Introduction Materials and Methods 60 Results and Discussion References CHAPTER 5. GENERAL CONCLUSIONS General Discussion Recommendations for Future Research References temperatures in the laboratoiy with seed lot quality, 100-seed mass, and field emergence; (ii) to assess progress realized from phenotypic recurrent selection for germination rate and seedling growth at low temperatures under laboratory conditions in six alfalfa populations; and (iii) to asses progress in the field from phenotypic recurrent selection for cold temperature germination and seedling vigor under laboratory conditions performed in six alfalfa populations. Dissertation Organization This dissertation has been organized into four parts. The first part, this chapter, is a review of literature pertinent to the overall subject of study. The remaining chapters are organized as manuscripts to be submitted to refereed publications. Each chapter includes an abstract, introduction, materials and methods, and results and discussion section. References are listed for each part. Literature Review Origin and Adaptation of Cultivated Alfalfa Alfalfa (Adedicago sativa L.) originated near Iran, with related species located throughout central Asia and into Siberia (Barnes and Sheaffer, 1995; Hill, 1987). Cultivated alfalfa may have been in use as early at 7000 B.C, but the earliest known reference to alfalfa was from Turkey in 1300 B.C. (Hill, 1987). The use of alfalfa as animal feed was documented in the Roman Empire as early as c. 490 B.C. (Bames and Sheaffer, 1995). Alfalfa, introduced to North America in 1736, is now worldwide in distribution (Bames and Sheaffer, 1995). About 57% of U.S. production is in the north central states (esp. Wisconsin, Iowa, South Dakota, Minnesota), where it is primarily harvested and stored as hay or silage for on-farm use (Bames and Sheaffer, 1995). 3 Alfalfa is adapted to growth in cool or warm, dry climates (Hill, 1987), and is tolerant of temperature extremes (below-25 C and above 50 C) (Barnes and Sheaffer, 1995). The number of harvests per year varies from one in northem and arid regions to ten under irrigation in the southwest (Bames and SheafTer, 1995). Production is generally defined as the amount of forage dry matter (DM) per hectare (Sollenberger and Chemey, 1995). Cultivated alfalfa is naturally outcrossing (Hill, 1987). Most alfalfa cultivars are synthetic populations, produced by intercrossing individual plants selected from a breeding program (Hill, 1987). Because most recently developed synthetics are broad-based populations, formed from more than 40 parents, they can be considered highly heterogenous populations of heterozygous individuals (Bames and Sheaffer, 1995, Hill, 1987). Breeding of alfalfa cultivars in the last 25 years has focused on increases in yield, especially by increased adaptation (such as winter hardiness) and by incorporation of multiple pest resistances (Bames and Sheaffer, 1995, Hill, 1987). Some breeding effort has also been applied to improvements in forage quality, and stand establi...