Effectiveness of combined inoculation of rhizobacteria and arbuscular mycorrhizal fungi on wheat performance

Plant growth promoting rhizobacteria (PGPR) and arbuscular mycorrhizal (AM) fungi could be employed in cereal crops for growth promotion, nutrient uptake and as an alternate source of inorganic fertilizer of crops. PGPR research endeavors employed for crop enhancement have recently received great attention from researchers with thousands of studies being conducted. A growth-chamber experiment was designed to evaluate the interactive effects of PGPR and AM fungi on the growth of two different American wheat cultivars (advanced and forefront) and the bacterial community structure. Confocal laser scanning microscope was used to show the colonization of B. subtilis on the roots of wheat cultivars as the response of AM fungi inoculation. Compared to the advanced cultivar, the fresh and dry weights of the shoot for the forefront wheat cultivar increased by 235% and 184%, respectively. The dual inoculation treatment by AM fungi and B. subtilis led to an increase in the shoot fresh weight by 69.1% and 207% and an increase in shoot dry weight by 38.9% and 169.1% in the forefront and advanced wheat cultivars, respectively. Moreover, the total number of B. subtilis cells found on root-hair zones significantly increased when the plants inoculated by B. subtilis plus AM fungi compared to those plants inoculated with B. subtilis alone. The bacterial population in the rhizosphere inoculated with AM fungi plus B. subtilis was 12.1 x 106 and 17.1 x 106 cfu g-1 oven dry soil for forefront and advance wheat cultivars, respectively, compared to inoculation with B. subtilis alone (5.8 x 106 and 10.6 x 106 cfu g-1 oven dry soil). The results of this study confirm the suitability of the combined application of PGPR and AM fungi to improve wheat growth.