The effect of paclobutrazol was evaluated on plantlet production of different vetiver genotypes (assay 1) and on plants under field conditions (assay 2). In the first assay, two vetiver genotypes from the Germplasm Repository of Sergipe Federal University, Brazil (UFS-VET001 and UFS-VET003), seven concentrations of paclobutrazol and two moments of application (7 and 14 days after planting) were evaluated. In the field assay, the treatments were three vetiver genotypes and three methods of application of paclobutrazol. Two product applications were performed at plantlet stage and one when plants were in the field. The application on 14-day old plants in the nursery reduced plant height and dry weight ofaerial part and roots. The highest paclobutrazol concentration (1,800 mg l-1) resulted in shorter plants and lower dry weight of aerial part. Paclobutrazol did not influence the number of tillers per plant and should not be recommended for production of vetiver plantlets. In the field assay, the genotypes UFS-VET001 and UFS-VET004 had major tillering at 133 days after transplanting; there were no significant differences between the genotypes for the variables number of ears, plant height, dry weight of aerial part and roots, and essential oil content. The application of paclobutrazol proportioned reduction on the number of ears and plant height, but did not affect dry weight of aerial part and roots. Paclobutrazol should not be recommended for commercial production of vetiver roots because it did not reduce the aerial part and did not increase roots and essential oil yield as well.
Chrysopogon zizanioides; medicinal and aromatic plant; genotype; growth regulator; tillering; essential oil
