Characterization of Egyptian Fluorescent Rhizosphere Pseudomonad Isolates with High Nematicidal Activity against the Plant Parasitic Nematode Meloidogyne Incognita

摘要

A total of 52 Egyptian rhizosphere fluorescent pseudomonad isolates (ERFP) were screened for their nematicidal activity in vitro. The screening results showed an inhibitory effect on hatching of Meloidogyne incognita eggs ranging from 57 % to 100 %. Similar to the chemical nematicide Videt in vitro experiment, cultures or cell-free supernatants (CFS) of the ERFP isolates showed complete inhibition of egg hatching and killed 100 % of the J,. In glasshouse pot experiments, cultures of these isolates, CFS and the chemical nematicide showed reduction in root galling ranging from 81.0-95.4, 61.3-84.5, 97.3%, respectively. Also, the reduction in nematode multiplication in soil was 91.9-95.7, 83.5-84.5 and 96.5% for cultures, CFS and the chemical nematicide, respectively, compared to the positive control (nematode only). Furthermore, these isolates showed significant increases in plant growth characters, phenolic content and activities of the plant defense-related enzymes. Based on 16S rDNA sequences and API NE kits, two major clusters were observed; strains Ps 36 and Ps 54 appeared to fall within the variability range of P. putida, while Ps 21, Ps 22 and Ps 14 are likely to be strains of P. aeruginosa. The distinctness of Ps 36 and Ps 54 from Ps 14, Ps 21 and Ps 22 was supported by their physiological characteristics, such as the ability of Ps 14 and Ps 21 and Ps 22 to utilize mannitol, N-acetyl-glucose amine and adipate.