Fire blight, caused by Erwinia amylovora, is a highly destructive bacterial disease that affects apple and pear orchards worldwide, leading to significant economic losses. In this study, we isolated and characterized endophytic bacterial strains from apple trees in Gyeongsangbuk-do, South Korea, to identify potential biocontrol agents against E. amylovora. Among the five antagonistic strains identified, Bacillus velezensis JE80 and JE250 exhibited the strongest inhibitory effects. Further analysis using culture filtrates (CFs) from these strains demonstrated that the CFs of JE80 and JE250 not only suppressed E. amylovora growth in a growth-phase-dependent manner but also significantly impaired bacterial motility and biofilm formation. Notably, in planta assays revealed that JE250 effectively reduced fire blight symptoms in apple blossoms, performing comparably to streptomycin sulfate. Whole-genome sequencing of JE250 identified biosynthetic gene clusters associated with the production of antimicrobial compounds, including difficidin, fengycin, bacillaene, macrolactin, bacillibactin, and bacilysin, further supporting its strong antagonistic potential. These findings suggest that B. velezensis JE250 is a promising biocontrol agent for sustainable fire blight management. Future research should focus on optimizing formulation methods for field application, characterizing specific antimicrobial compounds, and evaluating its long-term efficacy in orchard environments.

This study presents a comprehensive, long-term assessment of the performance and economic impact of virus-free (VF) apple seedlings distributed to commercial orchards in Korea. We compared VF and virus-infected (VI) ‘Hongro’ and ‘Fuji’ apple trees over five years, starting from four to five years after planting. VF trees maintained no reinfection for up to nine years, while VI trees showed a high infection rate (78.6%). VF trees consistently showed higher fruit set, greater yield, and superior fruit quality—including size, color, and soluble solids—than VI trees. VI trees produced more unmarketable fruit in both cultivars. Economic analysis showed that adopting VF seedlings increased net grower income by KRW 825,000 per 10 a. These results demonstrate that VF apple trees provide sustained improvements in productivity, fruit quality, and profitability in orchard conditions, supporting the continued expansion of VF seedling programs for sustainable apple production in Korea.

Burkholderia glumae, the causal agent of bacterial panicle blight and seedling rot (BSR), is a growing threat to rice production, yet effective and sustainable control measures remain limited. In this study, we evaluated Bacillus velezensis JBCS608 (JBCS608) as a promising biocontrol agent for the management of BSR in rice plants. Treatment with JBCS608 at an optimal concentration of 1 × 108 CFU/mL significantly reduced disease severity, achieving a control efficacy of up to 68.9%. The strain exhibited broad-spectrum antagonistic activity, inhibiting the growth of multiple seed-borne bacterial pathogens, including B. glumae, Burkholderia gladioli, and Burkholderia plantarii, as well as fungal pathogens such as Fusarium moniliforme. In addition to disease suppression, JBCS608 promoted rice seedling growth, likely through the production of indole-3-acetic acid and siderophores, and phosphate-solubilizing activity. For practical applications, we developed both talc-based wettable powder and molasses humic acid liquid formulations using JBCS608 endospores. Both formulations exhibited biocontrol efficacy comparable to that of fresh bacterial cells and maintained high cell viability for over 6 months under cold storage conditions. Collectively, our results indicate that JBCS608 is a potent and eco-friendly biocontrol and plant growth-promoting agent with strong potential for commercial use in the integrated management of BSR in rice.

Fire blight, caused by Erwinia amylovora, poses a significant threat to Rosaceae crops and has caused substantial damage to South Korea since its emergence in 2015. Traditional control methods, including antibiotic- and copper-based treatments, have shown limitations, underscoring the necessity for alternative solutions to enhance efficacy while addressing the concerns associated with antibiotics. This study evaluated the efficacy of FireFighter-A, a novel phage cocktail, in managing fire blight. Comprising four phages—Fifi318, Fifi451, pEa_27, and pEa_47—FireFighter-A demonstrates a broad host range that covers all recent isolates against E. amylovora and E. pyrifoliae, along with high stability under various conditions, including temperature, pH, and buffers. Trials with immature apple fruits, tissue culture rootstock plantlets, acclimated M26 rootstock plantlets, and blossoms have demonstrated that FireFighter-A provides superior biocontrol efficacy through synergistic effects, outperforming individual phages. Moreover, it significantly reduced fire blight symptoms and infection rates with a performance comparable to or exceeding that of streptomycin. These findings support the use of FireFighter-A as an effective and environment-friendly alternative for fire blight control.

