Genetic Interactions of Pillar (Columnar), Compact, and Dwarf Peach Tree Genotypes

Abstract

<jats:p>A study was conducted to determine genetic control of the columnar or pillar (PI) growth habit, and to evaluate the effects of interactions of various genes that influence peach [<jats:italic>Prunus persica</jats:italic> (L.) Batsch (Peach Group)] growth habit. The PI habit (<jats:italic>brbr</jats:italic>) examined in this study was inherited as a monogenic trait expressing incomplete dominance. The heterozygous <jats:italic>Brbr</jats:italic> derived from crosses between standard (ST) and PI genotypes was recognized as an upright (UP) tree with narrower branch angles than ST trees but wider than PI trees. The combination of <jats:italic>brbr</jats:italic> and brachytic dwarf (DW) (<jats:italic>dwdw</jats:italic>) produced dwarf-pillar (DWPI) trees. The effects of the heterozygous <jats:italic>Brbr</jats:italic> in combination with <jats:italic>dw</jats:italic> and/or compact (CT) (<jats:italic>Ct</jats:italic>) could not be recognized by visual observation. Compact pillar (CTPI) trees resulted from the expression of <jats:italic>Ct_ brbr</jats:italic>. These trees were distinguished from globe-shaped (GL) trees (<jats:italic>Ct_Brbr</jats:italic>) by the more upright growth habit of the CTPI trees. This genetic study highlights the genetic plasticity of tree growth habit in peach. The investigation of novel growth habits extends our concept of the peach tree. Some growth habits such as PI may have commercial potential for high-density peach production systems. Others, such as DWPI and CTPI may have potential as ornamentals.</jats:p>

Suitability of the dwarf (dw/dw) habit for the peach industry

“…But, to gain an advantage from the dwarf trait, breeders should in future focus not only on fruit quality, but also on characters such as internode length and leaf size, manipulating them to improve the agronomic characteristics of the dwarf tree. There appear to be ample possibilities of genetically manipulating peach tree growth habit and developing new grow types more suited for commercial peach production (Scorza et al, 2002).…”

Molecular basis of angiosperm tree architecture

“…Although br/br trees have an entirely columnar or pillar appearance, heterozygous individuals show a more spreading 'upright' phenotype ( Fig. 2f) (Scorza et al, 1989(Scorza et al, , 2002Tworkoski & Scorza, 2001). Physiological studies have shown that pillar peach trees display a range of physical alterations, including shorter lateral shoots (a result of shorter internodes), smaller stem diameter, decreased sylleptic branching and narrow crotch angles (Tworkoski & Scorza, 2001;Tworkoski et al, 2006).…”

“…Some dwarf phenotypes found in peach are shown in Fig. 2(h,i) (Scorza et al, 2002;Fideghelli et al, 2003). Dwarfism in plants is typically associated with reduced growth because of shorter internodesindicating a decreased ability to elongate and/or a reduction in cell division (Ross et al, 2005).…”

“…2a,k) (Van Well, 1974;Scorza et al, 1984Scorza et al, , 1999Mehlenbacher & Scorza, 1986). These characteristics result in a dense canopy with reduced light penetration, which is undesirable for fruit production because of the need for excessive pruning (Scorza et al, 1999(Scorza et al, , 2002. The compact peach phenotype has a Mendelian segregation pattern consistent with a single dominant allele, ct (Mehlenbacher & Scorza, 1986;Scorza et al, 2002).…”

Fine genetic mapping of the Co locus controlling columnar growth habit in apple

“…Peach pillar (PI), also known as columnar or broom, is controlled by a recessive allele at the br locus (Chaparro et al 1994;Rajapakse et al 1995;Scorza et al 2002;Werner and Chaparro 2005) on peach LG-2 (Sajer et al 2011;Sosinski et al 2000). Peach chromosome-2 shows strong synteny with apple chromosomes 1, 2 and 7 (Illa et al 2011), but not with apple chromosome-10 where the Co locus resides.…”