Promotion of Rooting and Growth of Some Types of Bougainvilleas Cutting by Plant Growth Promoting Rhizobacteria (PGPR) and Arbuscular Mycorrhizal Fungi (AMF) in Combination with Indole-3-Butyric Acid (IBA)

Divers studies have demonstrated that plant growth promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) can stimulate plant growth and more recently that they can increase rooting ability in vegetative material, especially when they are added with auxin. Considering this potential, the objective of this study was to verify the effect of PGPR and AMF in combination with IBA on rooting and growth of some types of bougainvilleas cutting. Three cutting types (tip, middle and basal) were prepared from four bougainvilleas, namely B. glabra var. sanderiana, B. glabra var. variegata, B. spectabilis Snow White and B. spectabilis Yellow Hybrid in both 2012 and 2013 years. The cuttings were taken from Bougainvillea mother plants in March and treated with three PGPR (Azospirillum brasilense, Pseudomonas fluorescens and Bacillus subtilis) and AMF (Glomus intraradices) in combination with 100 ppm IBA. The all combined treatments of IBA plus PGPR or AMF showed higher rooting percentages than hormone treatment (IBA alone). Among bougainvilleas used, average the highest rooting were observed in B. spectabilis Snow White (62.0 %), followed by B. glabra var. sanderiana (61.2 %), B. spectabilis Yellow Hybrid (60.5 %) and B. glabra var. variegata (54.7 %), respectively. The highest rooting percentages were obtained from basal cuttings treated with 100 ppm IBA plus either G. intraradices, A. brasilense or B. subtilis in all bougainvilleas. Overall, the lowest was observed in the IBA treatment alone. C/N ratio and endogenous root-promoting substances in cutting base were parallel with the rooting ability. The present investigation clearly showed that the combination of PGPR or AMF inoculums and rooting hormone can increase root initiation and potentially increase the quality of rooted cutting produced. Furthermore, the success of root promotion depends on the used strain and genotypic response of Bougainvillea species.