Pathogenic Variability Research Articles

Variation in SSRs at different genomic regions and implications for the evolution and identification of Armillaria gallica.

Armillaria spp. are devastating forest pathogens. Due to its low pathogenicity and abundant genetic variation, Armillaria gallica exhibited a unique and beneficial symbiosis with Gastrodia elata, which was used as a traditional Chinese medicine. However, the variation and population structure of A. gallica populations have rarely been investigated. Hence, we analyzed the evolution and variation in simple sequence repeats (SSRs) in three Armillaria genomes: A. gallica, A. cepistipes, and A. ostoyae to assess the genetic diversity and population structure of 14 A. gallica strains. Genome analysis revealed that SSRs were more abundant in the intergenic region than the intron and exon region, as was the SSR density. Compared with other two genomes, SSR density was the lowest in exon region and largest in the intron region of A. gallica, with significant variation in genic region. There were 17 polymorphic markers in A. gallica genome was identified, with 26.7% in genic region, which is higher than that of 18.8% in the intergenic region. Moreover, a total of 50 alleles and 42 polymorphic loci were detected among these A. gallica strains. The averaged polymorphism information content (PIC) was 0.4487, ranged from 0.2577 to 0.6786. Both principal coordinate analysis (PCoA) and population structure analyses based on the genotype data of SSRs divided the strains into two clusters. The cluster I included all the strains from high-altitude G. elata producing areas and some low-altitude areas, while the strains in Cluster II originated from low-altitude G. elata producing areas. These results indicated that substantial genome-specific variation in SSRs within the genic region of A. gallica and provide new insights for further studies on the evolution and breeding of A. gallica.

Genetic Diversity and Pathogenicity of Phytophthora infestans Isolates on Four Solanum tuberosum (Potato) Cultivars in Nariño, Colombia

Phytophthora infestans remains a major threat to global potato production. This study focused on characterizing and assessing the pathogenicity of P. infestans isolates on detached potato leaves and in greenhouse trials across four cultivars. Seven isolates were obtained from high potato-producing regions in the department of Nariño, Colombia. The isolates were analyzed using 12 microsatellite markers to determine genetic distances. Two genetically distinct isolates showed markedly different pathogenicity on detached leaves: isolate P00921 caused complete infection by day five, whereas P00321 showed no symptoms. These two isolates (P00921 and P00321) selected for having the greatest genetic distance and highest pathogenicity among the seven analyzed were further tested in a greenhouse setup on four potato cultivars using a randomized block design. Disease progression was monitored over nine days. The results indicated significant variations in pathogenicity linked to genetic diversity among isolates. Notably, Capiro and Margarita cultivars were more prone to severe disease than Suprema and Única. These findings highlight the complex nature of host–pathogen interactions and suggest the need for tailored approaches in disease management and cultivar selection.

Giant transposons promote strain heterogeneity in a major fungal pathogen.

No "one size fits all" option exists for treating fungal infections in large part due to genetic and phenotypic variation among strains. Accounting for strain heterogeneity is thus fundamental for developing efficacious treatments and strategies for safeguarding human health. Here, we report significant progress towards achieving this goal by uncovering a previously hidden mechanism generating heterogeneity in the major human fungal pathogen Aspergillus fumigatus : giant transposons called Starships that span dozens of kilobases and mobilize fungal genes as cargo. By conducting the first systematic investigation of these unusual transposons in a single fungal species, we demonstrate their contributions to population-level variation at the genome, pangenome and transcriptome levels. The Starship atlas we developed will not only help account for variation introduced by these elements in laboratory experiments but will serve as a foundational resource for determining how Starships shape clinically-relevant phenotypes, such as antifungal resistance and pathogenicity.

