Detection of Pseudomonas savastanoi pv. savastanoi from Olive and Other Hosts by Polymersae Chain Reaction (PCR)

Rakan Hijazin, Hamid Khlaif


Field inspection indicated that olive knot bacteria occur in different olive trees growing areas in Jordan including: Amman (Alhashmi Alshamali, Aljubiha, Dahiet Alrashid, Tla’a Ali and Wadi Assir), Madaba’a (Alsamik), Alkarak (Alrabah, Faculty of Agriculture, Mou’ta University) and Irbid (Aljohfieh). Olive knot bacteria were collected from different host plants grown in different locations in Jordan including: Jerash, Wadi Shouaib and Dairalla. One hundred isolates of Pseudomonas savastanoi pv. savastanoi were obtained from naturally infected olive trees. Another 30 isolates of the same microorganism were obtained from other host plants from different locations in Jordan.
The iaaL gene was detected by PCR amplification from 82% of DNA extracts from sap of knots formed on naturally infected olives and 97% from bacterial cultures, respectively. Pathogenic Ps. savastanoi pv. savastanoi was recovered on KB medium from 55% of the collected isolates. Detection of iaaL gene of the tested isolates was found to be more efficient in detecting Ps. savastanoi than by isolation on KB medium and the pathogenicity test. Culturing the isolates on KB medium prior to the iaaL amplification greatly improved the PCR efficiency. The iaaL gene was detected in 80%, 90% and 90% of the isolates obtained from naturally infected oleander, jasmine and ziziphus, respectively.
Moreover, Ps. savastanoi pv. savastanoi was isolated from symptomless olive plants, and iaaL gene was detected using PCR amplification. The results indicated that PCR was more efficient in detecting olive knot bacteria by iaaL amplification than by isolation on KB medium followed by the pathogenicity test.

الكلمات المفتاحية

Pseudomonas savastanoi pv. savastanoi, olive knot, host plant, latent infection.

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