Dwarf peach trees have been studied since the first recorded description by Monceau in 1786 (in Monet and Salesses, 1975). In 1867, Strong (1867) and Hooper (1867) described dwarf peach tree phenotypes. Conners (1928) observed semidwarf trees in progeny from self-pollinated ‘Elberta’, and concluded that the trait was recessive. Since then, three dwarf genotypes have been identified. Lammerts (1945) obtained dwarf trees in F2 populations from the cross of ‘Chinese Dwarf’ and a standard growth form and concluded that this dwarf type is monogenic and recessive. This dwarf, know as the “brachytic” dwarf (dwdw) type is characterized by short internodes and large leaves. Lammerts (1945) reported a semidwarf peach trait (“bushy”) that was inherited as a double recessive gene (bu1bu1bu2bu2). A semidwarf mutant ‘A72’ was described by Monet and Salesses (1975) that differs phenotypically and genetically from the commonly recognized “brachytic dwarf” described by Lammerts (1945). The ‘A72’ dwarf trait (nn) is incompletely dominant with the heterozygote expressing as a semidwarf tree. Gradziel and Beres (1993) reported an apparent mutant phenotype in a seedling of an open pollination of a clingstone breeding line. This tree (‘SD22–59’) resembled the ‘A72’ dwarf and the segregation of growth habits in progeny of ‘SD22–59’ × standard growth habit varieties (1 semidwarf:1 standard growth) was also suggestive of the phenotype produced by the ‘A72’ mutation. To our knowledge, there has been no study that characterizes the growth or architecture of the ‘A72’ dwarf (nn) or semidwarf (Nn), nor is there information on the interaction of the ‘A72’ growth type with other growth types, for example columnar (brbr). In this study, we characterize the morphological expression of this growth habit in segregating progenies and its interaction with columnar (pillar) peach.
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