Influence of an Arbuscular Mycorrhizal Fungus and Phosphate-Solubilizing Bacterium Inoculation at Stem Cutting Stage on P Uptake and Growth of Impatiens walleriana Plants in an Unsterile Field Soil

Microorganisms play an important role in the propagation and growth of plants. Propagation of plants through stem cuttings is a popular method widely practiced in horticulture and forestry. As the information on the interactive role of arbuscular mycorrhizal (AM) fungi and phosphate-solubilizing bacteria (PSB) in the regeneration and growth of clonally propagated plants is limited, we inoculated stem cuttings of Impatiens walleriana with Rhizophagus fasciculatus and Bacillus megaterium var. phosphaticum individually or in combination in an unsterile Alfisol field soil. The inoculated cuttings were harvested after 45 days of cultivation and various growth parameters and phosphorus (P) uptake were measured. Inoculation with the AM fungus or PSB individually improved plant growth parameters, whereas the dual inoculation did not give synergistic results. Plants inoculated at cutting stage with R. fasciculatus accumulated the highest plant biomass and showed maximum microbial inoculation effect and efficiency of P uptake. Inoculation with the PSB stimulated symbiosis with native AM fungi but a synergistic effect has not been found when both AM fungi and PSB were co-inoculated. It could be concluded that screening for compatibility between microorganisms is essential before selecting the bioinoculants for dual inoculation.