© Benaki Phytopathological Institute
Meloidogyne javanica
and
M. incognita
infecting resistant tomato
63
one in Crete and the other in Macedo-
nia, differed in their ability to reproduce
on susceptible pepper cultivars (Tzort-
zakakis and Blok, 2007; Tzortzakakis
et
al
., 2014).
In all the above studies referred, small
scale surveys had been conducted in two
cases: a) in Crete, in a random sampling on
37 greenhouses representative of the main
vegetable growing areas, where two resis-
tance-breaking populations of
M. javanica
were found (Tzortzakakis
et al
., 1999) and b)
in Preveza Epirus, a random sampling on ten
greenhouses, where the presence of four re-
sistance-breaking populations of
M. javan-
ica
was detected (Tzortzakakis
et al
., 2005).
The remaining records came from samples
which had been sent to the laboratory for
identification.
The results of the current study on RKN
populations collected in 2013-2014 are pre-
sented in Table 2. There was no infection in
the resistant tomato cv. Silvana inoculated
with the I5 and K populations, which prove
that the
Mi
gene was effective under the
certain experimental conditions. The pop-
ulation I5, identified as
M. javanica
, did not
reproduce on resistant tomato and pepper.
The population K, identified as
M. incognita
,
reproduced on pepper at lower rate than on
susceptible tomato but not on resistant to-
mato.
Six populations were found to repro-
duce on resistant tomato at a level which
did not differ significantly to that obtained
on the susceptible tomato. Furthermore,
their ability to reproduce on resistant to-
mato was stable as they sustained consis-
tent reproduction on resistant tomato for
at least four successive generations. The
egg masses which were randomly collect-
ed from roots of resistant tomato and pep-
per all contained a sufficient (>100) number
of eggs. From the resistance-breaking pop-
ulations, four were
M. javanica
which did not
reproduce on pepper while from the two
virulent
M. incognita
, the I4 reproduced on
pepper, at lower rate than on tomato, while
the I3 did not.
In the 20 tested RKN populations, the
resistance-breaking ones were found at
a quite high percentage (30%) compared
with that of the survey done 18 years ear-
lier (Tzortzakakis
et al
., 1999), in which that
percentage was 5% in 37 samples collected
from several areas of Crete. The population
which was identified as
M. incognita
(I3)
,
able
to reproduce on resistant tomato but not on
pepper, is similar to another population of
M. incognita
found earlier in another area of
Crete (
Mi
C1 in Tzortzakakis and Blok, 2007).
However, the
M. incognita
(I4), reproducing
on both the resistant tomato and pepper, is
reported for the first time in Crete and for
Table 2.
Number of egg masses produced by eight populations of root-knot nematodes
(
Meloidogyne
spp.) collected from greenhouses of Crete on susceptible tomato, resistant to-
mato and susceptible pepper.
Code Origin
Species
No of egg masses
Susceptible
tomato
cv. ACE
Resistant
tomato
cv. Silvana
Susceptible
pepper cv.
California Wonder
SED P value
I1 Tomato
M. javanica
56
44
0
1
7.9 >0.05
I2 Tomato
M. javanica
45
38
0
6.6 >0.05
I3 Tomato
M. incognita
44
41
0
7.7 >0.05
I4 Pepper
M. incognita
41
44
22
6.5 <0.05
I5 Cucumber
M. javanica
42
0
1
0
-
-
S Tomato
M. javanica
38
32
0
5
>0.05
V Tomato
M. javanica
39
36
0
6.7 >0.05
K Pepper
M. incognita
45
0
29
3.8 <0.01
Origins: I1-I5 Ierapetra, S: Skourvoula Messara, V: Vori Messara, K: Kisamos Chania; Average of five replicates per
treatment;
1
Ιn case of 0 values the data were excluded from analysis; SED and P values from ANOVA.
