The Cytogenetics of Facultative Apomixis in Malus Species

SoME OF THE ASIATIC SPECIES OF Malus produce predominantly maternal progeny, even when surrounded by other species which bloom at the same time.Since apple species and varieties are generally self-sterile, the production of uniform progeny from trees surrounded by other species or varieties would indicate that these trees are apomictic.The production of occasional variants and the production of occasional hybrids following artificial crosspollination indicate that apomixis is facultative in these species.Among the facultative apomicts are Malus sikkimensis from northern India, the related M. rockii from western China, M. toringoides and M. hupehensis from China and M. sargentit from Japan.Several of these apomictic apple species are excellent ornamental trees, and M. toringoides and M. sargentii are usually propagated from seed.For many years the apomictic Malus species have been tested as rootstocks for ornamental and horticultural apple varieties.If such seedlings proved to be compatible with the clonal varieties they would provide uniform rootstocks without the expense and long period of time needed to obtain uniform rootstocks by vegetative propagation.