Materials and methods

Plant materials: Twenty-nine cultivars of common wheat (Table 1) were investigated in this study. Two cultivars (Norstar and Bezostaya 1) are winter wheats, the other cultivars are spring wheat. Cook was developed in Australia, while Crocus was developed as an isogenic line of Columbus, with two crossability genes derived from cv. Chinese Spring. The remaining spring wheat cultivars were registered for production in western Canada.
DNA amplification and gel electrophoresis: DNA extraction was based on the methods described by Procunier et al. (1990). Oligonucleotide primers (10-mers) were purchased from the Biotechnology Laboratory, University of British Columbia, while 9-mer primers were synthesized on an Applied Biosystems Model 394 DNA synthesizer using beta-cyanoethyl phosphoramidite.
Data scoring and analysis: The presence of a amplified product was identified as "1" and the absence was designated as "0". Although a few faint bands were produced, only the bright ones were used in this study. The data were analyzed using the SIMQUAD (Similarity for Qualitative Data) to generate Jaccard similarity coefficients. These similarity coefficients we re used to construct dendrograms using the unweighted pair group method with arithmetic averages (UPGMA) employing the SAHN (Sequential, Agglomerative, Hierarchied, and Nested clustering) from the NTSYS-pc (Numerical Taxonomy and Multivariate Analysis System), version 1.80 (Applied Biostatistics) program.

Results and discussion.

Two hundred and thirty-five random primers (10-mers and 9-mers) were screened against four cultivars (Columbus, Oslo, Biggar and Grandin) to detect RAPD, polymorphisms. Forty-seven (20%) primers did not produce any amplified products. Twenty-five (10.6%) primers produced amplified DNA fragments, but the fragments were faint. One hundred and thirty-two (56.2%) primers produced fragments that were monomorphic across the four cultivars. Thirty-one (13.2%) primers produced polymorphisms. These primers and their sequences are listed in Table 2. A total of 214 reproducible amplified fragments were generated by these 31 primers against the 29 cultivars of common wheat listed in Table 1. The number of fragments produced by each primer varied from 3 to 12 with an average of 6.9 per primer. The size of fragments ranged from 280 bp to 2800 bp. Of the 214 amplified fragments, 54.7% were monomorphic and 45.3% were polymorphic, with an average of 3.1 polymorphisms per primer. Polymorphisms produced among the 29 common wheat cultivars by one primer (UBC229) are shown in Fig. 1. Ninety-seven polymorphisms were detected among the 29 wheat cultivars with the 31 pre-selected random 9- or 10- base primers. This result is similar to that reported by Joshi and Nguyen (1993), demonstrating that RAPD polymorphisms among common wheat cultivars are sufficient to allow some of them to be distinguished. Common wheat is a hexaploid species (42 chromosomes) and has a large genome consisting of 80% repetitive sequences (Peacock et al. 1981). Devos and Gale (1992) detected only a few polymorphisms in hexaploid wheat, attributing this to the large portion of repetitive DNA in the common wheat genome. However, their conclusion was based on data from only six primers. Compared to rice, a diploid species, where 80% of amplified fragments were polymorphic (Yu and Nguyen 1994), a smaller percentage of fragments were polymorphic (45.3%) in common wheat in the current study. However, more polymorphic bands might be revealed by improving the RAPD technique. Silver staining of acrylamide gels or denatured gradient gel electrophoresis might separate minor polymorphic bands which are unresolvable by agarose gel electrophoresis.