Use of Digital Analysis of Radicle Extension of Marigold Seedlings as an Early Indicator of Seed Vigor

Abstract

Several seed vigor tests were conducted on Marigold `Little Devil Flame' and correlated with digital analysis of radicle extension. Seed from a single lot was deteriorated by the accelerated aging (AA) method at 41 °C for 24 and 72 h. Seed moisture content of unaged seed was 15.23%, mildly aged seed (24-h AA) was 40.77%, and moderately aged seed (72-h AA) was 52.85%. After AA treatment, all seeds were dried to near 15% moisture. Vigor level was assessed 7 days after AA treatment by standard germination and soilless-mix plug emergence tests according to the Association of Official Seed Analysts Rules for Testing Seed. The standard germination test revealed an 84.5% germination for unaged seed, 49.5% germination for mildly aged seed, and 28.5% germination for moderately aged seed. The plug emergence test showed an 88.9% normal emergence for unaged seed, 65.28% germination for mildly aged seed, and 9.72% germination for moderately aged seed. Additionally, the radicle of seedlings established under standard germination conditions was digitally analyzed after 4 days. According to digital analysis, average radicle length for unaged seed was 2.10 cm, 1.91 cm, for mildly aged seed, and 1.27 cm for moderately aged seed. Radicle length after 4 days showed an R2 of 0.81 when regressed against standard germination and an R2 of 0.99 with seedling emergence tests. These results suggest that digital analysis of radicle extension could provide a sensitive, reproducible test for seed vigor.