Browsing by Author "Art H. Bruneau, Committee Co-Chair"

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    St. Augustinegrass Improvement for Freezing Tolerance and Semi-dwarf Growth Habit
    (2008-05-11) Li, Ruyu; Rongda Qu, Committee Chair; Art H. Bruneau, Committee Co-Chair; Melodee L. Fraser, Committee Member; Wayne W. Hanna, Committee Member; Grady L. Miller, Committee Member; David P. Livingston, Committee Member
    A significant crop produced by the industry and sold in many states is St. Augustinegrass. However, it is sensitive to freezing temperature and has coarse plant architecture. The NC sod industry demands new St. Augustinegrass cultivars with further improved freezing tolerance and finer plant architecture (semi-dwarf growth habit). The objective of this project was to use various approaches, including germplasm collection, induction of somaclonal variations, and irradiation mutagenesis, to create variations and to screen for plant clones to meet the industry demands. Techniques were developed, which include establishment of a freezing tolerance test system under controlled conditions and improved tissue culture conditions. It was found that treating plants at 13°C for one week, followed by 3°C for another week was an effective condition for cold acclimation of St. Augustinegrass in a controlled environment for freezing tolerance test at or around -4°C for 3 hrs. An efficient tissue culture system was established for the somaclonal variation approach. In that effort, 11 explant tissues and four callus culture media were examined for tissue culture response. The best response came from immature embryo 7-14 days after pollination (DAP) on Murashige and Skoog (MS) medium containing 1 mg L-1 2, 4-D and 0.5 mg L-1 6-benzyladenine. The callus induction and regeneration rates were 97.7% and 47.6%, respectively. Thirty six germplasm accessions were collected. Nearly 8000 plants were regenerated through tissue culture. And 3300 plants recovered from mutagenized plant materials. They were screened for improved freezing tolerance and/or semi-dwarf growth habit. Using the freezing tolerance test system, it was revealed that Elm4, collected from downtown Raleigh, and SVC3, a somaclonal variant, had significantly improved freezing tolerance. Ray, a collection from Polk County, had finer plant architecture and comparable freezing tolerance to Raleigh. In addition, nineteen somaclonal variants from tissue culture and 12 mutants from mutagenesis showed semi-dwarf growth habit and grew vigorously. Most of them had shortened internodes and stolons. Field performance of 11 lines was evaluated for development of potential new cultivars.