The variation of resistome, mobilome and pathogen in domestic and industrial wastewater treatment systems

Wastewater treatment plants (WWTPs), including both domestic and industrial facilities, are key contributors to antibiotic resistance genes (ARGs) and human pathogens in the environment. However, the characteristics and dissemination mechanisms of ARGs in domestic (SD) and industrial (SI) wastewater treatment systems remain unclear, leading to uncertainties in risk assessment. Based on metagenomic analysis, we observed significant differences in the compositions of resistome (ARGs and metal resistance genes, MRGs), mobilome (mobile genetic elements, MGEs), and bacterial community between SD and SI. SI exhibited lower diversity of ARGs but higher abundance of MRGs compared to SD. The removal efficiency of resistome was lower in the SI than that in the SD. MGEs emerged as the primary driver of ARG dissemination in the WWTPs, followed by the bacterial community. Environmental conditions (physicochemical parameters, heavy metals, and antibiotics) indirectly influenced the variation of resistome. Significantly, environmental conditions and MGEs highly influenced the composition of resistome in the SI, while bacterial community more associated with resistome in the SD. Additionally, we identified 36 human bacterial pathogens as potential hosts of ARGs, MRGs, and MGEs in wastewater samples. This study provides new insights on the dissemination mechanisms and risk assessment of antimicrobial resistance in the different types of WWTPs.

Brassica juncea pre-season cover crops reduce soybean root colonization by Macrophomina phaseolina, the fungus causing charcoal rot

Macrophomina phaseolina (Tassi) Goid. is a soilborne fungus that causes charcoal rot in numerous crop plants, reducing yield and profits. This study assessed the efficacy of pre-season mustard cover crops (Brassica juncea), a chemical fungicide seed treatment, a combination of both, and a non-treated control in a set of varieties that ranged in maturity. In 2016 and 2017, 'AG4135 RR2Y/SR' consistently yielded lower compared to other varieties. Early maturity varieties exhibited reduced yields relative to mid and late maturity pairs in 2016 and 2017. Root colonization was influenced by treatment, with the combined pre-season cover crop and seed treatment exhibiting the lowest colonization rates in 2015, while all treatments had significantly reduced colonization in 2017 compared to untreated controls. Additionally, differences in root colonization were observed among soybean varieties, suggesting genotype-specific responses to disease management strategies. M. phaseolina soil populations showed a marked increase from pre-cover crop to post-soybean harvest underscoring the pathogen's proliferation throughout the growing season. Correlation analyses revealed significant negative relationships between root colonization and yield for untreated controls, suggesting that higher root colonization adversely affected crop performance. These findings suggest that specific treatments may help mitigate M. phaseolina population build-up in roots and soil and indicate that the effectiveness of control measures may be influenced by pathogen variability in response to environmental conditions and management practices. These findings also contribute to our understanding of effective strategies for managing charcoal rot disease and highlights the importance of integrating chemical and biological control methods.

Virulence variation and pathotypes of Zymoseptoria tritici isolates causing wheat leaf blotch in Oromia, Ethiopia

Leaf blotch, caused by Zymoseptoria tritici, is a fungal disease that poses a severe threat to wheat production worldwide. Knowledge of virulence variability is crucial in choosing effective control measures. However, there have only been a few studies of the pathogenic variability and pathotypes within Ethiopian isolates. Hence, the objective of this study was to assess the virulence spectrum and variability of Z. tritici isolates. Forty-three isolates were tested for their virulence and pathotype against 7 wheat differential lines that have different resistance genes. A pathogenicity assay detected 41 differential line-specific virulent isolates among 301 interactions between a host and pathogen based on the percentage coverage of the leaf area by pycnidia. Some isolates were virulent against 50 %–60 % of the resistant genes, but most of them were virulent against some differential lines. Isolates such as EtA-11, EtSh-1, EtSh-2, EtSh-4, and EtA-19 expressed broad-spectrum virulence, highlighting that such isolates are useful for germplasm screening. The isolates were classified into 25 pathotypes, defined by their differential virulence responses. They were also assigned to two clusters according to their mean pycnidia percent. Pathotypes and principal component analysis detected 58.1 % and 62.2 % pathogenic diversity in Ethiopian isolates, respectively. The current findings provide information that breeders can use to identify and select more resistant varieties for farmers.