The Fusarium fujikuroi species complex (FFSC) includes numerous phytopathogenic and mycotoxigenic species of significant agricultural importance. In this study, 81 Korean isolates within the FFSC from the Korean Agricultural Culture Collection (KACC) were re-identified using multi-locus sequence analyses of partial gene fragments of the translation elongation factor 1-alpha (tef1), beta-tubulin (tub2), calmodulin (CaM), RNA polymerase II largest subunit (rpb1), and RNA polymerase II second largest subunit (rpb2). Phylogenetic analyses clarified the taxonomic identities of these isolates, revealing that many strains previously reported as F. proliferatum, F. subglutinans, and F. circinatum were re-identified as F. annulatum, F. dendrobii, and a novel species, F. ipomoeicola sp. nov., respectively. In total, eight species were confirmed within the FFSC, including seven known species (F. annulatum, F. concentricum, F. dendrobii, F. elaeagni, F. fujikuroi, F. planum, and F. thapsinum) and one novel species described herein. Notably, the taxonomic status of four recently described species was revised, indicating that F. hipposidericola, F. jacksoniae, F. xishuangbannaense, and F. oryzigenum are synonyms of F. annulatum, F. babinda, F. hechiense, and F. planum, respectively. In addition, F. annulatum, F. dendrobii, F. elaeagni, and F. planum are reported for the first time in Korea, and 22 previously undocumented fungus-host associations from Korea were identified, including 15 novel combinations not previously reported worldwide. However, the pathogenicity of these fungal species on their respective hosts was not confirmed in this study.

Abiotic stresses, such as drought and high salinity, threaten global food security by severely limiting crop yields. Among diverse agricultural practices, the usage of plant growth-promoting rhizobacteria has been expanding to enhance plant resilience against environmental stresses. In this study, we examined the effects of Bacillus subtilis W1-like strain (BsW1L) on increasing plant tolerance in lettuce plants (Lactuca sativa) grown under drought and high-salt stresses. BsW1L-treated plants exhibited improved tolerance to both stresses, as indicated by increased shoot and root growth, leaf area, and chlorophyll content. Application of the BsW1L strain enhanced the mRNA expression and activity of key antioxidant enzymes, catalase and ascorbate peroxidase. This facilitated the detoxification of reactive oxygen species, leading to decreased hydrogen peroxide levels, reduced malondialdehyde accumulation, and increased total soluble sugars. Notably, treatment with the BsW1L strain elevated proline levels in the leaves of lettuce plants grown under drought stress but reduced them in plants exposed to salt stress. Taken together, these findings suggest that BsW1L can serve as an eco-friendly biostimulant for improving plant tolerance to abiotic stresses, contributing to sustainable agricultural practices.

Podosphaera xanthii is an obligate biotrophic fungus responsible for powdery mildew disease in cucurbits. Its strict host dependency has hindered genomic studies due to challenges in isolating pure fungal DNA. In this study, we present a high-quality genome assembly of P. xanthii Race 1 using PacBio HiFi reads, Illumina short reads, and RNA-seq data, combined with stringent in silico filtering to remove host and microbial contaminants. The final assembly spans 151.7 Mbp across 67 scaffolds with 80.04% repeat content and 7,452 predicted genes. Functional annotation revealed effector-related features and gene categories consistent with biotrophic lifestyles. Comparative analyses with other P. xanthii genomes exposed variable contamination levels, underscoring the importance of strict data curation. Our work provides a reliable genomic reference for P. xanthii, enabling future research on pathogenicity, evolution, and host interactions in powdery mildew fungi and contributing to broader understanding of obligate biotrophic adaptation.

