ARTIFICIAL AND NATURAL HYBRIDS IN THE GRAMINEAE, TRIBE HORDEAE. VIII. FOUR HYBRIDS OF ELYMUS AND AGROPYRON

Abstract

CERTAIN North American representatives of Agrapyron, Elymus, Hordeum and Sitanion (tribe Hordeae, Gramineae) have been studied previously (Stebbins et al., 1946a, 1946b; Stebbins and Walters, 1949; Stebbins and Singh, 1950; Stebbins and Pun, 1953). Snyder (1950, 1951) made a detailed study of the morphological variability of Elymus glaucus and of the isolation barriers within this species. The present study deals with the morphology and cytogenetics of some North and South American entities of Agrop,yron and Elymus. These entities are: Agropyron spicatum var. inerme (Scribn. et Smith) Heller and Elymus glaucus Buckl., both from North America; and at the diploid (2n 14) and the tetraploid level (2n 28), respectively: Agropyron agroelymoides (Hicken) Hunz. from the center of Argentina (Buenos Aires, San Luis, Rio Negro), an unidentified species of Agropyron from western Argentina (Calmuco, Mendoza) which will be referred to as Agropyron sp. Calmuco and Elymus patagonicus Speg. from Southwestern Argentina (Neuquen to Santa Cruz), all hexaploids (2n 42). MATERIALS. The parental strains as well as the hybrids were grown in the experimental plots of the Department of Genetics, University of California, Berkeley. Herbarium specimens of the parental strains and hvbrids have been deposited in the University of California Herbarium (UC): and at the Instituto de Botinica, Ministerio de Agricultura y Ganaderia, Buenos Aires, Argentina (BAB). Parents.-The parental strains used in the experiments were: Agropyron spicatum var. inerme, U. S. Soil Conservation Service P-7413, collected at Lind, Washington. This is Stebbins' strain 544 (Stebbins and Singh, 1950; Stebbins and Pun, 1953). A. agroelymoides (981) , collected at Balcarce, Provincia de Buenos Aires,' Argentina. A. sp. Calmuco (983), collected by G. Covas, near Calmuco, Provincia de Mendoza, Argentina. Elymus glaucus, U. S. Soil Conservation Service P-10128, collected at Sebastopol, Sonoma County, California. E. patagonicus (982), collected by G. Covas, 56