Anthracnose caused by Colletotrichum spp. is one of the major problems in mango production worldwide, including Thailand. All mango cultivars are susceptible, but Nam Dok Mai See Thong (NDMST) is the most vulnerable. Through a single spore isolation method, a total of 37 isolates of Colletotrichum spp. were obtained from NDMST showing anthracnose symptoms. Identification was performed using a combination of morphology characteristics, Koch’s postulates, and phylogenetic analysis. The pathogenicity assay and Koch’s postulates on leaves and fruit confirmed that all Colletotrichum spp. tested were causal agents of mango anthracnose. Multilocus analysis using DNA sequences of internal transcribed spacer (ITS) regions, β-tubulin (TUB2), actin (ACT), and chitin synthase (CHS-1) was performed for molecular identification. Two concatenated phylogenetic trees were constructed using either two-loci of ITS and TUB2, or four-loci of ITS, TUB2, ACT, and CHS-1. Both phylogenetic trees were indistinguishable and showed that these 37 isolates belong to C. acutatum, C. asianum, C. gloeosporioides, and C. siamense. Our results indicated that using at least two loci of ITS and TUB2, were sufficient to infer Colletotrichum species complexes. Of 37 isolates, C. gloeosporioides was the most dominant species (19 isolates), followed by C. asianum (10 isolates), C. acutatum (5 isolates), and C. siamense (3 isolates). In Thailand, C. gloeosporioides and C. acutatum have been reported to cause anthracnose in mango, however, this is the first report of C. asianum and C. siamense associated with mango anthracnose in central Thailand.

Durian (Durio zibethinus L.) is an economically important crop in the southern and eastern parts of Thailand. The occurrence of die-back disease caused by plant pathogenic fungi poses a serious threat to the quality and quantity of durian products. However, the identification of causal agents has been a subject of mixed information and uncertainty. In this research, we conducted a comprehensive investigation of die-back disease in nine durian plantations located in Thailand. By analyzing a total of 86 Fusarium isolates obtained from infected tissues, we aimed to provide clarity and a better understanding of the fungal pathogens responsible for this economically significant disease. Through a combination of colony characteristics, microscopic morphology, and a multilocus sequence analysis (MLSA) of the internal transcribed spacer (ITS) region, translation elongation factor 1-α (TEF1-α) gene, and RNA polymerase II gene (RPB2) sequences, we were able to identify and categorize the isolates into three distinct groups, namely, Fusarium incarnatum, F. solani, and F. mangiferae. Koch’s postulates demonstrated that only F. incarnatum and F. solani were capable of causing die-back symptoms. This research represents the first report of F. incarnatum as a causal agent of die-back disease in durian in Thailand. Additionally, this study uncovers the association of ambrosia beetles and F. solani, highlighting the potential involvement of E. similia in facilitating the spread of die-back disease caused by Fusarium in durian.

Partitiviruses are one of the most prevalent double-stranded RNA viruses that have been identified mostly in filamentous fungi and plants. Partitiviruses generally infect host fungi asymptomatically but infrequently exert significant effect(s) on morphology and virulence, thus being considered a potential source of biological control agents against pathogenic fungi. In this study, we performed a screening for mycoviruses of a collection of Thai isolates of rice fungal pathogen Rhizoctonia oryzae-sativae, a causal agent of rice aggregated sheath spot disease. As a result, 36% of tested isolates carried potentially viral double-stranded RNAs with sizes ranging from 2 to 3 kbp. By conventional cDNA library construction and RNA-seq, we determined six new alphapartitiviruses that infected three isolates: tentatively named Rhizoctonia oryzae-sativae partitivirus 1 to 6 (RosPV1-6). Furthermore, RT-PCR detection of each virus revealed their omnipresent nature in different R. oryzae-sativae isolates. Although virus-curing of basidiomycetous fungi is generally difficult, our repeated attempts successfully obtained virus-free (for RosPV1, RosPV2, and uncharacterized partitiviruses), isogenic strain of R. oryzae-sativae TSS190442. The virus-cured strain showed slightly faster colony growth on the synthetic media and severe symptom development on the rice sheath compared to its virus-infected counterpart. Overall, this study shed light on the distribution of partitiviruses in R. oryzae-sativae in a paddy environment and exemplified a virus-curing protocol that may be applicable for other basidiomycetous fungi.

