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ARS Home » Plains Area » College Station, Texas » Southern Plains Agricultural Research Center » Crop Germplasm Research » Research » Research Project #434881

Research Project: Genetic Improvement of Perennial Warm-Season Grasses as Forage, Bioenergy, Turf, and Value-added Bioproducts within Sustainable Cropping Systems

Location: Crop Germplasm Research

2019 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
This is a new project that replaced project number 3091-21000-033-00D (and bridging 3091-21000-040-00D) and is continuing and expanding much of the research of the precursor project. During FY 2019, research associated with this project 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 (Objective 1). Work with collaborators at Texas A&M University determined the primary culm (stem) growth, basal tillering (extent of stems arising from the plant base), time of floral initiation, rhizome (shallow underground horizontal roots) development and spread, winter hardiness, and other traits of a population of Sorghum bicolor x S. propinquum hybrids (diploid F2 generation). Sixty-three hybrids over-wintered and the 10 best are being advanced to the next (F3) generation. In another collaboration with Texas A&M University scientists, a different approach of breeding perennial, winter-hardy forage/bioenergy sorghum evaluated progeny from a S. bicolor x S. propinquum hybrid. Elite second and third generation hybrids were established in replicated field trials and these are currently under evaluation (Objective 1). Cytological (detailed analysis of cellular structure/function) studies of this hybrid (known as a tetraploid) and its progeny revealed there is strong similarity (homology) between the S. bicolor and S. propinquum chromosomes. Seed set in the hybrids was high enough that they are being propagated by seed (Objective 2). Also under Objective 2, work with Texas A&M University collaborators generated more than 2,000 S. propinquum seed (known as diploids) that were treated with colchicine to induce chromosome changes (doubling their chromosomes) for the development of genetic types known as polyploids. The polyploids can be crossed with other sorghum polyploid lines to develop improved germplasm. The ploidy level of 586 treated plants was determined using a technique known as flow cytometry to identify plants with a doubled chromosome number. Thirty-two plants had doubled sectors (chimeras) and they will be used to recover further modified plants called tetraploids (Objective 2).


Accomplishments
1. Carbon sequestration by a perennial sorghum. Carbon sequestration by plants in the soil can be a major factor in capturing organic carbon such that it does not contribute to atmospheric carbon dioxide levels. In a collaborative study with Texas A&M University scientists, ARS scientists at College Station, Texas, used ground penetrating radar (GPR) to determine that a perennial forage sorghum (Columbusgrass) annually accumulated 25 tons per hectare of below ground biomass (roots and rhizomes) compared to 12 tons per hectare (about 2.5 acres) of above ground biomass. Subsequent total carbon analyses revealed that these roots and rhizomes sequestered 12 tons of carbon per hectare (44 tons of CO2-equivalent per hectare) annually which is 4 to 10 times greater than the amount accumulated by non-rhizomatous crops with only fibrous roots. Field trials have confirmed this perennial, rhizomatous, forage hybrid can increase soil organic carbon by 1% in five years on perennial grasslands, which is significantly more than either conservation tillage practices or growing perennial species with only fibrous root systems.


Review Publications
Dinato, N.B., Santos, I.I., Leonardecz, E., Burson, B.L., Quarin, C.L., Paula, A.F., Favero, A.P. 2018. Storage of bahiagrass pollen at different temperatures. Crop Science. 58:2391-2398. https://doi.org/10.2135/cropsci2018.03.0164.