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Abstract
SUMMARY.6
Erwinia carotovora subsp carotovora is the causal agent of the soft rot disease of potato tuber in stores and in the field where early decay of mother tubers or seed tuber pieces may occur. Therefore, the aims of the present work were identification and detection of soft rot erwinias by PCR and study the pathogenicity of E.c. subsp carotovora isolates on potato; Inhibition growth of these isolates by some synthetic and natural compounds in vitro, so that the results revealed to:
1- Isolation trails from diseased potato tuber samples collected from four locations (Kafr El-Zayat, El-Tahreer north, Kom-Hamada and Alexandria), resulted in 15 bacterial isolates.
2- Identification of the bacterial isolates which performed through studies of pathological, cultural, morphological, and physiological characteristics that showed agreement with those known for E. c. subsp carotovora
3- The degree of virulence of E. c. subsp carotovora isolates on five potato cultivars namely Oceania, Ladypalfor, Osprey, Winston and Harmony. Showed that 3 highly virulent isolates (Ecc5, Ecc6 and Ecc2), 3 moderately virulent isolates (Ecc10, Ecc4 and Ecc12) and 2 weakly virulent isolates (Ecc3 and Ecc15)
4- Extraction of total DNA from the nine isolates of E. carotovora and one isolate of Agrobacterium tumefaciens. Showed that the average concentration of total DNA in E. c. subsp carotovora isolates was 0.385 µg/µl
5- Detecting bacterial cells of E. c. subsp carotovora from DNA isolated and used into the polymerase chain reaction (PCR) analysis. Four specific primers were used, two specific primers amplify 434bp fragment of the E. carotovora DNA another two primers were specific to E. c. subsp atroseptica and amplify no specific fragment
6-Nine isolates of E.c. subsp carotovora were selected for Random Amplified Polymorphic DNAs (RAPDs) PCR to characterize these isolates, eight primers of arbitrary nucleotide sequences were used to amplify DNA segments from the genomic DNA of the nine tested isolates of E.c. subsp carotovora. Five out of eight primers tested gave clearly differences among the nine bacterial isolates on the bases of amplified product patterns and the numbers of amplified products produced by each primer varied from 27 with primer three to 66 with primer one and primers 6 to 8 failed to show any amplified bands
7- Results of dendrogram indicated that the nine bacterial strains were classified into two main clusters (cluster I and cluster II). Cluster I was divided into two sub-clusters, sub-cluster 1 that included Ecc 2 (Kafr El-Zayat - Highly virulent), whereas sub-cluster 2 included two highly virulent isolates, Ecc 5 (El- Tahreer north) and Ecc 6 (El- Tahreer north).The cluster 2 was divided into two sub-clusters: sub-cluster 1 divided also into two groups: Group 1 that included isolate Ecc10 (Kom-Hamada - moderately virulent), Ecc 14 (Alexandria - weakly virulent), whereas Group 2 : included isolates Ecc 15 (Alexandria - weakly virulent) and Ecc 3 (Kafr El-Zayat - weakly virulent) .Whereas sub-cluster 2 composed of two isolates were moderately virulent , Ecc 4 (Kafr El-Zayat) and Ecc 12 (Kom-Hamada).
8- All the tested antagonistic bioagents had inhibitory effect against the highly virulent isolate of E. c. subsp carotovora. However, Pf significantly affected on E. c. subsp