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ARS Home » Northeast Area » Kearneysville, West Virginia » Appalachian Fruit Research Laboratory » Innovative Fruit Production, Improvement, and Protection » Research » Publications at this Location » Publication #298328
Title: Auxin levels and MAX1–4 and TAC1 gene expression in different growth habits of peach

Author
item Tworkoski, Thomas
item Webb, Kevin
item Callahan, Ann

Submitted to: Plant Growth Regulation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/23/2015
Publication Date: 4/7/2015
Citation: Tworkoski, T., Webb, K.K., Callahan, A.M. 2015. Auxin levels and MAX1–4 and TAC1 gene expression in different growth habits of peach. Plant Growth Regulation. DOI 10.1007/s10725-015-0062-x.

Interpretive Summary: Peach trees have complex branching that is difficult and costly to manage. This is a significant hindrance to automated practices. A hormone and an accompanying molecular process were determined to be significant factors that can influence the shape and branching of the whole fruit tree. These branching processes may be used as selective factors for breeding and for chemical management to reduce counter-productive branching and assist with automation for pruning and harvesting.

Technical Abstract: Branch orientation and distribution establish a fruit tree’s canopy architecture; tree architecture is a core factor for orchard management including novel mechanized technologies. Endogenous hormone concentrations and gene expression of a key branching enzyme in herbaceous species, MAX4, were determined in peach trees [(Prunus persica L. (Batch)]. Three different branch orientation genotypes were evaluated, homozygous TAC1 mutant which is a pillar shaped tree, heterozygous TAC1 mutant which is an upright tree and homozygous wild type TAC1 which is a standard tree. The goal of the study was to identify genetically modifiable regulatory processes or those that can be managed culturally to customize tree architecture. Shoots of peach trees in the field and greenhouse were studied during periods of growth when bud break and branch spatial orientation develop. Endogenous IAA concentrations were determined by mass spectrometry and MAX4 gene expression was relatively quantified with real-time PCR. In the greenhouse, MAX4 expression in stems was highest in growth habits of pillar followed by upright and least in standard trees (2.7, 1.7, and 0.9 relative to actin, respectively). In the field, MAX4 expression was 6.5 and 4.8 relative to actin in shoots of pillar and standard trees, respectively. IAA was consistently highest in pillar tree shoots in both greenhouse and field. These results support the hypothesis that elevated IAA induces MAX4 which modifies a root signal that represses budbreak, and contributes to a growth form, such as pillar, that has strong apical dominance and repressed branch bud break. However, the role of MAX4 in tree development remains unclear though it appears to be associated with modification of strigolactone. MAX4 expression was higher in roots than shoots but it did not differ among different scion-rootstock combinations in root tissue. Nonetheless, the current work supports the hypothesis that IAA and MAX4 affect regulatory processes of growth and development of peach trees. In addition to breeding, new plant growth regulators that affect the modes of action of root-originating signals, such as strigolactone, may provide new cultural tools for managing tree growth and development.