Background: Anthracnose disease caused by the genus Colletotrichum is one of the crucial problems occurring in the field, along with postharvest diseases and affects mango quality in Thailand. In particular, the Nam Dork Mai See Tong cultivar, which is highly susceptible to the disease, is an important product for exportation. Methods: In this research, thirty-seven Colletotrichum species isolate were obtained from anthracnose disease in mango cv. Nam Dork Mai See Tong in three provinces in Thailand. Morphological studies and molecular techniques using species-specific primers were investigated; moreover, the diversity of pathogens was analyzed using PCR amplification of inter simple sequence repeats (ISSRs) with 6 primers, including pathogenicity tests. Result: Morphological studies and molecular detection with species-specific primers revealed that 32 isolates belonged to the C. gloeosporioides species complex and 5 isolates to the C. acutatum species complex. The genetic diversity of pathogens was analyzed. PCR amplification using 6 ISSR primers produced 35 polymorphic bands. These bands were used to construct UPGMA, in which cluster analysis divided the 37 isolates into 3 main groups and 8 subgroups at 61-73% Jaccard similarity coefficient with cophenetic correlation (r) = 0.6781. The ISSR technique showed the greatest genetic variation among isolates collected from different locations. Hence, a study based on ISSR markers was profitable to investigate the phylogenetic relationship of the genus Colletotrichum. Pathogenicity tests revealed that PC006 (Ca) and CS005 (Cg) showed the highest aggressiveness, with disease incidences of 84.74 and 80.90%, respectively. This study indicates that the diversity of pathogenic Colletotrichum species related to mango plantations in Thailand is increasing.

Bacterial leaf spot, particularly in chili peppers, is major concern worldwide, particularly in chili peppers. Enhancing pepper resistance to bacterial leaf spot addresses a key agricultural challenge while minimizing chemical usage. In this study, the efficacy of plant resistance inducers (PRIs) in controlling bacterial leaf spot in peppers was evaluated through molecular and secondary metabolite analyses. Pepper plant seedlings were treated with salicylic acid (SA), acibenzolar-S-methyl, β-aminobutyric acid, chitosan, Bacillus subtilis B01, and B. velezensis CH6 and inoculated with Xanthomonas euvesicatoria pv. euvesicatoria. Disease severity was assessed, and the expression level of genes (PR-1, PR-2, PR-4, and CAT) and the abundance of secondary metabolites were analyzed via quantitative PCR (qPCR) and gas chromatography-mass spectrometry (GC-MS), respectively. Soil drenching with B. subtilis B01 produced the best effects, reducing the disease severity by 80% and significantly inducing PR-1 expression 24–48 h post-treatment. SA was similarly effective in inducing systemic acquired resistance (SAR), while β-aminobutyric acid primed antioxidative defenses through sustained catalase (CAT) expression, and chitosan induced PR-4. GC-MS analysis revealed secondary metabolites associated with systemic resistance pathways including SAR and induced systemic resistance (ISR). Herein, B. subtilis B01 and SA were identified as potent resistance inducers that reduce the disease severity of bacterial leaf spot and activate key defense pathways in pepper plants. These findings contribute to the development of sustainable, integrated disease management strategies.

Kale (Brassica oleracea var. sabellica), known for its high nutritional value and health benefits, has gained significant popularity. Recently, kale grown in soilless systems has also become increasingly popular, as these systems offer better environmental control and improve overall quality, making them an ideal method for cultivating kale. However, in 2023–2024, several kale plants exhibited severe symptoms of seedling and stem rot leading to losses of over 70% in both quality and yield. In this study, the infectious isolates were obtained from stem rot kale grown in soilless cultivation greenhouses across three provinces in central Thailand. The pathogens were identified through a combination of morphological characteristics and molecular techniques, utilizing nucleotide sequences from the internal transcribed spacer (ITS1-5.8S-ITS2) and large subunit ribosomal RNA (LSU rDNA). Pathogenicity tests and Koch’s postulates on 2-month-old kale plants confirmed that the fungus was responsible for causing brown stem lesions and rot. Morphological features and multilocus sequence analysis (MLSA) identified the pathogen as Agroathelia delphinii. This research represents the first report of A. delphinii infecting kale in Thailand, offering crucial insights for accurate disease diagnosis and the development of effective management strategies in soilless cultivation systems, which is essential for improving productivity in increasingly variable environments.