Effects of Immersion Time and Indole-3-Butyric Acid Dosage on the Quality of Black Pepper (Piper nigrum L.) Seedlings

Vegetative propagation via cuttings is the primary technique used in commercial black pepper plantations; however, a moderate capacity for adventitious rooting limits the production of high-quality seedlings. Consequently, the application of exogenous auxins has emerged as a promising strategy to overcome this issue, yet gaps remain regarding the optimal treatment method for cuttings. It is hypothesized that the genotype interacts with immersion time (exposure duration) and auxin dosage to enhance seedling quality. Despite this, these factors have not been evaluated in combination, leading to the improper use of auxins and suboptimal results, hindering the adoption of this technology by nursery operators. Therefore, this study aimed to evaluate the effects of indole-3-butyric acid (IBA) dosages and exposure times on ‘Bragantina’ black pepper seedlings. To this end, an experiment was conducted using a randomized block design in a factorial arrangement; treatments consisted of three immersion times (0—immediate contact, 3 h, and 6 h) and six IBA dosages (0, 750, 1500, 3000, 4000, and 5000 mg L−1). At 120 days after planting, the seedlings were evaluated for growth, development, biomass, and quality characteristics. Strong modulation of shoot and root system development was observed in response to dosage and exposure time. Stem diameter and root length were directly proportional to IBA dosage, regardless of contact time. Exposure to IBA for 3 and 6 h resulted in increasing inhibition of leaf and shoot development as dosage increased, whereas immediate contact did not affect the aerial parts of the plant. Thus, the treatment involving immediate contact of the cuttings with a 3000 mg L−1 of IBA solution is more suitable, as it results in superior root development and seedling quality for the ‘Bragantina’ black pepper cultivar.