Evaluating the Effects of Plant Growth Promoting Rhizobacteria (PGPR) and Hormone Levels on In-vitro Micropropagation of Peperomia (Peperomia magnoliifolia)

Plant growth promoting rhizobacteria (PGPR) have been proposed as a useful tool for enhancing plant growth. However, only few studies have examined the application of PGPR in in-vitro plant micropropagation. This study was aimed at evaluating the effects of plant growth promoting rhizobacteria (PGPR) and hormone levels on in-vitro micropropagation of Peperomia. The experiment was conducted in a factorial design based on completely randomized design with three replications. Factors comprised of plant growth promoting rhizobacteria (including 0=control (without bacteria), 1=Azospirillum lipoferum, 2=Pseudomonas fluorescent) and hormone levels (including 0=control (without hormone), 1=1.5 mg/l IAA 1 mg/l 2ip and 2=double the treatment 1). Before planting, medium surface was inoculated with 0.08 ml of liquid culture of bacteria and then sterilized axillary buds were cultured. Growth characteristics were measured at two and four weeks after planting. Bacteria and hormone interaction effect was significant in terms of total root length and mean root length. Treating with Azospirillum (without hormone) led to a greater root number, compared to other treatments. Bacteria inoculation had a significant effect on shoot length and leaf number. Inoculation with both bacteria resulted in a greater shoot length compared to control, i.e. it led to a 1.5-fold increase in shoot length. Concomitant application of bacteria and hormone led to a decreased leaf number. In general, bacterial inoculation appeared to be more beneficial to the rooting attributes.