Submitted to: Proceedings of Plant Growth Regulation Society of America
Publication Type: Proceedings
Publication Acceptance Date: 9/19/2014
Publication Date: N/A
Technical Abstract: Branch orientation and distribution are fundamental aspects of tree architecture that influence orchard design and management. The goal of the study was to identify genetically modifiable regulatory processes or those that can be managed culturally to customize tree architecture. Peach [Prunus persica L. (Batch)] trees with three different branching genotypes were evaluated: nearly vertical branches (pillar), less vertical and more spreading branches (upright), and least vertical branches (standard). Auxin concentrations and gene expression of key branching enzymes in herbaceous species, MAX1, 2, 3, and 4, were determined. Also, expression of the gene, TAC1, that is associated with branch angle and serves as a marker for pillar peach trees, was measured. Shoots and roots of peach trees in the field and greenhouse were studied during periods of growth when bud break and branch spatial orientation develop. Endogenous auxin concentrations were determined by mass spectrometry and gene expression was relatively quantified with real-time polymerase chain reaction (PCR). Expression of TAC1 in shoots was greatest in standard and least in pillar trees. This supports previous work where unexpressed TAC1 was associated with narrow branch angles as found in pillar trees. Auxin and the branch-related genes, MAX1-4, were dissimilar between standard and pillar or upright growth habits and expression changed during the growing season. Gene expression of MAX1-4 was higher in roots than stems, but it did not differ among the roots or rootstocks of the different growth habits. The current work indicates that in stems, auxin and MAX1-4 genes, may influence regulatory processes that affect growth and development of peach trees with different growth habits. In addition to breeding, new plant growth regulators that affect the modes of action of root-originating signals, possibly strigolactone, may provide new cultural tools for managing tree growth and development.