Seed viability constants and the decline in germination rates for radish: a combined viability equation and population-based threshold model analysis

Aside from the leaves and roots, radish seedlings are consumed as a “microgreen”. Production of microgreens requires high viability, high vigour seeds. Knowledge of the rates of loss of viability and vigour decline during storage would therefore be useful for radish sprout production, but also in relation to the conservation of radish germplasm in seed genebanks. Seeds of radish ‘Kaiware’, a microgreen cultivar, were stored hermetically at seven moisture levels between 6% and 13% at 50°C. Seed viability (germination after removal from storage) was scored daily to determine germination progress curves. One-step analysis was used to simultaneously fit the population-based threshold (PBT) model describing the decline in germination rates with ageing and to estimate the effects of MC on longevity according to the viability equation. KE and CW were estimated as 6.54 and 3.22, respectively. The ageing-time constant for the PBT model, θage, increased as a function of storage moisture content, reflecting the faster decline in vigour at higher MC. The validity of the viability constants was tested by predicting viability loss in seeds of a different radish cultivar, ‘Sango Purple’, stored at 45°C and 8.61% MC.