6
the West was delayed by several years. Taxonomic treatments in North America
were mainly based on Hitchcock ( 1935 , 1951 ), which in turn were based on
Bentham ( 1882 ) and Hackel ( 1887 ). On the basis of observations made studying
crossing-relationships in the tribe, Stebbins ( 1956 ) argued that all taxa of the tribe
might be subsumed into a single genus Triticum. His proposal was made under the
infl uence of the biological species concept (Mayr 1942 ) that defi nes a species as
members of populations that can produce fertile offspring, and that are reproduc-
tively isolated from other such populations. Although a perfectly defensible pro-
posal, it was not adopted and was considered impractical to describe the diverse
Triticeae. The treatment of the Russian taxonomist Tzvelev ( 1976 ) considered sev-
eral additional annual and perennial genera in comparison to Hitchcock ( 1951 ) and
was quickly adopted in the USSR (for a review see Barkworth 2000 ).
1.4 Löve and Dewey’s Genomic System of Generic
Classifi cation ( 1984 )
Until the 1980’s, several classifi catory systems for members of the Triticeae had
been proposed. They differed in goals, taxonomic and regional scope, and were
adopted differently in different parts of the world. Furthermore, since the start of
genome analysis (Kihara 1930 ), a large amount of cytogenetic data had been accu-
mulated. To overcome existing taxonomical inconsistencies, Löve ( 1984 ) and
Dewey ( 1984 ) independently proposed a generic classifi cation for Triticeae that was
solely based on the recognition of so called genomes (i.e., the monoploid set of
chromosomes). They analyzed the pairing behavior of homologous chromosomes
in metaphase I of meiosis in interspecifi c hybrids and recorded the number of chias-
mata in a particular number of cells (often 50). Homologous chromosomes showing
near complete pairing are defi ned as belonging to the same genome. Both authors
considered hybrids sharing the same genome or genome combination to be conge-
neric, i.e., to be placed in the same genus. In contrast, hybrids showing little or no
pairing of homologous chromosomes have different genomes and were considered
intergeneric. Distinct genomes were depicted by different bold uppercase letters,
while genomes considered related but not identical are depicted with the same capi-
tal letter, extended by lowercase letters or a superscript extension (Baum et al.
1987 ).
Dewey’s revision treated perennial Triticeae, while Löve’s work was based on
the whole tribe. Thereby, Löve summarized extremely valuable information on all
synonyms he was aware of, together with their original citation, including chromo-
some number and genomic constitution. He also provided descriptions for all gen-
era and subgenera (Barkworth and von Bothmer 2005 ). Löve recognized 37 genera,
13 of which are treated as Aegilops by most taxonomists today. He defi ned one
genus per genome combination ( A , AB , ABD ) or ploidy level, respectively, for
what is unifi ed in Triticum s.str. today (van Slageren 1994 ). Although Löve was not
N. Bernhardt