Germplasm and Cultivar Development

Cool-season forage grasses have evolved, and continue to evolve, in natural ecosystems subject to environmental factors both in the presence and absence of human influences. The literature often lacks facts describing the evolution and domestication of forage grasses. Furthermore, the literature on this subject mainly deals with evolution of species in the broad scope, i.e., on a scale of hundreds of thousands or millions or years. Thus, some of our conclusions are necessarily speculative and are highly subject to the nature of the research that has been reported. We describe the forces of selection that act upon cool-season forage grasses and attempt to place each in historical perspective and in relation to each other. Because most economically important cool-season forage grasses are perennial, our principal focus will be on perennial species. There has been very little effort to quantify economic values of selection criteria or to empirically compare different breeding procedures in cool-season forage grasses. We attempt to summarize and compare some of the more important and thoroughly reported approaches used since the advent of formal breeding strategies in the late nineteenth and early twentieth centuries. These selection criteria and breeding procedures are as varied as the individual researchers who developed them. Examples are cited to illustrate principles and phenomena of historical or practical importance. More details of the agriculturally important species are discussed in the later chapters of this book. Space limitations prevent us from developing a thorough review, but we cite earlier reviews that thoroughly cover the first few decades of formal cool-season forage grass breeding. We also have summarized the limited amount of research on cool-season forage grasses where attempts have been made to use new technologies for hybridization, tissue culture, and genetic markers. Many of these techniques were first developed using other species and later adapted to cool-season forage grasses. Many are still undergoing rapid development and modification to allow more efficient use in breeding programs. Together they have had little practical impact on cool-season forage grass cultivars, but appear to offer considerable promise for creating new genetic variability and more efficient breeding procedures