Plant Pathology Journal最新文献

Disease dynamics are significantly influenced by insect vectors through their interactions with viruses and host plants. The objective of this study is to understand how increased temperatures affect virus transmission, providing insights critical for developing climate-resilient pest and disease management strategies. We investigated the effects of temperature on the survival and growth of Myzus persicae (Sulzer) (Hemiptera: Aphididae), a key vector of the cucumber mosaic virus (CMV). Experiments were conducted to assess aphid survival, reproduction, and intrinsic rate of increase on healthy and CMV-infected Nicotiana tabacum plants at 25℃ and 30℃. It was observed that higher temperatures did not negatively affect aphid survival. CMV transmission assay was performed by allowing aphids to acquire and inoculate the virus under varied temperature combinations, while the aphid feeding behavior was monitored at different temperatures. The transmission efficiency was markedly reduced at 30℃ compared to 25℃, regardless of variations in temperature during virus acquisition and inoculation. Analysis of probing behavior revealed that aphids' probing behavior differed at 30℃, likely contributing to reduced transmission efficiency at higher temperatures. These findings demonstrate the intricate interplay between temperature, vector behavior, and virus transmission. Together, this study emphasizes the importance of incorporating environmental temperature dynamics into the development of sustainable and climate-resilient strategies for managing vector-borne diseases in agriculture.

Streptomyces species are well-known for their antifungal properties and the production of diverse secondary metabolites, including non-ribosomal peptides and polyketides. These metabolites can be identified through various genetic techniques, allowing for the investigation of gene functions using whole-genome databases. Numerous studies have explored the genetic functions of Streptomyces using advanced techniques, such as CRISPR-Cas9 mutagenesis, to generate site-specific mutant strains. In this study, we re-identified Streptomyces sp. J6 as Streptomyces anandii J6 through whole-genome sequencing and average nucleotide identity (ANI) analysis. The type II and type III polyketide synthase clusters (PKS: clusters 9, 10, and 12) were further studied using CRISPR-Cas9 for functional analysis, revealing the role of srsA in the biosynthesis of alkylresorcinols, which are phenolic lipids with antifungal properties. These results indicate that metabolites belonging to the polyketide family produced by Streptomyces plays a significant role in the biocontrol activity of microorganisms against plant diseases. Furthermore, the findings suggest that specific PKS profiling enables the rapid and efficient screening of a large number of microbial candidates, thereby facilitating the selection of promising biocontrol agents.

Various strategies have been developed to control lettuce diseases on farms and in food-packing plants. Biological control is considered a promising alternative owing to its eco-friendly nature. In the present study, bacteria isolated from coastal mudflats were evaluated for their efficacy in controlling Sclerotinia rot, and the plant growth-promoting activity in lettuce was also assessed. Among the screened microorganisms from the coastal mudflats, 12 bacterial strains exhibited antifungal activity against Sclerotinia sclerotiorum selected. These isolates have shown beneficial characteristics, such as nitrogen fixation, indole-3-acetic acid production, phosphate solubilization, and siderophore production. Additionally, the selected isolates showed antifungal effects on the pathogens of major plant disease, such as Alternaria porri, Colletotrichum acutatum, Fusarium oxysporum, Phytophthora capsici, Pythium ultimum, Rhizoctonia solani, and Stemphylium lycopersici. Among the selected bacterial strains, Bacillus subtilis GCM190 exhibited a high sclerotinia rot control rate, similar to that of the tebuconazole-treated group, and showed a significant effect in promoting the growth of lettuce leaves, stems, and roots (least significant difference, P = 0.05). The selection of rifampicin-resistant mutants and their tracing on lettuce roots and soil confirmed that they were well established in both the soil and lettuce roots. The selected microorganisms also exhibited antifungal effects in vitro against other crop diseases affecting cucumbers, tomatoes, red peppers, and green onions, suggesting high potential for practical applications.

