Osmotic stress vigor test for wheat seed

Graduation date: 1989Seed vigor tests have been developed to evaluate the relative ability of seed lots to produce stands of seedlings in the field. Some workers have suggested the possibility of differentiating vigor levels by germinating seeds under osmotic stress, but have not conducted field trials to evaluate the usefulness of the test. This study was conducted to 1) develop an osmotic stress vigor test for wheat seed, 2) evaluate the effectiveness of this test in ranking seed lots for field emergence, and 3) compare the osmotic stress vigor test with other vigor tests. The effects of osmotic potential and temperature on germination of wheat seeds of different vigor levels were investigated. The conditions resulting in greatest differentiation of vigor levels were selected for an osmotic stress vigor test. The osmotic stress test and six other germination and vigor tests were compared for effectiveness in predicting seedling emergence in three field trials of 16 artificially aged and 19 naturally aged seed lots. Reduced osmotic potentials lowered the germination rate of low vigor seeds more than high vigor seeds, but total germination remained the same. The conditions selected for the osmotic stress vigor test were a sand substrate with 50 mL PEG 8000 solution at - 0.5 MPa, with a 10-day germination period in the dark at 20° C. Under adverse field conditions, the osmotic stress test was significantly correlated with field emergence of artificially aged (r = .85) and naturally aged seeds (r = .62). However, the predictive value of the osmotic stress test was lower than some of the other vigor tests, especially accelerated aging and the 4-day sand test. The vigor test rankings varied somewhat under more favorable field conditions. These results indicate the necessity of including several vigor tests and field planting dates when evaluating a specific vigor test. Research should continue to determine the potential of the osmotic stress test and four-day sand tests for application to other seed kinds