Plant Genome II Conference
Town & Country Conference Center, San Diego, CA, January, 1994.
PG-II: LEVELS OF DNA SEQUENCE POLYMORPHISM AMONG WHEAT BREEDING
VARIETIES
LEVELS OF DNA SEQUENCE POLYMORPHISM AMONG WHEAT BREEDING
VARIETIES
Glenn Bryan, Katrien Devos, Pauline Stephenson, Angela Collins,
Jim Smith and Mike Gale, Cambridge Laboratory, John Innes Centre,
Norwich, NR4 7UJ, UK
The genome of hexaploid bread wheat (Triticum aestivum)
exhibits very low levels of restriction fragment length
polymorphism (RFLP). This may be due to the relatively recent
origin of hexaploid wheat. A study has been undertaken to assess
the level of DNA sequence polymorphism present among wheat
varieties. Sequences corresponding to PCR-amplified genomic
segments of mapped RFLP clones have been determined for several
varieties of wheat. Analysis of these PCR products reveals
extremely low levels of sequence polymorphism between the
selected varieties. For the cDNAs analysed several PCR products,
differing in length, result from the amplification of genomic
sequences from more than one of the three wheat genomes. These
PCR products have been cloned and the genome of origin of the
individual fragments has been ascertained. Analysis of the
sequences corresponding to cDNAs from individual wheat genomes
has revealed very low rates of sequence divergence within coding
and non-coding regions. Furthermore, there is a high degree of
sequence conservation within coding regions between homoeologous
sequences. For one of the cDNAs, the differences in length of
the PCR-derived clones are clearly due to variation in intron
length between the homoeologous copies of the corresponding gene.
It is possible that these differences in intron size may be
useful in the design of genome specific primers or probes.
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