2011 Annual Report
1a.Objectives (from AD-416)
Objective 1: Develop and evaluate improved grass germplasm for the southern U.S. that is more productive, biologically diverse, tolerant of biotic and abiotic stresses, improved in quality, and easier to establish and maintain in pastures and rural landscapes.
Sub-objective 1.A: Develop and evaluate kleingrass (Panicum coloratum) germplasm with improved forage yield, seedling vigor, and persistence.
Sub-objective 1.B: Produce intraspecific Paspalum hybrids between different dallisgrass biotypes to develop improved forage types.
Sub-objective 1.C: Identify superior Texas bluegrass (Poa arachnifera) genotypes that are rust resistant and adapted to the humid southeastern U.S. to develop a synthetic population from these genotypes.
Objective 2: Use genomic techniques to develop and identify molecular markers associated with traits of interest in forage and turf grasses.
Sub-objective 2.A: Identify molecular markers to further saturate the genomic region controlling apomixis and survey candidate genes for seed sterility in buffelgrass (Pennisetum ciliare).
Sub-objective 2.B: Develop a genetic map of dallisgrass (Paspalum dilatatum) to identify markers linked to apomixis, disease and insect resistance, and other traits of interest.
Objective 3: Develop improved breeding methodologies by determining the cytology, reproductive biology, and genetic diversity of native and introduced germplasm for the production of improved forage and turf grasses.
Sub-objective 3.A: Determine the method of pollination, chromosome number, ploidy level, and mode of reproduction of species in the genera Panicum, Paspalum, Pennisetum, Sorghum, Chloris, Setaria, Stenotaphrum, Tripsacum, and others to facilitate their genetic improvement.
Sub-objective 3.B: Determine the genetic diversity and phylogeny of Paspalum and Pennisetum species using DNA fingerprinting techniques.
1b.Approach (from AD-416)
The long-term objectives of this project are to obtain a better understanding of the cytology, reproductive biology, and genetic diversity of selected forage grasses, and to use this fundamental information in the breeding and development of superior germplasm that will be released as improved cultivars.
During FY 2011, research under this project continued to make advances in developing and selecting superior germplasm that will be used to develop improved forage grass cultivars. Kleingrass (Panicum coloratum) forage evaluation plots were established at Beeville, College Station, San Angelo, and Stephenville, TX, to determine if a recently developed synthetic kleingrass line is more productive and better adapted than existing kleingrass cultivars. Seed were harvested from a recently established replicated polycross block consisting of nine kleingrass genotypes in an effort to develop germplasm with a more uniform upright growth habit to be used for hay production. More than 300 plants from controlled crosses between the yellow-anthered and Uruguayan dallisgrass (Paspalum dilatatum) were phenotypically evaluated in a field nursery, but unfortunately no hybrids were recovered and all the plants were self-pollinated progeny from the maternal parent. In a collaborative effort with a Louisiana State University scientist, 24 superior Texas bluegrass (Poa arachnifera) genotypes were selected from a germplasm evaluation nursery at Rosepine, LA. Several individual plants of each of the 24 genotypes were transplanted into a replicated polycross breeding plot at the cooperator's research station near Homer, LA. These plants will be allowed to cross-pollinate to develop a more productive, rust-resistant synthetic population that is adapted to the humid southeast. In cooperative research with a Texas A&M University scientist, cytological studies were conducted to determine the chromosome number of purported sorghum interspecific hybrids to identify the actual hybrids. These hybrids are being exploited to breed germplasm that will be used as a bioenergy crop. In other FY 2011 cooperative work with Texas A&M University scientists, 11 robust Johnsongrass (Sorghum halepense) genotypes were grown in soil-filled tubes at College Station and Commerce, TX, to determine the relationship between winter hardiness and various metabolites in the rhizomes. Data obtained thus far has shown that accessions with higher fructan content had better winter survival the following spring.
Improved switchgrass germplasm. Switchgrass has great potential as a biofuel feedstock, but the establishment of stands can be a problem because of low seed germination, primarily due to seed dormancy. Recently a switchgrass germplasm line (TEM-LoDorm) that has low seed dormancy was developed and released by ARS scientists at College Station, TX, and cooperators at Texas A&M University for the purpose of providing other switchgrass breeders with a germplasm source with low seed dormancy that can be used in their breeding programs. However, difficulties in generating enough seed to provide to other researchers and breeders have limited its distribution. During FY 2011 sufficient seed was harvested from each of the 24 genotypes in this synthetic line to fulfill the needs of all interested switchgrass breeders. The accomplishment will greatly facilitate ongoing efforts to genetically improve switchgrass as a productive feedstock for efficient and profitable biofuel generation.
Increasing genetic diversity of sorghum. Sorghum is an important grain crop in the U.S. as well as other countries in the warmer regions of the world; plant breeders continue efforts to improve the crop. The recent transfer of the genetic trait iap/iap (inhibition of alien pollen) into agronomically desirable sorghum lines increases the possibility of improving the crop by wide hybridization because grain sorghum with this trait can be successfully crossed with distantly related sorghum species. ARS scientists at College Station, TX, working cooperatively with scientists at Texas A&M University, established that grain sorghum with this genetic trait can be successfully crossed with grasses belonging to different genera. This work established that the iap genetic allele allowed pollen from other grasses to germinate and the pollen tubes to grow into the pistil of grain sorghum. This demonstrates that the genetic diversity of grain sorghum can be increased through wide hybridization with members of other grass genera and will greatly broaden the breeding strategies available for the improvement of this important crop species.
Jessup, R., Renganayaki, K., Reinert, J., Genovesi, A., Engelke, M., Paterson, A., Kamps, T., Schulze, S., Howard, A., Giliberto, B., Burson, B.L. 2011. Genetic mapping of fall armyworm resistance in Zoysiagrass. Crop Science. 51:1774-1783.