Efecto de los contenidos de sal del medio en el crecimiento y viabilidad de aislados de F. oxysporu

Cara Garcia, Miguel de

Iglesias Gonzalez, Concepcion

Moreno, Marta Maria

Palmero Llamas, Daniel

Tello Marquina, Julio

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Stimulation of mycelial growth of pathogenic and seabed isolates of Fusarium oxysporum in presence of salts

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African Journal of Microbiology Research Vol. 4(17), pp. 1859-1861, 4 September,  2010 
Available online http://www.academicjournals.org/ajmr 
ISSN 1996-0808 ©2010 Academic Journals  
 
 
 
 
Short Communication 
 
Stimulation of mycelial growth of pathogenic and 
seabed isolates of Fusarium oxysporum in presence of 
salts 
 
Daniel Palmero1*, Miguel De Cara2, Marta María Moreno3, Concepción Iglesias1 and  
Julio Cesar Tello2 
 
1Universidad Politécnica de Madrid (UPM). EUIT Agrícola. Ciudad Universitaria s/n. 28040 Madrid, Spain. 
2Universidad de Almería (UA), Dpto. Producción Vegetal. Cañada de San Urbano s/n. 04120 Almería, Spain. 
3Universidad de Castilla-La Mancha (UCLM). EUIT Agrícola. Ronda de Calatrava, 7. 13071 Ciudad Real, Spain. 
 
Accepted 19 March, 2010 
 
The mycelial growth of eleven Fusarium oxysporum strains, eight isolated from seabed soil of the 
South-eastern Mediterranean coast of Spain and three formae speciales from diseased plants were 
tested on potato-dextrose-agar adjusted to different osmotic pressures with either KCl or NaCl (-1.50 to 
-144.54 bar) at 10°C intervals ranging from 15 to 35°C. The extent of growth of F. oxysporum shows the 
same pattern for isolates from the seabeds that for isolates of Formae speciales. Maximal growth was 
observed at -13.79 bar of osmotic pressure at 25°C with an acute decrease at -41.79 bar and lower. At 
35°C maximal growth was observed at -41.79 bar of osmotic pressure not only for seabeds isolates but 
also for pathogenic F. speciales isolates. These findings could indicate that F. oxysporum is well 
adapted to exist in moderate saline habitats. It does not seem that the pathogenicity of the isolates is a 
factor that determines the response to the salinity, but that behavior seems to be common to all the 
isolates studied and it could be speculated to be a specific behavior. 
 
Key words: Salinity, soilborne pathogens, conductivity, osmotic pressure. 
 
 
INTRODUCTION 
 
The Fusarium genus is one of the most ubiquitous fungus 
in the terrestrial ecosystems and a relevant pathogen for 
the cultivated plants. It seems to have a special physio-
logical mechanism that would allow it to survive in arid 
environment (Tresner and Hayes, 1971; Mandeel, 2006). 
Caracuel et al. (2003) demonstrated that the transcription 
factor PacC plays an essential role in salt tolerante of 
Fusarium oxysporum correlating with rapid and increased 
expresión of sodium efflux system in the studied strain. 
Authors worked with a single strain of F. oxysporum f. sp. 
lycopersici strain 4287 (race 2). Previous studies stated 
the existence of a Na+-(Li+)-ATPase as the main system 
involved in the efflux of these cations. Although it is 
unknown if such  regulation  also exists in non pathogenic 
 
 
 
*Corresponding author. E-mail: daniel.palmero@upm.es. Tel: 
+34 913363713. 
isolates. The effect of this regulation, if any, on micelial 
growth remains to be elucidated.  
Fusarium has been collected from such a salty 
environment as the marine bottom of Mediterranean Sea 
(Palmero et al., 2009b). This paper is closely connected 
to Palmero et al. (2008, 2009a) dealing with Fusarium 
solani and Fusarium culmorum strains.  
In general, the Fusarium species have optimal growth 
between -5 and -25 bar and do not grow at all at -100 to -
120 bar (Cook, 1981), with the exception of Fusarium 
nivale that displays its optimal growth between -1 to -2 bar 
and prevent growing at -50 bar. 
Manandhar and Bruhel (1973) showed that Verticillium 
dahliae and F. oxysporum have an optimal growh rate in 
vitro between -10 and -30 bar (4 g/l of salt) and the 
conidial germination diminishes when the concentration 
of salt (NaCl) increases, in the same way, the mycelial 
growth stops growing when salt concentration reaches 80 
g/l (Tran van Canh and Meyer, 1971).
  