Morphological, genetic and pathogenic variability among Botrytis cinerea species complex causing gray mold of strawberry

The necrotrophic fungus Botrytis cinerea is capable of infecting more than 1400 plant species, encompassing both dicotyledons and monocotyledons. Recognized as the world's second most destructive fungal pathogen, B. cinerea is responsible for significant pre- and postharvest diseases, especially gray mold on a variety of economically important crops, vegetables, and fruits. This study focused on characterizing the variability of ten B. cinerea isolates from strawberry fruits harvested across various regions in Egypt. The differentiation among these isolates was evaluated through morphological, genetic, pathogenic, and biochemical methods. The isolates exhibited variation in cultural development, colony color, shape, margin, and texture. The study highlighted morphological differences in conidiophores, variations in conidia size, and sclerotia production on three different media. The ten Botrytis isolates have differed in mycelial growth rate and pathogenicity on strawberry fruits and positively correlated with oxalic acid production. Isolate B3 of B. cinerea was the most aggressive, while isolate B5 demonstrated the lowest. Two isolates of Botrytis represented the first occurrence of Botrytis species in Egypt, B. californica and B. eucalypti, which were identified using ITS sequencing and combined with morphological characteristics. They were also responsible for causing gray mold on strawberry fruits. These results are expected to greatly contribute to the knowledge of morphological and genetic variability in B. cinerea isolates, as well as offer valuable insights for the development of disease management strategies.

Natural Occurrence, Morpho‐Molecular Characteristics, and Pathogenicity of Fusarium spp. Associated With Chrysanthemum Wilt in Vietnam

ABSTRACTChrysanthemum Fusarium wilt (CFW) is a devastating soil‐borne disease affecting the cut chrysanthemum industry globally. In Vietnam, this disease has been occurring silently and is posing a risk of epidemic outbreaks in the southern provinces, especially Lam Dong. Results from a survey in 2023 showed that stunted growth, curved and small stems, dried‐rot roots, leaf drooping and green or yellow wilting of plants after transplanting or at their flower bud initiation were common symptoms observed across the main chrysanthemum‐growing farms in Lam Dong. The occurrence of CFW was recorded in relation with the host cultivar, irrigation method and fungicide‐spraying regime. Among the cultivars grown in Lam Dong, ‘Doa cu’ was the most susceptible to CFW. The use of sprinkler irrigation and infrequent application of fungicides were attributed to increase both disease incidence and severity. Thirty fungal isolates obtained from diseased plants were identified as Fusarium oxysporum and F. falciforme based on morphological features and molecular analysis of ITS and TEF‐1α genes. The detection frequency of these two species was almost equal, which shows their balanced role in the occurrence of CFW in Lam Dong. In‐planta pathogenicity assays of Fusarium isolates against plantlets grown from cuttings and invitro propagation showed a variation in pathogenicity and a specialisation of isolates for these planting materials. These results suggest that the profiles of population and aggressiveness of Fusarium isolates diverged with the type of planting material, and between the stock and the commercial farms.

Variability in forgoing life-sustaining treatment practices in critically Ill patients with hospital-acquired bloodstream infections: a secondary analysis of the EUROBACT-2 international cohort

BackgroundThe decision to forgo life-sustaining treatment in intensive care units (ICUs) is influenced by ethical, cultural, and medical factors. This study focuses on a population of patients with hospital-acquired bloodstream infections (HABSI) to investigate the association between patient, pathogen, center and country-level factors and these decisions.MethodsWe analyzed data from the EUROBACT-2 study (June 2019–January 2021) from 265 centers worldwide, focusing on non-COVID-19 patients who died in the hospital or within 28 days after HABSI. We assessed whether death was preceded by a decision to forgo life-sustaining treatment, examining country, center, patient, and pathogen variables. To assess the association of each potentially important variable with the decision to forgo life-sustaining treatment, univariable mixed logistic regression models with a random center effect were performed.ResultsAmong 1589 non-COVID-19 patients, 519 (32.7%) died, with 191 (36.8%) following a decision to forgo life-sustaining treatment. Significant geographical differences were observed, with no reported decisions to forgo life-sustaining treatment in African countries and fewer in the Middle East compared to Western Europe, Australia, and Asia. Once a center effect was considered, only health expenditure (Odds ratio 1.79, 95%CI: 1.45–2.21, p < 0.01) and age (Odds ratio 1.02, 95%CI: 1.002–1.05, p = 0.03) were significantly associated with decisions to forgo life-sustaining treatment, while other patient and pathogen factors were not.ConclusionEconomic and regional disparities significantly impact end-of-life decision-making in ICUs. Global policies should consider these disparities to ensure equitable end-of-life care practices.

