Colonization of Wheat Roots (Triticum aestivum L.) by N₂-fixing Cyanobacteria

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Two heterocystous cyanobacteria strains, belonging to the genera Anabaena and Nostoc isolated from sandy and clay soil samples, soils were collected from superficial surface crust at El-Ismailia Research Farm, El-Ismailia Governorate, (30°35’41.901’’N, 32°16’45.834’’E) and Sids Res. Farm Beni Sweif Governorate, (29°4’54.349’’N, 31°5’25.775’’E), Agric. Res. Center, Egypt. Cyanobacteria strains were tested for their ability to form tight associations with the roots of wheat seedlings (15 days old) under Lab. conditions. Both Nostoc muscorum and Anabaena variabilis and /or their mixed culture were inoculated to wheat seedlings. Nostoc muscorum was able to form close associations with wheat plants, and was able to enter through root hairs and penetrate the epidermal layer of wheat roots. While, Anabaena variabilis formed loose association with wheat seedling roots. The mixture of both cyanobacteria strains formed weak association with root of wheat seedlings. The tight association of Nostoc muscorum with the roots of wheat seedling resulted in the accumulation of Chlorophyll a in wheat roots and also exhibited nitrogenase activity by the roots. The tight association of Nostoc muscorum increased significantly the dry weight of seedlings plants. In contrast, Anabaena variabilis formed loose association against weak association for the mixture of both Nostoc muscorum and Anabaena variabilis.