Axillary Bud Fate Shapes Plant Architecture in Horticultural Crops

Javier Andrés,Elli Koskela

doi:10.3390/horticulturae8020130

Abstract

Above-ground plant architecture is dictated to a large extent by the fates and growth rates of aerial plant meristems. Shoot apical meristem gives rise to the fundamental plant form by generating new leaves. However, the fates of axillary meristems located in leaf axils have a great influence on plant architecture and affect the harvest index, yield potential and cultural practices. Improving plant architecture by breeding facilitates denser plantations, better resource use efficiency and even mechanical harvesting. Knowledge of the genetic mechanisms regulating plant architecture is needed for precision breeding, especially for determining feasible breeding targets. Fortunately, research in many crop species has demonstrated that a relatively small number of genes has a large effect on axillary meristem fates. In this review, we select a number of important horticultural and agricultural plant species as examples of how changes in plant architecture affect the cultivation practices of the species. We focus specifically on the determination of the axillary meristem fate and review how plant architecture may change even drastically because of altered axillary meristem fate. We also explain what is known about the genetic and environmental control of plant architecture in these species, and how further changes in plant architectural traits could benefit the horticultural sector.

Highlights

Plant architecture determines resource allocation within a plant and has a great influence on, for example, harvest index, yield potential, cultural practices and even the choice of mechanical versus manual harvesting
Breeding for improved plant architecture does not necessarily require detailed knowledge on the identities of the genes controlling the traits. This is exemplified by the success of the “Green Revolution” cereal cultivars, whose breeding was based on conventional hybridization and selection, ideotype breeding, and the introduction of recessive “dwarfing” loci from exotic germplasm
Due to the diverse growth patterns, we focus this review on the apple (Malus domestica Borkh.), for which the molecular mechanisms regulating tree architecture have started to emerge during the recent years

Summary

Introduction

Plant architecture determines resource allocation within a plant and has a great influence on, for example, harvest index, yield potential, cultural practices and even the choice of mechanical versus manual harvesting Cultural practices, such as pruning or the use of growth control substances to regulate plant architecture, may be quite costly. Breeding for improved plant architecture does not necessarily require detailed knowledge on the identities of the genes controlling the traits This is exemplified by the success of the “Green Revolution” cereal cultivars, whose breeding was based on conventional hybridization and selection, ideotype breeding, and the introduction of recessive “dwarfing” loci from exotic germplasm. Depending on the plant species, the fates of different meristems are determined by endogenous or exogenous signals, or a mixture of both (reviewed in [4]). The plant species were selected so as to highlight known different genetic mechanisms controlling plant architecture and to include both annual and perennial, woody and herbaceous crops

Plant Architecture in Selected Crop Species

Tomato

Strawberry

Citrus

Concluding Remarks