Seasonal variations of empyema in Taiwan: A 10-year analysis

BackgroundEmpyema is a serious infection in pleural space. Finding out seasonal variations of empyema and its pathogens can help in providing preventive measures, and implicating future researches. MethodsThis study is a 10-year observational study in a single center. Patients with empyema thoracis receiving thoracoscopic decortication between January 2012 and December 2021 were included in the study. ResultsThere were 1082 empyema patients enrolled in this study. No seasonal variation was noted (spring = 25.7 %, summer =25.5 %, autumn = 24.8 %, winter = 24.0 %). However, we observed seasonal variations in pathogens. Streptococcus species had slightly higher prevalence in winter and spring than summer and autumn (54.3 % vs. 45.7 %) without significant difference (p = 0.251). On the contrary, Staphylococcus species occurred more often in summer and autumn than winter and spring (61.5 % vs. 38.5 %) (p = 0.035). Klebsiella species were more likely found in autumn (34.9 %) (p = 0.050), and Pseudomonas species showed no peak prevalence in any season (p = 0.423). The incidence of Streptococcus species increased over the years. ConclusionsAlthough no seasonal variation was found in severe empyema patients requiring surgery, there were seasonal variations for the pathogens in Taiwan. The medical community should focus on Streptococcus species in winter and spring and Staphylococcus species in summer and autumn.

The Biology, Epidemiology, Host Variability and Management of Sorghum Smut Diseases in Nigeria: A Review

Sorghum Smut diseases in Nigeria are widely circulated and are economically important in most of the regions of the country growing Sorghum. Perhaps, all the four types of smut can co-exist on the same field and are co-extensive with sorghum cultivation. The four smut diseases are incited by four species belonging to two genera of the order ustilaginales, namely; Sporisorium or Sphacelotheca and Tolyposporium. The distribution of the four smut diseases depend on several interacting factors of epidemiology and pathogenesis. It has been reported that all the four species that causes smuts in sorghum have narrow host range. As a consequence therefore, they do not vary remarkably in their biology and pathogenesis. However, their severity, distribution and prevalence depend on the environmental conditions, seasons and variety of sorghum. Several control as well as management strategies have been suggested by workers for the prevention and control of sorghum smuts including the pre-sowing seed treatment using fungicides, the use of resistant plant variety and modification of cultural and handling practices. However, only few of these measures have been found suitable and promising. Moreover, there is scarce of scientific information on the incidence of sorghum smuts probably because they were thought to have been eradicated or that they are economically less important in most sorghum growing areas in Nigeria. But with the current climatic changes coupled with the negligence from the poor resource sorghum farmers, sorghum smut diseases are re-emerging with high threshold as such they are becoming very important in Nigeria’s sorghum growing regions. This paper reviews the epidemiology, biology and variability of smut pathogens and their possible control strategies.

Comparative transcriptomic analysis of hepatopancreas reveals that more genes are involved in the exposure response of Vibrio parahaemolyticus PirAvp compared to PirBvp

