wheat evolution

Tom Michaels TMICHAEL at CROP.UOGUELPH.CA
Thu Oct 7 09:49:06 EST 1993


A few weeks ago there was a question about the evolution of wheat...



       A FEW WORDS ABOUT THE ORIGIN OF THE HEXAPLOID WHEAT

     The hexaploid wheat species are divided into two groups. The
genome formula of the larger one is AABBDD, and in this group are
the following species: Triticum aestivum (the most important wheat
species), T. compactum, T. macha, T. spelta, T. vavilovi and T.
sphaerococcum. The single representative of the second group, with
the formula AAAAGG is T. zhukovskyi.
     It is considered that the hexaploid wheat from the first group
is a result of amphiploidy between T. dicoccum (AABB) and Aegilops
squarrosa (DD). The first hexaploid wheat was probably  T. macha,
and the others arose later, as a result of mutations.
     The original donor of the A genome was probably the wild
diploid species T. urartu. The donor of the B genome is uncertain.
Aegilops speltoides used to be widely accepted for the origin of
this genome, but more recent studies do not support this theory.
The current evidence implies that the donor was a diploid (or were
diploids) with genomes similar to those of the present members of
the Sitopsis section of the genus Aegilops.

Jon Popi, jpopi at crop.uoguelph.ca



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