7, 14 and 21 days after inoculation. Seed soaking combined with foliar spraying at 14 DBI using 1.5% extract showed significant disease reduction similar to that of the chemical control using Starner 20WP. Induced resistance involved in the disease reduction through increased activities in rice tissues of the four defense-related enzymes, i.e., peroxidase (POX), catalase (CAT), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL). Activities of POX, CAT and PPO generally increased while those of PAL decreased after pathogen inoculation. By extract application, activities of POX, PPO and PAL increased earlier compared to those of CAT. Activities of these enzymes reached higher levels with the presence of both extract application and pathogen inoculation.

Assessment of genetic diversity in Colletotrichum sp. causing cucumber anthracnose using random amplified polymorphic DNA and inter-simple sequence repeat markers

Nguyen Thi Lien — 2026-07-09

Anthracnose caused by Colletotrichum sp. is an important disease causing severe damage to the quality and yield of cucumbers in the Mekong Delta of Viet Nam. This study was conducted to assess the genetic diversity of Colletotrichum isolates collected from the Mekong Delta using 13 random amplified polymorphic DNA (RAPD) and 10 inter-simple sequence repeat (ISSR) primers. In addition, associations between these molecular markers and pathogenicity were explored using stepwise multiple regression analysis (MRA). The molecular markers showed high percentages of polymorphic bands (71-100%). Similarity coefficients among the isolates (74-82%) derived from the combined RAPD-ISSR data indicated a moderate to high level of genetic similarity. Two isolates, DT and CT, had the highest similarity coefficients. A total of 13 significant alleles were found to be associated with disease severity and AUDPC indices. S1189-458 and ISSR848-675 were the most significant alleles associated with both disease severity and AUDPC indices. Overall, RAPD and ISSR markers are useful for assessing genetic diversity, while their association with pathogenicity requires further validation.

Detection of bioactive compounds in methanol Kalanchoe pinnata leaf extracts capable of reducing rice bacterial leaf blight

Truong Van Xa — 2026-07-09

Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae severely damages rice production, particularly under climate change conditions. This study detected bioactive compounds from leaf extracts of Kalanchoe pinnata (Lam.) Pers. and tested their disease-reducing effects against BLB. Methanol leaf extracts of K. pinnata were prepared by liquid-liquid extraction combined with ultrasonication. Using gas chromatography–mass spectrometry, 27 compounds were identified in the extracts. Based on their abundances and reported involvements in plant defense responses against pathogens, three compounds were selected for further tests, i.e., 5-oxotetrahydrofuran-2,3-dicarboxylic acid, dimethyl ester; ethyl linolenate and 1,3-benzenedicarboxylic acid, bis(2-ethylhexyl) ester. To have adequate amounts of these compounds for subsequent bioassays under net house conditions, their commercially available analogs were employed, i.e., dimethyl furan-2,5-dicarboxylate (FDME), water-soluble linoleic acid (LinA) and bis(2-ethylhexyl) phthalate (DEHP). Rice seeds were soaked in six different concentrations of each compound (3, 5, 10, 15, 20, and 25 ppm) for 24 h before sowing. Seed soaking with either FDME or DEHP significantly reduced BLB lesion lengths after pathogen inoculation. The effects of FDME were maintained until 21 DAI. Moreover, seed soaking using a mixture of FDME and DEHP provided similar protection as that of the chemical control using Starner 20WP.

Isolation and characterization of Colletotrichum gloeosporioides species complex causing chili anthracnose in Lao Cai province, Viet Nam and evaluation of antifungal activity of selected local plant extracts

Xuan-Phong Ong — 2026-07-09

This study aimed to investigate the occurrence of chili anthracnose, characterize the associated pathogen, and evaluate the antifungal potential of plant-derived products as sustainable management options in the Muong Khuong area, Lao Cai province. Field investigations showed that anthracnose was prevalent on both hot chili and sweet chili, with disease incidences of 50.50% and 70.48%, respectively, during the July survey. Anthracnose symptoms were observed on leaves and fruits of chili types. The pathogen was isolated from symptomatic tissues and characterized based on colony morphology, microscopic features, pathogenicity tests, and ITS sequence analysis. Re-inoculation on detached chili leaves and fruits reproduced anthracnose symptoms, confirming the pathogenicity of the isolate. BLASTn analysis of the ITS region revealed 100% sequence identity with species within the Colletotrichum gloeosporioides species complex. In vitro antifungal assays demonstrated that extracts from Piper betle, Elsholtzia ciliata, and Ocimum basilicum inhibited the pathogen's mycelial growth. Among them, Piper betle showed the strongest inhibitory effect (62.16% inhibition at 5 days after treatment), followed by Elsholtzia ciliata (23.91% inhibition at 5 days after treatment) and Ocimum basilicum (15.68% inhibition at 3 days after treatment). These findings support the potential use of plant-derived products for sustainable management of chili anthracnose.

Biology and pathogenicity of Pestalotiopsis microspora and Colletotrichum siamense associated with circular leaf spot of rubber (Hevea brasiliensis)

Nguyen Don Hieu — 2026-07-09

Circular leaf spot disease (CLSD) has recently emerged as an important foliar disease of rubber (Hevea brasiliensis) in Viet Nam, yet information on its associated pathogens remains limited. This study investigated the biological characteristics and pathogenicity of Pestalotiopsis microspora and Colletotrichum siamense associated with CLSD. Sixteen isolates of each species were obtained from diseased leaves collected in major rubber-growing regions of Viet Nam. Morphological characteristics were evaluated on different culture media and temperature regimes, while pathogenicity was assessed under laboratory and greenhouse conditions and confirmed through Koch’s postulates. Pestalotiopsis microspora showed optimal growth on malt extract agar at 25°C, whereas C. siamense grew most rapidly on potato-based media at 25–30°C. ITS sequence analysis showed ≥99% similarity between all isolates and reference sequences of P. microspora and C. siamense in GenBank. Disease severity index values on detached leaves ranged from 34.4–52.1% for P. microspora, 54.5–99.8% for C. siamense, and 92.0–100% for mixed inoculations (ANOVA, p < 0.01). Greenhouse inoculations showed a similar pattern. Among six rubber clones, RRIV 124 was the most susceptible under laboratory conditions. These results indicate that CLSD in Viet Nam is associated with a pathogen complex in which C. siamense is more pathogenic than P. microspora, while...