Reduction of pectin may decrease the embryogenicity of grapevine (Vitis vinifera) pro-embryonic masses after 10 years of in vitro culture

•The embryonic properties of grape pro-embryonic masses decreased after 10 years of subculture.•Enlargement of intercellular space in the cell wall of grape pro-embryonic masses subculture for a long time.•Methylated and de-methylated pectins reduction in long-term subculture pro-embryonic masses.