1860          Afr. J. Microbiol. Res. 
 
 
 
 
         4.5 
 
         4 
 
         3.5 
 
         3 
 
         2.5 
 
         2 
 
         1.5 
 
         1 
 
 
         0.5 
 
         0 
G
ro
w
th
 
(cm
)  
    -1.5          -13.79        -41.79         -70.37        -99.56       -144.54 
 
 
Figure 1. Growth of pathogenic Formae speciales and seabeds isolates of F. oxysporum versus temperature and osmotic 
pressure (variance does not exceed 5% of the means).  
 
 
 
The aim of this research is to study the interactive 
effects of temperature and osmotic pressure on the 
growth of the isolates of F. oxysporum. The different 
sources of Fusarium isolates used in the study (diseased 
plants and marine bottoms of the Mediterranean coast) 
will provide information on whether or not the 
physiological effect of the salinity is linked to the 
pathogenicity of the isolate or not.  
To determine the interactive effects of temperature and 
osmotic pressure on the growth of F. oxysporum, a 11 x 2 
x 3 x 6 x 5 factorial experimental design was used, 
wherein strains 1 to 11 were the first factor, salt type was 
the second factor (NaCl and KCl), temperature (15, 25 
and 35°C) was the third factor, osmotic pressure (-1.50, -
13.79, -41.79, -70.3, -99.56 and -144.54 bar) was the 
fourth factor; each combination of isolate, temperature, 
and osmotic pressure was replicated 5 times. 
A total of 11 strains were used in salinity and 
temperature tests. Three Formae speciales were used (F. 
oxysporum f. sp. melonis race 1, F. oxysporum f. sp. 
lycopersici race 0 and F. oxysporum f. sp. radicis 
cucumerinum) and eight isolates collected from the 
mouth of the Andarax Riverbed (4 m in depth) and from 
the mouth of the Albuñol Riverbed (1.50 m in depth) in 
previous works (Palmero et al., 2009a). 
There were no significant differences in the number of 
isolates that exhibited growth at different salt composition 
for the F. oxysporum isolates from seabeds (2 = 0.062; 
P = 0.804) and neither for the pathogenic formae 
specialis (2 = 1.548; P = 0.21). Of all the isolates, 56.7% 
of the seabed isolates tested and 54.6% of the isolates of 
the F. speciales grew in media amended with NaCl. 
While 65.3% of the seabed isolates and 63.0% of the 
isolates of the F. speciales grew when KCl was used as a 
solute. No significant difference in the amount of growth 
was observed with the different salt compositions for the 
seabeds isolates [F (1.286) = 0.000; p = 0.983] and for 
the pathogenic F. speciales tested [F (1.214) = 0.109; p = 
0.742] with a mean of 0.972 and 0.885 cm for the seabed 
and F. speciales isolates, respectively.  
The extent of growth of F. oxysporum at different 
osmotic pressures shows the same pattern for isolates 
from the seabeds that for isolates of F. speciales (Figure 
1). Maximal growth was observed at -13.79 bar of 
osmotic pressure at 25°C with an acute decrease at -
41.79 bar and lower. At 35°C, maximal growth was 
observed at -41.79 bars of osmotic pressure not only for 
seabeds isolates, but for pathogenic F. speciales 
isolates. The highest growth occurred at 25°C at all 
osmotic pressures. The differences in extent of growth at 
different osmotic pressures were statistically significant 
(Figure 1). 
The 2 test showed that there were significant 
differences in the growth capacity versus osmotic 
pressure for isolates from the seabeds (2 = 149.908; P < 
0.001) and for isolates of F. speciales (2 = 77.147; P < 
0.001). 
There was minimal or no effect on cultural viability at 
15°C   in   the   first   two   pressure   tests,  with an acute 
decrease in growth capacity (>50%) at  -70.37  bar. Cultural 
  
