Location: Crop Germplasm Research
2020 Annual Report
Objectives
Objective 1: Develop and evaluate improved germplasm of perennial forage sorghum genotypes, napiergrass, pearl millet x napiergrass hybrids, and kleingrass that are more productive, biologically diverse, tolerant of biotic and abiotic stresses, improved in quality, and easier to establish and maintain in sustainable agroecosystems.
Subobjective 1A: Produce intra- and interspecific and intergeneric perennial forage Sorghum hybrids and evaluate them for winter-hardiness, perenniality, biomass production, forage quality, disease/insect resistance, seed fertility, and weediness mitigation.
Subobjective 1B: Develop improved napiergrass (Pennisetum purpureum) genotypes and pearl millet (Pennisetum glaucum) x napiergrass hybrids and evaluate them for improved winter-hardiness, higher forage yield and quality, drought tolerance, seed fertility, and weediness mitigation.
Subobjective 1C: Develop and evaluate kleingrass (Panicum coloratum) synthetic varieties with improved forage yield and quality, seed weight, seedling vigor, and persistence.
Objective 2: Determine the reproductive biology, cytology, crossability, and genetic diversity of all new germplasm of different Sorghum species, napiergrass and other Pennisetum species, and their interspecific hybrids to support development of more efficient forage and bioenergy grass breeding strategies.
Subobjective 2A: Determine the method of pollination, chromosome number, ploidy level, and reproductive behavior of species of Sorghum, Pennisetum, and other genera used in the wide hybridization program to facilitate hybridization and the genetic improvement of recovered wide hybrids.
Subobjective 2B: Utilize molecular markers to identify and assess parental contribution of interspecific and intergeneric hybrids via species-specific markers and characterize the genetic diversity within targeted germplasm.
Approach
Better adapted and more productive forage grasses are needed to improve livestock production and the ecological stewardship of the southern U.S. Species that produce large quantities of biomass also have potential as bioenergy crops and value-added bioproducts. This is an ongoing, long-term, 1-Scientific Year project that collaborates closely and effectively with Texas A&M University (TAMU) scientists. Many warm-season perennial grasses are complex polyploids, which makes improvement utilizing conventional breeding methods a difficult undertaking. Apomixis, a vegetative form of reproduction, is prevalent within many of these species, and this further complicates improvement. Interspecific hybridization and induced polyploidization are often required to create germplasm and this complicates improvement. The first objective addresses the breeding and genetic enhancement of perennial forage sorghum, napiergrass including napiergrass x pearl millet hybrids, and kleingrass. Elite germplasm from these breeding efforts will be evaluated in anticipation of selecting and releasing better adapted and more productive cultivars to be used as forage for livestock. Perennial forage sorghum and napiergrass germplasm also will be evaluated sustainable bioenergy feedstocks and as sources for value-added bioproducts. The second objective investigates the reproductive biology, cytology, pollination/incompatibility mechanisms, and genetic and genomic relationships of all new germplasm of different Sorghum species, napiergrass accessions, and other Pennisetum species introduced into and used in the breeding programs. Similar information will be determined for all interspecific hybrids recovered from crosses between napiergrass and other Pennisetum species and between perennial forage sorghums and wild Sorghum species. This basic information is needed to establish more efficient breeding strategies for the production and selection of improved forage and bioenergy grasses.
Progress Report
During FY2020, research associated with this project under Objective 1 continued to make advances in the development, selection, and evaluation of superior sorghum germplasm for the purpose of developing improved perennial sorghum cultivars to be used for forage and bioenergy purposes. ARS researchers at College Station, Texas, collaborating with Texas A&M University scientists, characterized the second and third generations from a chemically induced genetic variant (tetraploid) Sorghum bicolor x S. propinquum hybrid. Field trials were conducted to determine their overwintering ability and to evaluate various agronomic and morphological traits. The populations overwintered well (60–85% survival) and had promising yield potential. The tetraploid entries were intermediate to both parents for most morphological traits. Flowering in the tetraploid was mostly short day photoperiodic like S. propinquum. Some tetraploid individuals expressed positive tendency (transgressive segregation) for plant height. Although segregation did not increase from the second to the third generation, there was enough variability that selection should be successful in improving performance. The next step of Objective 1 is to make selections to establish a recurrent selection program to develop synthetic cultivars. During fiscal year 2020, research associated with this project under Objective 2 continued to make advances in determining the cytological relationship between S. bicolor and S. propinquum. A detailed cytological investigation was conducted of the meiotic chromosome pairing behavior in both parental species (S. bicolor and S. propinquum), the diploid first generation S. bicolor x S. propinquum hybrid, and the chemically (colchicine) induced tetraploid first generation S. bicolor x S. propinquum hybrid and its progeny. Both parental species were stable diploids with primarily bivalent chromosome pairing during meiosis. The chromosomes in the diploid first generation hybrids also paired primarily as 10 bivalents, indicating that the chromosomes of S. bicolor and S. propinquum are very similar (homologous). The colchicine induced tetraploid first generation S. bicolor x S. propinquum hybrid and its progeny all had 40 chromosomes and a somewhat regular mean meiotic pairing behavior of 0.45 univalents, 17.77 bivalents, 0.02 trivalents and 0.98 quadrivalents per cell. Pollen stainability and seed set in the tetraploid hybrids were lower than either parent, but this level of fertility is high enough that these hybrids can be propagated with seed. This germplasm has the potential of being developed into a commercial noninvasive perennial forage/bioenergy sorghum.
Accomplishments
Review Publications
Shen, X., Foster, T., Baldi, H., Dobreva, I., Burson, B.L., Hays, D., Tabien, R., Jessup, R. 2019. Quantification of soil organic carbon in biochar amended soil using ground penetrating radar (GPR). Remote Sensing. 11(23):2874. https://doi.org/10.3390/rs11232874.
Xu, Y., Porter, N., Foster, J., Muir, J., Schwab, P., Burson, B.L., Jessup, R. 2020. Silica production across candidate lignocellulosic biorefinery feedstocks. Agronomy. 10(1):82. https://doi.org/10.3390/agronomy10010082.
Foster, T., Baldi, H., Shen, X., Burson, B.L., Klein, R.R., Murray, S., Jessup, R. 2020. Development of novel perennial Sorghum bicolor x S. propinquum hybrids. Crop Science. 60:863-872. https://doi.org/10.1002/csc2.20136.
