الفهرس 
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Abstract
Afaf Zein El-Abdeen Abd El-Aziz El-Meneisy: Pathological and Molecular
Studies on Bacterial Wilt Disease of Potato. Unpublished Ph.D. Thesis,
Department of Plant Pathology, Faculty of Agriculture, Ain Shams University,
2011.
This work aimed to elucidate variation in pathogenicity for different Ralstonia
solanacearum isolates which collected from potato fields in Egypt, characterize
Ralstonia solanacearum at biochemical and molecular level and to determine the
possible role of avirulent isolates of Ralstonia solanacearum in disease control. A
total of 108 isolates of Ralstonia solanacearum were isolated from different sources
and identified, according to Physiological and bacteriological tests and confirmed
using Immunofluorescent Antibody Staining (IFAS) test and Real time PCR, as R.
solanacearum race 3 biovar II. Soil drench or stem inoculation methods were used
in pathogenicity test on potato and tomato plants. All tuber isolates were highly
virulence compared with soil and water isolates. Total isolates were divided into two
groups according to disease incidence; the first group contained virulent isolates
which isolated from tuber samples and the second group contained avirulent isolates
which isolated from soil and water samples. Variability on colony phenotypic and
cell morphology was observed between virulent and avirulent isolates. Virulent
isolates showed high content of either lipopolysaccharide or total sugars in LPS
compared with avirulent isolates. Total sugars in LPS were determined using gas
liquid chromatography (GLC). The glucose was the major content of R.
solanacearum lipopolysaccharide in all examined isolates. Lipopolysaccharide for
virulent isolates of R. solanacearum showed high amount of arabinose, xylose,
mannose and galactose compared with avirulent isolates, while the amount of
mannitol was the highest in Lipopolysaccharide for avirulent isolates compared
with virulent isolates. There is no significant difference between the amount of
rhamnose, fructoseand sorbitol in lipopolysaccharide in all isolates. Virulent and
avirulent isolates were varied in their fatty acid content. High amount of pectin lyaseand cellulase enzymes was observed in cultural filtrate of virulent isolates, while the
amount of polygalacturonase was low. No significant difference was observed
between different bacterial isolates in SDS-PAGE electrophoresis. Both phcA and
hrpA genes were detected and expressed in inoculated potato either by virulent or
avirulent isolates. Avirulent isolate of R. solanacearum (SM4) was effective as
antagonistic bioagent against virulent one under laboratory and greenhouse
conditions.
Key words:
Ralstonia solanacearum, Potato, Bacterial wilt, Virulent isolates, Avirulent
isolates, Lipopolysaccharide, phcA gene, hrpA gene