Insertion Mutation of Pollen SFB Gene in Self-compatibility of Japanese Apricot Cultivars Native to China Identification of RAPD and SCAR Markers Linked to the Single2double FlowerGene in Japanese Apricot ( Prunus mume Sieb. et Zucc. ) Insertion Mutation of Pollen SFB Gene in Self-compatibility of Japanese Apricot Cultivars Native to China Identification of RAPD and SCAR Markers Linked to the Single2double FlowerGene in Japanese Apricot ( Prunus mume Sieb. et Zucc. )