Bioenergy Crop Breeding and Production Research in the Southeast, Final Report for 1996 to 2001

Switchgrass (Panicum virgatum L.) is a native grass species to much of the US. It has shown great potential for use in production of fuel ethanol from cellulosic biomass (Lynd et al., 1991). Work in Alabama demonstrated very high dry matter yields can be achieved with switchgrass (Maposse et al. 1995) in the southeastern US. Therefore, this region is thought to be an excellent choice for development of a switchgrass cropping system where farmers can produce the grass for either biomass or forage. Another report has shown success with selection and breeding to develop high yielding germplasm from adapted cultivars and ecotypes of switchgrass (Moser and Vogel 1995). In the mid 1990s, however, there was little plant breeding effort for switchgrass with a potential for developing a cultivar for the southeast region. The main goal of the project was to develop adaptive, high-yielding switchgrass cultivars for use in cropping systems for bioenergy production in the southeastern US. A secondary objective was to assess the potential of alternate herbaceous species such as bermudagrass (Cynodon dactylon L.), bahiagrass (Paspalum notatum Flugge.), and napiergrass (Pennisetum purpureum Schumach.) that may compete with switchgrass for herbaceous bioenergy production in the southeast. During the conduct of the project, another goal of developing molecular markers useful for genetic mapping was added. The ''lowland'' cultivars, Alamo and Kanlow, were found to be the highest yielding switchgrass cultivars. Although most summers during the project period were hot and dry, their annual dry matter yield continue to outperform the best ''upland'' cultivars such as Cave-in-Rock, Shawnee, NE Late, and Trailblazer. The use of a breeding procedure based on the ''honeycomb design'' and multi-location progeny testing, coupled with the solid heritability and genetic gain estimates for dry matter yield in lowland type switchgrass germplasm, indicated excellent potential to isolate parental genotypes for producing higher yielding synthetic cultivars. The four experimental synthetics produced thus far, and now in performance tests, could provide this cultivar. Initial performance results of these experimentals have been very promising demonstrating a 30% yield enhancement over Alamo and Kanlow. Future testing, including testing in other states, will be critical before a determination can be made to release one or more of these into the commercial seed trade. In the genetic mapping project, 42 genotypes of switchgrass were surveyed using restriction fragment length polymorphism (RFLP) probes from different grass species. The different genotypes included 24 from Alamo, 15 from Kanlow, and 3 from ''Summer. '' A majority of the probes (87%) hybridized to the switchgrass DNA and 81% were polymorphic. Most of the polymorphism observed was between the cultivars. A mapping population consisting of 100 progeny from a cross between the most dissimilar Kanlow and Summer genotypes was produced during 2001. The parents and progeny population are now maintained at the University of Georgia and will be used to construct a map based on the polymorphic RFLP probes. When compared to ''Tifton 85'' bermudagrass, ''Tifton 9'' bahiagrass, and ''Merkron'' napier-grass, Alamo switchgrass was found to show poorer yields than Merkron and Tifton 85, but better yields than Tifton 9 in the coastal plain region. The exceptional performance of Tifton 85 bermudagrass is extremely noteworthy because this hybrid bermudagrass is also a variety of choice for many commercial hay producers in the lower south and would give any producers a very good option to produce either biomass for a biofuels initiative or sell as hay on the open market. Merkron has consistently showed the highest dry matter yields. However, there continues to be some winter damage each year on this species at the Athens location indicating its real potential lies mainly in the Gulf Coast region of the southeastern United States. The excellent characteristic of Tifton 85 and Merkron should therefore be enough to initiate more basic research for their chemical ability as a biofuels crop.