Morphological characterization and pathogenicity of Pythium sp. infecting cucumber seedlings in greenhouses

الملخص EN

Greenhouse-grown cucumber seedlings exhibiting typical symptoms of Pythium damping-off and root rot were collected.

The causal agents were isolate on Pythium selective medium; nystatin, ampicillin, rifampicin, and miconazole (NARM) in potato dextrose agar (PDA).

Four different isolates was isolated and their pathogenicity was tested using cotyledon and young seedlings assays.

Results of these isolates showed variation in their ability to infect cucumber seedling.

Isolate "GZ-11" was highly pathogenic, caused 100 % pre- and post-emergence damping-off.

The isolate was identified to the species level based on morphological characters along with sequences of the internal transcribed spacer (ITS) of the ribosomal DNA and showed 99% similarity to Pythium spinosum (Synonym of Globisporangium spinosum).

Aggressiveness of P.

spinosum was investigated at two levels of inoculum concentrations (10 and 20 g/kg soil).

Results reported that P.

spinosum was highly aggressive and significantly reduced cucumber seed germination compared to the control.