الفهرس 
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Abstract
This study was carried out in the laboratory and greenhouse of Agric. Microbiology Dept. at the Faculty of Agriculture, Zagazig University, Egypt, to isolate, identificate and select efficient indigenous strains of cyanobacteria, from soils of different locations at Sharkia governorate having various physico-chemical properties. During this study the ecological impacts on the cyanobacterial strains had also been investigated in order to be used as biofertilizers for rice plants. Forty two cyanobacterial cultures were isolated from 10 diverse sites along Sharkia governorate. On the basis of morphological and physiological studies, the forty two cyanobacterial isolates were classified to 3 genera and 5 species isolated from fertile soils and 7 genera and 8 species isolated from newly reclaimed soils. Nostoc spp strains were the most common filamentous heterocyst-forming cyanobacteria (22 isolates) inhabitant both fertile and reclaimed soils of the governorate. Two species of Nostoc including 11 isolates of N. muscorum and 11 isolates of N. calcicola. Anabaena spp. includes 10 isolates in three species (A. oryzae, A. circinalis and A. oscillarioides. Nodularia spumigena was represented in this work by two isolates from fertile soils. In addition 2 isolates of Calothrix clavata, and 3 isolates of Synechococcus sp. and one isolate of each of Oscillatoria homogenea, Dermocarpa olivacea and Xanococcus kerneri. The distribution of the different cyanobacterial genera in the different soil textures indicates that Nostoc spp. and Anabaena spp. were spreading in fertile soils more than reclaimed soils, meanwhile the rest of cyanobacterial genera were common in reclaimed soils.