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Pestalotiopsis and related genera, including Neopestalotiopsis and Pseudopestalotiopsis have damaged many plants for many decades; however, there is little available information about the fungi on tropical fruit in Thailand. This study isolated and characterized pestalotioid fungi on tropical fruit, investigated host specificity, and screened whether plant extracts could control the fungi. In total, 53 diseased fruit samples were sampled from eight types of fruit trees (jackfruit, rose apple, mangosteen, plum, snake fruit, rambutan, strawberry, and avocado). Based on morphological characteristics, 44 isolates were classified as belonging to pestalotioid taxa. Of these isolates, seven with distinct characteristics were selected for identification using molecular analysis, and six isolates were identified as Neopestalotiopsis and one as Pseudopestalotiopsis . In the cross-inoculation experiment, the isolates exhibited nonhost specificity and could infect at least two host plants. The isolates were used to screen for a potential biocontrol resource using six crude plant extracts (clove, ginger, lemongrass, mangosteen, roselle, and turmeric). All crude extracts except mangosteen could inhibit the growth of Neopestalotiopsis and Pseudopestalotiopsis . Application of crude plant extracts could be a potential treatment to control these diseases on tropical fruit.

Background Identifying the DNA-binding specificities of transcription factors (TF) is central to understanding gene networks that regulate growth and development. Such knowledge is lacking in oomycetes, a microbial eukaryotic lineage within the stramenopile group. Oomycetes include many important plant and animal pathogens such as the potato and tomato blight agent Phytophthora infestans , which is a tractable model for studying life-stage differentiation within the group. Results Mining of the P. infestans genome identified 197 genes encoding proteins belonging to 22 TF families. Their chromosomal distribution was consistent with family expansions through unequal crossing-over, which were likely ancient since each family had similar sizes in most oomycetes. Most TFs exhibited dynamic changes in RNA levels through the P. infestans life cycle. The DNA-binding preferences of 123 proteins were assayed using protein-binding oligonucleotide microarrays, which succeeded with 73 proteins from 14 families. Binding sites predicted for representatives of the families were validated by electrophoretic mobility shift or chromatin immunoprecipitation assays. Consistent with the substantial evolutionary distance of oomycetes from traditional model organisms, only a subset of the DNA-binding preferences resembled those of human or plant orthologs. Phylogenetic analyses of the TF families within P. infestans often discriminated clades with canonical and novel DNA targets. Paralogs with similar binding preferences frequently had distinct patterns of expression suggestive of functional divergence. TFs were predicted to either drive life stage-specific expression or serve as general activators based on the representation of their binding sites within total or developmentally-regulated promoters. This projection was confirmed for one TF using synthetic and mutated promoters fused to reporter genes in vivo. Conclusions We established a large dataset of binding specificities for P. infestans TFs, representing the first in the stramenopile group. This resource provides a basis for understanding transcriptional regulation by linking TFs with their targets, which should help delineate the molecular components of processes such as sporulation and host infection. Our work also yielded insight into TF evolution during the eukaryotic radiation, revealing both functional conservation as well as diversification across kingdoms.

Potato tubers are a primary source of infection with phytopathogens, which temporarily colonize their surfaces. Therefore, soil management practices are necessary to reduce pathogen accumulation. In Thailand, potato production typically involves soil amendment and crop rotation to decrease the quantities of soilborne pathogens before and during cultivation. In this study, we investigated the influence of microbial diversity, taxonomy, and functions of bacterial and fungal communities, as well as environmental factors, intra‐ and interkingdom microbial correlations, on potato tubers grown in Tak and Chiang Mai Provinces in northern Thailand, using 16S and ITS amplicon sequencing. The results show that soil properties significantly influenced the species composition of the bacterial and fungal communities on the potato tubers, although they did not distinctly affect overall species richness and evenness. Redundancy analysis also revealed that pH and organic matter are the main factors driving bacterial and fungal taxon enrichment and reduction. These factors also affect microbial composition and enhance the stability of cooperative and competitive microbial interactions. These findings demonstrate that pH and organic matter potentially impact the fluctuation of beneficial and phytopathogenic bacterial and fungal quantities in the potato tuber microbiome. Therefore, a comprehensive understanding of these dynamics could help us develop environmentally friendly strategies for supporting farming practices by promoting beneficial microbial interactions. Microbial communities on potato tubers in northern Thailand were studied with 16S and ITS amplicon sequencing. It was found that soil pH and organic matter are key drivers of bacterial and fungal composition, affecting the balance between pathogens and beneficial microbes. This discovery suggests that modifying soil properties can be a strategy for boosting crop production and sustainable disease control.

