Phosphate solubilizing efficiency of cyanobacteria isolated from paddy soil and their effects on rice (Oriza sativa L.) yield and phosphorus uptake

Phosphorus is one of the most important and essential elements for plant growth but it is not available for plants in many soils. Inoculation of paddy soils with phosphate solubilizing cyanobacteria is an efficient procedure for supplying phosphorus for rice plants. In this study, cyanobacteria isolated from Guilan paddy fields and purified. Cyanobacteria isolates identified by using morphological characteristics and molecular techniques. Their phosphate solubilization ability was evaluated and then superior strains for rice pot planting (Tarom Hashemi cultivar) was selected. A greenhouse experiment was conducted to evaluate the selected cyanobacteria isolates. The experiment carried out in a factorial completely randomized design with four levels of nitrogen (0, 0.23, 0.45 and 0.46 g urea per pot) and seven strains of cyanobacteria and control without bacteria with three replications. The results showed that the isolates were classified into four phyla of Chroococcales, Oscillatoriales, Nostocales and Stigonematales. Anabaena sp. GGuCy-17 strain had the highest phosphate solubilizing potential (641 mg.L-1) compared to other strains, and the Cylendrospermum sp. GGuCy-25 (130 mg.L-1) was the second in this respect. The highest grain yield (15.6 g.pot-1), the highest total nitrogen (14.3 g.pot-1) and phosphorus uptake (2.8 g.pot-1) were obtained in plants inoculated with Cylindrospermum sp. GGuCy-25. After further studies in different paddy field conditions, these efficient strains could be accounted for production of cyanobacterial biofertilizers to improve rice growth and yield.