Plasma membrane H+‐ATPase activity and graft success of breadfruit (Artocarpus altilis) onto interspecific rootstocks of marang (A. odoratissimus) and pedalai (A. sericicarpus)

Y. Zhou, S. J. R. Underhill

Breadfruit (Artocarpus altilis) is primarily grown as a staple tree crop for food security in the Oceania. Significant wind damage has driven an interest in developing its dwarfing rootstocks. Due to the predominantly vegetative propagation of the species, grafting onto interspecific seedlings is an approach to identifying dwarfing rootstocks. However, grafting of breadfruit onto un-related Artocarpus species has not been investigated. Here we first reported the success of breadfruit grafting onto interspecific rootstocks, marang (A. odoratissimus) and pedalai (A. sericicarpus). To address the low graft survival, we investigated the relationship of plasma membrane (PM) H+ -ATPase activity to graft success. We provided the first evidences for a positive correlation between PM H+ -ATPase activity and graft survival. The graft unions of successful grafts had higher PM H+ -ATPase activity compared to those of failed grafts. Rootstocks with low PM H+ -ATPase activity in leaf microsomes before grafting had lower graft survival than those with high enzyme activity, with graft success of 10% vs 60% and 0% vs 30% for marang and pedalai rootstocks respectively. There was a positive correlation between graft success and the PM H+ -ATPase activities measured from the rootstock stem microsomes two months after grafting (marang, r(7) = 0.9203, P= 0.0004; pedalai (r(7) = 0. 8820, P = 0.0017). Removal of scion's own roots decreased the leaf PM H+ -ATPase activity of grafted plants regardless of the final graft outcome. The recovery of the enzyme activity was only found in the successful grafts. The function of PM H+ -ATPase in graft union development and graft success improvement is discussed. This article is protected by copyright. All rights reserved.