Methodology of the Tetrazolium Test for Evaluating Physiological Quality in Pitaya (<i>Hylocereus undatus</i>) Seeds

Abstract

The germination test is routinely used for evaluating physiological quality of seeds, but it has not been satisfactory, since it requires relatively long periods to obtain results. In this sense, there is the possibility to resort to vigor tests, although the absence of standardized methodologies has hindered your applicability and reproducibility. The goal of the present study was to establish a methodology for the tetrazolium test that is effective for evaluating physiological quality in pitaya seeds. So, we used five seed batches obtained from mature fruits of pitaya (Hylocereus undatus), harvested in the years of 2008, 2009, 2010, 2011, and 2012. The experimental design was the completely randomized design, with four replicates of 50 seeds. The tetrazolium test was conducted in a 5 × 4 × 3 factorial plot, corresponding to five batches of pitaya seeds (2008, 2009, 2010, 2011, and 2012), four concentrations of the tetrazolium solution (0.075%, 0.1%, 0.5%, and 1.0%) and three immersion periods (2, 3, and 4 h). In addition, the germination test for the seed batches was carried out and the analyzed variables were: percentage of germination (PG), germination speed index (GSI) and mean germination time (MGT). Data were submitted to ANOVA and means were compared by the Scott-Knott test (p ≤ 0.05). Tetrazolium test conducted at a solution concentration of 0.5% and an immersion period of 3 h proved to be efficient for evaluating physiological quality of pitaya seeds, in order to stratify the seed batches into more viability levels compared to the germination test.