The effect of significant SNP PitaSNP287174 on linkage Group 5 on height varied across four families, suggesting variation in linkage phase between this marker and a linked QTL. Phenotype distributions for height (m) for the two genotypic classes within the four families segregating at the marker are shown here. Full-sib families ACE76 and ACE37 share one common parent. The effect of the marker was statistically significant only in family ACE37 (Supplementary Table S1).