Location: Crop Genetics and Breeding Research2010 Annual Report
1a. Objectives (from AD-416)
To develop and evaluate bermudagrass, napiergrass, pearl millet, and rhizoma peanut for forage production and for alternative uses in the southeastern U.S.; to enhance bioenergy production from warm-season grasses; and to apply molecular genetic technology to improve grass species adapted to the southeastern U.S.
1b. Approach (from AD-416)
Develop and select improved populations and germplasms of bermudagrass for forage, bioenergy, and turf; develop and select improved populations and germplasms of napiergrass for forage and bioenergy; develop and select improved populations, inbreds, and hybrids of pearl millet for forage, bioenergy, and wildlife; and select improved rhizoma peanut germplasms for forage. Evaluate genotype and production effects on ethanol production from pearl millet; assess genotypic differences in bermudagrasses, napiergrass, and pearl millet for conversion to fermentable product or through thermochemical techniques to syngas; and improve selection efficiency for superior forage and cellulosic feedstocks. Measure genetic diversity within bermudagrass, napiergrass, and pearl millet using molecular markers; and identify associations of molecular markers in bermudagrass and pearl millet with traits important for forage or alternative uses.
3. Progress Report
Activities focused on the genetic improvement of pearl millet, napiergrass, bermudagrass, and rhizomatous peanut for forage, bioenergy, and alternative uses. New bermudagrass populations were established, assessed for yield and will be used in recurrent selection and for mapping cell wall traits. The bermudagrass core collection continued to be evaluated for differences in shade tolerance and nitrogen use efficiency. A population of napiergrass hybrids was evaluated for a third year for growth traits, and selections were established in a replicated yield trial. In vitro and fiber traits were analyzed for napiergrass and a near infrared resonance (NIR) calibration established for these traits. A manuscript was published on genetic variability of the napiergrass parental nursery. Experimental pearl millet varieties and inbreds were evaluated in multilocation yield trials to identify those with superior yield, disease and pest resistance, and stalk strength. Two hybrids were identified with 30% greater yield over the commercial standard. Inbreds used in developing these hybrids were characterized for release. Backcrossing of new forage inbreds into a male-sterile cytoplasm continued. These varieties were evaluated to assess genotype by environment interaction for proximate composition and fermentation to ethanol. No-till practices were evaluated to improve production economics for pearl millet. A mapping population of pearl millet was characterized for diversity of molecular markers and root-knot nematode resistance. Thirty-one nucleotide binding site leucine-rich repeat (NBS-LRR) homologs were isolated from diploid, triploid, and hexaploid bermudagrass that have tolerance to certain insects and nematodes. Nineteen markers were generated from the identified bermudagrass nucleotide binding site leucine-rich repeat (NBS-LRR) homologs in addition to database searches, and were mapped on a bermudagrass map. Clustering of bermudagrass nucleotide binding site leucine-rich repeat (NBS-LRR) homologs was evident on the T89 linkage groups 1a, 5a, and 19. Furthermore, three of these markers also amplified disease resistance orthologs in zoysiagrass and seashore paspalum. The collection of markers may be linked to disease resistance genes of interest such as sting nematode tolerance or dollar spot resistance. This study resulted in one publication. Bermudagrass expressed sequence tags - simple sequence repeat (EST-SSR) markers were developed and used to create bermudagrass genetic maps (Cynodon dactylon and Cynodon transvaalensis) and work indicated that tetraploid bermudagrass is an allotetraploid. The expressed sequence tags - simple sequence repeat (EST-SSR) markers were further shown to be able to differentiate many of the commercially used bermudagrass cultivars and these markers can be used for cultivar and pedigree identification among bermudagrass turf types. First of their kind simple sequence repeat (SSR) markers for measuring diversity in centipedegrass were developed.
1. Development of genetic tool for turf grass breeding. Molecular markers could greatly reduce the amount of time, expense and effort needed for traditional breeding of turf. ARS researchers at Tifton, Georgia generated fifty-two unique DNA sequences to create 21 single sequence repeat (SSR) markers and evaluated one of the largest centipedegrass collections for genetic diversity and for sting nematode resistance. Because many centipedegrass accessions are phenotypically very similar, the genetic diversity information is vital as the crossing of a resistant line (ex. sting nematode tolerance) to a more diverse line is needed for marker-assisted selection. For bermudagrass, a genetic map was created with the addition of 53 markers for desirable turf traits (bright green color, lack of seed head development, deep root systems) as well as sting nematode tolerance. These markers are currently being used in our lab to identify bermudagrass cultivars for golf course superintendants, sod farm businesses, and university researchers (University of Georgia).
2. Determination of the effects of nutrient deprivation or addition on potential bioenergy feedstocks. Warm-season perennial grasses will be part of the biomass production system in the Southeast for the emerging bioenergy industry. Data is lacking but necessary to determine the need for nutrient inputs such as nitrogen on biomass production and how these crops effect carbon sequestration. The first of two studies was initiated in fall 2005 by ARS researchers at Tifton, Georgia, to assess the performance of perennial grasses under rainfed conditions with no fertilizer inputs. Dry matter (DM) yield was highest in the second year for all species, and averaged over three years, yields of energycane, and napiergrass were significantly higher than switchgrass, but switchgrass had higher nitrogen use efficiency. A second study initiated in the fall of 2006 consisted of napiergrass grown under three rainfed fertilizer treatments (no additions, poultry litter and inorganic fertilizer at approximately equivalent N, P, and K rates). Poultry litter and inorganic fertilizer treatment of napiergrass resulted in similar yields each year and were 17% and 48% greater than the unfertilized control in the second and third year of growth, respectively. These results are critical in the determination of cost and environmental impacts of producing biomass crops for the renewable fuel industry and will be used to develop best management practices for the Southeast bioenergy industry.
3. Genetic relationships among napiergrass accessions for the biofuel industry. Napiergrass is a perennial grass used for forage and has considerable potential as a biofuel feedstock primarily because of its high biomass yield. ARS researchers at Tifton, Georgia used amplified fragment length polymorphisms (AFLPs) to assess the genetic variation and genetic relatedness among 89 accessions from the Tifton nursery. Using 218 polymorphic markers, the 89 accessions were clustered into 5 groups using a dendrogram (or genetic tree). These five groups include three groups collected from Kenya, a group from Puerto Rico, and accessions derived from the cultivar Merkeron. This research was the first molecular characterization of the Tifton nursery (a nursery based on over 40 years worth of collections and breeding) and displays the relationships among accessions. Furthermore this work provides potential parents for napiergrass and pearl millet breeding improvement that is currently underway in collaboration with university personnel at Florida and with the bioenergy industry. Data from this manuscript will be used to identify genes involved in height and nitrogen use efficiency in napiergrass.
Harris, K.R., Schwartz, B.M., Paterson, A.H., Brady, J.A. 2010. Identification and mapping of nucleotide binding site-leucine rich repeat resistance gene homologs in bermudagrass. Journal of the American Society Horticultural Science. 135:74-82.