A STUDY ON POPULATION DIFFERENTIATION OF MALUS TORINGOIDES HUGHES AND ORIGIN OF M. SETOK VASS.

Malus toringoides Hughes is a hybrid complex formed through one-way introgressive hybridization between M. transtoria Schneid and M. kansuenses Schneid. The hybrid complex eventually becomes M. setok Vass. through the process of variation among population and differentiation of local and geographical races. The three species are readily distinguishable by their plant characters and M. setok Vass. is extensively distributed. Therefore, it is classified as a different species on the principles of morphology and geography. It is a related species of M. transtoria Schneid and M. toringoides Hughes and belongs to M. kansuenses Schneid. M. setok Vass. is a unique species of the western part of China and further research will be helpful to understand the new germplasm and its possible exploitation.