الفهرس 
Introductionيوجد فقط 14 صفحة متاحة للعرض العام
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المستخلص
SUMMARY
a) Effect of the fungicides Vitavax Captan a~d
Topsin M 70 on total bacterial count:
The application of fungicides gradually inhibited
the rhizosphere microflora of cotton plants, at the early
stages of plant groWth. This was found with the normal
recommended dose and this trend lasted till 15 days from
sowing, then microorganisms gradually increased till the
end of the experiment where the total bacterial count
approximated that of control with Vitavax Captan and
surpassed that of control with Tpsin M 70- •
However, with both fungicides the harmfUl effect of fungicides
on the total count was more obvious at the higher
dose (10 fold) than the lower dose (normal dose) and in
the uncultivated than cultivated soil.
b) Effect of fungicides on spore-former bacteria:
The applioation of fungicides reduced the density
of $pore-former bacteria. M±nimal spore-former counts
were obtained after 15 days from sowing. At the normal
dose of Vitavax Capt an , spore-former count in the rhizo138
sphere of cotton plants surpassed that of control after
90 days from sowing. However, the effect of Vitavax
Captan was more drastic on the spore-former count in the
uncultivated soil. Topsin M 70 greatly decreased sporeformers
counts at both ooncentrations used in the cultivated
and uncultivated soils allover the experimental
period.
c) Effect of fungicides on actinomycetes count:
Fungicides application reduced the,actinomycetes
count. ~he extent of inhibition was in line with the rate
of application. By the end of the experiment; at the normal
dose of fungicides, actinomycetes count mostly surpassed
that of control. This was found with both fungicides in
the cultivated and uncultivated 80ils. With the higher
dose of fungicides, actinomycetes count at the end of the
experiment approximately levelled that of control.
d) Effect of fungicides on fungal count:
The application of fungicides highly decreased the
density of fungi in the rhi.zosphere of cotton plants and in
the unoultivated 8011 till the end of the experiment (90
days from sowing). This was found with both f’ungicides.
The reduction in fungal count was in line with the rate of’
application.
e) Effect of fungicides on anaerobic nitrogen fixers count:
The application of Vitavax Captan at the normal dose
deoreased the anaerobic nitrogen fixers count in the rhizosphere
of cotton plants till 7 days from so~ then anaerobic
nitrogen fixers started to increase and ,counts surpassed
that of control after 30 days from sowing and thereafter.
In case of the 10 fold dose of Vitavax Captan and
both rates of Topsin M70% application, anaerobic nitrogen
fixers counts were lower than their respective control in
the majority of the investigated samples till the end of
the experiment.
f) Effect of fungicides on aerobic nitrogen fixers oount:
This group was also affected by the application of
fungicides. At the normal dose of fungicides application,
Azotobacter count decreased in the early stages after fUngicides
application, then counts levelled or even surpassed
their respective control. !he higher dose of the fungicides
greatly dec~ased. Azotobacter count in all treatments allover
the experimental period.
g) Effect of fUngicides on nitrifying bacteria:
Both fungicides showed drastic effect on nitrifiers
count in the cultivated and uncultivated soils.
A- Effect of the fungicides Vitavax Captan and Topsin M70%
on pathogenic fungi, in vitro.
The minimal concentrations of the fungicides Vitavax
Captan which completely inhibited the growth of the
pathogenic fungi,in vitro, were:
_ 500 ppm of Vitavax Captan were necessary for the complete
inhibition of Fusarium 0xYsporum.
_ 100 ppm of Vitavax Captan completly inhibited R.solani.
_ 5 ppm or lower of Vitavax Captan completely inhibited
the growth of ~.rolfsii.
The minimal concentrations of the fungicide
Topsin It70%, which completely inhibited the growth of
the pathogenic tungi, in vitro I were
_ 1000 ppm of Topsin II70% were required for the complete
inhibition of R-.solani.
_ 100 ppm of Top.in JI70% completely inhibited ~.oxysporum
_ 10000 ppm of Tops1n • 70% were not sufficient for the
complete inhibition of -Scl.rolfsii.
B- Effect of fungicides Vitavax Captan and Topsin M70%
on f’ungal count in soil and rhizosphere of cotton
plants, sown in sterile soil infested with the pathogens
R.solani and ~.rolfsii.
The application of fungicides, decreased the fungal
count in sterilized soil infested with the pathogens. The
effect was more dras~ic in the uncultivated soil. The toxic
effect was obvious after 7 days from fungicide application
and thereafter. V1tavax Captan seemed to be more toxic
than Topsin K 70’ •
c- Effect of fungicides on reducing the dampLng-off in
cotton plants sown in sterilized soil infested with
the root-rot pathogens.
Fungicides application increased the percentages of
germination and survival plants and a1most decreased the
the pre- and post-emergence damping-off percentages as
compared to their respective oontrol (sterilized Boil
infested with the pathogen, without fungicide application).
This was found with both fungicides and for all investigated
pathoge:cs.
