الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 114 |  |  |
| | | from | 114 | | |
Abstract
The obtained data of the present study could be summarized as follow:
I. Pathological studies:
- Leaves of cucumber and snake cucumber plants grown under hot weather conditions during summer of 2019 showed water-soaked spots that developed to small specks then enlarged to form irregular spots to destroy all leaves and plants underwent die backed.
- The occurrence of bacterial leaf spots was recorded in the most inspected cucumber/ snake cucumber in El-Minya governorate. As for cucumber, the occurrence of bacterial leaf spots was recorded the highest prevalence, diseases incidence and diseases severity in Mattay district followed by Beni-Mazar district. Regarding snake cucumber bacterial leaf spots, the highest prevalence was observed in Samalott district followed by Beni-Mazar district and Mattay district. Beni-Mazar district exhibited the highest disease severity followed by Mattay district while Samalott district explored the least disease severity value.
- Seven infective bacterial isolates viz Cu1, Cu2, Cu4, Cu5, Cu6, C7 and Cu8 were isolated from both cucumber (Cu5, Cu6, Cu7 and Cu8) and snake cucumber (Cu1, Cu2 and Cu4) leaves.
- Bacterial isolates from snake cucumber viz Cu1, Cu2 and Cu4 were more pathogenic than of cucumber ones (Cu5, Cu6, Cu7 and Cu8).
- Only three bacterial isolates were subjected for identification through morphological, physiological, and biochemical characteristics which revealed that all bacterial isolates could be identified Enterobacter cloacae.
- Furthermore, isolates were subjected for DNA profile analysis and confirmed that the three pathogenic isolates have DNA patterns with 99-100% similarly to Enterobacter cloacae.
- Infection reaction of E. cloacae was varied with cucumber genotypes and snake cucumber Balady genotype was the highest susceptible than all cucumber genotypes tested. Two cucumber genotypes (Hayle and Hakeem) reacted as resistant, while Shehab, Madaen and Lava were reacted very susceptible genotypes, but they were lesser than snake cucumber genotype.
- All bacterial isolates of E. cloacae were exhibited leaf spots to squash, melon, and cantaloupe. Meantime, all E. cloacae isolates reacted as soft rot bacteria towards fruits of (melon, tomato and pepper), onion bulbs, sugar beet storage roots and cowpea pods. In addition, E. cloacae isolates caused leaf blight symptoms to pepper, eucalyptus, sugarcane apical meristem, mulberry and tomato.
II. Physiological studies:
- The obtained data revealed a vital role for temperature on E. cloacae growth was addressed the maximum turbidity as the optimum growth was recorded at 30 ◦C followed by 25 ◦C and 35 ◦C within insignificant variances among them, the least optical density was expressed at 15 ◦C. Increasing temperature increased bacterial growth till 35◦C.
- Growth of E. cloacae was strongly affected by using safety chemicals, the highest inhibitory effect was provided by AA+ H2O2 mixture followed by ASA+H2O2 and H2O2 alone. ASA alone and p-CA give inhibition but lower than H2O2-mixed compounds. As for copper salts, copper oxy chloro showed more inhibitory effect than copper sulphate but their efficiencies to inhibit E. cloacae growth were lower than H2O2-mixed compounds.
- In vitro experiment resulted bacterial leaf spots elicited by E. cloacae in detached leaves of eucalyptus. Infectivity of E. cloacae was significantly affected by temperature. At low temperature 15-20◦C, E. cloacae failed to elicit infection signs. The highest disease severity in eucalyptus detached leaves was provided at 30◦C and noticable leaf spots was recorded at 25 and 35◦C.
- The bacterium E. cloacae-CCF has potential toxic effects towards eucalyptus detached leaves. Toxicity of E. cloacae-CCF was greatly affect by bacterial cultures age where 20-day old cultures give the highest toxic effects causing the highest necrotic lesions severity (NLS). Values of NLS affected by CCF concentrate, increasing CCF concentration increasing NLS. Heating CCF lowered its toxic effect.
- Using CCF to RCC caused great toxic effect that correlated to deed cells through 2h exposure. Toxic effect to CCF increased with increasing CCF concentration and exposure time.
III. Management of bacterial leaf spots:
- Application of ASA to snake cucumber foliar either pre- or post-inoculation treatments suppressed E. cloacae infection. Efficiency of ASA to protect snake cucumber against E. cloacae infection was higher values on application of post-inoculation than pre-inoculation treatments.
- Using ASA+ H2O2 as pre- or post-inoculation treatments of snake cucumber give the satisfaction against E. cloacae but, lower than PAA. However, H2O2 efficiency to protect snake cucumber plants against E. cloacae infection was lower than PAA or ASA + H2O2 but without significant variances between them.
- p-coumaric acid has efficiency to inhibit bacterial growth and activate resistance of snake cucumber plants against E. cloacae.
- Efficiency of p-CA acid to reduce AUBLSPC values under E. cloacae infection was the least as compared H2O2-based compounds or ASA. Using p-CA, pre-inoculation foliar treatment was higher than post-inoculation treatments.
- All safety chemicals tested either H2O2-mixed compounds or non H2O2-based compounds give a positive effect towards Photosynthesized chl a, chl b, total chl a+ chl b and carotene. The foliar treatment of un-inoculated of snake cucumber improved pigment content than un-treated ones. Inoculated un-treated snake cucumber leaves drastically decreased specially chl a, chl b and carotene. Application of ASA to snake cucumber inoculated leaves prevented pigment degradation indicating its efficiency to improve snake cucumber pigments and activate plant resistance against E. cloacae infection.
- p-coumaric acid foliar application, an increasing in pigments content was observed. To be mentioned p-coumaric efficiency in this respect merely to ASA efficiency in increasing chl a while p-coumaric efficiency to enhance chl b content was more effective than ASA that give total chl a + b content highest than ASA.
- H2O2-mixed compounds viz, AA + H2O2, ASA+ H2O2 and H2O2 alone revealed the highest efficiencies to protect snake cucumber against E. cloacae infection as increasing pigments content.
- A synergistic efficiency was expressed between ASA and H2O2 that reacted protectant and curative in this respect, that also resulted chl a, chl b and carotene enhancement.
- Using H2O2 alone became the third to improve pigment contents after PAA and ASA+ H2O2.
- Enterobacter cloacae could be considered as a new phytopathogenic bacteria to cucurbitaceous plants rather than its pathogenic to cucurbitaceous plant Enterobacter cloacae was aggressive pathogen to other plant species, eucalyptus, pepper, tomato and mulberry. In addition, Enterobacter cloacae crude culture filtrate (CCF) as toxic effects towards detached leaves, cuttings and root cap cells.