ROLE OF THE MICROORGANISMS OF THE RHIZOSPHERE ON THE GROWTH AND PRODUCTION OF ONE CUCURBETAE AND BIOLOGICAL CONTROL OF ROOT ROT DISEASE

Abstract

Different isolates of Azospirillum spp., Azotobacter spp. and actinomycetes were collected from the rhizosphere of different plants from different localities.

The nitrogen fixing ability were studied for N2-fixing bacteria, and the antagonistic activities against Rhizoctonia solani which cause root rot and damping off were also studied by N2-fixing bacteria and actinomycetes.

The most active isolates of both N2-fixing bacteria and actinomycetes were evaluated for their ability to colonize the roots of cucumber plants and identified as : Azotobacter chroococcum (Rf), Azospirillum lipoferum (Kc), and Streptomyces lydicus (Ncu1) A green house pot experiment was carried out in Desert Research Center to study the effect of these strains on the microbial counts (total microbial counts, actinomycetes counts, Azotobacter and Azospirillum counts), diffrent growth parameters of cucumber plant, disease severity index (DSI), pre and post emergence damping off and survival of cucumber plants.

Generally, inoculation with the selected strains from Egyptian soils increased the soil microbial activities, improved the growth parameters and yield of cucumber and at the same time decrease the harmful effect of Rhizoctonia solani on both microbial and growth parameters of cucumber plants.

Streptomyces lydicus gave the highest reduction in DSI, Pre and Post emergence damping off but Azotobacter chroococcum and Azospirillum lipoferum gave the highest effect on the improvement of the growth parameter of cucumber plant.

Key words: Azospirillum lipoferum, Azotobacter chroococcum, Streptomyces lydicus, Rhizoctonia so/ani, Root rot, Damping off, cucumber.