Old_research
Because North Carolina is in the transition zone, both warm- and cool-season grasses can be grown in our state. However, cool-season grasses get severely stressed during our hot and humid summer months, and warm-season grasses can suffer significant winterkill during cold winters. Therefore, a big emphasis of our program is to improve cold-tolerance in warm-season grasses and heat and drought tolerance in cool-season grasses. Currently, we have ongoing research projects in tall fescue, bermuda, St. Augustine, Zoysia and centipedegrass.
One of the main areas of interest in our program is the combination of modern technologies with conventional methods for turfgrass improvement. Molecular markers, tissue culture, flow cytometry, chromosome doubling with colchicine, linkage and QTL mapping, and mutagenesis are some of the methods we are currently applying. The following list -though not all-inclusive- is a good representation of the width of projects we are presently working on.
ST. AUGUSTINEGRASS
Breeding for cold tolerance:St. Augustinegrass is a desirable turfgrass because of its shade tolerance and low input requirements, but it has poor cold tolerance. Our goal is to increase this grass’ adaptability area by improving its cold tolerance. This project includes multiple aspects including a diallel study to understand more about the heritability of the trait, the use of freezing tests in the laboratory to elucidate the physiological aspects of cold tolerance and to develop better screening methodologies, histological preparations to improve our understanding of how different tissues in the node respond to freezing, and field evaluations in the mountains of North Carolina where higher elevations allow for better selection pressure.
Understanding levels of genetic diversity in Stenotaphrum germplasm:Flow cytometry, chromosome counts, and AFLP markers have been used to investigate genetic diversity and ploidy levels in publicly available plant introductions and cultivars of St. Augustinegrass as an aid to more effective use of these materials in breeding programs. Cytological investigations indicated five different ploidy levels (diploid, triploid, aneuploid, tetraploid, and hexaploid) and marker data separated genotypes into distinct groups that were mostly consistent with ploidy levels.
Mapping QTL for cold tolerance: SSR and AFLP markers are currently being used in a pseudo-F2 population of Raleigh x Seville to build a genetic map, which will be used to associate specific regions of Raleigh’s genome with cold tolerance. Our ultimate goal is to develop more efficient selection methods to breed for this trait.
Evaluation of germplasm for pest resistance:Our St. germplasm collection has been screened for gray leaf spot and chinch bug resistance. GLS screenings were conducted under controlled environmental conditions in the NCSU phytotron. Diploid accessions with high levels of resistance to the fungus have been identified. The chinch bug resistance work was conducted by the Cardoza lab in the entomology department. St. Augustinegrass accessions that sustain less damage and that hinder chinch bug reproduction have been identified.
Use of Next Generation Sequencing (NGS) for development of SSR makers:NGS was used on St. Augustinegrass to provide a wealth of sequence information which has been used to isolate numerous SSRs at a fraction of the cost and time of conventional techniques. The 190 SSR primer pairs developed, the first for the species, represent a significant advance in the development of genomic tools for St. Augustinegrass. These markers can be used in the future for linkage map construction, assessment of genetic diversity and germplasm characterization, and marker-assisted selection.
Mapping QTL for gray leaf spot resistance: Genetic linkage maps of St. Augustinegrass have been constructed for quantitative trait loci (QTL) analysis of resistance to gray leaf spot using a total of 125 SSR and 225 AFLP markers on a pseudo F2 population of 77 progeny. Six putative QTL were identified through interval and composite interval mapping. These results represent the first linkage map produced for St. Augustinegrass, which provides a template for further genetic mapping.ZOYSIAGRASS
Breeding for cold tolerance: Our Zoysiagrass germplasm collection has been evaluated for cold tolerance at two locations in the mountains of North Carolina. Materials with superior cold tolerance and faster establishment rates were advanced to replicated trials. Additionally, these lines will be tested under controlled environmental conditions.
Understanding levels of speciation within Zoysia spp.: Understanding the population structure present within Zoysia germplasm can assist plant breeders in exploiting available variation. The objectives of this study were to assess simple sequence repeat (SSR) allelic diversity within and among Zoysia spp., evaluate the genetic constitution of putative interspecific hybrids, and determine if Zoysia spp. and hybrids can be differentiated by inflorescence traits.
Mapping QTL for cold tolerance SSR markers are currently being used in a pseudo-F2 population to construct a linkage map, which will be used to identify QTL associated with cold tolerance.
Evaluation of zoysiagrass germplasm for large patch resistance: Our zoysiagrass germplasm collection is currently being evaluated for large patch resistance under controlled environmental conditions in the NCSU phytotron. A few lines with superior resistance to local isolates of the fungus have been identified. Additional evaluations with more virulent isolates are underway.BERMUDAGRASS
Breeding for shade tolerance: Bermudagrass is one of the most commonly grown turfgrasses in North Carolina. The grass is extremely drought tolerant which makes it a very desirable species especially under new demands for water allocation. However, bermudagrass lacks shade tolerance, a valuable trait for use in smaller residential landscapes where trees are dominant, as is the case in many neighborhoods in NC. A set of nine bermudagrass accessions collected from South Africa have been evaluated for their ability to perform well under low light conditions. The top performers will be used in crosses to develop populations that segregate for shade and cold tolerance among other traits of interest.CENTIPEDEGRASS
Mutation breeding in centipedegrass:The goal of this project is to generate morphological and stress tolerance variation through the use of a chemical mutagen. A total of 3000 M1 progenies have been planted at the Sandhills Research Station and are currently under evaluation for aggressiveness, genetic color, and leaf texture, among other traits.
Comparing levels of genetic diversity between germplasm collections: SRAP markers have been used to compare levels of genetic diversity between centipedegrass accessions collected from China with germplasm previously available in the U.S. Our results indicate that while the U.S. collection has high levels of diversity, there are alleles in the Chinese materials not represented in this collection. These materials could represent additional sources of variation to be used in centipedegrass cultivar development programs.SPECIALTY CROPS RESEARCH INITIATIVE (SCRI)
This is a coordinated project among five universities in the southeast (University of Florida, Texas A&M University, Oklahoma State University, University of Georgia and North Carolina State University) to jointly develop and evaluate cultivars of seashore paspalum, bermuda, zoysia and St. Augustinegrass with improved drought and salinity tolerance. Breeding materials are crossed-evaluated at seven locations in NC, FL, GA, OK and TX. A total of 576 lines developed by five breeding programs have been evaluated each year since 2011.TALL FESCUE
Breeding for heat and drought tolerance: Recurrent phenotypic selection is being used to improve heat and drought tolerance in tall fescue. Plots are maintained under a rain-out shelter at the Sandhills Research Station (Jackson Springs, NC) where sandy soils allow for severe drought conditions. Plots are subjected to drought during the hottest summer months. Surviving plants are then selected and allowed to cross-pollinate to generate new populations for selection. Several cycles of recurrent selection are conducted. After this time, populations are evaluated in replicated trials.
