POLANS, NEIL O.*, JEFFERY A. NELSON, AND DAYLE E. SAAR. Department of Biological Sciences and Plant Molecular Biology Center, Northern Illinois University, Dekalb, IL 60115. - Phylogenetic studies of pea comparing different data sets.
Pisumis often divided into three wild species, fulvum,
(northern and southern) humile and elatius, in addition
to the cultivated sativum. In this study, pea taxa representing
both wild populations and cultivated accessions are scored for
morphological characters, allozymes, RAPDs and ITS sequences. The
relatively small number of morphological characters and allozymes
precisely organize the species into traditional taxonomic groupings,
perhaps in part reflecting the role morphology plays historically in
pea classification. A much larger RAPD data set supports several of
these same groupings. P. fulvum is clearly the most distinct of
the pea taxa, while humile, elatius and sativum
form a monophyletic group. RAPD trees, however, often show the
southern humile populations forming a clade that is distinct
from elatius, sativum and even northern humile.
These results may support previous studies which suggest that northern
humile may be the sister taxon to sativum. The current
study presents only modest support for northern humile as the
single closest relative of the domesticated pea. Additionally, a very
small number of polymorphic ITS sites actually places northern
humile further from sativum and reemphasizes the close
affinity among all the non-fulvum peas. ISSR data are presently
being collected to provide yet another measure of relationship among
these taxa. Comparisons among all the data sets are also being made,
and particularly the informativeness of increasing the number of RAPD
markers.
Key words: ISSR, ITS, morphology, phylogenetics, Pisum, RAPDs