Chromosome Numbers and Hybrids in Zoysia1

THE introduction of Zoysia species from the Orient into the United States, and the recognition of their possible value as turf-forming grasses has stressed the desirability of developing superior turf varieties by breeding and selection. A search of the literature dealing with the Zoysia spp. revealed almost a total lack of information concerning the cytology and genetics of these grasses. No information was available on meiosis, interspecific hybrids, self or crossfertility, inheritance, or any other aspect of sexual reproduction. Only one investigator has ever attempted to determine the chromosome number of a species in this genus (7). The taxonomy and distribution of these grasses have been treated more fully, but even in this respect, the genus has escaped any concentrated study. As a result, the number of species recognized and their distribution is somewhat uncertain. The lack of cytogenetic information, which is essential for the improvement of these species by breeding, has necessitated this investigation. The objectives of this preliminary study were: to determine the chromosome number of the introduced species of Zoysia, to determine whether interspecific hybrids can be produced from them, and to develop practicable breeding techniques for these grasses. This report covers two seasons of work, 1947-48 and 1948-49. A preliminary study of flowering habit and breeding technique was conducted in the greenhouse during the winter of 1947-48. Interspecific hybridization and cytological studies were carried on during the winter of 1948-49.