Vanda is a highly valued and important orchid in the horticultural industry; however, it is usually damaged by black rot disease, caused by Phytophthora species, leading to substantial economic losses. This study aims to evaluate multiple fungicides for black rot control. Oomycetes were isolated from diseased plants, and these isolates brought about a 100% disease incidence in Vanda with water-soaked lesions, becoming necrotic within 24 h. The isolates were identified as Phytophthora palmivora based on a phylogenetic analysis of internal transcribed spacers (ITSs) and cytochrome oxidase spacer regions. For controlling black rot disease, eight fungicides or mixtures with different target sites and modes of action were screened, including cyazofamid, dimethomorph, fosetyl-aluminum, metalaxyl, thiophanate-methyl, a mixture of fluopicolide and fosetyl-aluminum, a mixture of mancozeb and valifenalate, and a mixture of quintozene and etridiazole. All tested fungicides showed 33%–100% growth inhibition using the poisoned food technique. In greenhouse experiments, seven tested fungicide formulations, except for thiophanate-methyl, exhibited 20%–66% reduced lesion sizes compared with the no-chemical control. The information on fungicides with different filicide group codes could assist a fungicide spray program for black rot management in orchids.

Anthracnose of mango is one of the major postharvest diseases of mango fruit caused by members of the Colletotrichum gloeosporioides species complex such as Colletotrichum siamense. Crude extracts from dry trunk bark of four Cinnamomum species (C. burmanni, C. iners, C. loureiroi, and C. verum), a commercial cinnamon powder, cinnamaldehyde, eugenol, and cinnamon oil were assayed for their antifungal activity against Colletotrichum siamense. The crude extract of C. verum at 500 mg L−1 showed the highest inhibition of mycelial growth. At a concentration above 10 g L−1 cinnamaldehyde, eugenol, and cinnamon oil showed 100% mycelial inhibition. Using the microdilution assay, C. burmanni and C. verum crude extracts were effective against Colletotrichum siamense spore germination and showed a minimum inhibitory concentration (MIC) value of 625 mg L−1 while the MIC value of cinnamaldehyde was 50 mg L−1. The direct bioautography of the C. verum extract and the fractions obtained by column chromatography over silica gel against Cladosporium herbarum revealed clear inhibition zones on TLC plates. The treatment of Colletotrichum siamense spores with this active fraction led to severe membrane damage which was observed by scanning electron microscopy. Comparative HPLC analyses of the Cinnamomum extracts and the active fraction of C. verum, cinnamon power, and the cinnamaldehyde and eugenol as standards indicated cinnamaldehyde as the major compound. The C. verum fraction reduced disease severity and disease incidence on inoculated mango fruit. Moreover, uninoculated mango dipped into C. burmanni and C. verum extracts reduced the naturally occurring disease while total soluble solid, titratable acidity, and weight loss of dipped mango were insignificantly different from the untreated fruit control.

Potato scab is a common potato tuber disease that affects quality and cost in the marketplace, shortening storage, and increasing the chance for secondary infection. The tubers with disease severity of 1 to 4 are accepted and stored in potato storage for cheap selling in Thailand. However, there are few studies of the bacterial community of the scabby tuber during storage. Thus, we aim to elucidate the diversity, structure, and function of the bacterial community of 30-day storage potato scabby tubers stored in different temperatures using 16S amplicon metagenomic sequencing. Bacterial communities of storage potato scabby tubers (Spunta cultivar) collected from different storage temperatures, 4 °C (MEP1) and 6 °C (MEP2), were characterized using 16S rRNA amplicon metagenomic sequencing. The alpha-diversity abundance in the bacteriome of the scabby tubers stored at 6 °C was higher than in those stored at 4 °C. Actinobacteria (34.7%) was a dominant phylum in MEP1, while Proteobacteria (39.9%) was predominant in MEP2. The top 10 genera of both communities were Rhizobium group, Streptomyces, Pectobacterium, Ruminococcus, Cellulomonas, Promicromonospora, Prevotella, Enterobacter, Pedobacter, and Paenarthrobacter. Moreover, functional profile prediction of both communities reveals essential genes in the pathosystem: nos, bglA, and cebEFG-msiK for potato scab disease and phc and peh operons for rot disease. Our findings are the first study to explore details of the bacteriome of the accepted potato scabby tubers for selling during storage in Thailand and strongly indicate that although potatoes were stored at low temperatures, diseases still occur by secondary pathogens.

Phytophthora infestans causes the late blight disease of potato and tomato. Spores of Phytophthora are important for dissemination and causing infection. In this thesis, I studied several aspects of Phytophthora spore biology. (1) I performed RNA-seq of sporangia from rye media, potato leaflets, tomato leaflets, and potato tuber slices to investigate whether sporangia from artificial media and from plants are functionally equivalent. I found that sporangia from these different sources had only modest differences in transcriptional profiles, but showed similar infection potential using single-zoospore infection assays. This is an important piece of information indicating that spores from artificial media are good models for the natural situation. (2) I studied a MADS-box transcription factor to understand the regulation of sporangia development in P. infestans. MADS was shown to regulate many sporulation-induced genes, to act before previously known regulators, and to be regulated both at the transcriptional and post-translational levels. (3) I checked for potential artifacts associated with the homology-based gene silencing method that is commonly used to study gene function in Phytophthora. Based on studies of two target genes, the cis-spread of silencing was frequently observed within 500 nt distance of the target gene; however, this did not occur in all transformants generated by the same silencing vector. This suggests that the expression of neighboring genes should be checked to ensure that phenotypes assigned to genes based on silencing data are reliable.