Hop stunt viroid (HSVd) infection reduces grapevine (Vitis vinifera) yield and quality, leading to significant economic losses. Conventional methods for producing virus-free plantlets often fail to completely eliminate viroids, necessitating alternative strategies. In this study, RNA interference (RNAi) was induced by applying HSVd-specific double-stranded RNA (dsRNA) to infected grapevine plantlets. Exogenous dsRNA treatment significantly reduced HSVd levels, as confirmed by reverse transcription polymerase chain reaction and digital PCR. Fluorescently labeled (Cy3) dsRNA uptake was detected in plant tissues, while small RNA sequencing revealed an accumulation of HSVd-derived small interfering RNA, indicating RNAi activation. Notably, the inhibitory effect persisted through three successive generations without additional treatment, and similar suppression was observed in HSVd-infected cucumber plants. These findings highlight the efficacy and durability of exogenous dsRNA applications as a sustainable and non-transgenic approach for viroid control in grapevine cultivation.

Magnaporthe oryzae is the causal agent of rice blast disease, a major threat to global food security. Although M. oryzae infects a broad range of monocotyledonous plants, it fails to colonize dicot species such as Nicotiana benthamiana, offering a useful system to investigate nonhost resistance (NHR). In this study, we characterized the immune responses of N. benthamiana to M. oryzae by profiling defense-related gene expression, analyzing fungal invasion, and functionally dissecting key immune components. Time-course expression analyses revealed sustained upregulation of NbBAK1, NbEAS, NbWRKY22, and NbPR1, alongside dynamic regulation of NbCYP71D20 and NbSGT1. Virus-induced gene silencing demonstrated that silencing of NbSGT1, but not NbEAS or NbBAK1, significantly enhanced fungal colonization. Furthermore, salicylic acid (SA)-deficient NahG plants exhibited increased susceptibility, suggesting that SA and SGT1-dependent immunity synergistically contribute to NHR. Visualization of infection using a GFP-expressing fungal strain confirmed that suppression of SGT1 and SA signaling facilitated hyphal expansion into adjacent host cells. High-throughput screening of 179 M. oryzae candidate effectors revealed that 70 induced hypersensitive response-like cell death in N. benthamiana, a response that was abrogated by NbSGT1 silencing. These findings collectively demonstrate that SA signaling and SGT1-dependent effector-triggered immunity are critical barriers against M. oryzae invasion and highlight the potential of nonhost immune components as resources for engineering durable resistance in crops.

Korean oak wilt disease associated with Dryadomyces quercus-mongolicae recently emerged as a major tree disease in South Korea. A comprehensive transcriptome analysis is presented for D. quercus-mongolicae grown in vitro on three different culture media, identifying nearly 7,000 expressed transcripts. Most transcripts are associated with proteins essential for fungal survival and growth. The 40S ribosomal protein S25, ceramide very long chain fatty acid hydroxylase, Epl1 protein, and ADP/ATP translocase are particularly important due to their critical roles in the metabolism and environmental adaptation of fungi. Gene ontology analyses revealed that 39.4%, 61.2%, and 43.3% of transcripts were successfully annotated to biological process, molecular functions, and cellular component aspects, respectively. Furthermore, key metabolic pathways were elucidated, including sphingolipid metabolism, L-tryptophan biosynthesis, and glycolysis, which provide important information on physiological functioning of D. quercus-mongolicae. Overall, these findings provide key information on fundamental biological mechanisms of D. quercus-mongolicae.

Acidovorax citrulli (Ac) is a Gram-negative phytopathogenic bacterium causing bacterial fruit blotch (BFB) on cucurbit crops, specifically in the watermelon industry. However, cultivars of watermelon that are resistant to Ac have not been identified. Therefore, virulence factors/mechanisms in Ac must be characterized to develop alternative control strategies. Functions of a histidinol dehydrogenase, which is an essential enzyme for histidine biosynthesis, remain elusive in Ac. This study aims to elucidate the roles of histidinol dehydrogenase in Ac (HisDAc) using phenotype assays and proteomic analysis. The virulence of a mutant lacking a histidinol dehydrogenase, hisDAc:Tn5(EV), was diminished in geminated-seed inoculation and leaf infiltration assays, and the bacterium was impossible to grow without histidine in minimal media. However, treatment with exogenous histidine completely restored the virulence of the mutant on watermelon and its growth in minimal media, demonstrating that HisDAc is required for histidine biosynthesis, which contributes to virulence and growth. The comparative proteomic analysis indicates that HisDAc is involved in not only amino acid metabolism but also other biological mechanisms, including cell wall/membrane/envelope functions. This suggests that HisDAc may have pleiotropic effects. It was also confirmed that when Escherichia coli was incubated with Ac strains in water, the population level of E. coli increased in the presence of the mutant but not in the presence of the wild-type. This study leads to new insights regarding enzymes related to the production of primary metabolites and provides a promising target to discover an anti-virulence reagent to control BFB.

