Applicability of the tetrazolium test to coffee seeds with different types and levels of stresses.

For sale or use of coffee seeds after harvest, the coffee grower must have information regarding their initial quality, which must meet the standards established in the Sistema Nacional de Sementes e Mudas (SNSM). However, slow germination of coffee seeds makes it difficult to obtain results from evaluation of the seed physiological quality. An alternative for quick evaluation of coffee seed viability is the tetrazolium test. However, there are still questions regarding the true potential of the test for estimating the quality of seed lots with different levels of quality. The aim of this study was to eval-uate the applicability of the tetrazolium test in estimating the viability of coffee seeds with different types of stress and levels of quality. Seeds of Coffea arabica L. were used, which were placed under the following treatments to obtain different types and levels of stresses: natural processing or fully-washed processing, different times of artificial aging, drying at high temperature, exposure to below-zero (°C) temperature, and storage under conditions without climate control. After obtaining the seed lots, the seeds were evaluated physiologically by the tetrazolium test and the germination test. The tetrazolium test overestimates the potential for production of normal seedlings of seed lots of Coffea arabica L. that have the lowest level of quality. The discrepancies between the results of viability in the tetrazolium test and the germination test vary according to the level of physiological quality and the type of stress the coffee seeds were under. We emphasize that the tetrazolium test in the SNSM as an alternative to the germination test in ascertaining the quality of coffee seeds must be reviewed since the results may significantly differ from the ability to produce normal seedlings.