This study was conducted with the objective of adjusting the methodology of the tetrazolium test for physiological quality evaluation of watermelon seeds. In the first stage, the most appropriate tetrazolium test procedure was determined. The following procedures were evaluated: seed moistening in wet paper towel for 16 and 24 h and immersion in water at 40ºC for 30, 40 and 60 minutes for tegument removal , and for 30, 40 and 60 minutes for removal of embryo surrounding membrane. Then, the seeds were placed in 0.075% tetrazolium solution at 40ºC, in the dark, for 30, 40 and 60 minutes. Each sample tested by tetrazolium test was also evaluated for germination and seedling emergence tests establishing criteria for viability and vigor evaluation. In the second stage, the most appropriate tetrazolium methodology was applied to eight seed lots and the results were compared for germination, first count, accelerated aging and seedling emergence tests. Five classes of viability were established: vigorous (classes 1 and 2), viable (classes 1 to 3) and non-viable and dead seeds (classes 4 and 5, respectively). The results indicated that the tetrazolium test was efficient for viability and vigor evaluation of watermelon seeds. The seeds should be immersed in water at 40ºC for 40 minutes for removal of the tegument followed by 60 minutes for the removal of the endosperm membrane. The ideal staining was obtained after 60 minutes immersion in a 0.075% tetrazolium solution at 40ºC.
Citrullus lanatus; viability; vigor
