الفهرس 
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Abstract
SUMMARY
The present work was carried out to study effect of adding some
biocontrol agents, are used to control root rot disease in broad bean and soybean
plants, on non-target beneficial microorganism. These studies were carried out
under laboratory, greenhouse and field conditions to confirm correlate scientific
facts with application in field. Results obtained from this work could be
summarized as follow: -
Isolation and identification of root rot patho2ens, beneficial bacteria and
some anta2onists.
Rhizoctonia solani and Sclerotium rolfsii were isolated from rotted
samples of broad bean and soybean as the main causal pathogens of root
rot and damping off diseases. The nodule bacteria Rhizobium
leguminosarum, and Bradyrhizobium japonicum, were also isolated from
the active root nodules of broad bean and soybean, respectively.
Azotobacter bacteria were isolated also from rhizospheric soils of soybean
and broad bean. The antagonists Trichoderma harzianum, T. viride,
Gliocladium vixens and Bacillus subtilis were isolated from rhizosphere of
healthy roots of broad bean and soybean plants.
Patho2enicity tests:
2- Most dangerous effects of R. solani and S. rolfsii singly or in combination
was occurred at stage of pre-emergence damping off. Rhizoctonia solani
caused higher pre-emergence than S. rolfsii, while S. rolfsii + R. solani
caused the highest pre-emergence damping-off on both broad bean and
soybean. Pre-emergence was higher on soybean than broad bean whereas
the post-emergence showed the opposite trend. Post-emergence caused by
R. solani or S. rolfsii each alone was significantly higher than combination
(S. rolfsii + R. solani). Finally, R. solani + S. rolfsii produced the lowest
SUMMARY
percentages of survived seedlings of both broad bean and soybean
followed by R. solani and S. rolfsii, respectively.
Antibiosis studies in vitro:
3- All tested antagonists and their cultural filtrates caused significant
reduction in the linear growth of both R. solani and S. rolfsii. Trichoderma
harzianzini was most effective followed by T viride, B. subtilis and G.
virens, respectively. Reduction in growth was significantly higher in S.
rolfsii than R. solani.
4- Reduction due to culture filtrates of the antagonistic fungi was increased
sharply and significantly, in particular with R. solani, by increasing age of
antagonist-culture from 5 to 10 days then decreased significantly again to
reach its minimum value with 20 days-old culture filtrates. However, 3
days old culture filtrates of the antagonistic bacteria Bacillus subtilis
was more effective than 2 and 5 days old filtrates.
5- Reduction in growth was significantly increased by increasing
concentrations of different culture filtrate to 10, 30 and 50%, respectively.
S. rolfsii was more sensitive to elevating concentration filtrates than R.
solani.
6- Efficacy of the antagonistic culture filtrates in reducing growth of tested
pathogens was affected by pH values of the antagonist-growth medium.
The pH 71 was the most effective than pH 6.2 or 8.2.
The nature of anta onist _natho en interaction morphol ical studies ~
7- The tested antagonists (T harzianum and Bacillus subtilis) caused
malformation and changed color in the growing hyphae of S. rolfsii and R.
solani.
SUMMARY 119
Evaluafion of different anta20nists in c i ntrollin • info • n wi h h .tQ.$,
root rot path02ens under 2reenhouse conditions on:
8- The incidence of damping off but not root rot caused by S. rolfsii and R.
solani singly or in combination in pots was significantly decreased and
healthy plants increased by treating broad bean seeds with a tested
antagonist at rate of 4gIKg seeds. Treating seeds with T. harzianum, B.
subtilis, and G. Wrens against S. rolfsii, R. solani and S. rolfsii + R. solani,
respectively resulted in the lowest incidence of damping off and highest
increase in healthy plants. In soybean, T. harzianum, G. virens or B.
subtilis had no significant effect on pre-emergence damping off caused by
S. rolfsii, R. solani and S. rolfsii + R. solani, respectively. Also, G. virens
and B. subtilis had no significant effect on % post-emergence damping off
caused by S. rolfsii and R. solani, respectively.
