7completely consistent (e.g., Elymus consisted of three different genome constitu-
tions; Dewey 1984 ) and genus affi liations were partly inferred from morphological
similarities (as at that time genome composition was not analyzed for all taxa), this
treatment was the start of the modern taxonomy of Triticeae (Barkworth and von
Bothmer 2009 ).
1.5 Criticism on the Genomic System
The genomic concept was sharply criticized, (1) mainly because the pairing behav-
ior of homologous chromosomes was interpreted as single-character classifi cation
by most taxonomists. Löve and Dewey, themselves interpreted pairing behavior as
an indication of overall genetic similarity along the chromosomes, and therefore as
a result of multiple characters (Barkworth and von Bothmer 2005 ). Severe disap-
proval was also mentioned, when (2) interpreting the extent of chromosomal pairing
as an indicator for similarity between the genomes. This was considered a random
division of a continuum, and therefore no reliable taxonomic trait. Further criticism
(3) was based on the fact that the failure of chromosomes to pair does not necessar-
ily indicate dissimilarity. At this time, it was already known that a number of loci
control the pairing behavior and recombination of chromosomes. It was suggested
that 50 loci might have an impact on the chromosomal pairing in Pisum (Gottschalk
1973 ; Farooq et al. 1990 ; Seberg and Petersen 1998 ). Today, Ph1 is the most exten-
sively studied locus involved in this trait (Moore 2009 ). Additionally, (4) the system
was considered overall unstable, meaning each time new genomes or combinations
of them are recognized, species need to be transferred between genera, and (5)
impractical in the fi eld, when each time a new species is discovered, an appropriate
name can only be given after the genome compositions have been identifi ed (Baum
et al. 1987 ; Kellogg 1989 ; Frederiksen and Petersen 1998 ; Barkworth 2000 ;
Barkworth and von Bothmer 2005 ).
1.6 Impact of the Genomic System
After publication of the genomic system of generic classifi cation, taxonomists split
into two different directions: On the one hand, the group rejecting the genomic
concept, due to the lack of complete understanding of pairing behavior in meiosis,
and on the other hand, the group acknowledging the additional information it pro-
vides, e.g., considering the possible convergent evolution of morphological and
physiological traits. In any case, Löve’s revision was apprehended as a valuable and
comprehensive collection of nomenclature names of members of Triticeae, and the
information about pairing behavior of chromosomes, i.e., information about the
potential of species to exchange genetic information, which is of use to plant
breeders.
1 Taxonomic Treatments of Triticeae and the Wheat Genus Tr it icu m