View
2
Download
0
Category
Preview:
Citation preview
(SUB)MICROSCOPIC INVASIVE
SPECIES
• Categories of submicroscopic invasive species
• Consequences of their occurrence in Croatia
• Pathogenicity (infectivity, virulence) vs. invasiveness
• Control strategies
(SUB)MICROSCOPIC INVASIVE
SPECIES
In databases, often under 100 worst and/or listed as neither
plants nor animals.
www.invasive.org – North America invasive species
Categories: plants, animals, diseases, other species
http://www.iucngisd.org/gisd/search.php - Global invasive
species database has virus, bacteria, fungi categories
DAISIE – European database, bacteria, fungi…not many
Invasiveness – impact on ecosystem (biodiversity) and/or
human activities
Importance of other factors (vectors, biology…)
Algae, planktonic organisms (diatoms, dinoflagellates), fungi,
oomycetes
Bacteria
Viruses
Subviral pathogens:
ViroidsCoconut cadang cadang viroid (CCCVd)
PrionsChronic waisting disease (CWD)
Others – deficient classification at different taxonomy levels
(incertae sedis)
CRYPHONECTRIA PARASITICA
Class Sordariomycetes, order Diaporthales, family Cryphonectriaceae
Aggressive phytopathogenic fungus, amongst 100 worst –
serious threat to biological diversity. It causes chestnut blight.
Infects wood through bark cracks and leads to chestnut tree
disease and death – canker, callusing canker, biocontrol.
C. parasitica lifecycle and dissemination
Invasion history
C. parasitica – very pathogenic in European and American
chestnuts but not in East Asian species.
Fungus-host coevolution- Japanese and Chinese chestnuts
very tolerant to infection. Both plant and fungus can survive
and reproduce.
North American scenario
American chestnut (Castanea dentata) – very sensitive, over
40 years, 3.5 billion trees destroyed.
American chestnut distribution pattern before the introduction of
the fungus in 1904.
European scenario
European chestnut – sensitive but infecting fungus is mostly of
hypovirulent strain.
European chestnut
distribution pattern
(Castanea sativa Mill.)
Chestnut blight first recorded in 1938 near Genoa. It spread to
all chestnut growing regions in Europe. In Croatia, first recorded
near Opatija in 1955.
Hypovirus
Cryphonectria hypovirus 1-4 (CHV-1 to -4) - dsRNA detected
in the fungus cytoplasm but the virus has +ssRNA genome.
It has no capsid proteins. Virus like particles in the fungus
cytoplasm.
It modifies fungus transcriptome.
In Europe, out of 4 viruses only CHV-1 recorded.
It reduces parasitic growth of the fungus and its sporulation
capacity resulting in lowered pathogenicity and invasiveness.
Virus distribution in nature:
• vertical– by asexual spores (conidia) 1-99%, requires
moisture (mainly splash distribution 1-2 m) but possible by
birds, mites and wind
• horizontal – hyphal fusion amongst vegetatively compatible
(vc) types of fungi
• human activities – uncontrolled plant import and trade, biocontrol efforts
Biocontrol by a hypovirus depends on vc types (fungus), the
mode of its distribution in nature, on the virus type (CHV-1 is
good biocontrol agent in Europe).
C. parasitica and CHV sampling sites in Croatia
Prof. Mirna Ćurković-Perica kindly provided slides 4-11.
Phytoplasmas
class Mollicutes
• intracellular phytopathogenic bacteria, pleomorphic 200-800 nm, MLOs (mycoplasma-like organisms) until 1993.
• Taxon ‘Candidatus Phytoplasma’ – members cannot be
cultured in axenic media.
• Parasites in two kingdoms – plant phloem and insects feeding
on plant sap (Cixiidae, Psyllidae).
• In plants, they cause serious diseases but usually not in
insects!
Grapevine Phytoplasmas
• cause Grapevine Yellows diseases (GY) - 8 taxa.
•The most important GY agents in Europe:
Flavescence Dorée (FD)
– quarantine pathogen
Bois Noir (BN), Vergilbungskrankheit (VK), Stolbur (Stol),
‘Ca. P. solani’ – endemic
Flavescence dorée phytoplasma (FDp)
• FDp first recorded in1950s in SW France.
• Scaphoideus titanus Ball – American Nearctic ampelopfagous cicadellidinsect is the principal vector in Europe.
• AldYp and PGYp are similar to FDp – quarantine pest and epidemicdisease agent.
