© Benaki Phytopathological Institute
Karajeh & Al-Nasir
24
1971). A higher ammonium level in nutrient
medium, in the presence or absence of ex-
cised roots, decreased the total number of
J2s that hatched from dispersed eggs and
egg-masses (Sudirman and Webster, 1995).
Increasing of ammonium levels reduced the
percentage of J2s, which penetrated the
roots over time as compared to the control
(Sudirman, 1992).
The mode of action of ammonium on
the root-knot nematode can be explained
by the assumption that higher concentra-
tions of ammonium may have been suffi-
cient to modify malate dehydrogenase ac-
tivity (Viglierchio, 1979). This would have
subsequently a) decreased the energy avail-
able for egg hatching and plant invasion
processes and/or b) significantly affected
the electrical potential around the root tip
area where J2s penetrated and thus influ-
enced nematode penetration of the roots
through diminished attractiveness of the
root tips (Scott and Martin, 1962) and/or c)
significantly inhibited giant cell formation
and nematode development without affect-
ing root growth (Orion
et al
., 1980; Orion
et
al.
, 1995).
Increasing the salt EC level from EC2 up
to EC8 resulted in decreasing the develop-
ment of the root-knot nematode on tomato
and increasing plant growth. The higher salt
EC did not affect the pH of the rhizospher-
ic soil but slightly increased its measured EC
and salinity. Hence, (NH
4
)
2
SO
4
is a more suit-
able candidate for the control of the nema-
tode than NH
4
Cl, which showed similar sa-
linity level to NaCl.
In a previous report where the effect of
concentration gradient of KNO
3
on horizon-
tal migration of
M. javanica
J2s was studied,
the juveniles moved preferentially toward
the lower mineral salt concentration region
(Prot, 1979). However, in our experiments,
high concentrations of nitrate as KNO
3
did
not considerably affect nematode infec-
tion or reproduction on the host. This is in
an agreement with the results of other stud-
ies (Marks and Sayre, 1964; Ismail and Saxe-
na, 1977).
Generally, ammonium was more effi-
Table 2.:
Main and interaction effects (probability values) of the nematode
Meloidogyne javanica
, salt and electrical conductivity (EC) on root
galling, plant and root fresh and dry weights, plant contents of proteins, phosphorus and potassium of tomato and on measured pH, EC and
salinity of rhizospheric soil at a pot experiment.
Source
GI
1
PFW RFW PDW
RDW Protein
P
K
pH
EC
Salinity
Salt
0.028
2
0.002
0.031
0.003
0.032
0.320
0.123
0.799
0.115
0.001
0.629
Nematode
0.002
0.353
0.718
0.726
0.011
0.084
0.415
0.310
0.062
0.659
0.577
EC
0.171
0.320
0.320
0.295
0.715
0.210
0.251
0.766
0.061
0.276
0.322
Salt x Nematode
0.030
0.284
0.803
0.609
0.081
0.224
0.124
0.104
0.048
0.046
0.892
Salt x EC
0.111
0.310
0.722
0.797
0.894
0.198
0.078
0.233
0.592
0.158
0.530
EC x Nematode
0.245
0.110
0.967
0.706
0.583
0.145
0.141
0.257
0.764
0.057
0.540
Salt x Nematode x EC
0.039
0.317
0.612
0.478
0.101
0.157
0.400
0.147
0.806
0.097
0.288
Experimental analysis based on 6 replicates for NH
4
Cl, NH
4
NO
3
, KNO
3
, NaCl, and (NH
4
)
2
SO
4
salts at EC 2, 4 and 8 mS/cm.
1
GI: root galling index, PDW: plant dry weight, RDW: root dry weight, P: phosphorus, K: potassium.
2
Probability values ≤ 0.05 are significant.
1...,16,17,18,19,20,21,22,23,24,25 27,28,29,30,31,32,33,34,35,36,...52