Manipulating Fruit Tree Structure Chemically and Genetically for Improved Performance

Abstract

Among the growth regulators routinely used to manipulate tree structure are M&B 25-105 (n-propyl-3-t-butylphenoxyacetate) and benzyladenine with or without gibberellic acid to enhance branching, Off-Shoot-O (a fatty acid ester mixture) to replace hand-pruning, and Promalin (benzyladenine + gibberellic acid) to increase lateral shoot production. Mutagenesis, especially by radiation treatment, has been successfully applied to apple and cherry breeding to produce compact growth forms. Conventional breeding has centred on spreading and dwarfing or semi-dwarfing tree shape in pears, brachytic dwarfing forms in peach and columnar shape in apples.