Location: Crop Germplasm ResearchTitle: Breeding for reduced post-harvest seed dormancy in switchgrass: registration of TEM-LoDorm switchgrass germplasm Author
Submitted to: Journal of Plant Registrations
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/11/2008
Publication Date: 1/27/2009
Citation: Burson, B.L., Tischler, C.R., Ocumpaugh, W.R. 2009. Breeding for reduced post-harvest seed dormancy in switchgrass: Registration of TEM-LoDorm switchgrass germplasm. Journal of Plant Registrations. 3:99-103. Interpretive Summary: Switchgrass is native to the United States and it has been grown to produce forage for livestock and to control soil erosion problems for many years. Because the grass produces large amounts of forage, it is now being planted to produce forage that will be used to produce alcohol (ethanol) as an alternative fuel for gasoline. However, farmers have determined that it is often difficult to obtain a good stand of switchgrass by planting its seed into the soil. There are several factors that can cause this but one is that switchgrass seed are often dormant and will not germinate until the seed have undergone an aging period in the soil. When the seed have aged and germinated, the seasonal weather conditions are not always such that the young seedlings will survive. If the dormancy in switchgrass seed could be decreased, then enough seed would germinate shortly after planting and the seedlings would have a better chance to survive because the weather conditions would be conducive to better seedling growth and establishment. This would result in better stands of the grass. We initiated a program to identify and select seed that were not dormant immediately after the seed were harvested. We germinated switchgrass seed that had just been harvested and selected those seedlings that came from the seed that germinated immediately after being placed in a germinator. The plants that developed from these seedlings were crossed and the seed from those plants were then screened for early germination. Plants from those seedlings were then cross-pollinated and this selection and crossing procedure was repeated for several years. Twenty-four plants with the least amount of dormancy in their fresh seed were selected and equal amounts of seed from these plants were bulked and used for the switchgrass TEM-LoDorm germplasm. This germplasm will be used by grass breeders to develop new switchgrass cultivars that will produce seed with less post-harvest dormancy and this will improve stand establishment.
Technical Abstract: The switchgrass (Panicum virgatum L.) germplasm line TEM-LoDorm (Reg. No. GP-98, PI 636468) was developed by the USDA-ARS in cooperation with the Texas Agricultural Experiment Station (currently Texas AgriLife Research) and was released in May 2007. Establishment of desirable stands of switchgrass from seed can be problematic because of post-harvest seed dormancy. This germplasm line has reduced post-harvest seed dormancy and was developed to provide switchgrass breeders with germplasm to improve seed germination and enhance stand establishment. The highly heterogeneous switchgrass cultivar 'Alamo' was used as a base population from which TEM-LoDorm was developed using four cycles of recurrent selection. During the first three cycles, recently harvested seed from 150 to 200 entries were bulked, threshed, and germinated to evaluate immediacy of germination. Seedlings from the seed that germinated from 3 to 14 days after being placed in a germinator were transplanted into pots and used to establish a polycross nursery to intercross and produce seed for the next cycle of selection. For the third cycle, only seedlings that initiated germination within 3 days were selected. 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 a majority of these clones was significantly (P<0.05) higher than unselected Alamo seed. Percent germination of seed from some clones was ten or more times greater than the corresponding values for the unselected Alamo plants. Equal quantities of seed from each of the 24 plants were bulked to constitute the TEM-LoDorm germplasm.