Testes de vigor em sementes de Urochloa brizantha cv. marandu

Abstract

The increase in commercial demand for high seed quality has generated a growing interest of companies in the forage grass sector for effective tests in determining seed vigor. Seeds with high performance after sowing and longer shelf life are desirable. The aim of this study was to identify the viability and vigor methods suitable for determining the physiological quality of Urochloa brizantha seeds cv. Marandu during storage. The study was carried out from September 2018 to June 2019 from the physiological evaluation of 12 lots of seeds from 5 different locations in Brazil, stored for 0, 90, 180 and 270 days in natural conditions in the warehouse of Facholi Seeds Company, in Santo Anastácio, SP. The tests performed were: germination, germination speed index, seedling emergence, seedling emergence speed index, precocity of primary root emission and tetrazolium. For each lot and storage period, the accelerated aging method was applied for 48, 60 and 72 hours at 41oC using water and saturated NaCl solution. The statistical design was completely randomized with four replications, considering the factorial arrangement of lots by evaluation periods during storage (4 x 12), valid for each test and within each methodological variation of each accelerated aging and tetrazolium test. Among the different seed tests, those based on accelerated aging were superior to the other due to the sensitivity in detecting changes in seed quality during storage. Through accelerated aging, the results of germination, seedling emergence, early emission of the primary root and tetrazolium tests were effective in determining seed vigor. All these tests can be evaluated by applying a temperature of 41oC for 60 hours in a saturated NaCl solution, with the exception of the germination test, which must be in water. However, the tetrazolium test with unaged seeds can also be applied for this purpose with the same efficiency.