9- In broad bean, most tested antagonists used as seed treatments significantly
decreased incidence of root rot in pathogen-free soil, significantly
increased it in pathogen-infested soil. In soybean, all seed treatments
decreased root rot caused by S. rolfsii while root rot caused by R. solani
was significantly increased compared with untreated seeds.
10- In broad bean, S. rolfsii (8) and R. solani (R) singly or in combination (8 +
R) decreased the shoot fresh weight significantly while S + R only
decreased shoot dry weight significantly. Number of pods / plant was
decreased by Sand 8 + R. The fresh weight of shoots and dry weight of
shoots and roots seemed not affected significantly in S- and R- infested
soils compared with control (non-infested soil). In soybean, both pathogens
singly or in combination caused significant decrease in the fresh weight of
shoots and roots and number of pods / plant. The dry weight of shoots was
not affected whereas dry weight of roots was significantly reduced by
SUMMARY 120
infection with 5 + ]( only. The dry weight of roots was not affected
whereas dry weight of roots was significantly reduced by infection with 5
+ 1?only compared with control (non-infested soil).
Il---In broad bean, applying T harzianum as seed treatment against tested
pathogens particularly (8 + R) was the best for increasing the fresh and dry
weight of shoots and roots compared with control. In soybean, most tested
antagonist-seed treatments increased the fresh weight of roots, using G.
virens. B. subtilis and T harzianum against 5, R, and 8 + R, respectively
produced the highest significant increase. Using B. subtilis and T. harzianum
only increased shoot fresh weight significantly. In general, using B. subtili.s
and T harzianum against S. rolfsii produced the highest significant increase
in the dry weights of shoots and roots.
12---Infection with 5, Rand 8 + R significantly decreased nitrogen content in
broad bean and soybean plants. Most tested antagonist-seed treatments
increased nitrogen content significantly. Applying B. subtilis or T.
harzianum as seed treatments against 8 + R led to the highest increase in
the nitrogen content.
13---Population of Azotobacter bacteria was significantly increased in soil by
time elapsed after sowing and increased further by the tested antagonistseed
treatments. It was significantly lowered in pathogen-infested than in
pathogen free-soil. Soil infested with S + R exhibited the lowest
populations. Applying B. subtilis as seed treatment was better than T.
harzianum or G. virens for increasing population of Azotobacter bacteria
in soils infested with 8, R or 5 + R. This trend was true in both broad bean
and soybean.
141nfection with the tested pathogens led to significant decrease in number
and weight of Rhizobium nodules on roots of broad bean or soybean plants
SUMMARY 121
(using untreated seeds). Infection with S + R caused the highest decrease
followed by Sand R, respectively. All antagonist-seed treatments
significantly increased number and weight of Rhizobium nodules, B.
subtilis used as seed treatment against S, R or S+ R was the best.
Effect of applyin2 different anta20nists at different doses under field
conditions:
15- All tested antagonist- seed treatments decreased pre-emergence and postemergence
damping off and increased survivals significantly compared
with control. Treating broad bean seeds with T. harzianum at rate of 4g /
Kg seeds was the best for suppressing incidence of pre- and postemergence
damping off and producing the highest survivals.
In soybean, pre-emergence damping off was significantly reduced only by
using B. subtilis (at 2 and 4), T. harzianum (at 4g), T. viride (at 2g) and G.
virens (at 8g). However, all tested seed antagonists decreased postemergence
damping off and increased survivals significantly in
comparison with control. In general, T. viride followed by B. subtilis and
T harzianum each (at 4g) were the best treatments for increasing survivals,
respectively.
16- The fresh and dry weight of shoots and roots of broad bean and soybean
plants exhibited different degrees of improvement due to applying tested
seed treatments. In broad bean, applying B. subtilis and G. virens (at 4g)
only could increase all parameters. In soybean, using B. subtilis and T
harzianum (at 4g) induced the highest increase in the fresh and dry weight
of shoots. The fresh weight of roots was not significantly affect by all
tested seed treatments compared with control, while, B. subtilis, T
harzianum, T’viride (at 4g) and G. virens (at 2 and 4g) significantly
increased the dry weight of roots without significant variations in between.
