Tests for Risk Assessment of Root Infection by Plant Pathogens

From the roots to the stem: unveiling pear root colonization and infection pathways by Erwinia amylovora

FEMS Microbiology Ecology ◽

10.1093/femsec/fiaa210 ◽

2020 ◽

Vol 96 (12) ◽

Author(s):

Ricardo D Santander ◽

José F Català-Senent ◽

Àngela Figàs-Segura ◽

Elena G Biosca

Keyword(s):

Fire Blight ◽

Plant Pathogens ◽

Erwinia Amylovora ◽

Fluorescent Protein ◽

Epifluorescence Microscopy ◽

Economic Losses ◽

Root Infection ◽

Pome Fruit ◽

Infection Pathways ◽

Biofilm Development

ABSTRACT Fire blight caused by Erwinia amylovora affects pome fruit worldwide, generating serious economic losses. Despite the abundant literature on E. amylovora infection mechanisms of aerial plant organs, root infection routes remain virtually unexplored. Assessing these infection pathways is necessary for a full understanding of the pathogen's ecology. Using the pathosystem Pyrus communis–E. amylovora and different experimental approaches including a green fluorescent protein transformant (GFP1) and epifluorescence microscopy (EFM) and laser confocal scanning microscopy (LCSM), we demonstrated the pathogen's ability to infect, colonize and invade pear roots and cause characteristic fire blight symptoms both in the aerial part and in the root system. Plant infections after soil irrigation with E. amylovora-contaminated water were favored by root damage, which agreed with EFM and LCSM observations. E. amylovora GFP1 cells formed aggregates/biofilms on root surfaces and invaded the cortex through wounds and sites of lateral root emergence. Sugars, sugar-alcohols and amino acids typically secreted by roots, favored the in vitro biofilm development by E. amylovora. Migration of E. amylovora cells to aerial tissues mainly occurred after xylem penetration. Overall, our findings revealed, for the first time, common root infection patterns between E. amylovora and well-known soil borne plant pathogens and endophytes.

Download Full-text

Diagnosis of Plant Pathogens and Implications for Plant Quarantine: A Risk Assessment Perspective

Detection and Diagnostics of Plant Pathogens ◽

10.1007/978-94-017-9020-8_12 ◽

2014 ◽

pp. 167-193 ◽

Cited By ~ 3

Author(s):

Vittorio Rossi ◽

Thierry Candresse ◽

Michael J. Jeger ◽

Charles Manceau ◽

Gregor Urek ◽

...

Keyword(s):

Risk Assessment ◽

Plant Pathogens ◽

Plant Quarantine

Download Full-text

Location of overseas botanic gardens with New Zealand Myrtaceae in relation to myrtle rust occurence

New Zealand Plant Protection ◽

10.30843/nzpp.2018.71.215 ◽

2018 ◽

Vol 71 ◽

pp. 356 ◽

Cited By ~ 1

Author(s):

M. Virginia Marroni ◽

Kirsty Boyd-Wilson ◽

Rebecca E. Campbell ◽

Mark R. McNeill ◽

David A.J. Teulon

Keyword(s):

Risk Assessment ◽

New Zealand ◽

Plant Pathogens ◽

Assessment Tool ◽

Botanic Gardens ◽

Natural Ecosystems ◽

Sentinel Network ◽

Myrtle Rust ◽

Ex Post ◽

Potential Impact

New Zealand’s productive systems and natural ecosystems depend on a robust biosecurity framework to exclude invasive pests, diseases and weeds. Risk assessment is an important component of this biosecurity framework identifying potential threats posed by invasive organisms to specific plants and plant systems before they arrive in New Zealand. A major challenge in risk assessment is determining the potential impact of a pest or disease when it is not present in New Zealand. The International Plant Sentinel Network (IPSN), a network of botanic gardens and arboreta, aims to provide early warning of new and emerging tree and plant pests and diseases. The utility of the IPSN in providing information on the potential impact of myrtle rust for New Zealand’s indigenous Myrtaceae. Botanic gardens were identified around the world with New Zealand Myrtaceae and where myrtle rust is present. This is a first step in an ex-post study on the use of sentinel or expatriate plants as a biosecurity risk-assessment tool. The approach could be extended to other plant pathogens or pests to explore their impact on New Zealand indigenous or cultivated plant species overseas.

Download Full-text

Freeze substitution fixation of fungal reproductive structures and spores

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100156936 ◽

1989 ◽

Vol 47 ◽

pp. 990-991

Author(s):

C. W. Mims ◽

E. A. Richardson

Keyword(s):

Plant Pathogens ◽

Freeze Substitution ◽

Uranyl Acetate ◽

Chemical Fixation ◽

Dialysis Membrane ◽

Razor Blade ◽

Thin Sections ◽

Reproductive Structures ◽

Dry Down ◽

Diamond Knife

The advantages of freeze substitution fixation over conventional chemical fixation for preservation of ultrastructural details in fungi have been discussed by various authors. As most ascomycetes, basidiomycetes and deuteromycetes do not fix well using conventional chemical fixation protocols, freeze substitution has attracted the attention of many individuals interested in fungal ultrastructure. Thus far most workers using this technique on fungi have concentrated on thin walled somatic hyphae. However, in our laboratory we have experimented with the use of freeze substitution on a variety of fungal reproductive structures and spores with promising results.Here we present data on freeze substituted samples of sporangia of the zygomycete Umbellopsis vinacea, basidia of Exobasidium camelliae var. gracilis, developing teliospores of the smut Sporisorium sorghi, germinating teliospores of the rust Gymnosporangium clavipes, germinating conidia of the deuteromycete Cercosporidium personatum, and developing ascospores of Ascodesmis nigricans.Spores of G. clavipes and C. personatum were deposited on moist pieces of sterile dialysis membrane where they hydrated and germinated. Asci of A. nigricans developed on pieces of dialysis membrane lying on nutrient agar plates. U. vinacea was cultured on small pieces of agar-coated wire. In the plant pathogens E. camelliae var. gracilis and S. sorghi, a razor blade was used to remove smal1 pieces of infected host issue. All samples were plunged directly into liquid propane and processed for study according to Hoch.l Samples on dialysis membrane were flat embedded. Serial thin sections were cut using a diamond knife, collected on slot grids, and allowed to dry down onto Formvar coated aluminum racks. Sections were post stained with uranyl acetate and lead citrate.

Download Full-text