Browsing by Author "David P. Livingston, Committee Member"

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    New Advances in Fall Sown Oat Winter Hardness
    (2009-12-04) Maloney, Peter Vincent; J. Paul Murphy, Committee Chair; Gina Brown-Guedira, Committee Member; David P. Livingston, Committee Member; David Marshall, Committee Member
    Fall sown oats (Avena sativa L.) are plagued by a poor ability to tolerate freezing temperatures. Of all the fall sown small grain cereals, oats have the poorest winter field survival. Advances in marker technology and mapping techniques have allowed for more efficient and accurate location of quantitative trait loci (QTL). With these new technologies, breeders can more accurately screen early segregating generations for winter hardiness component traits. The objectives of this research were: (i) screen and validate new microsatellite or simple sequence repeat (SSR), single nucleotide polymorphism (SNP), and cleaved amplified polymorphic sequences (CAPS) markers; (ii) map new SSR, SNP, and CAPS markers to the Fulghum (winter tender) x Norline (winter hardy) recombinant inbred population (iii) screen the Fulghum x Norline population for QTL linked to winter hardiness component traits and (iv) develop a association mapping population to test for marker associations across a wider oat genetic base for winter hardiness component traits and validate marker use in marker assisted selection (MAS). Selected primer pairs derived from oat, including 315 SSR primers, four SNP markers and one CAPS maker were tested on a panel of 11 oat lines. Two hundred fifty two of the 315 primers amplified products in oat, and 168 were polymorphic for at least one of the 11 oat lines tested. Markers supplied by Dr. Joseph Anderson, USDA-ARS (JAO) were screened and PIC scores were generated. Among the JAO primers, 106 were co-dominant and 11 were dominant makers. Polymorphic information content (PIC) scores were generated for JAO primers with an average PIC score of 0.64 and an average of five alleles per primer pair. ii Sixty-five new SSR markers, four SNP markers and one CAPS marker were added to the Fulghum x Norline linkage map. This brought the total number of markers mapped on the population to 101. The map contained 19 different linkage groups for a total distance of 326.9 cM. Four major QTL were identified for winter field survival. Norline contributed three of the QTL and Fulghum contributed one QTL for increased winter field survival. Most of the winter field survival QTLs were located around the TC7-17 translocation event characteristic of Norline. Other QTL were identified for crown freezing tolerance, photoperiod effect, vernalization effect, heading date, and plant height. An association mapping population comprised of 63 fall-sown and spring-sown oats was selected for testing. Cultivars selected were released anywhere from 1775 to 1995 and consisted of two facultative, 25 spring sown and 36 fall sown type cultivars. The cultivars were chosen based on their linage and significance to the oat breeding community. The basis of the research was done on 29 unlinked simple-sequence repeat markers. The population was phenotyped for crown freezing tolerance and winter field survival. An admixture model in Structure v3.2.1, was used for subpopulation analysis, where we showed eight sub populations. Tassel 2.1 was used to conduct all the association mapping techniques including kinship and the mixed linear model. Association mapping yielded six loci linked to traits of interest. The six loci found are readily available to be used in a marker assisted selection program.
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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.