Vigor relativo: uma nova abordagem para classificação de lotes de sementes

Abstract

Vigor tests have been developed to identify possible differences in the physiological potential of seed lots, thereby providing complementary information to germination tests. The premise of these tests is to test the resilience of seed lots to unfavorable conditions for development. The results of vigor tests are usually expressed in absolute quantities and despite this inconvenience, absolute measures of vigor persist in research and in companies. However, lots with marginal germination percentages, which maintain maximum germination percentages under stress conditions, may not have absolute vigor that is compatible with the other lots that are vigorous, but they have high relative vigor. Therefore, it is necessary to relativize vigor tests to minimize the disposal of lots with marginal or intermediate quality, in addition to allowing research to remove part of the subjectivity of vigor in its absolute form. The objective of this research was to propose a new measure, namely, relative vigor (RV), for seed vigor tests expressed as a percentage. This RV is obtained by dividing the result of the vigor test by the result of the germination test, multiplied by 100. For the calculation of relative vigor (RV), data were obtained in three ways: information acquired from a commercial production system with germination and vigor percentages from 4411 soybean seed lots; measures of vigor cited in articles published in Seed Science and Technology from 1977 to 2002, and data acquired through simulation in software R. As the relative vigor has no known sample distribution, a fact that makes it impossible to make statistical inferences, we used the bootstrap technique for obtaining confidence intervals in data from company and journal articles. Relative vigor is a new approach to classifying seed lots; this measure is able to change vigor rating, especially those of marginal and intermediate-quality lots. In conditions of high germination, the use of relative vigor is optional, but it allows greater efficiency and safety in the interpretation of results of vigor tests and in decision-making regarding seed lots. RV shows whether the problem lies in germination or vigor, pointing out the need to repeat germination or vigor tests.