Expression of Gibberellin Metabolism Genes and Signalling Components in Dwarf Phenotype of Breadfruit (Artocarpus altilis) Plants Growing on Marang (Artocarpus odoratissimus) Rootstocks.

Yuchan Zhou,Steven J R Underhill

doi:10.3390/plants9050634

Abstract

Breadfruit (Artocarpus altilis) is a traditional staple tree crop throughout the tropics. The species is an evergreen tree 15–20 m; there are currently no size-controlling rootstocks within the species. Through interspecific grafting, a dwarf phenotype was identified in breadfruit plants growing on Marang (Artocarpus odoratissimus) rootstocks, which displayed ~60% reduction in plant height with ~80% shorter internodes. To gain insight into the molecular mechanism underlying rootstock-induced dwarfing, we investigated the involvement of gibberellin (GA) in reduction of stem elongation. Expression of GA metabolism genes was analysed in the period from 18 to 24 months after grafting. In comparison to self-graft and non-graft, scion stems on marang rootstocks displayed decrease in expression of a GA biosynthetic gene, AaGA20ox3, and increase in expression of a GA catabolic genes, AaGA2ox1, in the tested 6-month period. Increased accumulation of DELLA proteins (GA-signalling repressors) was found in scion stems growing on marang rootstocks, together with an increased expression of a DELLA gene, AaDELLA1. Exogenous GA treatment was able to restore the stem elongation rate and the internode length of scions growing on marang rootstocks. The possibility that GA deficiency forms a component of the mechanism underlying rootstock-induced breadfruit dwarfing is discussed.

Highlights

Trees with reduced stature allow high-density planting and facilitate tree management and harvesting
Our current work focused on the involvement of GA in the scion stem elongation of breadfruits growing on marang rootstocks in relation to dwarf phenotype
Shorter internodes were observed in breadfruit plants growing on marang rootstocks, with 79.8% reduction in final internode length compared to those on self-grafts (Figure 1a)

Summary

Introduction

Trees with reduced stature allow high-density planting and facilitate tree management and harvesting. Tree dwarfing has been achieved through the widespread use of dwarfing rootstocks. The mechanism underlying rootstock-induced dwarfing has been extensively studied but remains poorly understood [1,2,3,4]. Breadfruit (Artocarpus altilis) is a traditional staple tree crop throughout the tropics. The species is an evergreen tree from 15 to 20 m. Breadfruits comprise fertile and sterile diploids and sterile triploids and has hundreds of cultivars [5], but there is currently no size-controlling rootstock within the species. A dwarf phenotype was recently identified in breadfruit plants growing on marang (Artocarpus odoratissimus) rootstocks [6]

Methods

Results

Conclusion