Tetraploid apple forms for the polyploid level selection

Abstract

Features of female and male gametophyte development in a tetraploid apple form of ‘Spartan’ cultivar (4x) are discussed in connection with its use in breeding with polyploidy using. Multicellular archesporium (8-13 cells), additional tetrads (T-like, linear and square) and sometimes the formation of two embryo sacs in one nucellus are noted during the formation of the female gametophyte. During the formation of the male gametophyte despite some deviations the most part of cells (67 %) have correct pictures of division and therefore the basic mass of gametes will have a balanced set of chromosomes. Morphologically normal one-sized pollen grains are formed (73,9 %) and the pollen fertility is high - up to 98 %. Our data allow making a conclusion for the possibility of using a tetraploid apple form of ‘Spartan’ (4x) in breeding with polyploidy using as a donor of diploid gametes. This is confirmed by a cytological analysis of hybrid progeny where this tetraploid was used as a pollinator while the output of triploid plants made up to 85 % in crossing combinations 29-34-35 [Arbat x 23-1528 (814 - open pollination)] (2x) x Spartan (4x).