الفهرس 
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Abstract
Summary
A virus was found naturally infecting Lactuca sativa in a field near
Benha, Kalubia, Egypt. The virus induced severe mosaic mottling, sharp
distortion and abnormalities on the leaves.
In a trial to identify the virus physical properties, electron
microscopy and host range were studied.
The histopathological changes of Hibiscus schizopetalus leaves
showing necrotic local lesions induced by the virus were also studied.
The results revealed that:
The virus is mechanically transmissible and is also transmitted by
the seed.
The thermal inactivation point is70° C for 10 min. Its dilution end
point is 1:4x l 0.6 and completely inactivated after 210 days at 20_30
0
C.
Electron microscopy showed the virus particles with mean length
740 x 13nm.
There are many hosts to this virus some hosts show local lesions as
Acalypha wilkesiana Mall. Arg.,Brassica rapae L. var. rapifera koch
.Chenopodium album L.(white goose foot), Colocacia antiquorum schott,
Corchorus olitorius L, Eruca sativa Miller(Rocket), Gazania splendens
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Hort.ex E.G.Renders. and A.Henders.(Treasure flower),Helianthus
annuus L.(sun-flower), Hibiscus schtzopetalus (M. T. Mast.) Hook. F.,
Lupinus termis Forssk (Egyptian lupin), Malva parviflora L. (small
tlowered mallow), Pelargonium zonale Ait., Raphanus sativus L. var.
aegyptiaca Sick. (Radish), Solanum melongena L. var. atroviolacea Sick.
Solanum tuberosum 1. (potato), Sonchus oleraceus 1. (sow-thistle),
Spinacia o/eracea 1. (Garden-spinach) and Zinnia elegans Jacq .
Other hosts show local lesions followed by systemic symptoms as
Chenopodium quinoa willd, Lycopersicon esculentum Mill. (Tomato) and
Pisum sativum 1. (Garden pea).
from the above results it was deduced that the virus under test is a
new resistant strain of lettuce mosaic virus.
The histopathological studies of Hibiscus schizopetalus leaves
infected with the virus and showing necrotic local lesions revealed that
the blade is not clearly flat. The thickness of the blade is unequal on both
sides of the midrib.
The upper and lower edges of the midrib showed clear
collenchyma cells. The epidermal cells has few distorted stomata and
covered with thick cuticle.
The mesophyll cells appear compact without differentiation into
palisade and spongy tissues. The chloroplasts are few and the number of
druses calcum oxalate crystals is clearly few.
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Necrotic spots appear on both upper and lower epidermis densely
stained with safranin.
The virus has no effect on xylem and phloem cells. The
parenchyma cells surrounding the vascular tissue appear wavy walled.