14.3
on fungal counts in cultivated and uncultivated soils
during 7-15 days from application. At the later stages,
fungal counts increased, but were always lower than oontrol
in the rhizosphere of’ the cultivated and in the
unoultivated soil.
Effect of soil infestation with ~.rolfsii and fungicides
applioation on microbial counts:
Soil infestation with Scl.rolfeii increased the
total baoterial, actinomycetes and fungal counts. Fungicides
application decreased the bacterial, actinomycetes
and fungal counts in the cultivated and uncultivated soils.
The extent of inhibition was in line with the rate of
application.
IV.A- Antagonistic fungi:
The study showed that out of 675 fungal isolates
investigated, 170 isolates antagonized R.so1ani. Out of
these antagonists, 82 isolates were potent antagonists
against R.solani. All the light brown Aspergillus isolates
(30 isolates), the Trichoderma isolates (16 isolates)
and 80% of the 25 isolates of the olive green Penicillium
were potent antagonists against R.so1aniThe study showed that out of 675 fungal isolates
investigated, 150 isolates antagonized Scl.rolfsii, out of
these, 83 isolates were potent antagonists. All the investigated
isolates of the light brown Aspergillus (30 isolates),
olive green Penicillium (25 isolates) and Trichoderma (16
isolates) proved to be potent antagonists against Scl.rolfsii.
B- Antagonistic bacteria:
1- Bacterial antagODi.sts against !.aola.ni:
The study indicated that out of 722 bacterial
isolates investigated. 160 islates antagonized !.solani, out of
these antagonists -. 34 isolates highly antagonized !.solani. Most of
the potent antagonists were found to belong to genera Pseudomonas
and Bacillu8.
2- Bacterial antagonists against ~.ro1fsii:
The study showed that out of 722 bacterial isolates,
171 isolates antagonized Scl.rolfeii, out of these
antagonists, 54 isolates proved to be efficient antagonists
against Scl.rolfsii. The preliminary identification showed
that most of the pGtent antagonists belonged to genera
Pseudomonas and Bacillus.
c- Antagonistic actinomycetes:
1- Actinomycetes antagonists against ~.solan1:
The investigation showed that out of 627 actinomycetes
isolates investigated, 281 isolates antagonized
!.solani, out of which, 122 isolates proved to be potent antaggonists.
~he maJor! ty fit the coloured aetinomycetes showed
higher percentages e£ antagonists than non coloured
actinO]Q”cetes • Among the coloured antagonists, 86.~ of
the violet antagonists, 80% of the yellow antagonists and
66.7 of the orange pis-ented antagonists were potent antagonists
against R.solani as compared to their respective
groups.
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2- Antagonistic actinomycetes isolates against Scl.rolfsii:
The study showedthat out of 627 actinomycetes isolates
investigated, 279 isolates antagonized Scl~rolfsii.
Out of these antagonists, 99 isolates were found to be
potent antagonists.
Many of the coloured actinomyceteBshowed hi
higher percentages of antagonists against Sel. rolfs!1
than uncoloured actinomycetes ’ • Amongthe coloured
antagonists, 57.3%of the grey antagonists and 52%of the
violet antagonists proved to be potent antagonists against
~.rolfsi1.
Effect of fungicides on the potent antagonists, in vitro.
The potent antagonist, Aspergillus ap. isolate was
very sensitive to Vitavax Captan, but could tolerate high
concentrations of Topsin 1170%. !he potent antagonist
Penicillium. ap, isolate was sensitive to Topsin ]I 70 than
Vitavax Captan. The efficient antagonist, Trichodermaap,
isolate was 8ensitiTe to Topsin • 70, but could tolerate
moderate ooncentrations of Vitavax Captan.
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BVitavax Captan was more toxic, than Topsin M 70, to
the potent bacterial antagonists. Vitavax Captan inhibited
4 bacterial antagonists at very low conoentrations, while
the fifth isolate tolerated 10,000 ppm. It was found that
potent antagonists belonging to the same genus differed in
their tolerenoe to different fungicides.
Antagonistio actinomyoetes showed more sensitivity
to Vitavax Captan than Topsin JC70. Potent antagonistio
aotinomyoetes isolates having the same pigment (colour)
differed in their tolerence to different trmgicides.
Biological oontrol &8 compared to chemical control of
damping-off in cotton:
Seed inoculation with the potent antagoniat,Aspergillus
ap. isolate ~incr.a8ed the percentages of germination and
survival plants ana decreased the damping-off percentages
as oompared to oontrol.
J.48
Seed inoculation with the potent antagonist,
Penicillium sp. isolate was not efficient 8S the
Aspergillus sp. isolate inoculation. However, seed
inoculation with a mixture of the two potent antagonists
(Aspergillus sp. isolate + Penicillium sp.
isolate) showed the greatest effect than when any of
the antagonists was inoculated solely.
The study showed that biological control nearly
levelled chemical control of damping-off in cotton.