چکیده:
Many agricultural researches have been performed to improve soil productivity. Nitrogen (N) and Phosphorus (P) are essential elements which are utilized by the plants in large amounts. Phosphorus can be provided by applying chemical fertilizers. Microorganisms convert insoluble phosphate to the soluble form and some bacteria such as rhizobacteria play an important role in this process. This research was designed to determine the plant growth promoting (PGP) abilities, especially phosphate solubilization, of different isolates of indigenous rhizobia and their effect on growth characteristics of wheat, corn and alfalfa. 446 isolates belonging to different species of rhizobia
were examined regarding inorganic and organic P solubilization, siderophore, auxin (IAA and homologes), 1- aminocyclopropane-1-carboxylate (ACC) - deaminase and hydrogen cyanide (HCN) production. It was found that 7% of the strains could produce HCN, 86% siderophores and 74% IAA and 44% were able to solubilize phosphorus. 8 rhizobial isolates were found as superior plant growth promoting rhizobacterial (PGPR) strains. Green house experiments using these strains evaluated the promoting effects of different strains on legume (alfalfa) and nonlegume
(wheat and corn) plants. Total biomass to the above mentioned plants was determined and the amount of N, P and iron (Fe) in shoots were also measured. The results were analyzed by the RCBD contrast method using SAS software V6.12. In conclusion, the green house experiment showed that P1B2 and a mixture of 4 plant growth stimulating rhizobacterial strains are the best suited as growth promoting inoculants.
خلاصه ماشینی:
Potential use of Iranian rhizobial strains as plant growth- promoting rhizobacteria (PGPR) and effects of selected strains on growth characteristics of wheat, corn and alfalfa Abstract Many agricultural researches have been performed to improve soil productivity.
This research was designed to determine the plant growth promoting (PGP) abilities, especially phosphate solubilization, of different isolates of indigenous rhizobia and their effect on growth characteristics of wheat, corn and alfalfa.
446 isolates belonging to different species of rhizobia were examined regarding inorganic and organic P solubilization, siderophore, auxin (IAA and homologes), 1- aminocyclopropane-1-carboxylate (ACC) - deaminase and hydrogen cyanide (HCN) production.
Plant growth promotion by microorganisms via phytohormone production (specially IAA), phosphorus solubilization or release of poorly characterized low molecular mass compounds such as siderophores are well documented in the literature (Abd-Alla 1994; Zimmer, & Bothe, 1988; Zaat, et al 1989).
The current study was designed to determine the ability of 5 selected plant growth promoting rhizobacterial (PGPR) strains to mobilize inorganic and organic phosphate and production of indole acetic acid (IAA), siderophore and hydrogen cyanide (HCN), in order to allow the identification of the best growth promoting rhizobacterial strains as appropriate inoculants for legume and non-legume plants in Iran.
Greenhouse experiments were designed to include three individual experiments which evaluated the promoting effects of different PGPR strains on various legume (alfalfa) and non-legume (wheat & corn) plants.
The superiority of P1B5 as compared to P1B2 indicated that the rhizobial strains used in P1B5 caused an increased in yield by solubilizing phosphate in addition to producing the plant growth phytohormones IAA, siderophore and ACC- deaminase.