Follicle-stimulating hormone (FSH) plays an important role in female reproduction by binding to a specific receptor (FSHR) through the β-subunit of FSH on the surface of the ovarian granulosa cells. This study aimed to characterize the FSH β-subunit gene (FSHβ) polymorphism and its association with litter size (LS) using a sample of 118 Mehraban sheep. Polymerase chain reaction (PCR) was performed to amplify fragments 300 bp and 431 bp of the ovine FSHβ gene (Oar_v4.0; Chr 15, NC_019472.2). Polymorphisms in the studied fragments were then explored using single strand conformational polymorphism (SSCP) and DNA sequencing methods. Seven single-nucleotide polymorphisms (SNPs), including g.59078564 C>G, g.59078624 T>C, g.59078655 T>C, g.59078691 T>C, g.59078754 C>A, g.59080186 G>C and g.59080365 C>T, were found among the six detected SSCP patterns A to F. Moreover, two novel indel polymorphisms called e.g., g.59078702del8-bp−ins64-bp and g.59078726ins54-bp were identified among the three different SSCP genotypes patterns G to I. We found significant differences in prolificacy categories between the SSCP genotypes patterns D, E and F (P<0.01) that simultaneously represented SNP polymorphisms of g.59078754 C>A, g.59080186 G>C and g.59080365 C>T. Similarly, novel indel polymorphisms revealed a significant difference in prolificacy categories between the SSCP genotypes patterns G, H and I (P<0.05). Our results suggested that FSHβ is a strong candidate gene to associate with the LS in sheep.