Vibrio parahaemolyticus (VP-AHPND) is regarded as one of the main pathogens that caused acute hepatopancreatic necrosis disease (AHPND) in the Pacific white shrimp Litopenaeus vannamei. PirAvp and PirBvp toxin proteins are the main pathogenic proteins of AHPND in shrimp. Knowledge about the mechanism of shrimp response to PirAvp or PirBvp toxin is very helpful for developing new prevention and control strategy of AHPND in shrimp. In this study, the pathological sections showed that after 4 h treatment, significant pathological changes were observed in the PirBvp treated group, and no obvious pathological changes was found in PirAvp treated group. In order to learn the mechanism of shrimp response to PirAvp and PirBvp, comparative transcriptome was applied to analyze the different expressions of genes in the hepatopancreas of shrimp after treatment with PirAvp or PirBvp. A total of 9978 differentially expressed genes (DEGs) were identified between PirAvp or PirBvp-treated and PBS control shrimp, including 6616 DEGs in the PirAvp treated group and 3362 DEGs in the PirBvp treated group. There were 2263 DEGs that were commonly expressed, 4353 DEGs were only expressed in PirAvp VS PBS group and 1099 DEGs were uniquely expressed in PirBvp VS PBS group. Among these DEGs, the anti-apoptosis related pathways and immune response related genes significantly expressed in the commonly expressed DEGs of PirAvp VS PBS group and PirBvp VS PBS group, and small GTPase-mediated signaling and DNA metabolic process might relate to the host special reaction towards PirAvp and PirBvp exposure. The data suggested that the differential expression of these immune and metabolic-related genes in hepatopancreas might contribute to the pathogenicity variations of shrimp to VP-AHPND. The identified genes in this study will be useful for clarifying the response mechanism of shrimp toward different toxins of VP-AHPND and will further provide molecular basis for understanding the pathogenic mechanism of VP-AHPND.

Genomic and culture-based analysis of Cyclaneusma minus in New Zealand provides evidence for multiple morphotypes

Cyclaneusma needle cast, caused by Cyclaneusma minus, affects Pinus species world wide. Previous studies suggested the presence of two distinct morphotypes in New Zealand, ‘verum’ and ‘simile’. Traditional mycological analyses revealed a third morphotype with clear differences in colony morphology and cardinal growth rates at varying temperatures. Genome sequencing of eight C. minus isolates provided further evidence of the existence of a third morphotype, named as ‘novus’ in this study. To further analyse these morphotypes, we predicted candidate effector proteins for all eight isolates, and also characterized a cell-death eliciting effector family, Ecp32, which is present in other pine phytopathogens. In concordance with their distinct classification into three different morphotypes, the number of Ecp32 family members differed, with patterns of pseudogenization in the ‘simile’ morphotype, and some members being found exclusively either in the ‘simile’ or ‘verum’ morphotypes. We also showed that the Ecp32 family proteins trigger cell death in non-host Nicotiana species, and, as previously demonstrated in other plant pathogens, the Ecp32 family proteins in C. minus adopt a β-trefoil fold. These analyses provide further evidence that the three morphotypes might be distinct species that need formal descriptions. Understanding the geographical range of different Cyclaneusma species and variations in virulence and pathogenicity will provide a better understanding of pine needle diseases and enable the development of more durable methods to control this disease.

Single-particle rotational sensing for analyzing the neutralization activity of antiviral antibodies

Due to the pathogen-specific targeting, neutralization capabilities, and enduring efficacy, neutralizing antibodies (NAs) have received widespread attentions as a critical immunotherapeutic strategy against infectious viruses. However, because of the high variability and complexity of pathogens, rapid determination of neutralization activity of antiviral antibodies remains a challenge. Here, we report a new method, named as out-of-plane polarization imaging based single-particle rotational sensing, for rapid analysis of neutralization activity of antiviral antibody against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Using the spike protein functionalized gold nanorods (AuNRs) and angiotensin-converting enzyme 2 (ACE2) coated gold nanoparticles (AuNPs) as the rotational sensors and chaperone probes, we demonstrated the single-particle rotational sensing strategy for the measurement of rotational diffusion coefficient of the chaperone-bound rotational sensors caused by the specific spike protein-ACE2 interactions. This enables us to measure the neutralizing activity of neutralizing antibody from the analysis of dose-dependent changes in rotational diffusion coefficient (Dr) of the rotational sensors upon the treatment of SARS-CoV-2 antibody. With this technique, we achieved the quantitative determination of neutralization activity of a commercially available SARS-CoV-2 antibody (IC50, 294.1 ng/mL) with satisfying accuracy and anti-interference ability. This simple and robust method holds the potential for rapid and accurate evaluation of neutralization activity against different pathogenic viruses.

