Detennining the cause of seedlessness in seedless citrus fruit varieties selected in nature on field is of great scientific and practical significance, which not only contributes to understanding their naq.re of genetics of them, but also plays as the scientific basis of breeding and establishing appropriate cultivation protocols for developing the seedless citrus fruit varieties and the selected plants stably and sustainably. The research has found that the reasons of seedlessness on some citrus fruit varieties, such as Da Xanh pummelo, V2 orange and some the other selected seedless citrus fruits in nature (Orange: Cam mat H-1, Xa Doai XM-2
mandarin: Quyt Cao, Quyt Ngot) are completely different Varieties of Da Xanh pummelo, Quyt Ngot mandarin (QN-l) are self-incompatibility varieties, V2 orange, Mat orange (H-l), Quyt Cao mandarin (QC-l) and Xa Doai orange (XM-2) are male sterility varieties
and none of these are aneuploidy (3x, 5x, 7x).