Page 13 - Volume 1, Issue 1, January 2008

New plant pathogens in Greece 11
different research groups in Plant Patholo-
gy/Virology laboratories both in Academ-
ic and Research Institutions in Greece.
These laboratories have adopted the
modern molecular detection developed
worldwide and also contributed to the de-
velopment of new ones. As a result, since
1990 a significant number of new viruses
and viroids has been identified and char-
acterized as causal agents of new diseas-
es or as the actual causal agents of known
and established ones. This increased ap-
pearance of new virus/viroid pathogens
is mainly due to the extensive internation-
al trade of plant propagation material. The
risk that these agents represent after their
introduction in the country greatly de-
pends upon the exclusion measures un-
dertaken by the farmers and the Ministry
of Agriculture (Crop protection division),
the availability of efficient virus vectors
assuring their further spread and estab-
lishment either in the native flora and/or
cultivated susceptible crop plants and fi-
nally upon the agricultural practices ad-
opted. Also, following the above work on
characterization of new viruses/viroids a
number of research projects related to the
development of reliable detection molec-
ular methods, the production of virus-free
propagative material in fruit trees and
grapevine and the control of virus-vectors
are in progress.
This review paper describes epidemio-
logical data on newly characterized virus-
es and viroids and attempts to highlight
the risks they represent for the crops con-
cerned. Viruses are described and listed
according to their mode of transmission.
3.1. Graft transmitted viruses
and viroids
Cherry leaf roll virus 
(CLRV, genus Nepovirus)
The virus was first reported in walnut
(Juglans regia L.) trees in Peloponnese (Ilia,
Argolida) and Central Greece (Evritania) in
2006 (Sclavounos et al., 2006). Affected trees
produced fewer fruits exhibiting external
necrosis whereas their leaves were showing
chlorotic mosaic and ring patterns. CLRV is
an important pathogen of walnut where is
both seed and pollen transmitted, thus ag-
gravating its potential risk for the crop.
The virus was also detected in asymp-
tomatic olive trees (Olea europea L.) (Ka-
poni and Kyriakopoulou, 2006).
Cherry necrotic rusty mottle virus  (CN-
RMV, genus Foveavirus) and Little cherry
virus I (LChVI, genus Closterovirus)
In 2003, a limited scale survey of cher-
ry trees (Prunus avium L.) in three counties
of Northern Greece (Pieria, Pella, Imathia)
revealed a high incidence of CNRMV (36%)
and LChVI (32%). Both are perpetuated and
spread by infected vegetative propagation
material (Maliogka et al., 2006a). Further in-
vestigations are needed to estimate their
presence and effects on production.
Grapevine angular mosaic virus 
(GAMV, genus Ilarvirus)
In 1994, characteristic virus-like symp-
toms were observed on grapevine hybrid
Baresana × Baresana in the collection of
the Grapevine Institute in Athens, Greece.
In 2000, a new grapevine ilarvirus was iso-
lated from affected plants, characterized
and identified as the causal agent of the
disease by fulfilment of Koch’s postulates
(Girgis et al., 2000). In addition, the virus
is pollen transmitted, but its overall eco-
nomic importance remains unknown.
Grapevine  leafroll-associated viruses
Grapevine leafroll disease has been
known to occur in all grapevine regions in
Greece. A number of filamentous viruses are
associated with the disease: Grapevine lea-
froll-associated virus 1, 3, 5 (GLRaV-1, GLRaV-3,
GLRaV-5, genus Ampelovirus), Grapevine leaf
roll-associated virus 4, 6, 8 , 9 (GLRaV-4, GL-
RaV-6 GLRaV-8, GLRaV-9, unclassified genus
Ampelovirus), Grapevine leafroll-associated
virus 2 (GLRaV-2, genus Closterovirus), Grape-
vine leafroll-associated virus 7 (GLRaV-7, un-