COL3A1 region is a candidate causal genomic region affecting body size differentiation between MMS and SMS. (A) COL3A1 region demonstrated significant selection signals between MMS and SMS. At the top panel is three Fst statistics: SMS compared with MMS (SMS vs. MMS), SMS compared with large body size pig breeds (SMS vs. LBS), SMS compared with small body size pig breeds (SMS vs. SBS). The dashed line is the Fst significance threshold. At the bottom panel is heat map of MMS and SMS haplotypes within COL3A1 region. Blue is MMS major allele and red is SMS major allele. SBS represents small body size pig breeds including SMS, LBS represents large body size pig breeds including MMS and LW represents Large White pig. (B) NJ-tree of different body size pig breeds for COL3A1 region. Blue lines represent SMS, green lines represent SBS except SMS, red lines represent MMS, and orange lines represent LBS except MMS. SBS represents small body size pig breeds, LBS represents large body size pig breeds. (C) is violin plot for haplotype association analysis of Suhuai body length trait. Among which, Q is MMS major haplotype and the others are q haplotype.