Tetrazolium test for evaluating viability of stored rice (Oryza sativa) seeds

Germination testing of rice seeds takes 14 days, while the tetrazolium test can characterise seed viability in hours. The goal of this study was to evaluate the viability of stored rice seeds cv. Chiang Phatthalung by a practical and efficient tetrazolium method. Seeds were stored at room temperature (28°C) and in cold storage (10°C) for 0, 3, 6, 9 and 12 months and then their viability and physiological quality was tested. Seeds of all treatments were soaked in water for 18 hours, cut longitudinally and immersed in 1% tetrazolium solution for two hours at 30°C according to the ISTA method, or in tetrazolium solution at different concentrations (0.0625, 0.125, 0.25 and 0.5%) and staining temperatures (30, 35, 40 and 45°C). The modified tetrazolium test with 0.125% tetrazolium concentration and staining at 40°C of stored rice seeds correlated positively with standard germination (r = 0.98, P < 0.01), soil seedling emergence (r = 0.98, P < 0.01), shoot length (r = 0.78, P < 0.01), root length (r = 0.81, P < 0.01) and seedling dry weight (r = 0.75, P < 0.01). Thus, this staining condition can be used to efficiently estimate the viability of freshly harvested and stored rice seeds.