• Devastating disease, fast spread, epidemic nature (F, I, PT, CH, SLO, H,SRB, HR 2010).
In Croatia, Bois Noir (BN) is also important. Polyphagous
Hyalesthes obsoletus Sign. is the main vector. It feeds on the
grapevine occasionally but prefers weeds.
bindweed nettleeggs in the roots
• FDp i BNp cannot be differentiated on the basis of symptoms!
Vitis vinifera L. ‘Pošip’
‘Plavac Mali’
• Identification by molecular tools (16S rDNA) and for the
molecular epidemiology MLST (multilocus sequence typing) is
required. Control strategies should be based on molecular
epidemiology data.
CTV virion 2000 x 11 nm, phloem
limited
Niblett et al. 2000, Virus Res. 71, 97-106.
Known from 1930s.
It destroyed 100 million citrus trees (SwO, mandarin, grapefruit
grafted on sour orange), new CTV foci even in the 21st century!
Citrus tristeza virus (CTV)
All tristeza faces Stem Pitting
(SP)
Photos: C. Roistacher
Quick Decline (QD)
Symptom expression depends on: rootstock/scion combination,
CTV strain (genotype), environmental factors.
Aphid vectors of CTV:
Toxoptera citricida (invasive!)
6-25x more efficient vector than Aphis
gossypii,
A. spiraecola,
Myzus persicae
CTV long-distance transfer by man!!!
Infected planting material (budwood (twigs), young grafted
plants).
T. citricida (foto G. Nolasco)
Citrus production in Croatia
Split
Dubrovnik
• 2 counties, 1500 ha
• Japanese mandarin
(Satsuma, C. unshiu)
300t/y, some lemon,
sweet orange
• Neretva River basin
• Institute for Adriatic Crops, Split – collection
Zagreb
CTV pilot study (2002-2004)
• CTV occurrence and distribution?
• Strains (biogrups) of CTV - virulence?
Mexican lime – universal indicator
Vein corking
Stem pitting
spooning
Vein clearing
gra
fting
Highly pathogenic CTV strains (SP, QD, SY) recorded
previously thought not to be present in the Mediterranean
basin.
Mixed infections are frequent (55%).
CTV populations have high variability, recombinant genotypes
are recorded.
64%
36%
1
2
55%
45%1
2
ELISA – 50% trees CTV-positive!
Satsuma/P.trifoliata combination is symptomless!
Similar results in Satsuma collection.
CTV-SP strains recorded in the northern Mediterranean –
coldest citrus growing area.
Satsuma mandarins are symptomless reservoir hosts
important for CTV distribution within and outside the country.
CTV populations and strains need to be monitored as well as
potential vectors especially since Toxoptera citricida arrived to
Portugal and Spain in 2003.
TRISTEZA !!!
• Emerging viruses
SARS
Avian flu
Nipah
Hendra
mumps
human metapneumovirus
bluetongue
Ebola
Monkey pox
Sin Nombre
Monkey pox
West Nile
Sin Nombre
Adapted from Carter&Saunders, 2007
West Nile virus (WNV) invasive in the USA.
WNV - Uganda 1937, recorded in the NYC only in 1999.
Flavivirus
East Africa, Middle East, Eastern Europ– occasional
outbreaks.
Transmitted by mosquitoes.
About 20% human cases results in a flu-like disease, less
than 1% out of the symptomatic cases presents neurological
complications (encephalitis).
Firs birds symptoms in birds of NY, than horses and humans.
Within 5 years, WNV spread to Canada, Mesoamerica, the
Caribbean's…in 2012 recorded in Croatia in humans but
before that in horses.
Intuitions:
WHO, EPPO, EU agencies, Croatian institutions
Parliament, Ministries and Agencies
Legislation (e. g. CTV):
CTV status in the EU is regulated by:
1) Directive EU 2000/29 Annex II/AII European isolates (EU Annex II /AI non
European isolates)
2) EPPO Quarantine A2 list.
CTV Status in Croatia additionally regulated by:
1) Ordinance - Pravilnik o mjerama za sprečavanje unošenja i širenja
organizama štetnih za bilje, biljne proizvode i druge nadzirane predmete i
mjerama suzbijanja tih organizama (NN 74/2006) Prilog 2 II-A-II te
2) Ordinance - Pravilnikom o stavljanju na tržište reprodukcijskog sadnog
materijala i sadnica za proizvodnju voća (NN 124/06)
EDUCATION, CONTROL, ERADICATION, CERTIFICATION!
Recommended