USE OF A LEAF COLOR MARKER GENE TO DETECT APOMIXIS IN MALUS SPECIES AND OBSERVATIONS ON THE VARIABILITY OF THE APOMICTIC SEEDLINGS

Abstract

Controlled pollinations, using pollen from a diploid cultivar that was homozygous for a dominant gene controlling leaf anthocyanin, enabled Malus seedlings to be sorted into maternal types and hybrids soon after germination. The facultatively apomictic species M. sargentii, M. sieboldii, and M. sikkimensis gave 37 to 79% hybrids, whereas M. hupehensis gave only maternal types but produced much nonviable seed. The progenies of M. baccata, M. honanensis, M. micromalus, M. prunifolia, M. robusta, M. rockii, and M. zumi consisted almost entirely of sexual hybrids. Within each progeny, the hybrids of the three partly apomictic species were more variable than the maternal types in height, stem diameter and shoot weight, but the differences within the progeny of M. sikkimensis were not significant because of the remarkable uniformity of the hybrids from this 3n × 2n cross. Coefficients of variation for the apomictic seedlings showed that those of M. sikkimensis were the most uniform, those of M. sieboldii were the least uniform, and the apomicts of M. sargentii were intermediate.