Volume 9, Issue 2, July 2016 - page 14

© Benaki Phytopathological Institute
Tzortzakakis et al. 62
(c. 5-10) were randomly collected from roots
of each plant, transferred into an aqueous
solution of sodium hypochoride to release
eggs (Hussey and Barker, 1973) and checked
under the stereoscope for the presence of
eggs. The number of egg masses produced
on susceptible tomato, resistant tomato and
pepper were compared by ANOVA. The ex-
periment was conducted once.
Results and Discussion
A review of 13 described resistance-break-
ing populations of RKN from Greece during
the period 1994-2013 (Table 1) reveals the
following characteristics:
From 1994 until 2013, 13 RKN popula- 1.
tions, from which 11 M. javanica and two
M. incognita, able to reproduce on resis-
tant tomato, have been recorded in five
different regions of Greece: Crete, Epirus,
Thrace, Peloponissos and Macedonia.
Four populations, three from Crete ( 2. M.
javanica and M. incognita) and one from
Peloponissos (M. javanica), collected
from heavily infected roots of nematode
resistant tomato, reproduced at high
rates on resistant tomatoes in pot tests
(Tzortzakakis et al., 1999, 2005, 2008).
Seven populations, two from Crete ( 3. M.
javanica), four from Epirus (M. javanica)
and one from Macedonia (M. incognita),
collected from nematode susceptible
crops with no recent history of resistant
tomato cultivation in the field sites, re-
produced at high rates on resistant to-
matoes in pot tests (Tzortzakakis et al.,
1999, 2005, 2014).
Two populations, one from Thrace ( 4. M.
arenaria collected from balm) and one
from Crete ( M. incognita collected from
susceptible tomato), were unable to re-
produce on resistant tomato in pot tests,
when six eggmasses were inoculated per
plant. However, when resistant tomatoes
were inoculated with 30 egg masses per
plant, a virulent M. javanica was revealed
in both cases, composing a minor per-
centage in the original population which
was undetected in the identification pro-
cess (Tzortzakakis et al., 2008).
The only two resistance-breaking popu- 5.
lations of M. incognita found in Greece,
Table 1. Root-knot nematode populations (Meloidogyne spp.) from Greece, virulent on resis-
tant tomato hybrids with the Mi gene, reported within the period 1994-2013.
Code Nematode
species
Region Host plant found References
1HVa and HVb ,
4/1 and 4/21
M. javanica Crete Resistant tomato Tzortzakakis and Gowen, 1996;
Tzortzakakis et al., 1999
16, 17 M. javanica Crete Susceptible tomato Tzortzakakis et al., 1999
Mj P1, MjP2, Mj P3,
Mj P4
M. javanica Epirus Susceptible tomato,
cucumber
Tzortzakakis et al., 2005
Mj C1 M. javanica Crete Resistant tomato Tzortzakakis et al., 2005
Mi C1 M. incognita Crete Resistant tomato Tzortzakakis et al., 2005;
Tzortzakakis and Blok, 2007
T M. javanica2 Thrace Balm Tzortzakakis et al., 2008
C M. javanica3 Crete Susceptible tomato Tzortzakakis et al., 2008
P M. javanica Peloponissos Resistant tomato Tzortzakakis et al., 2008
Mi NG M. incognita Macedonia Beet Tzortzakakis et al., 2014
1 Τhe lines 4/1 and 4/2 are the same with lines 1HVa and 1HVb (single egg mass lines from the same nematode
population). In the reference Tzortzakakis et al., 1999 they were characterized by molecular and biochemical
methods.
2 Τhe original population identified as M. arenaria, which was avirulent and the virulent M. javanica consisted a
minor component selected by resistant tomato.
3 Τhe original population identified as M. incognita, which was avirulent and the virulent M. javanica consisted a
minor component selected by resistant tomato.