Single-count radicle emergence test to predict field emergence of rice (<i>Oryza sativa</i> L.) seed lots

Abstract Standard laboratory germination tests guarantee the quality of certified seeds; however, seeds with a high germination percentage (GP) do not always exhibit high field emergence (FE). Conversely, seed lots produced in different seasons and agroecosystems display varied levels of vigor and GP. The Radicle Emergence (RE) test is a rapid vigor test compared to others. However, RE counts carried out several times periodically are impractical and time-consuming. It is necessary to determine the optimal timing for a single RE count. This research aimed to identify the timing of a single RE count that is highly correlated with FE. Twenty lots of rice seeds with varying seed longevity were tested for GP, vigor with accelerated ageing (AA), FE, and RE at 48 hours (48h), 52h, 56h, and 72h after the initiation of germination. The study used a completely randomized block design with four replications. Seed lot differences, including variety and longevity, significantly influenced GP and vigor, while ecological factors such as agroecosystems and crop seasons also contributed to variations. The results showed strong possitive correlations between all single RE counts with GP, AA, and FE. Correlation coefficient (r-value) increased with longer RE times, with RE56h and RE72h showing strong and comparable results. No significant differences were observed in the R 2 -values of FE regression with RE56h and RE72h. Additionally, images of RE56h and RE72h were clear and analyzable. Based on these findings, RE56h is the optimal single count for estimating FE across various levels of rice seed vigor.