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Re: Maize origins [was re: "Corn" in medieval Europe]

In article <5cvveg$6kb$1@trends.ca>, yuku@mail.trends.ca (Yuri Kuchinsky)
wrote:

> With recent scientific advances in genetics, this "mystery" [the presence
of maize in pre-Columbian Old World] will most
> likely not remain a mystery for too long, but will be resolved one way or
> another. 

As far as the origin of maize goes, the work of John Doebly has already
shown it to be descended from a central Mexican grass, teosinte. Maize and
teosinte can be fertilly crossed.  There are numerous differences between
maize and teosinte, (teosinte is multi-branched, the kernels are enclosed in
a hard shell, and there is only a single row of kernels in each cob).  But
the genes which confer some of these traits have been isolated (see
references).  This does not discount the possibility of maize being present
in the old world before Columbus, but if it was, it was certainly brought
there from the new world.
Some references:

11. Doebley J.
      Mapping the genes that made maize.
    Trends in Genetics, 1992 Sep, 8(9):302-7.
        (UI:  95099570)

Abstract: George Beadle proposed that the striking morphological differences
    between cultivated maize and its probable wild progenitor (teosinte)
were
    initiated by a small number of mutations with large effects on adult
    morphology. Recent genetic analyses using molecular markers provide some
    support for this view and show where in the maize genome the putative
loci
    are likely to be located. This work sets the stage for fine-scale
linkage
    mapping of these genomic regions and the eventual cloning of the genes
    involved in this remarkable evolutionary transformation.
  
2. Szabo VM; Burr B.
     Simple inheritance of key traits distinguishing maize and teosinte.
   Molecular and General Genetics, 1996 Aug 27, 252(1-2):33-41.
       (UI:  96397507)

Abstract: The segregation of key traits distinguishing maize and teosinte
was
    analyzed in three F2 and three backcross populations derived from
crosses
    of the modern maize inbred T232 with Zea mays ssp. parviglumis. These
    traits were (i) paired vs. single female spikelets; (ii) two-ranked vs.
    many-ranked ears; (iii) non-indurated vs. indurated glumes; (iv)
    inclination of the kernels toward the rachis, and (v) distichous vs.
    polystichous central staminate spike. All traits showed a simple mode of
    inheritance except for paired female spikes, which appeared to be
    controlled by two genes. The loci controlling these major changes were
    mapped with RFLP markers to four chromosomal regions. These results
support
    the suggestion that maize became differentiated from teosinte with as
few
    as five major gene changes.

4. Doebley J; Stec A; Gustus C.
     teosinte branched1 and the origin of maize: evidence for epistasis and
the
     evolution of dominance.
   Genetics, 1995 Sep, 141(1):333-46.
     Type D 4 AB to see abstract.  (UI:  96042916)


10. Doebley J; Stec A.
      Inheritance of the morphological differences between maize and
teosinte:
      comparison of results for two F2 populations.
    Genetics, 1993 Jun, 134(2):559-70.
        (UI:  93314942)



J. Emery
Dept. of Plant Pathology
UC Davis
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