Radicle Length in Agar is a Reliable Predictor of Seed Vigor

Radicle emergence and development are commonly used parameters for evaluating seed vigor. This research investigated germination behavior and radicle elongation in agar of different concentrations, as predictors of seed vigor. Early radicle elongation under two agar concentrations (0.65 and 0.75%), using lettuce and broccoli seed samples with known differences in vigor, was evaluated and compared to germination parameters based on radicle emergence counts. Of the three evaluated germination parameters, time to 50% germination, mean germination time, and AUC (a parameter that combines germination capacity, speed and uniformity information), only AUC could consistently reflect the small differences in vigor between the samples, regardless of agar concentration. Differences in radicle elongation rates were indicative of differences in vigor, especially at the higher agar concentration. The magnitude of the difference in radicle length between high and low vigor seeds was wider in 0.75% agars, mainly due to reduced elongation rates of the lower vigor sample. The differential radicle elongation rates, revealed by testing in different agar concentrations, were a reliable indicator of even small differences in seed vigor, and could form the basis of a new simple and practical vigor test.