Optimizing Soybean Speed Breeding: Harvesting and Germinating Immature Pods

Abstract

Speed breeding is a method used by plant breeding programs to reduce the time between generations. This is achieved by subjecting plant populations to conditions that decrease the time to flowering. Planting immature seeds is a viable strategy to decrease the time between generations, at the expense of decreased seedling vigor and health. We planted seeds of varying maturity (green, yellow, and brown) in greenhouse and growth chamber environments and recorded several factors indicative of seedling health. This methodology was repeated using seeds that had been air dried for several days to determine drying’s effect on seedling germination and vigor. The germination rate was equivalent between all pod stages, but undried immature seeds resulted in the weakest seedlings for all factors contributing to health. Drying seeds before planting resulted in equivalent seedling vigor among the three pod maturity stages. The time saved in speed breeding by planting seeds that have not fully matured will result in decreased seedling vigor which may cause the resulting plants to mature more slowly. The effect of planting undried immature seeds on the resulting plant’s ability to produce seed must be evaluated before undried immature soybean seeds can be incorporated into soybean speed breeding programs.