عنوان مقاله [English]
Azospirillum plays a significant role in the quantitative and qualitative enhancement of cropyield. Its isolates, however, exhibit extreme differences as reflected in their impacts on crop yield. In this study, isolates of Azospirillum were initially compared with respect to their morphological traits and such growth promoting characteristics as nitrogen fixation; solubility of insoluble phosphorus; and their auxin, sidrophore, hydrogen cyanide (HCN), and ACC-deaminas enzymeproduction. Furthermore, five isolates characterized by superior growth promoting characteristicswere investigated for their effects on yield and its components in wheat Morvarid cultivar. For this purpose, an experiment was conducted in a randomized complete block design with 6 bacterial treatments including five Azospirillum isolates and one control treatment (without bacterial inoculation) with 4 replicates at Iraqimahaleh Station, Golestan Agricultural and Natural Resources Research Center, where the soil is classified in the large Torriorthents Group. Results of seed inoculation in selected isolates showed that the impacts of different Azospirillumisolates on wheat yield components such as panicle length, peduncle length, number of seeds per panicle, number of panicles per square meter, weight of 1000 seeds, seed yield, and straw yield were statistically significant at 1% confidence level, as evidenced by increases of 14.91, 47.94, 25.98, 24.97, 82.86, 20.42, and 37.88%, respectively, in the above traits of Mordavid cultivar relative to those of the control with no inoculation.