 
 
 
 
viability at 25°C was still present at -99.56 bar, where all 
of the isolate cultures were viable. At 35°C the viability 
decreased visibly, but the addition of salts to the 
environment produced an increase of the growth 
capacity, the increase was more accused in the case of 
isolates procedents from the marine bottoms where it 
reaches to 87.5% at -70.37 bar, although in lesser extent 
the higher increase of growth capacity in isolates of F. 
speciales was also observed at -70.37 bar. 
There was a clear differences in the growth response of 
pathogenicity. F. oxysporum graphic at 15°C, where 
growth was maximal at the highest osmotic pressure and 
the response at 25 and 35°C, where growth was maximal 
at -13.79 and -41.79 bars, respectively. 
It is worth noting the difference in the response of the 
number of isolates that exhibited growth and the extent of 
growth. This was particularly striking at 25°C, where 
growth capacity only diminished at very low osmotic 
pressures, while the average growth initially increased 
with decreasing osmotic pressure to -13.79 bar and 
declined gradually with increasing salinity. Different 
patterns occurred at 35°C, where the pressure of -41.79 
bar produced the maximum number of isolates that 
exhibited growth and also the maximum mycelial growth 
as well for isolates from the seabeds as for isolates of F. 
speciales. 
The study of the interaction between temperature and 
osmotic pressure showed statistically significant dif-
ferences in the response to temperature for isolates from 
the seabeds [F (2.287) = 363.369; P < 0.001; 2 = 0.729] 
and for isolates of F. speciales [F (2.215) = 243.377; P < 
0.001; 2 = 0.711]. Statistically significant differences 
were also observed in the response to osmotic pressure 
for isolates from the seabeds [F (5.287) = 120.684; P < 
0.001; 2 = 0.691] and for isolates of F. speciales [F 
(5.215) = 82.853; P < 0.001; 2 = 0.677] and in the 
interaction between temperature and osmotic pressure 
for isolates from the seabeds [F (10.287) = 39.907; P < 
0.001; 2 = 0.596] and for isolates of F. speciales [F 
(10.215) = 33.918; P < 0.001; 2 = 0.631].  
A significant interaction between temperature and 
osmotic pressure causes the previously noted change in 
the growth response at lower osmotic pressures; it seems 
that this interaction is not different in function of the origin 
or pathogenic capacity of the isolates. 
Our results suggest that the survival of F. oxysporum 
could be possible in moderately saline soils with high soil 
temperatures (near 35°C). 
Hyphal growth may be stimulated at low osmotic 
pressures (-41.79 bar) over 25°C. This agrees with the 
results of Cook et al. (1972) for F. culmorum and are 
consistent with those obtained by Cook and Christen 
(1976) for F. culmorum and Fusarium graminearum and 
by   Palmero   et   al.  (2008,   2009a)  for   F.  solani  and                  
 
 
Palmero et al.         1861 
 
 
 
F. culmorum. 
Experimental results show that F. oxysporum has the 
capacity of growing at low osmotic pressures which could 
explain the prevalence of the Fusarium genus in soils in 
the seabeds of the Mediterranean Sea and within semi-
arid environments. Pathogenicity of the isolates is not a 
factor that determines the response to the salinity, but 
seems to be common to all the isolates studied. It could 
be a specific behavior. Further work is necessary to 
understand the physiological mechanism of salt tolerance 
in F. oxysporum as well as its effects on their 
pathogenicity. 
 
 
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Cook RJ (1981). Water relations in the Biology of Fusarium. In: Nelson 
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Cook RJ, Christen AA (1976). Growth of cereal root rot fungi as affected 
by temperature and water potential interactions. Phytopathology, 66: 
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Cook RJ, Papendick RI, Griffin DM (1972). Growth of two root rot fungi 
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Stimulation of mycelial growth of pathogenic and seabed isolates of Fusarium oxysporum in presence of salts

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