Seed Source May Determine Field-Specific Germination and Emergence: The Source by Planting Environment Interaction

Farm environmental characteristics and management practices can result in within-cultivar differences in seed quality. Transgenerational plasticity (effects of the farm environment on offspring, or TGP) can be important in germination and emergence dynamics. We chose two commonly-used cultivars (Lodorm and Pryor) and one prevariety registered germplasm (P-7) of three perennial bunchgrass species (green needlegrass, slender wheatgrass, and bluebunch wheatgrass) to determine if seeds exhibit TGP and if the effect of that plasticity changes depending on planting environment (i.e. context-dependent TGP). We conducted laboratory germination experiments in 2013 in four temperature regimes and placed seeds in four field environments to examine emergence. We stored seeds in four different environments for ten months and performed similar laboratory and field experiments in 2014 to test if seed storage environment mitigated TGP. Context-dependent TGP determined emergence for the two cultivars in both years, however only Pryor exhibited context-dependent TGP for germination in the lab in 2013. Farm sources with low performance in the field and the lab were less likely to exhibit context-dependent TGP. Some transplant environments did not show differences among farm sources, but in some transplant fields, the effect of farm increased emergence as much as 24%. Laboratory experiments on germination did not provide an assay for context-dependent TGP found in the field, and the effect of seed storage (which was only significant for Pryor) was opposite for lab and field studies, with room-temperature stored seeds having best emergence in the field and the worst germination in the lab. When seed is costly and increasing emergence by 10 to 24% is important, such as in restoration applications, understanding the contribution of farm and storage environments to site-specific field performance will contribute significantly to the success of these enterprises.