Quick Test with Tetrazolium Chloride on Coffee Seed Viability

Abstract

The germinative capacity of coffee seeds may be evaluated within 2 days by using the following procedure: 1. The parchment is removed from a representative sample of coffee seeds and the seeds are soaked in water for an hour or more. Soaking for 24 hours is recommended for older and drier seeds. 2. The silverskin then is rubbed off, the seed rinsed, and kept in water ready for sectioning. 3. With a sharp blade, the seed is sectioned longitudinally through the embryo (slicing off a small portion of the cotyledons and radicle) which is imbedded in the endosperm but visible from the dorsal side. 4. The part with the larger section of the embryo is fully immersed for 16 to 24 hours in the TZ test solution (0.5 to 1.0 percent 2,3,5 triphenyl tetrazolium chloride in distilled water, adjusted to pH 5 to 7). 5. After immersion, the seed sections are rinsed and the embryo and endosperm examined carefully. Uniform red pigmentation on the embryo and endosperm indicates healthy viable seed. Pink or mottled coloration indicates weak seed of doubtful germinative capacity. White or no color change indicates dead seed. 6. Reading of results may be delayed several days by rinsing the treated seeds with water and storing them underwater at 8° to 10° C. It is recommended that more tests be conducted to determine more accurately the relationship between TZ test results and actual germination tests, especially those borderline cases exhibiting pink or mottled coloration. An easier method of exposing the uninjured whole embryo to the test solution could help in these cases. It also may be worth looking into a much longer duration of soaking before sectioning as this affects speed of reaction to the test, especially on older and drier seeds.