Bioprospecting of microbial agents and their metabolites as potential inhibitors of Phytophthora cinnamomi, the causal agent of avocado root rot

Phytophthora Root Rot (PRR) is one of the economically important diseases infecting avocado causing substantial yield losses worldwide. In this study, the root rot pathogen infecting avocado has been characterized and potential bioagents targeting PRR have been identified through molecular approaches. Field surveys revealed varying degrees of disease severity (54 %–17.5 %) and incidence (50 %–10 %) in Western Ghats of Tamil Nadu, India. The pathogen was isolated and identified as Phytophthora spp. based on morphology which depicted typical coralloid-type growth patterns. Besides, phylogenetic analysis with the ITS, ras-related protein and COX genes showed closed similarity with P. cinnamomi. The isolates showed significant variation in pathogenicity, with PC(TKI)-10 exhibiting the highest severity (70 %) developing typical symptoms. In vitro efficacy assays through dual-plate and volatiles revealed potential inhibitory effects of Trichoderma harzianum T (MP)-7 (81.11 %) and Bacillus amyloliquefaciens B (TI)-3 (76.67 %) against P. cinnamomi, and Scanning Electron Microscopy (SEM) provided insights into the antagonistic mechanisms, revealing physical interactions and enzymatic lysis of the pathogen by T (MP)-7 and B (TI)-3. Furthermore, Gas Chromatography-Mass Spectrometry (GC-MS) analysis identified bioactive compounds in the crude extracts of these bioagents, elucidating their metabolic pathways and potential modes of action against P. cinnamomi. Our findings highlights the importance of P. cinnamomi in avocado and the mechanism of fungal and bacterial bioagents in the sustainable management of the disease.

Diversity in the population of Fusarium oxysporum f. sp. ricini causing castor wilt disease in India

A major constraint on castor crop productivity is wilt disease caused by Fusarium oxysporum f. sp. ricini (For). In this study, morphological, pathogenic and molecular features of F. oxysporum f. sp. ricini isolates collected from different castor-growing agro-climatic zones of India were analyzed. Eighty-nine F. oxysporum f. sp. ricini isolates were obtained from wilt-infected root samples of castor plants from different states of India viz., Andhra Pradesh, Bihar, Gujarat, Haryana, Karnataka, Madhya Pradesh, Maharashtra, Odisha, Rajasthan, Telangana and Tamil Nadu. Morphology assessment in terms of variability in radial growth, size of micro and macroconidia and number of septa, grouped the isolates into 5 clusters in biplot analysis. A genotype-by-isolates bi-plot analysis ranked genotypes for pathogen susceptibility, with JI-35 being closest to the ideal and most susceptible, and DCS-9, and Kranthi being less susceptible. In contrast, 48–1 and JI-258 showed resistance, while Haritha and VP-1 exhibited intermediate susceptibility levels. K-means cluster analysis found 5 groups for pathogenic variability studies of isolates. The six isolates viz., For-12-5 (61.8 %), For-12-10 (50.5 %), For-13-47 (51.4 %), For-113 (86.1 %), For-13-33 (77.9 %) and For-53 (62.2 %) recorded as highly virulent isolates against wilt disease which showed >50 % average wilt incidence mean value across cultivars. Out of 40 ISSR primers tested, 11 primers gave polymorphic bands and analysis of genetic variability among 36 F. oxysporum f. sp. ricini isolates showed polymorphism with PIC, heterogygosity index, effective multiplex ratio, Marker index, and Shannon Diversity Index which ranged (in %) between 0.22 and 0.69, 0.19–0.44, 11.09–27.9, 6.14–8.98, and 0.78–3.04 respectively. The dendrogram analysis revealed 53 % similarity among the isolates studied and these isolates grouped broadly into 6 clusters. Variability among isolates was significant in morphological, pathogenic and molecular characters of F. oxysporum f. sp. ricini.

