Between 661,600,411 and 899,700,085 genome sequence read pairs where generated for each of the four wheat cultivars (Table 1). Of these, between 4.70% and 3.10% mapped to the group 7/4AL reference as read pairs. As the reference is estimated to cover 14% of the complete genome, the number of mapped reads is less than predicted. This is likely due to many read pairs mapping to multiple locations in this highly repetitive genome and subsequently being ignored due to the SOAP -r 0 option. SGSautoSNP identified a total of 881,289 SNPs across the group 7 chromosomes. These consisted of 68% transitions and 32% transversions. This bias in transition/transversion ratio is commonly observed in SNP discovery and reflects the high degree of methlyl C to U mutation in genomes. It may be expected that the bread wheat genome is highly methylated due to the two rounds of polyploidy and high repeat content. The observed transition/transversion bias provides a level of confidence in SNP prediction accuracy since erroneously called SNPs caused by sequence read errors
or mismapping would be unlikely to display such a bias.