A power analysis for detecting aging of dry-stored soybean seeds: Germination versus RNA integrity assessments

Deterioration of seed during dry storage is a major problem for genebanks and seed companies. Germination tests are the gold standard to monitor seed viability; however, these prove to be insensitive during the early stage of storage when viability changes are subtle. Recent findings demonstrate that decline in RNA integrity may be an early indicator of seed longevity during dry storage. The goal of this study was to determine the sensitivity of RNA integrity, measured as RNA integrity number (RIN), regarding how soon changes can be detected and how many seeds are required. We compared the statistical power of germination and RIN assays using a well-characterized collection of 'Williams 82' soybean seeds, with cohorts harvested between 1989 and 2019 and stored at 5 degrees C. Germination was monitored in 1- to 3-yr intervals since 1989, and RIN was monitored in 1- to 2-yr intervals since 2016 providing an extensive dataset to conduct statistical power analyses. Decline in RIN can be detected in soybean seeds within 10 yr with a RNA monitor test that consumes approximately 30 seeds. In contrast, a germination test detects deterioration in 16 yr using approximately 50 seeds, and by this time, the seed lot is near the limit of longevity and has entered the phase of rapid mortality. Work from this study indicates that early detection of aging using RIN decline can be used to predict the longevity threshold to optimize viability monitoring and regeneration times, preventing loss of valuable samples by overtesting or missing the longevity threshold.

Automated summary

Deterioration of seed during dry storage is a major problem for genebanks and seed companies. Recent findings suggest that decline in RNA integrity may serve as an early indicator of seed longevity. This study used a well-characterized collection of soybean seeds to compare the sensitivity of RNA integrity and germination tests, and found that RNA integrity decline can be detected within 10 years using a small number of seeds, while germination tests require more seeds and detect deterioration after 16 years.