Endophytic bacteria with multifunctional characteristics can benefit plants through different mechanisms, as well as promoting growth in an efficient, low-cost and ecofriendly way. This study analyzed the potential of the multifunctional endophytic isolate Acinetobacter lwoffii Bac109 in promoting the early in vitro growth of sugarcane seedlings. The Bac109 strain showed potential to solubilize phosphate in a solid medium (solubilization index: 3.73). In addition, the bacterium was an efficient biocontrol agent against the phytopathogenic fungi Rhizoctonia sp., Fusarium oxysporum, Phoma sp. and Bipolaris papendorfii, showing a performance equal to or better than the commercial antifungal hygromycin B. An in vitro assay confirmed the biofilm production, which increased in the presence of sugarcane root extract. Additionally, A. lwoffii Bac109 showed a strong adhesion to the sugarcane roots. The inoculation of this bacterium in micropropagated sugarcane seedlings increased the shoot length (35 %) and regulated the nonphotochemical energy dissipation after 28 days of cultivation. At the end of the experiment, the bacterium showed a great potential for survival, with 5.72 × 107 CFU mL-1 recovered from the substrate, what is crucial for plant interaction. The results showed the potential of the biotechnology application for A. lwoffii Bac109 by evaluating multifunctional traits of plant growth promotion and by specific interactions with sugarcane, which may help to improve micropropagation protocols for this crop.

Sugarcane is a commercially important species for sugar and biofuel production and because of the high demand for plant material in planting, new means of propagation are being developed and require improvements. Therefore, the objective of this study was to evaluate the effect of different concentrations of indole-butyric acid (IBA) applied in the form of talc on the initial growth and emergence of sugarcane mini-cuttings used for the system of pre-sprouted plantlets (PSP). Mini-cuttings were treated with concentrations of 0, 500, 1000, 1500 and 2000 mg kg-1 of IBA in the form of talc and evaluated for emergence and initial growth. There was no difference between IBA concentrations for the physiological, biometric and dry mass variables analyzed. The sugarcane plantlets formed had emergence above 89%, functional photosynthetic apparatus, 4.4 leaves on average, stem diameter of 11.90 mm, shoot length of 12.18 cm, leaf area of 108.81 cm² and root area of 142.17 cm². Shoot dry mass and root dry mass were equal to 2.27 and 1.20 grams, respectively. Thus, concentrations of up to 2000 mg kg-1 of IBA applied in the form of talc in sugarcane mini-cuttings had no effect on rooting and initial growth of plantlets.