Dispersal Of Plant Pathogens Research Articles

Dust Storms as Global Disseminators of Plant Pathogens

This contemporary mycological inquiry investigates into the escalating threat to global food security posed by the dispersal of plant pathogens through airborne dust, exemplified by the simulation of a colossal dust storm, named “Godzilla”. Employing advanced computational models, researchers trace the route of Fusarium oxysporum spores from North Africa across the Atlantic, settling in the Caribbean and southeastern United States. The study estimates the conveyance of over 13,000 viable spores, raising concerns about their impact on agricultural regions, particularly southeastern Louisiana, Mexico, Haiti, the Dominican Republic, and Cuba. While ultraviolet radiation typically neutralizes airborne spores within three days, the focus shifts to spore viability upon landing in vulnerable agricultural zones. Proximity to the dust source in intercontinental regions intensifies the risk, emphasizing the need to understand fungal disease dynamics and identify susceptible agricultural areas. Global prevalence of F. oxysporum and its capacity to infect over 100 crops highlight the potential for significant crop losses and economic consequences. The research underscores the urgency of comprehending disease dissemination dynamics and protecting global food security, emphasizing regions like sub-Saharan Africa as critical sources of viable spores. The study’s preliminary nature prompts a future focus on observational data acquisition, including comprehensive dust storm mapping and genetic comparisons of F. oxysporum, to validate the model’s findings. This research work calls for proactive measures to address the escalating threat of disease, laying the ground work for forthcoming mycological endeavors

Hybrid inferiority and genetic incompatibilities drive divergence of fungal pathogens infecting the same host.

Agro-ecosystems provide environments that are conducive for rapid evolution and dispersal of plant pathogens. Previous studies have demonstrated that hybridization of crop pathogens can give rise to new lineages with altered virulence profiles. Currently, little is known about either the genetics of fungal pathogen hybridization or the mechanisms that may prevent hybridization between related species. The fungus Pyrenophora teres is a global pathogen of barley. The pathogenic fungus P. teres exists as two distinct lineages P. teres f. teres and P. teres f. maculata (Ptt and Ptm, respectively), which both infect barley but produce very distinct lesions and rarely interbreed. Interestingly, Ptt and Ptm can, by experimental mating, produce viable progenies. Here, we addressed the underlying genetics of reproductive barriers of P. teres. We hypothesize that Ptt and Ptm diverged in the past, possibly by adapting to distinct hosts, and only more recently colonized the same host in agricultural fields. Using experimental mating and in planta phenotyping in barley cultivars susceptible to both P. teres forms, we demonstrate that hybrids produce mixed infection phenotypes but overall show inferior pathogenic fitness relative to the pure parents. Based on analyses of 104 hybrid genomes, we identify signatures of negative epistasis between parental alleles at distinct loci (Dobzhansky-Müller incompatibilities). Most DMI regions are not involved in virulence but certain genes are predicted or known to play a role in virulence. These results potentially suggest that divergent niche adaptation-albeit in the same host plant-contributes to speciation in P. teres.

Unselective Transport of Phytopathogenic Fusarium Fungi from Litter and Soil by Ground-Dwelling Arthropods Links Semi-Natural and Agricultural Habitats.

The dispersal of propagules, such as fungal spores or seeds by actively moving animals, connects and shapes communities. The dispersal of plant pathogens by arthropods might be a crucial mechanism in the spread of several crop diseases. Ground-dwelling arthropods are potential linkers between fungal communities in semi-natural and agricultural habitats by transporting propagules of Fusarium fungi. We compared the Fusarium communities on the body surface of ground-dwelling arthropods with litter in semi-natural and soil in agricultural habitats with a focus on the Fusarium community. We found three relatively distinct Fusarium communities with moderate overlap. We detected a higher richness of Fusarium species on the body surface of arthropods compared to litter and soil communities. The results suggest that the Fusarium community on the body surface of arthropods relates to the composition observed in litter and soil with limited filtering mechanisms between communities. Ground-dwelling arthropods are relevant agents for the distribution of Fusarium and therefore link fungal communities in adjacent habitats.

