Management of clonal mini-garden with gibberellic acid in guava rootstock propagation

Abstract

The viability of the mini-cutting technique requires seedling regrowth ability and continuous propagule production. It is hypothesized that the application of gibberellic acid (GA) can stimulate vegetation and increase the production of mini-cuttings. The aim of this study was to increase the mini-cutting yield of Psidium guajava (L.) × Psidium guineense (Sw.) (‘BRS Guaraçá’) as a function of foliar application of GA and season of the year. The experiment was laid out in a randomized-block design with split-plots in time, in which the plots consisted of different GA concentrations applied (0, 50, 100, 150 and 200 mg L-1) and the subplots were represented by two application periods or seasons (summer and winter). Four replicates were used, with two plants per plot. After the seedlings were topped, GA was applied at different concentrations and the emerged shoots were evaluated over 30 days. Mini-stump yield was assessed by collecting and evaluating the potential number of mini-cuttings. Shoot length and mini-stump yield increased linearly with the increasing GA concentrations during the summer. In the winter, this response was quadratic, with optimal concentrations estimated at 65.3 mg L-1 for shoot length and 76 mg L-1 for mini-stump yield. The GA concentration of 200 mg L-1 provided shorter internodes in the summer, whereas in the winter the use of GA did not interfere with this trait. The increasing applications of GA induced a linear increase in stem diameter at both seasons of the year. Gibberellic acid did not interfere with the rooting of the mini-cuttings. The highest rooting percentage occurred in the summer, with an average of 95%. In the winter, this value was 77.2%, demonstrating that mini-cuttings are a promising technique for ‘BRS Guaraçá’. Foliar spraying of GA promoted an increase in mini-cutting production, without interfering with their rooting.