© Benaki Phytopathological Institute
Fusarium
and
Rhizoctonia
infecting native Greek tomato varieties
73
at anthesis and fruit set, respectively.
A
s
,
g
s
and
E
were measured using a LC
pro
+ port-
able photosynthesis system (ADC BioScien-
tific Ltd. Great Amwell, Herts, UK). Record-
ings were made between 10:00 and 12:00
a.m on fully expanded young
leaves of sim-
ilar size. Photosynthetic photon flux density
(PPFD) in the leaf chamber was set at 1100
μmol/m
2
/sec with a halogen lamp at 25°C,
while CO
2
reference ranged between 380
and 437 ppm.
Statistical analysis
Both experiments were factorial with va-
riety and time of assessment (i.e. dpi) as the
main factors. Experimental data were sub-
jected to one-way ANOVA and means were
separated using the Duncan’s multiple range
test at
P
= 0.05. Prior to analysis, DI percent-
age data were transformed to logarithmic
values (i.e. Log
10
) to highlight significant dif-
ferences between means, although, the un-
transformed data are presented in the tables.
Scale data of DSI were analysed using the
Kruskal-Wallis non-parametric test. Statistical
analysis was performed with SPSS for Win-
dows, Version 12.0 (Chicago, SPSS Inc., USA).
Results and Discussion
Disease symptoms
F. oxysporum
f. sp.
lycopersici
infected the
root and the vascular system of tomato vars
‘Chondrokatsari Messinias’ and ‘Katsari San-
torinis’ (Figure 1). No visual symptoms were
observed on the experimental plants 40 dpi.
However, tomato plants of ‘Chondrokatsa-
ri Messinias’ and, to a lesser extent, ‘Katsa-
ri Santorinis’ showed a limited degree of leaf
epinasty and leaf yellowing 60 dpi. Di Pietro
et al.
(2003) described the symptoms caused
on tomato plants infected by
F. oxysporum
as leaf epinasty, followed by stunting, yel-
lowing of the lower leaves, progressive wilt-
ing, defoliation and finally plant death. In
the present study, symptoms were also ob-
served on the surface of the roots as dark
brown to black, necrotic, circular or irregular
lesions (Figure 1A). According to Olivain and
Alabouvette (1999),
F. oxysporum
f. sp.
lyco-
persici
was able to perform a vascular infec-
tion of tomato root tissue producing lesions
on the roots. However, these lesions had lim-
ited expansion probably due to intense de-
fense reactions occurring in the superficial
cell layers (Olivain and Alabouvette, 1999).
Brown discoloration of the vascular system
of the plants was also observed in the pres-
ent study indicating colonization of xylem
vessels by the pathogen (Figure 1B). This is
considered a typical symptom of infection
of tomato plants by
F. oxysporum
f. sp.
lyco-
persici
following root tissue penetration and
colonization of the vascular system by the
pathogen (Bishop and Cooper, 1983; Agrios,
1997; Olivain and Alabouvette, 1999).
R. solani
infected the plants of both vari-
eties at the stem base (Figure 2). Symptoms
were recorded as volcano-like cankers of
various sizes, with a brown centre and dark
brown to black margin (Figure 2A). Cankers
increased in size with time resulting in plant
collapse 40 dpi (Figure 2B). Usually,
R. so-
lani
infection progresses quickly, especial-
ly when conditions are favourable (i.e. low
temperatures and increased soil humidity)
(Baker, 1970; Agrios, 1997).
Disease assessments
DSI on tomato plants of vars ‘Chon-
drokatsari Messinias’ and ‘Katsari Santorinis’
inoculated with
F. oxysporum
f. sp.
lycopersi-
ci
was low and ranged between 0.5 and 2.5
(on a 0-4 scale). In general, DSI and DI did
not significantly (P < 0.05) increase with time
(from 40 to 60 dpi) with the exception of DSI
on var. Katsari Santorinis (Table 1). More spe-
cifically, DSI on ‘Katsari Santorinis’ increased
by 5-fold from 40 to 60 dpi (Table 1).
In general, CN, ACD and DI on ‘Chon-
drokatsari Messinias’ and ‘Katsari Santorin-
is’ tomato plants inoculated with
R. solani
significantly (P < 0.05) increased with time
(from 40 to 60 dpi) with the exception of CN
on ‘Katsari Santorinis’ (Table 2). More spe-
cifically, CN, ACD and DI on ‘Chondrokatsa-
ri Messinias’ increased with time by 7-, 23-
and 67%, respectively (Table 2). ACD on var.
‘Katsari Santorinis’ increased by 4-fold from
