Changes in Seed Germination With Time for Polycross Progenies of Cicer Milkvetch

Abstract

Relatively few seed‐longevity studies have been concerned with differences among cultivars or genotypes within a species. The purpose of this study was to evaluate the change, if any, in longevity and early seedling vigor of cicer milkvetch (Astragalus cicer L.) seed from selected populations when stored at ambient temperature in an unheated, uninsulated building and subsequently germinated at high (15/25 °C) and low (5/20 °C) alternating temperatures. Seed of polycross progenies from four populations were evaluated for rate of germination when the seed were about one year of age and after 12 yr of storage. Percentage seed germination on a daily basis through Day 14 after planting and total germination at 15/25 °C were similar for the four populations and for the 1‐ and 12‐yr‐old seeds. Progenies within populations differed significantly (P ≤ 0.05) for rate of germination except on Day 14 after planting with 1‐year‐old seed. Germinability on Day 14 ranged from 87 to 100% after 12 yr of storage. When evaluated at 5/20 °C, large differences were noted among populations and among progenies within populations for both rate of germination and total germination. This indicates that the populations and progenies within populations differed genetically for rate of germination. Genetic differences among populations were expressed at 5/20 °C, but not at 15/25 °C. The decline in early seedling vigor as measured by rate of germination at 5/20 °C suggests that care should be taken when increasing the seed supply with older seed from a synthetic cultivar of cicer milkvetch and, perhaps, with seed of other species held in a seed storage facility.