© Benaki Phytopathological Institute
Tzortzakakis
et al.
64
the second time in Greece (Tzortzakakis
et
al
., 2014). It is important to notice that in Ier-
apetra which is the most important area of
greenhouse vegetable production in Crete,
four out of the eight tested RKN popula-
tions were resistance-breaking populations.
These results are in contrast with the study
conducted 18 years ago (Tzortzakakis
et al
.,
1999), where no resistance-breaking popu-
lations were found in this area.
Since commercial nurseries provide
nematode-free tomato seedlings, a possi-
ble explanation for such a ‘rise’ in the per-
centage of resistance-breaking populations,
could be a ‘potential selection’ by the in-
creased cultivation of resistant to RKN toma-
to hybrids. However, in the fields where the
pathotypes were found, there was no recent
history of cultivation of resistant tomatoes.
Furthermore, previous studies in pots indi-
cated that single egg mass lines of
M. javan-
ica
did not have the capacity of adapting to
resistant tomatoes (Tzortzakakis
et al
., 1999).
Thus it is difficult to provide an explanation
for the increase in the percentage of the re-
sistance-breaking RKN
populations within
the last 18 years period.
In the Mediterranean area, resistance-
breaking populations of
M. javanica
and
M. incognita
have been reported in several
countries e.g. Cyprus, France, Italy, Morocco,
Spain, Tunisia and Turkey, with the majori-
ty of them being
M. javanica
(Castagnone-
Sereno
et al
., 1994; Devran and Sogut, 2010;
Eddaoudi
et al
., 1997; Molinari and Miacola
1997; Ornat
et al
., 2001; Philis and Vakis, 1977;
Robertson
et al
., 2006). The results present-
ed herein, constitute additional records on
the occurrence of virulent
M. javanica
and
M. incognita
populations in the area of Ier-
apetra, Crete.
We thank the agronomists A. Thomadakis, G.
Troulinakis, D. Stavrianakis and H. Anousakis
for providing most of the nematode samples
and N. Anastasakis from Elanco Hellas S.A.C.I.
for providing the resistant tomato cv Silvana
seeds.
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