Inheritance of pollen enzymes and polyploid origin of apple (Malus x domestica Borkh.)

Electrophoresis of 7 pollen enzymes was applied to 5 progenies from controlled crosses and one self-progeny of apple. Segregation data were examined according to three kinds of hypotheses: monogenic disomic, bigenic disomic and tetrasomic inheritance Twenty codominant alleles and a recessive null were identified. Results provided evidence of bigenic disomic inheritance in most cases: 6 pairs of homoeologous loci carrying identical homoeoalleles were revealed; only 2 enzymes exhibited a simple monogenic control. Preferential pairing between pairs of homologous chromosomes in meiosis can be postulated. These results indicated an allopolyploid origin of apple genome. Fixed heterozygosity occurred for several enzymes, which is a typical feature of allopolyploidy. Loss of duplicate gene expression can account for the monogenic control of 2 of the enzymes.