Significant differences in expression relative to the A. majus allele were observed among different species hybrids. Allele ratios in F1 hybrids with various species (spp) were obtained from competitive RT-PCR and pyrosequencing on cDNA from flower buds (stage 11). The species heterozygous with A. majus are: bra, A. braun-blanquetii; cha, A. charidemi; lat, A. latifolium; lin, A. linkianum; maj, A. majus; meo, A. meonanthum; pul, A. pulverulentum; str, A. striatum; tor, A. tortuosum. Expression levels were also obtained for heterozygotes carrying A. charidemi alleles in the A. majus background (cha-BC). Genomic DNA was used to calculate PCR amplification biases. Standard errors are shown.