Breeding for Reduced Post-Harvest Seed Dormancy in Switchgrass.

Switchgrass (Panicum virgatum L.) is a native, perennial, warm-season, bunchgrass that recently has received considerable attention as a bioenergy crop for the production of cellulosic ethanol. Because of its potential as a renewable biofuels crop, interest in the grass is increasing and the land area being planted to switchgrass is expanding. However, establishment of desirable stands can be a problem because post-harvest seed dormancy causes low germination and slow seedling development. Post-harvest dormancy in recently harvested seed of some switchgrass cultivars can be as high as 95%, and the seed can require up to 2 years of after-ripening to become germinable. This lengthy after-ripening period can be reduced by cold stratifying the seed but this also can be problematic. Consequently, we initiated a breeding program to develop germplasm with reduced post-harvest seed dormancy to improve germination and stand establishment. The cultivar Alamo was used as a base population and four cycles of recurrent selection were used to develop the germplasm. During the first three cycles, recently harvested seed from about 200 entries were germinated to evaluate immediacy of germination. Seedlings from seed that germinated within 3 to 14 days were used to establish a polycross nursery to produce seed for the next cycle of selection. Twenty-four plants in the cycle 3 crossing block that produced seed with the most rapid germination rate were dug and used to establish cycle 4 crossing blocks. Over a two-year period, germination of recently harvested seed from most of these 24 plants was significantly (P<0.05) higher than seed from unselected. Some plants were ten or more times higher than. Equal quantities of seed from these 24 plants were bulked and used to constitute the switchgrass germplasm line TEM-LoDorm. It was recently released by the USDA-ARS in cooperation with Texas AgriLife Research.