تأثیر باکتری آزوسپیریلوم بر برخی شاخص‌های رشد و عملکرد سه رقم گندم

Azospirillum brasilense is one of the N2-fixing microorganisms which, in symbiosis with the roots of cereals and other graminae, enhances growth and development of plants. In this research, wheat seeds (Triticum aestivum) of three cultivars (Ghods, Roshan and Omid) were inoculated with Azospirillum strains (Sp7 and Dol). Inoculation increased growth parameters and yield of wheat cultivars, the effect being directly dependent on the strain-cultivar combination. Strain Sp7 induced the greatest grain yield, 1000-seed weight, number of grains per spike, root and shoot dry weight in Cv. Roshan, whereas strain Dol stimulated the best effect on these growth parameters in Cv. Ghods. The response of Cv. Omid was lower as compared to the other cultivars. Thus, it may be concluded that compatible strains are necessary for increasing yield and enhancing growth and development of wheat cultivars. These experiments also illustrated similar results regarding the effect of strains on N content of seeds. The observation of nitrogenase activity of Azospirillum strains in the In vitro experiments and the significant increases in N content in some inoculated cultivars support the hypothesis that biological nitrogen fixation by Azospirillum could be responsible for the observed beneficial effects on growth parameters. The comparison of nitrogenase activity of two strains showed that acetylene reduction rate for strain Dol was 1.5 times more than that for strain Sp7. Also strain Dol had more pronounced effects on growth parameters, yield and N content of grains than did strain Sp7. Strain Dol is a local strain whereas strain Sp7 is a Brazilian isolate thus, it may be concluded that the local isolates should be preferred to the foreign bacteria, as they are better suited to traditional cultivars, environment and soil conditions of the region.