CYTOGENETIC STUDIES IN THE GENUS HORDEUM VI. THE MURINUM-COMPLEX

Abstract

Horclez~nt 7~zzni1zz~nq, the ubiquitous species common to most of Europe and Western Asia, call also be found in many parts of North and South America and Australia. It and two other species, H. lepori~zuwz, another tetraploid, and H . glnucz~~n, a diploid, all having remarltably similar morphological features, are frequently referred to as the murhzz~m-complex (Covas, 1949, and Morrison, 1958). In 1960 W. M. Bowden, Plant Research Institute, Ottawa, received seed samples labelled H. nzz~rinz~m from Turlcey and Afghanistan which had 2n = 42 cl~romoson~es. This new form increased the number of species in the con~plex to four and the chromosonle number to the hexaploid level. The most striking feature of the coinplex is that the plants look very much alike. Therc has, therefore, been much confusion in classification although there are minor differences as shown by IVlorrison (1958). H e also clearly showed that both H . ~ ? T z L ~ ~ ' I ~ z L ~ ~ z and H . leporhzum are allotetraploids. Previous lists of chromoson~e numbers had indicated that H. 7mninum was a diploid (Hubbard 1954), an error that led Covas (1949) to propose that H. lepori1zzr7/1 was an allotetraploid derivative of H. glaz~cz~nz and H. muri7zzmz. The purpose of this study is to clarify the status of the various species, to learn about their interrelationships and to find genetical explanation for thc inorpl~ological uniformity of species in the complex. This is also the first paper in this series which deals with a group of Old World species of Hordenzuz. Since the approach is primarily cytogenetic, hybrids were produced among the four species to study their infertility and chromosome relationships.