Seedling Vigor of Switchgrass Influenced By Cold Storage Temperatures.

Switchgrass (Panicum virgatum L.) is a perennial warm season grass that produces small seeds with high percentage of dormancy. The seeds produce scattered seedling emergence in the field, resulting in weak competition for resources against vigorously growing weeds during the establishment year. Our group has observed that the seedling vigor of switchgrass was enhanced when seeds were stored in a freezer. The objective of this study is to examine the influence of storage temperatures and time on the seedling vigor of switchgrass. Seeds of Kanlow (seedlots: 2008, 2010, and 2010), Blackwell (seedlots: 2010 and 2011), and Trailblazer (seedlots: 2010 and 2011) were stored at three temperatures (room temperature, -20°C, and -80°C) for 1, 6, or 12 months. The seeds were planted in square pots in a greenhouse condition (Day/night, 22/17°C; 16 hours photoperiod). Emergence rate index (ERI) was used to assess the seedling vigor and was calculated based on the number of seedlings emerged each day. Plants were harvested when three fully collared leaves were observed. Leaf and root dry mater were obtained from the harvested samples. The seed storage conditions that produced the highest ERI was at -20°C and -80°C with 1 month storage for the three seedlots of Kanlow, and at -20°C with 1 month storage for two seedlots of Blackwell and Trailblazer. Dry matter of leaf and root were greater for the seeds stored at -20°C and -80°C for 1 month for all cultivars, compared to the seeds stored at room temperature.  Short term cold storage is recommended to enhance seedling vigor and early stage seedling biomass of the three cultivars of switchgrass.