Abstract

Lack of water and salinity are commonly encountered problems in many regions worldwide. For this reason, certain robust cactus species may represent promising crops. Because it is necessary to assess the ability of cactus species to survive and adapt under conditions of natural stress, the present study aimed to evaluate the effect of water and salt stress on the vigor and viability of seeds of pitaya genotypes using different osmotic potential gradients and different osmotically active agents. The experiment had a completely randomized design with a 3 × 6 × 4 factorial scheme corresponding to three pitaya genotypes (white, hybrid I, and hybrid II), six osmotic potential gradients (0.0, -0.2, -0.4, -0.6, -0.8, and -1.0 MPa), and four osmotically active agents (PEG 6000, KCl, NaCl, and MgCl₂), with four replicates. The following variables were analyzed: germination percentage, germination speed index (GSI), and mean germination time (MGT). Statistical analyses were performed for each pitaya genotype. The data pertaining to germination were fitted to a binomial model; the data pertaining to GSI and MGT were fitted to regression models. The germination, GSI, and MGT values for all three pitaya genotypes were optimal with the osmotically active agents KCl and NaCl, regardless of the osmotic potential gradient. At osmotic potential gradients lower than -0.2 MPa, the PEG 6000 polymer was detrimental to pitaya seed vigor and viability. The pitaya hybrid I seeds were more resistant to the adverse conditions, exhibiting higher rates of germination and GSI than those of the other genotypes. The osmotic effect negatively influenced the vigor and viability of seeds of the three pitaya genotypes to a greater extent than the salt effect.

Key words: Cactaceae, Hylocereus undatus, Hylocereus costaricensis, polyethylene glycol, vigor.