Page 22 - Volume 6, Issue 1, January 2013

© Benaki Phytopathological Institute
Karajeh & Al-Nasir 20
The objectives of this study were to in-
vestigate the effects of five salts at four elec-
trical conductivity (EC) levels (2, 4, 6 and 8
mS/ cm) on the control of the root nema-
tode M. javanica. The test salts comprised of
four nitrogen containing salts; ammonium
chloride (NH 4Cl), ammonium nitrate (NH-
4NO3), potassium nitrate (KNO3) and ammo-
nium sulfate ((NH 4)2SO4), and sodium chlo-
ride (NaCl). The interaction of the effects
of the salts, the EC levels and the root-knot
nematode on the susceptibility and growth
of tomato were also assessed under growth
chamber and greenhouse conditions.
Materials and Methods
Analytical reagent grade of five salts,
NH 4Cl, NH4NO3, KNO3, NaCl and (NH4)2SO4,
was used. Electrical conductivity for each
salt solution used was 2 (EC2), 4 (EC4), 6 (EC6)
and 8 (EC8) mS/ cm and was achieved by
dissolving 1.07, 2.14, 3.21 and 4.28 g/l NH4Cl,
1.60, 3.20, 4.80 and 6.39 g/l NH4NO3, 2.02,
4.04, 6.06 and 8.08 g/l KNO3, 1.17, 2.34, 3.50
and 4.67 g/l NaCl or 2.63, 5.28, 7.92 and 10.55
g/l (NH 4)2SO 4, respectively, in water.
A field population of M. javanica previ-
ously collected from a cucumber field at
Ein-Sarah region in Karak Province of Jordan
and extracted in the laboratory was used for
this study. The nematode population was
morphologically identified and molecular-
ly characterized using the sequence charac-
terized amplified region-polymerase chain
reaction (SCAR-PCR) test (Karajeh, 2004).
Infectivity test
Two-week-old seedlings (ca. 5 cm tall) of M.
javanica-susceptible tomato cv. GS12 were
transplanted into 100 ml plastic pots (one
seedling/ pot), filled with a sterilizedmixture
of 1:1:1 peat: sand: perlite. For each treat-
ment, one thousand 2nd stage juveniles
(J2s) of M. javanica were picked and trans-
ferred into a small Petri dish containing 10
ml of each solution at each EC or sterile tap
water (served as control). The juveniles were
two-days-old and hatched from eggs which
were surface-sterilized with 0.5% NaOCl.
All Petri dishes were kept at room tem-
perature for one hour before inoculating
the tomato seedlings through pouring the
solutions into the rhizospheric region of
each seedling one week after transplant-
ing. Each treatment was replicated five
times. The plants were regularly irrigated
with water. The treated and control plants
were arranged according to a completely
randomized design (CRD) and maintained
in a growth chamber at 25°C and 16/8 hour
light/dark regime.
Six weeks after inoculation, the plants
were up-rooted and the galling index eval-
uated according to the 0-5 scale: 0=no
galling, 1=1-2 galls, 2=3-10, 3=11-30, 4=31-
100 and 5=over 100 galls (Taylor and Sass-
er, 1978). Egg-masses were picked from the
roots, extracted with a 0.5% NaOCl solution
for 30 seconds (Hussey and Barker, 1973)
and quantified under a compound micro-
scope at 10X magnification level. Nematode
reproduction factor (RF) was calculated as
the number of eggs per plant (Pf) divided
by the initial J2 inoculum number (Pi).
Greenhouse experiment
To determine the effects and interactions of
M. javanica with variable levels of electrical
conductivity of the five salts on the growth
of tomato in greenhouse conditions, one-
month old seedlings (about 15cm tall) of to-
mato cv. GS12 were tested. The seedlings
were planted in 5dm3 pots filled with 1.5
kg of a 1:2 mixture of water-washed sand
and a non-sodic, non-saline sandy loam soil
(EC 1.3 mS/ cm, pH 7.1, 0.6% organic matter,
1.1mg/g total nitrogen, and 43% CaCO3) that
had been previously sterilized at 85ºC for 5
days. One week after transplanting, the de-
sired level of electrical conductivity (EC2,
EC4 and EC8) was achieved and maintained
by irrigating the soil with saline solutions
to field capacity level for three consecutive
weeks. For the control treatments, the same
procedure was followed except that tap wa-
ter replaced the salt solution.
Each treatment was replicated six times
(one plant per pot) and each seedling was