Response of Container-grown Nursery Plants to Chlorine Used to Disinfest Irrigation Water

The recycling of irrigation water may cause the dispersal of plant pathogens. Irrigation water disinfected with 2.4 mg·L−1 of free chlorine for 5 min was overhead-applied to 17 container-grown nursery plants for 11 weeks in a commercial nursery to evaluate the response of container-grown nursery plants to chlorine. No visual symptoms of injury or growth reduction were observed on the evergreen shrubs (Juniperus horizontalis, Thuja occidentalis, Buxus microphylla, Picea glauca, Rhododendron catawbiense, Taxus media, and Chamaecyparis pisifera), but there were visual injuries and/or growth reduction on some of the deciduous shrubs (Salix integra, Hydrangea paniculata, Prunus ×cistena, Weigela florida, Physocarpus opulifolius). Symptoms of anthracnose were reduced on Cornus alba plants treated with chlorinated water. The chlorine treatment did not affect leaf chlorophyll content. The chlorine treatment killed all fungi and oomycetes in the irrigation water (DNA multiscan). Although there were visible leaf injuries and growth reduction on some of the deciduous plants, chlorine injury did not render them unsalable. Results suggest that irrigation water treated with 2.4 mg·L−1 free chlorine for 5 min will effectively control the dispersal of common plant pathogens without reducing the market value of container-grown plants.

Amplification of DNA of Xanthomonas axonopodis pv. citri from historic citrus canker herbarium specimens

Herbaria are important resources for the study of the origins and dispersal of plant pathogens, particularly bacterial plant pathogens that incite local lesions in which large numbers of pathogen genomes are concentrated. Xanthomonas axonopodis pv. citri ( Xac), the causal agent of citrus bacterial canker disease, is a notable example of such a pathogen. The appearance of novel strains of the pathogen in Florida and elsewhere make it increasingly important to understand the relationships among strains of this pathogen. USDA-ARS at Beltsville, Maryland maintains approximately 700 herbarium specimens with citrus canker disease lesions up to 90 years old, originally collected from all over the world, and so is an important resource for phytogeographic studies of this bacterium. Unfortunately, DNA in herbarium specimens is degraded and may contain high levels of inhibitors of PCR. In this study, we compared a total of 23 DNA isolation techniques in combination with 31 novel primer pairs in order to develop an efficient protocol for the analysis of Xac DNA in herbarium specimens. We identified the most reliable extraction method, identified in terms of successful amplification by our panel of 31 primer pairs. We also identified the most robust primer pairs, identified as successful in the largest number of extracts prepared by different methods. We amplified Xac genomic sequences up to 542 bp long from herbarium samples up to 89 years old. Primers varied in effectiveness, with some primer pairs amplifying Xac DNA from a 1 / 10,000 dilution of extract from a single lesion from a citrus canker herbarium specimen. Our methodology will be useful to identify pathogens and perform molecular analyses of bacterial and possibly fungal genomes from herbarium specimens.

Plant Pathogens and Plant Diseases

This book, written by a team of Australian plant pathologists, is design to give students and researchers a background in the principles of plant pathology and of managing plant diseases. The book is divided into five sections. The first deals with the agents that cause disease and includes fungi, bacteria, phytoplasmas, viruses, viroids, nematodes, parasitic plants and abiotic agents. There is also a useful and up-to-date chapter on serological and molecular techniques to detect and identify plant pathogens. Part two deals with the survival and dispersal of plant pathogens, including airborne and soilborne inoculum, and the role played by vectors. Part three covers infection processes, epidemiology and crop-loss assessment and this is something of a mixed bag, as it includes chapters on plant defence, disease prediction, and biocontrol of weeds using plant pathogens. Quantitative concepts of epidemiology feature in the introduction to part four, which concerns disease management. This may not appeal to the purist or disease modellers but does have the virtue for students of introducing disease growth curves in the context of strategies for control. The remainder of this section covers all aspects of disease management including quarantine and sanitation, chemical, cultural, genetic and biological approaches to disease control. The final part gives specific examples of different types of plant diseases and their control, based on the different types of pathogens, as well as a chapter on disease in natural communities and another on postharvest pathology. Inevitably the book has an Australian emphasis in the examples chosen, but the principles developed are universal and it should prove very useful for a variety of plant pathology courses. The editors have done well to compile such a range of information from different authors in a uniform style. The book is strong on the biology of the different pathogens, and particularly on practical aspects of disease management, which occupy approximately one third of the 550 pages. It is well illustrated with tables, keys and diagrams, although the production standards are not as high as in some other recent texts where glossy paper and even colour photos are included. It is easy to read and accessible for students, and with the very wide range of topics covered deserves to be considered as a core text for both introductory and intermediate level plant pathology courses. At the price of $A49 it is good value.