Navigating Host Immunity and Concurrent Ozone Stress: Strain-Resolved Metagenomics Reveals Maintenance of Intraspecific Diversity and Genetic Variation in on Pepper.

The evolving threat of new pathogen variants in the face of global environmental changes poses a risk to a sustainable crop production. Predicting and responding to how climate change affects plant-pathosystems is challenging, as environment affects host-pathogen interactions from molecular to the community level, and with eco-evolutionary feedbacks at play. To address this knowledge gap, we studied short-term within-host eco-evolutionary changes in the pathogen, , on resistant and susceptible pepper in the open-top chambers (OTCs) under elevated Ozone (O) conditions in a single growing season.

sp. nov. isolated from watermelon and muskmelon in Serbia.

Six strains isolated from muskmelon and watermelon seedlings affected by stem rot and wilting in Serbia were reported as based on pathogenicity, LOPAT and cell wall fatty acid analyses. Recent bacterial isolates from cucurbit crops displaying -like symptoms in Alabama, USA, were identified as , prompting polyphasic re-evaluation of the Serbian strains. All six strains were found to cause severe disease in watermelon and squash seedlings under greenhouse conditions.

sp. nov., and sp. nov., isolated from watermelon in Florida.

Three fluorescent bacterial strains, K1, K13 and K18, were obtained from watermelon () foliage symptomatic of bacterial leaf spot of cucurbits in Florida. The strains underwent phenotypic characterization, including LOPAT (levan production, oxidase activity, pectolytic activity on potato, arginine dihydrolase production and hypersensitive response (HR) on both tobacco and tomato) and pathogenicity testing on watermelon and squash seedlings. Whole-genome sequencing of the isolates was performed, and multi-locus sequence analysis (MLSA) utilizing housekeeping genes , , and placed the isolates into two distinct clades within the genus.

Evolution of copper resistance in pv. population.

The widespread use of antimicrobials that target bacterial pathogens has driven evolution of resistance, compromising the efficacy of these bactericides. Understanding the emergence and spread of resistance genes via mobile genetic elements is crucial for combating antimicrobial resistance. Copper resistance (CuR) in pv.

Phylodynamic Insights into Global Emergence and Diversification of the Tomato Pathogen pv. .

The emergence of plant pathogens is often associated with waves of unique evolutionary and epidemiological events. pv. is one of the major pathogens causing bacterial spot disease of tomatoes.

Genetic and Functional Diversity Help Explain Pathogenic, Weakly Pathogenic, and Commensal Lifestyles in the Genus Xanthomonas.

The genus Xanthomonas has been primarily studied for pathogenic interactions with plants. However, besides host and tissue-specific pathogenic strains, this genus also comprises nonpathogenic strains isolated from a broad range of hosts, sometimes in association with pathogenic strains, and other environments, including rainwater. Based on their incapacity or limited capacity to cause symptoms on the host of isolation, nonpathogenic xanthomonads can be further characterized as commensal and weakly pathogenic.

as a Model System for Studying Pathogen Emergence and Evolution.

In this review, we highlight studies in which whole-genome sequencing, comparative genomics, and population genomics have provided unprecedented insights into past and ongoing pathogen evolution. These include new understandings of the adaptive evolution of secretion systems and their effectors. We focus on pathosystems that have seen intensive study and improved our understanding of pathogen emergence and evolution, particularly in the context of host specialization: citrus canker, bacterial blight of rice, and bacterial spot of tomato and pepper.

Transcriptome profiling of type VI secretion system core gene mutant of highlights regulators controlling diverse functions ranging from virulence to metabolism.

T6SS has received attention due to its significance in mediating interorganismal competition through contact-dependent release of effector molecules into prokaryotic and eukaryotic cells. Reverse-genetic studies have indicated the role of T6SS in virulence in a variety of plant pathogenic bacteria, including the one studied here, . However, it is not clear whether such effect on virulence is merely due to a shift in the microbiome-mediated protection or if T6SS is involved in a complex virulence regulatory network.

Unexpected Diversity of Pseudomonads Associated with Bacterial Leaf Spot of Cucurbits in the Southeastern United States.

Bacterial leaf spot of cucurbits (BLS) is an emerging disease in the southeastern United States that is capable of causing widespread outbreaks under conducive conditions. Historically attributed solely to the bacterium pv. , recent studies have identified additional pathovars as causal agents of the disease.

