الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
SUMMARY
Macrop.10mina phaseolina, Rhizoctonia solani and
Sclerotium Iolfsii are considered the most common destructive
patho1rens that cause root-rot, charcoal-rot and
damping-off diseases on sunflower. Fusarium Oxysporum is
considered also one of the most pathogenic fungi that infect
roots of sunflower plants causing damping-off, wilt, and
sometimes rClot-rot.
The present investigation was planned to study the
causal orga~isms of sunflower root diseases, the effect of
some physiological and environmental factors on the isolated
fungi and their control.
The attained results could he summarized as follows:
1. Macrol’homina phaseol ina, Rhizoctonia solani, Sci eroti um
rolfsii and Fusarium Oxysporum were isolated fom
diseased sunflower plants collected from different
Goverlorates in A.R.E. Fusarium Oxysporium were more
frequ~ncy isolated than the other fungi.
2. Patho~enicity tests proved that S. rolfsii was the most
destluctive fungus causing high percentage of pre-or
post-emergence and root-rot. M.pbaseolina was less
effective in the pre-emergence phase hut becomes more
serious in the post-emergence phase and later stages of
-g-rol’<t:h c au s’Ln c charcoal-rot and root-rot after
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relatively long time.
3. Pathoger.icity tests of the other fungi showed generally
that t.heae fungi could be arranged descendingly according
to their virulence in the pre- and post-emergence
phases is follows: S.rolfsii, F.oxysporum, R.solani and
M.pbaseolina. However.
4. The conbinations of fungal inoculations revealed that
all cOllbinations included S.rolfsii showed very high
percen1.ages of pre- and post-emergence phase, which may
indica’:e its synergistic effect to other tested fungi.
Other .louble combinations including M.phaseo1 ina showed
low pe~centage of pre- and post-emergence phases, which
may ir.dicate its antagonistic effect to other tested
fungi. However, when all the isolated fungi were used,
the p,~rcentages of pre-, post-emergence and diseased
plant~ were high.
5. Under greenhouse condi tions, the bacterial, actinomrcetes
and fungal counts, including the appearance
of T1 i choderma sp. and the hi gh frequency of Peni ci 1-
lium spp., Aspergillus spp. and the low frequency of
Fusali um spp., in the rhizosphere region of Giza 2 cv .
were more than that in the rhizosphere of Miak cv.
duriIlq the seedling and vegetative stages and thus the
perc~ntaqes of pre- and post-emergence phases were
lowe~ than that of Miak cv. In the second and third
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6.
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stages of plant growth (flowering, seed formation and
maturity I the former count was reversed and hence the
percenta;re of infection with wilt and/or root-rot was
lower in Miak cv. than Giza 2 cv. Generally, the rhizosphere
effect increase by increase of plant age.
In v i t:r o, three out of the four bacterial isolates
isolatec from the rhizosphere region of sunflower cultivars
a.nd identified as Bacillus sp . were antagonistic
to S. ro : fs i i and M.phaseol ina and reduced the growth of
the twc fungi. On the other hand, these bacterial
i so Lat.e.s were not antaogonisti c to R. solani and did not
cause a~y growth reduction. The other 4 Bacillus isolates
w er e antagonistic to the wilt fungus F.oxysorum
and caused growth reduction.
7. Additic,n of Trichodermia harzianum isolated from the
rhizQsphere region, to soil infested with the 4 tested
fungi :’educed the pre- and post-emergence phases and
the pe:~centaqe of diseased plants compared with soil
i.nfes t e.d only with the fungi. This trend was found in
both cllitivars under study.
8. Labora.:ory screening of various fungicides for the control
of the 4 sunflower pathogenic fungi, showed that
the 4 fungicides tested gave partial or complete
inhibition to the fungal growth. The inhibition power
varied among the fungicides and the concentration used,
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as thi s :)ower increased with the increase in fung icide
concentration. The fungicides Rhizolex and Homai 80
were t.he most effective fungicides against the 4
pathogers, on the other hand, Topsin M and Monceren
were less effective against the pathogens.
9. In vi t.s:o experiments were confirmed by in vivo experiment.
Soed dressing with the fungicide Rhizolex (3g/kg
seeds) Jave the best results in controlling the preemergence
damping-off phase and reducing the percentage
of diseised plants, followed by Homai 80, Monceren and
Topsin M. These results were true for both cultivars
under study.
10. Giza 2. Miak, Hybrid ”All., Hybrid ”B” and Hybrid ”en
sunflo~er cultivars were tested under field conditions
for thl~ir suscept ib i1ity to pre- and post- emergence
dampin~’-off, root-rot and wilt diseases and the results
showed that Hybrid ”B” and Hybrid ”crt were highly susceptib
ie to the pre- and post-emergence phases, whi Le
Miak end Giza 2 cv s . were tolerant to both phases.
Hybrid ”A” was susceptible to the pre-emergence phase
and irrmune to the post-emergence phase, Hybrid ”B” and
Giza 2 cvs. were highly susceptible to wilt disease and
resis~ant to root-rot disease. On the other hand,
Hybric. ”Cit and Miak cvs. were resistant to wilt infection
Lod hiqhly susceptible to root-rot infection.
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14. Generally, under field conditions it could be recommended
to treat Giza 2, Miak and HYbrid ”A” seeds
cUlti’rars with 3g/Kg seeds of either Rhizolex or Homai
80 or Topsin M or Monceren for obtaining best yield
comporents (Head diameter, seed yield/plant, weight of
100 s~ed and number of seeds/laO g seeds). These
fungicides were also to some extend good in controlling
the di3eases under field conditions.
15. Plants infected with F.oxysporum have less seed oil
conten1 and lower iodine value than the healthy ones.
On the other hand, infection with the wilt fungus
caused an increase in the acid number of diseased
seeds. Diseased seeds showed also a change in the normal
col’ur of oil except in case of Miak cultivar .