Seeds harbor diverse microbial communities, including endophytes, some of which are vertically transmitted and may contribute to plant health and productivity. However, the temporal dynamics of seed endophytic communities remain poorly understood in many crop species. In this study, we monitored the composition of bacterial and fungal endophytes in soybean (Glycine max) seeds, along with rhizosphere microbiomes, across three plant generations using a culture-independent approach. Our results revealed two key patterns: seed endophytic communities are distinct from those of bulk soil and rhizosphere microbiomes; and the composition of seed endophytes fluctuates over generations, likely influenced by both pre-existing endophytes, environmental factors, and microbial influx from the surrounding soil and rhizosphere, suggesting possible microbial transmission from the rhizosphere into seeds. Interestingly, despite generational variation, the seed fungal endophyte communities consistently maintained higher phylogenetic diversity compared to bacterial endophytes, which showed limited overlap across generations and were composed of fewer, closely related taxa. Analysis of community assembly mechanisms indicated that both seed and rhizosphere microbiomes significantly contributed to the next generation of seed microbiota, primarily through stochastic drift and homogeneous selection processes. Collectively, our findings offer valuable insights into the intergenerational dynamics of seed endophytes in soybean and provide a foundation for future efforts to harness seed-associated microbiomes for improving crop health and productivity.

Northern corn leaf blight (NCLB), caused by Exserohilum turcicum (Setosphaeria turcica), is a major disease that negatively impacts the yield and quality of sweet corn. Plant-associated microbes hold great potential for enhancing crop productivity and sustainability. This study investigated the fungal and bacterial communities associated with NCLB in resistant and susceptible sweet corn cultivars using amplicon metagenomic sequencing. The structural composition and diversity of the fungal community in symptomatic NCLB-susceptible cultivars differed significantly from those in asymptomatic NCLB-resistant cultivars. In contrast, the bacterial communities showed no significant differences between resistant and susceptible cultivars in both the phyllosphere and rhizosphere. Exserohilum and Alternaria were significantly more abundant in the phyllosphere of symptomatic NCLB-susceptible plants, while fungal genera such as Sporobolomyces and Aureobasidium, along with the order Dothideales and the bacteria Bacillus, were significantly more abundant in the phyllosphere of asymptomatic NCLB-resistant cultivars. Microbial metabolic functions related to sugar metabolism—including sucrose biosynthesis and the degradation of glucose and xylose, compounds abundant in plant cell walls—were enriched in the phyllosphere of symptomatic NCLB-susceptible plants. In contrast, functions associated with detoxification and defense responses to plant phenolic compounds were enriched in microbes from asymptomatic NCLB-resistant cultivars. Additionally, Bacillus, identified as part of the core microbiome, and the epiphytic yeast Sporobolomyces, identified as a hub in the microbial network, exhibited antimicrobial activity that may suppress E. turcicum. These findings offer valuable insights into the role of microbial communities in plant health and disease resistance, with promising implications for developing microbiome-based strategies to manage NCLB.

Bacterial panicle blight (BPB) is a serious rice disease that causes spikelet abortion and yield loss under high-temperature and humid conditions. To identify the genetic basis of BPB resistance, we performed a genome-wide association study (GWAS) using 307 Korean rice cultivars. A significant quantitative trait locus (QTL), qBG6.1, was identified on chromosome 6, with a lead single nucleotide polymorphism surpassing the genome-wide significance threshold. Within this QTL, haplotype analysis based on whole-genome resequencing data from 157 accessions revealed two candidate genes significantly associated with the percentage of healthy seeds per panicle: Os06g0255900 and Os06g0259850. These genes encode proteins with functions related to exocyst-mediated vesicle trafficking (EXO70F5) and pathogen response (tobacco mosaic virus [TMV]-related protein), respectively, indicating their potential involvement in BPB resistance mechanisms. Our findings highlight the value of integrating GWAS and haplotype analysis to dissect complex traits such as disease resistance. Although the functional roles of these candidate genes require further validation, they represent promising targets for molecular breeding and future genetic studies aimed at developing BPB-resistant rice cultivars.