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B. PICKERSGILL, M.I. CHACÓN SÁNCHEZ and D.G. DEBOUCK
parallel those in wild beans, and strongly suggest that beans were domesticated independently
in Middle and South America, from local wild types (GEPTS et al. 1986,
GEPTS 1990, KHAIRALLAH et al. 1992, BECERRA and GEPTS 1994).
Tab. 1: Haplotypes found in landraces of common bean and their geographic
distribution in wild common bean
Haplotype
C
I
K
L
Distribution in domesticated
beans
Andean gene pool
(Races Nueva Granada, Peru
and Chile)
Mesoamerican gene pool
(Races Mesoamerica and Guatemala)
Mesoamerican gene pool
(Races Mesoamerica and Durango)
Mesoamerican gene pool
(Races Mesoamerica, Durango
and Jalisco)
Geographic distribution in wild
beans
Central and southern Peru
Southern Mexico; western, central and
eastern Guatemala; eastern Honduras;
central Colombia
Northern Mexico; west-central and
southern Mexico
Western and central Mexico; western
Guatemala; Costa Rica; Colombia
It has also been suggested that P. vulgaris was domesticated more than once in
each continent. In Mesoamerica, analysis of RAPDs (BEEBE et al. 2000) separated
domesticated beans into groups which corresponded well to the three Mesoamerican
races (Mesoamerica, Durango, Jalisco) recognised by SINGH et al. (1991). BEEBE et
al. (2000) also recognised a fourth race (Guatemala) and considered that their RAPD
data implied two or more domestications from distinct wild populations. However,
Mesoamerican domesticated beans nearly all carry the S type of phaseolin even
though more than 15 types of phaseolin are present in Mesoamerican wild beans
(GEPTS and DEBOUCK 1991). GEPTS (1998) therefore argued that, in Mesoamerica,
common beans were domesticated once only, in west central Mexico (Jalisco) where
S phaseolin predominates among local wild beans, then diversified into the presentday
races. In South America, Andean landraces have been classified into three further
races (Nueva Granada, Peru, Chile) thought, like the Mesoamerican races, to
represent distinct evolutionary lineages (SINGH et al. 1991). Several different phaseolins
are present in these landraces, so GEPTS (1998) suggested multiple domestications
in the Andean region. However, the DNA of Andean landraces has diverged
very little, so BEEBE et al. (2001) argued that the three Andean races must have diversified
after domestication.
Chloroplast DNA has some advantages over nuclear DNA in studies of the domestication
and spread of crop plants. It does not recombine, and is usually inherited
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