The aim of this study was to investigate the biocontrol potential of Trichoderma spp. against plant pathogenic fungi. Forty-four Trichoderma strains isolated from freshwater environments were evaluated for their biocontrol potential against Phytophthora capsici and Fusarium solani, as well as for their siderophore production, phosphate solubilization, and enzymatic activities. Seven Trichoderma strains showed excellent performance and were selected for further experiments. These strains were identified as T. longibrachiatum and T. capillare based on the internal transcribed spacer and translational elongation factor 1-alpha gene sequences. The selected strains demonstrated strong antifungal activity against six fungal pathogens in dual-culture and volatile organic compound (VOC) assays. Strain FBCC-F1645 exhibited particularly high antifungal activity and completely inhibited the growth of P. capsici in the VOC assay. All the selected strains significantly enhanced the growth parameters of red pepper seedlings, and flowering was effectively promoted in the treatment groups. Additionally, these strains demonstrated preventive effects against Fusarium oxysporum and P. capsici, the causative agents of Fusarium wilt and Phytophthora blight, respectively, achieving notable control efficacy. Notably, strain FBCC-F1547 completely inhibited wilting and exhibited a strong preventive effect against blight. In the pepper anthracnose prevention experiment, all the tested strain suspensions (diluted 100-fold and 500-fold) effectively inhibited Colletotrichum acutatum. These findings suggest that Trichoderma spp. isolated from freshwater environments have the potential to reduce chemical pesticide use and promote sustainable agriculture.

Cucumber powdery mildew, caused by Podosphaera xanthii, can lead to significant yield losses in greenhouse cultivation. A calendar-based fungicide spray program is commonly employed by farmers, often leading to excessive spraying irrespective of disease conduciveness under certain weather conditions. Therefore, a disease model that can predict the onset of symptoms for determining when to start the first spray applications during a season is needed. This study developed a disease onset forecasting model, which uses growing degree days and leaf wetness duration as input variables, to aid the spray program for cucumber powdery mildew in the greenhouse environment. The model was calibrated using disease onset dates and corresponding weather data collected from two consecutive greenhouse experiments in 2022. As a result, we successfully simulated the symptom onset date with a margin of error of 5.5 days across two validation trials in 2023 and 2024. Further improvements to the model are needed to establish a model-based fungicide program in the greenhouse environment, which can be done by securing more data from additional trials for further modification and calibration of the model.

Colletotrichum species are commonly known as important phytopathogens causing anthracnose in Korea and worldwide, with a diverse range of host plants. Colletotrichum isolates preserved in the Korean Agricultural Culture Collection (KACC) are important resources for scientific research as well as anthracnose disease management strategies in Korea. Many Colletotrichum isolates in KACC had been identified using morphological characteristics and their host plants by depositors, this could lead to inaccurate species names. In this study, 38 KACC isolates were, therefore, re-identified as 13 known species (C. boninense, C. caudasporum, C. coccodes, C. echinochloae, C. karsti, C. liriopes, C. nigrum, C. sansevieriae, C. spaethianum, C. sublineola, C. sydowii, C. truncatum, and C. zhaoqingense) and a new species candidate, based on multi-locus sequence analyses of the nuclear ribosomal internal transcribed spacers, glyceraldehyde-3-phosphate dehydrogenase (gapdh), chitin synthase 1 (chs-1), histone-3 (his3), actin (act), beta-tubulin 2 (tub2), and manganese-superoxide dismutase (sod2). Of these, C. caudasporum, C. echinochloae, and C. zhaoqingense are unrecorded species in Korea. The results also revealed 16 new host-fungus combinations in Korea, including 13 new combinations worldwide. However, the pathogenicity of the fungal species in this work on their hosts was not confirmed.