Barley (Hordeum sp.) is a principal cereal crop throughout much of the world and is of great economic importance in the United States. Spring barley is a leading cereal crop in Utah. Barley has many desirable characteristics which make it an excellent plant for genetic studies. Some of these characteristics are low chromosome number, almost complete self-fertilization, relative ease of hybridization, and easily classified hereditary characters. The establishment of genes or factors at definite loci in linkage groups is a valuable aid in furthering breeding programs and the ultimate improvement of barley. All seven linkage groups have been established although the location of only a small number of genes is known in some of them and most of these genes were mapped from information obtained from crosses involving only two or three factor pairs. Theis thesis deals with determining the location of five genes belived to be in linkage group IV and to establish new linkages if possible. specifically planned crosses involving from tow to five of these genes were used in this study.

Plant breeding and the development of new or better varieties of plants are essential parts of modern agronomy, horticulture and forestry. The basis for such improvement is a knowledge of the factors and principles of genetics. A number of genetic studies have been made with barley in recent years. This is partly because of the many distinct heritable characters of barley plants. The cultivated species of barley offers the plant breeder and geneticist a wealth of material for genetic studies. Varieties differ in a great many readily distinguishable characters, species hybridize readily, and their small number of chromosomes make it good material for inheritance studies. The barley genetic work has been divided among the principal workers in the U.S., each being responsible for one linkage group. This station has been assigned group IV of which this study is a part. A study of the inheritance of other genes not located in linkage group IV, but appearing in the crosses used, has also been made. This investigation is a by-product of the cereal breeding and improvement program being carried on the Utah Agricultural Experiment Station.