Association of Indolebutyric Acid with Azospirillum brasilense in the Rooting of Herbaceous Blueberry Cuttings

Association between auxins and plant growth-promoting bacteria can stimulate root growth and development of fruit crop nursery plants, and can be a promising biological alternative to increase the rooting of cuttings. The objective of this study was to assess the viability of producing 'Powderblue' blueberry nursery plants from cuttings using different doses of indolebutyric acid (IBA) in association with Azospirillum brasilense. The following treatments were tested: 0 (control); 500 mg L-1 of IBA; 1000 mg L-1 of IBA; A. brasilense; 500 mg L-1 of IBA + A. brasilense; and 1000 mg L-1 of IBA + A. brasilense. The experimental design was completely randomized, with six treatments and four replicates, and each plot (box) consisted of 10 cuttings. The boxes were arranged in a mist chamber with an intermittent regimen controlled by a timer and solenoid valve. After 90 days, the following variables were assessed: rooted cuttings; survival of cuttings; foliar retention; sprouting; cuttings with callus; root dry mass per cutting; number of roots per cutting; and root length. It was observed that the application of IBA with the A. brasilense rhizobacteria increased the number of roots of 'Powderblue' blueberry cuttings, while the treatments with IBA alone and IBA 1000 mg L-1 + A. brasilense increased the root length of cuttings. However, treatments with IBA and A. brasilense had no impact on % rooted cuttings and % survival of cuttings.