SUMMARY 122
17- All tested antagonist-seed treatments significantly increased the nitrogen
content in both broad bean and soybean plants compared with control.
Applying G. virens and T harzianum (at 4g) in broad bean and B btili , . SU 1 lS,
T harzianum and T viride (at 4) in soybean induced the highest increase in
the total nitrogen content.
18- In broad bean and soybean fields, populations of Azotobacter bacteria
were significantly increased by all tested seed treatments as well as by
increasing days after sowing (plant age) compared with the control
treatment. Treating seeds with the middle dose (4gm) of B. subtilis, T
harzianum, T viride and G. virens produced the highest significant
Increases.
19- Treating broad bean and soybean seeds with any tested antagonists at rate
of 2, 4 or 8 g/kg seeds led to significant increase in the determined yield
parameters. Applying B. subtilis led to the highest significant increase in
the number and weight of pods/plant and dry weight of 100 seeds in both
crops ..
Effect oftreatin~ seeds with combination of both anta~onists and
beneficial bacteria under field conditions:
20- In broad bean, applying antagonists combined with the beneficial bacteria
did not significantly improved disease control compared with antagonists
alone. Rhizobium or Azotobacter combined with B. subtilis or T.
harzianuni and Rhizobium combined with T viride were the best for
decreasing damping off and increasing survivals compared with Rhizobium
and Azotobacter each alone. In soybean, Rhizobium and Azotobacter
combined with B. subtilis were the best treatments for suppressing preemergence
damping off. Most combinations between Rhizobium or
Azotobacter and antagonists significantly reduced post-emergence
SUMMARY 123
damping off whereas Rhizobium or Azotobacter combined with B. subtilis
resulted in the highest significant increase of survivals compared with
Rhizobium or Azotobacter each alone.
21- All combinations between tested antagonists and Rhizobium or
Azotobacter significantly and positively affected the fresh and dry weights
of shoot and roots. Among all treatments, Azotobacter combined with B.
subtilis in broad bean or G. virens in soybean were the best for improving
all these parameters.
22- All tested antagonists each alone or combined Azotobacter or Rhizobium
caused significant increase in the total nitrogen content in broad bean and
soybean plants compared with control (untreated seeds). Using Rhizobium
combined with B. subtilis and G. virens produced the highest nitrogen
content in broad bean and soybean, respectively. Azotobacter alone
induced the lowest nitrogen content in both crops.
23- In broad bean, tested antagonists either alone or in combination with
Rhizobium or Azotobacter significantly improved nodulation. Among all,
B. subtilis, T harzianum and G. virens each alone or combined with
Rhizobium and T. harzianum and G. virens combined Azotobacter were the
best, produced the highest number and weight of nodules/plant. As for
soybean, B. subtilis alone and Azotobacter combined with G. virens
produced the highest increase in number of nodules and weight of nodules,
respectively.
24- The populations of Azotobacter bacteria in soil were significantly
increased by increasing plant age as well as by treating seeds with
antagonists alone or combined with Rhizobium or Azotobacter.In broad
bean B. subtilis alone or combined with Rhizobium or Azotobacter induced
the highest increase. As for soybean, T harzianum combined with
SUMMARY 124
Rhizobium and B. subtilis combined with Azotobacter resulted in the
highest increase in population of Azotobacter bacteria, respectively.
25- Applying any of the tested antagonists alone, in particular B. subtilis, or
in combination with Rhizobium or Azotobacter led to significant increase
in yield components of broad bean and soybean compared with control
(untreated seeds). In broad bean, B. subtilis combined with Rhizobium
produced the highest increase in number, weight of pods/plant and dry
weight of IOO-seeds. In soybean, B. subtilis combined with Azotobacter
produced the highest increases in the number of pods and weight of
pods/plant whereas B. subtilis combined with Rhizobium produced the
highest increase in the dry weight of I DO-seeds without significant
differences between the two treatments.
SUMMARY 125