الفهرس 
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Abstract
Pepper plants showing typical powdery mildew disease symptoms
were collected from five different pepper production areas in five
governorates i.e., Alexandria, Behaira, Minufiya, Qalubiya and Giza,
as well as six different districts in Minufiya Governorate i.e., Sadat,
Shebin El-Kom, Minuf, El-Shohada, Ashmoun and El-Bagour
representing all soil types and climatic conditions in different growing
areas of pepper plants in Egypt.
Isolation of the conidia spores of the causal organism from the disease
materials was done and the complementary studies was done. Results
could be summarized as follows:
1. Microscopic examinations of infected areas of pepper leaves,
revealed that, the mycelium of the fungus causing powdery mildew
of pepper is extensive, branched and intercellular. The hyphae are
cylinder and septate. The superficial hyphae are 3.25 – 7.85 μ with
an average width 3.95μ . Conidiophore arise from the endophytic
hyphae and emerge through the stomata of the host leaf. A
conidiophore was observed bearing one conidium. The
conidiophores typically unbranched about 25.50 – 66.95 μ with an
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average of 46.25 μ length. Conidia are formed singly on the
conidiophore.
2. The dimorphic conidia were either pyriform or cylindric in shape
with the former conidia larger than the latter. Spore dimensions for
all field isolates were very uniform with range of 59.4 to 66.2 μm
and 58.8 to 63.6 μm for length of pyriform and cylindric spores,
respectively (Table, 2). The average length and width for field
isolates of pyriform conidia was 64.18 μm and 14.3 μm,
respectively, while for cylindric conidia it was 61.24 μm and 14.6
μm, respectively. The mean spore length to width ratio was fairly
consistent with variation from 4.37 to 4.75 μm and a mean of 3.87
and 4.37 μm for pyriform and cylindric conidia, respectively.
3. On the other hand, in contrast, the greenhouse isolate had pyriform
and cylindric spores with length of 70.62 μm and 66.47 μm
respectively, while the width was 19.8 μm and 18.4 μm,
respectively. Consequently, the greenhouse isolate had a much
lower spore length to width ratio with variation form 3.32 to 3.82
μm.
4. The highest infection (%) on ”Pasodoble RZ” pepper genotype was
recorded at October 5th in Giza governorate where high temperature
degree and relative humidity %, it was 37.0%, followed by 35.0%
that was recorded in Qalubiya governorates at the same time.
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5. ”Dabka RZ” genotype was reacted as the lowest susceptible one.
The maximum severity of infection was noticed on ” Pasodoble
RZ” genotype (25%(, followed by ”Sympathy RZ”, variety (13.5%)
while the minimum severity of infection was noticed on ”Dabka
RZ”, (4.0 and 6.5%, respectively).
6. All commercial genotype of pepper, as well as two of the weeds
often associated with pepper crops were susceptible to powdery
mildew causing by Leveillula taurica . Only three of the plants spp.
tested, Euphorbia heterophylla , Solanum oleraceus and Euphorbia
sonchifolia, were not affected and revealed as non host plants.
Marked differences in susceptibility were detected, with
commercial pepper and artichoke the most susceptible, followed by
tomato and poinsettia.
7. Significant differences in powdery mildew infection can be detected
among the levels of nitrogen. Increasing nitrogen doses increased
the disease severity and the percentage of infection too, while
increasing potassium and phosphorus doses led to decrease the
same mentioned disease parameters.
8. The lowest disease severity and the percentage of infection were
obtained with 120 + 60 + 192 NPK, 120 + 30 + 192 NPK and 120
+ 15 + 192 NPK unit/feddan, respectively. On the contrary, the
highest disease severity and percentage of infection were obtained
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when 200 + 15 + 48 NPK, 200 + 30 + 48 NPK and 200 + 60 + 48
NPK unit/ feddan were applied, respectively.
9. The highest yield production was obtained when the highest level of
potassium, 192 K unit, was applied, followed by 96 K and 48 K
unit/feddan treatment, respectively, regardless to N and P. An
obvious and interaction effect among the different fertilizers was
noticed. The highest yield was obtained at 160 + 30 + 192 NPK
unit/feddan, followed by 160 + 30 + 96 NPK and 160 + 30 + 48
NPK unit/feddan.
10. When disease severity was increased the yield loss was also
increased and vice-versa. Also, disease severity and percentage of
infection were highly in 2013 than in 2012 season.
11. The highly disease severity was obtained with the latest
transplanting date, while transplanting on 15th March exhibited the
first rank in this regard. The percentage of seventy of infection and
the yield of pepper differed according to the transplanting date. The
lowest percentage of infection and the highest yield of pepper were
obtained with the earliest transplanting date, while the highest
percentage of infection and the lowest yield was obtained with the
latest one.
12. The tested plant densities affected disease severity and percentage
of infection. Transplanting at 50 cm exhibited the lowest disease
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severity as well as percentage of infection. The yield was higher
compared with 20 cm distance in 2012 and 2013 seasons.
Transplanting at 30 cm between plants was fell in between.
13. The disease severity and percentage of powdery mildew infection
were increased with decreasing the distances between plants and
vise-vera, while the yield of plants (10 plants) was increased with
increasing distance between plants, regardless of the total number
of plants/feddan.
14. Application (Fe) resulted the lowest disease severity of powdery
mildew infection and percentage of disease infection, as well as
high yield. Combination of the three tested microelements showed
the lowest disease severity infection and percentage of infection
and high yield. Spraying with (Fe + Zn), (Fe + Mn) and (Mn + Zn)
were resulted mediated disease infection and yield.
15. Cabrio Top was the most effective fungicide on disease severity
and % of infection, where the lowest powdery mildew infection
was noticed, followed by Bellis fungicide. The least effective
fungicide for controlling powdery mildew disease on pepper plants
cv. Pasodoble was Kumulus-S, followed by Altrazole during 2012
season under natural infection.
16. Yield of 10 plants in kg were raised by fungicide application and
compatable with decreasing the disease incidence. Cabrio Top
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fungicide in 100 concentration (recommended dose) were resulted
the lest disease severity, % of infection and highest yield kg of 10
plants.
17. The reduction in infection due to the fungicidal action was
correlated by substantial increase in the yield. In regard to
percentage of powdery mildew infection in treated and nontreated
plants, it could that, each spray led to highly significant decrease in
powdery mildew infection.
18. Calcium carbonate with both used concentrations was the most
effective salt in decreasing disease parameters. Calcium chloride
was come at the second rank in the effectiveness of calcium salts
on powdery mildew disease incidence.
19. The yield production resulted as the maximum production, also by
spraying calcium chloride, followed by Calcium carbonate. The
least effective calcium salt was Calcium sulphate in both treated
concentrations on disease parameters, as well as yield production.
20. Generally, Calcium salts great affecting powdery mildew disease
incidence and disease parameters in comparing to control treatment
(about ½ disease parameters as well as double results in yield
production in both tested seasons.
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21.The most effective antioxidant was Ascorbic acid (in both 200 and
400 ppm concentrations) followed by Oxalic acid. Whereas the
least effective antioxidant was citric acid.
22. Generally, antioxidants decreased disease parameters and
increased fruit yield in comparing to control treatment that resulted
disease severity 70.0 and percentage of infection 35.0%.