Influence of Co-occurring Weakly Pathogenic Bacterial Species on Bacterial Spot Disease Dynamics on Tomato.

Mixed infections caused by multiple pathogenic and weakly pathogenic strains inhabiting the same host plants are common in nature and may modify pathogen dynamics. However, traditional plant pathogen studies have mostly focused on the binary interaction between a single host and a single pathogen. In this study, we have looked beyond this binary interaction and evaluated the impact of coinfection on disease dynamics on tomato using the bacterial spot pathogen (), the co-occurring weakly pathogenic strain of (), and the co-occurring potential weak pathogenic strain of ().

Xanthomonas infection and ozone stress distinctly influence the microbial community structure and interactions in the pepper phyllosphere.

While the physiological and transcriptional response of the host to biotic and abiotic stresses have been intensely studied, little is known about the resilience of associated microbiomes and their contribution towards tolerance or response to these stresses. We evaluated the impact of elevated tropospheric ozone (O), individually and in combination with Xanthomonas perforans infection, under open-top chamber field conditions on overall disease outcome on resistant and susceptible pepper cultivars, and their associated microbiome structure, function, and interaction network across the growing season. Pathogen infection resulted in a distinct microbial community structure and functions on the susceptible cultivar, while concurrent O stress did not further alter the community structure, and function.

Evaluation of and Nematode-resistant Cotton Cultivars with Supplemental Corteva Agriscience Nematicides.

- and -resistant new cotton cultivars have recently become available, giving growers a new option in nematode management. The objectives of this study were: (i) to determine the yield potential of the new cultivars PHY 360 W3FE (-resistant) and PHY 332 W3FE (-resistant) in nematode-infested fields and (ii) to evaluate the effects of combining the nematicides Reklemel (fluazaindolizine), Vydate C-LV (oxamyl), and the seed treatment BIO Nematicide 100 (heat killed and its non-living spent fermentation media) with resistant cotton cultivars on nematode population levels and lint yield. Field experiments in 2020 and 2021 indicated population levels were 73% lower on PHY 360 W3FE (R) and 80% lower for on the PHY 332 W3FE (R) at 40 days after planting.

Complete functional analysis of type IV pilus components of a reemergent plant pathogen reveals neofunctionalization of paralog genes.

Type IV pilus (TFP) is a multifunctional bacterial structure involved in twitching motility, adhesion, biofilm formation, as well as natural competence. Here, by site-directed mutagenesis and functional analysis, we determined the phenotype conferred by each of the 38 genes known to be required for TFP biosynthesis and regulation in the reemergent plant pathogenic fastidious prokaryote Xylella fastidiosa. This pathogen infects > 650 plant species and causes devastating diseases worldwide in olives, grapes, blueberries, and almonds, among others.

Crosstalk and trade-offs: Plant responses to climate change-associated abiotic and biotic stresses.

As sessile organisms, plants are constantly challenged by a dynamic growing environment. This includes fluctuations in temperature, water availability, light levels, and changes in atmospheric constituents such as carbon dioxide (CO ) and ozone (O ). In concert with changes in abiotic conditions, plants experience changes in biotic stress pressures, including plant pathogens and herbivores.

Corrigendum: Comparative genomic analysis of the lettuce bacterial leaf spot pathogen, pv. , to investigate race specificity.

[This corrects the article DOI: 10.3389/fmicb.2022.

Natural language processing approach to model the secretion signal of type III effectors.

Type III effectors are proteins injected by Gram-negative bacteria into eukaryotic hosts. In many plant and animal pathogens, these effectors manipulate host cellular processes to the benefit of the bacteria. Type III effectors are secreted by a type III secretion system that must "classify" each bacterial protein into one of two categories, either the protein should be translocated or not.

Comparative Genomic Analysis of the Lettuce Bacterial Leaf Spot Pathogen, pv. , to Investigate Race Specificity.

Bacterial leaf spot (BLS) of lettuce caused by pv. () was first described over 100 years ago and remains a significant threat to lettuce cultivation today. This study investigated the genetic relatedness of the strains and the possible genetic sources of this race-specific pathogenicity.

Taxonomic Refinement of .

comprises a number of economically important fruit tree pathogens classified within different pathovars. Dozens of nonpathogenic and taxonomically unvalidated strains are also designated as , leading to a complicated taxonomic status in the species. In this study, we have evaluated the whole-genome resources of all available spp.