Plant Genome I Conference
Town & Country Conference Center, San Diego, CA, November, 1992.
PG-I: 58pg1
USE OF RAPD TAGS TO MAP CHICKPEA ROOT NODULATION GENES
Thomas M. Davis 1, Patrick J. McGowan 1, and Charles J. Simon 2,
1) Plant Biology Department, University of New Hampshire,
Durham, NH 03824; 2) USDA/ARS Grain Legume Genetics and
Physiology Research, Washington State University, Pullman, WA
99164.
Using a combination of bulk segregant and individual
segregant analyses, RAPD marker tags are being identified for
chickpea root modulation genes as part of a larger genetic
investigation of legume root modulation at the University of New
Hampshire (UNH). In a parallel investigation at Washington
State University (WSU), numerous RAPD, isozyme, and RFLP markers
are being added to a growing chickpea linkage map. Because both
the UNH and WSU studies employ interspecific crosses between
chickpea (Cicer arietinum L.) lines and a common pollen parent,
Cicer reticulatum P.I. 489777, many RAPD tags identified at UNH
can be located on the WSU map. In this manner, modulation genes
rn1 (Nod- phenotype) and Rn7 (Nod+, Fix-phenotype) both map into
a common cluster of RAPD-markers on linkage group 3. RAPD tags
have also been found for unlinked modulation genes rn2 and rn3.
One RAPD tag is a codominant marker with unusual characteristics.
Specifically, the two pertinent bands appearing in heterozygous
individuals are slightly altered in electrophoretic mobility
relative to the respective parental bands. The heterozygous
pattern can be mimicked by mixing separately amplified parental
DNAs, but only if the mixture is heated to 94C before
electrophoresis. The possibility that heteroduplex formation
between alternate RAPD "alleles" accounts for this phenomenon is
being investigated.
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