Precision Medicine Approaches in Diabetes Management: Targeting Individualized Pathways

This article primarily focuses on novel approaches for managing diabetes, with a particular emphasis on type 2 diabetes. Insulin- and glucagon-secretagostimulating peptide-1 (GLP-1) is an essential element of incretin-based therapies. Its function is contingent upon the levels of glucose in the body. Incretin-based treatments consist of orally active dipeptidyl peptidase-IV inhibitors and injectable GLP-1 receptor agonists. The main objective of current treatments for DM is to achieve glycemic control. However, this strategy overlooks other pathogenic variables that have a role in treatment failure and the development of the illness. Moreover, the existing anti-diabetic drugs now in use have a range of adverse effects with prolonged use. Consequently, researchers will continue to actively seek novel approaches to address DM. Diverse research conducted globally has proposed novel therapy techniques that target various and alternative pathogenic hotspots associated with DM. This review article aims to examine novel therapy options that have significant potential for transforming these revolutionary candidate drugs into effective therapies for DM. It will offer compelling evidence of their safety and assess the associated adverse effects.

Spatial Variation of Oomycetes and Bacteria on Surfaces, Solutions, and Plants from a Commercial Hydroponic Greenhouse

The spatial distribution and diversity of plant pathogens and other microbial communities in commercial operations is the first step in identifying critical control points where crops may be at risk of disease. Our objective was to characterize the spatial variation of oomycete pathogens and bacteria across the production system of a greenhouse producing lettuce in hydroponics. We utilized DNA metabarcoding to identify oomycetes and 16S rRNA gene sequencing of bacteria from different production stages and sample types (surfaces, solutions, and roots) collected from a commercial greenhouse producing lettuce in deepwater culture. Pythium was the genus with the highest relative abundance (41 to 100%) across all production stages. P. dissotocum was detected in most samples, except for sowing and seedling surfaces and municipal water, where P. myriotylum was the most abundant species. Oomycete communities showed distinct clustering by production stages and sample types, where sowing and seedling surfaces and municipal water were separated from the rest. Proteobacteria had the highest relative abundance in the surfaces at the sowing (98%) and seedling (85%) stages. Municipal water was the only sample with less than 20% relative abundance of Proteobacteria and dominated by Cyanobacteria. Negative correlations between Pythium and 13 bacteria genera point to potential antagonists in hydroponics that should be further studied. Mapping the spatial variation of oomycetes and bacterial communities in a commercial greenhouse indicates that production stage and sample type influence microbial composition and potentially the risk to disease.

Genome variation in the Batrachochytrium pathogens of amphibians.

Genome variation in the Batrachochytrium pathogens of amphibians.

Variation in Pathogenicity and Subsequent Production of Sclerotia of Sclerotinia sclerotiorum Isolates in Different Cover Crops, Flower Strips, and Weeds.

Cover crops and flower strips are used in agricultural fields as part of integrated pest management strategies. However, their potential as secondary hosts of soilborne pathogens such as Sclerotinia sclerotiorum in oilseed rape cultivation is not fully comprehended. In the current study, we evaluated the effect of pathogen virulence on the development of Sclerotinia stem/leaf rot and sclerotia production in 33 plant species from 11 botanical families using two S. sclerotiorum isolates. Furthermore, the effect of sclerotial size on carpogenic germination was studied. Results showed that the pathogen's virulence significantly affected the occurrence and development of Sclerotinia stem/leaf rot and the subsequent production of sclerotia. Among all plant species tested, 26 were more susceptible to the highly aggressive S. sclerotiorum isolate, which produced more and bigger sclerotia in 17 species than the less aggressive isolate. Moreover, a stronger positive correlation was found between the relative lesion length of plants inoculated with the highly aggressive isolate and the number of sclerotia produced by this isolate (Spearman's rank correlation coefficient [rs] = 0.572; P = 0.004). Additionally, we found that larger and heavier sclerotia produced stipes and apothecia earlier and at a greater rate than smaller ones. The heavyweight class had the highest carpogenic germination rate (82.4%), followed by the average (67.2%) and lightweight classes (59.5%). Our findings highlight the need for further investigation into the potential risks associated with cover crops, weeds, and flower strips as secondary hosts of soilborne pathogens in agricultural fields.