A study of Elliptical Vibration Cutting in Ultra Precision Machining

Ph.DDOCTOR OF PHILOSOPH

Genetic Maps of Diploid Orchardgrass (\u3cem\u3eDactylis glomerata\u3c/em\u3e L.)

Orchardgrass (Dactylis glomerata L.) is indigenous to Eurasia and northern Africa. It has been naturalized on nearly every continent and is one of the top four economically important perennial forage grasses grown worldwide (Stewart and Ellison 2010). It has been used widely as forage due to its quality, biomass production and good shade tolerance. Despite its various agricultural uses, little information is available for functional and comparative genetic analysis and concomitant genetic improvement of this species. To date, a number of linkage maps have been constructed for forage grasses such as perennial ryegrass (Lolium perenne L.) (Jones et al. 2002), tall fescue (Lolium arundinaceum (Schreb.) Darbysh.) (Saha et al. 2005), and Zoysiagrass (Zoysia japonica) (Cai et al. 2005). Until recently, there have been no reports of genetic linkage studies in orchardgrass. In the present study, a genetic linkage map of diploid orchardgrass based on two-way pseudo-testcross mapping strategy was constructed using SRAP and SSR markers. This is the first step towards genomic mapping for this species

Genetic Variation and Geographical Differentiation of \u3cem\u3eElymus nutans\u3c/em\u3e (Poaceae: Triticeae) from West China

Elymus nutans Griseb. is not only an important alpine forage grass, but also as a crucial gene pool for improving cereal crops. Understanding and maintaining the genetic diversity of the species are essential for both conservation strategy and breeding programs. However, little is known about its genetic and geographical differentiation patterns. E. nutans is a perennial, caespitose and allohexaploid (2n=6x=42) species that contains the St, H and Y genomes. It is native to temperate and tropical Asia, ranging from western and central Asia in the west to China and Mongolia in the east, from Russia in the north to India and the Himalayas areas in the south (Clayton et al. 2006). It is distributed in the north, northwest and southwest China, particularly in the Qinghai-Tibet Plateau. E. nutans is a valuable forage grass in the alpine regions that is resistant to cold, drought and pests, which can be used to improve cereal crops. In addition, it can play an important role in the restoration of disturbed grasslands and the establishment of artificial grasslands, especially at altitudes from 3,000 to 4,500 m (Chen and Jia 2000). During recent decades, its distribution has contracted because of over-exploitation, habitat destruction and fragmentation. Therefore, it is urgent to understand and monitor the genetic and geographical differentiation of wild germplams of E. nutans

Genetic Diversity and Relationships in Cocksfoot by Molecular Markers

Cocksfoot (Dactylis glomerata L.) originated from the Northern Hemisphere, including Eurasia and North Africa. It is widely distributed in temperate climates and has been widely used in the world more than 100 years, especially in North America, Europe and Japan. Genetic variability of cocksfoot had been detected by RAPD (Kölliker et al. 1999), and the correlation between genome size of natural populations of cocksfoot and location altitude has been analyzed by AFLP (Reeves et al. 1999). To date, information on the genetic diversity of cocksfoot at the molecular level is still scarce, This study is the first to combine the genetic diversity research of cocksfoot with SRAP (Sequence Related Amplified Polymorphism) and ISSR (inter-simple sequence repeat) markers evaluating genetic diversity among 45 populations of cocksfoot collected from eight different countries from four continents. The objectives of the research were: (1) to evaluate the levels and patterns of genetic diversity about cocksfoot; (2) to compare ISSR and SRAP markers for the molecular characterization of cocksfoot, including the evaluation of the degree of polymorphism generated from each technique as a pre-requisite for (3) their applicability to formulate appropriate strategies for the conservation and utilization of the wild cocksfoot genetic resources available and to discuss scientific breeding measures according to the status of cultivars