Transcriptome analysis reveals gene associated with fruit size during fruit development in pear

•Pear fruit exhibited a single sigmoid pattern during fruit development.•Fruit size was determined by both of cell number and cell size during fruit development.•342 differentially expressed genes (DEGs) were screened in the fruits early and late enlargement.•14 DEGs were located within the reported quantitative trait locus (QTL) regions related to fruit size.