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

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

Improving non-communicable disease remediation outcomes in Tonga: the importance of domestic fruit production systems: an analysis

Non-communicable diseases (NCD) are the leading cause of mortality in the Pacific Island nation of Tonga. Current remedial strategies have focused on promoting healthy food choices based on increased intake of fruits and vegetables. While researchers seek to overcome complex social, gender and cultural practices that impede dietary transition, discontinuous domestic fruit supply chains undermine this effort. With the view to supporting a more holistic approach to NCD remediation in Tonga, this paper provides a preliminary assessment of domestic horticultural supply chains constraints, in support of diversification and expansion of local fruit production. Current impediments and constraints to enhanced local fruit production are presented and possible strategies to increased domestic fruit supply discussed. We present a case for a more consumer-centric approach to industry development, with an emphasis on production systems that are compatible with existing social structures, customary land ownership constraints, and local nutritional needs

Postharvest diseases of mangoes in Fiji

Despite considerable research globally on postharvest diseases of mango, virtually no work has been done to determine the occurrence of these diseases and their causal agents in Fiji. This study is the first major field and market survey of postharvest diseases of mango in Fiji. For the field survey, fruits from five local mango cultivars were harvested at each of five locations. Fruits from five imported cultivars were also harvested from one location in Nadi. For the market survey, vendors were selected at five municipal markets for fruit collection, along with ten roadside stalls. For field and market surveys, fruits were incubated at 23°C and assessed for postharvest disease (incidence and severity of body rots and stem end rots) when ripe. Isolations were made from disease lesions and fungal cultures were identified using multilocus sequence typing. High incidences of body and stem end rots were recorded across all surveys. In the field survey of local cultivars, ?Salusalu? fruits were found to have the lowest severity of body rot and stem end rot on average, while for imported cultivars, ?Nam Doc Mai? had the lowest average severity of these diseases. The market survey showed that ?Salusalu? had a lower incidence of anthracnose on the body of fruit compared to all other cultivars, although it did have a surprisingly high incidence of stem end rot at some localities. Fungal isolates from anthracnose lesions in the field and market surveys were identified as Colletotrichum asianum, C. simmondsii and C. fructicola. C. asianum was the predominant species associated with anthracnose symptoms, accounting for 97% of isolations. Lasiodiplodia theobromae and Neofusicoccum parvum were the predominant species found in association with mango stem end rot symptoms. Other species isolated from mango stem end rot in lesser numbers included L. brasiliensis, N. umdonicola and N. kwambonambiense. All of these fungi represent new reports for Fiji

Total Flavonoid Contents and the Expression of Flavonoid Biosynthetic Genes in Breadfruit (<i>Artocarpus altilis</i>) Scions Growing on Lakoocha (<i>Artocarpus lakoocha</i>) Rootstocks

Breadfruit (Artocarpus altilis) is a traditional fruit tree of 15–30 m height in the tropics. The presence of size-controlling rootstock in the species is not known. A small tropical tree species, lakoocha (Artocarpus lakoocha), was recently identified as a potential vigor-controlling rootstock, conferring over a 65% reduction in breadfruit tree height. To better understand the intriguing scion/rootstock interactions involved in dwarfing, we investigate flavonoid accumulation and its regulation in breadfruit scions in response to different rootstocks. To this end, we isolated a chalcone synthase cDNA, AaCHS, and a full-length bifunctional dihydroflavonol 4-reductase cDNA, AaDFR, from breadfruit scion stems. The expression of both AaCHS and AaDFR genes was examined over the period of 16 to 24 months following grafting. During the development of the dwarf phenotype, breadfruit scion stems on lakoocha rootstocks display significant increases in total flavonoid content, and show upregulated AaCHS expression when compared with those on self-grafts and non-grafts. There is a strong, positive correlation between the transcript levels of AaCHS and total flavonoid content in scion stems. The transcript levels of AaDFR are not significantly different across scions on different rootstocks. This work provides insights into the significance of flavonoid biosynthesis in rootstock-induced breadfruit dwarfing

A Dwarf Phenotype Identified in Breadfruit (<i>Artocarpus altilis</i>) Plants Growing on Marang (<i>A. odoratissimus</i>) Rootstocks

Breadfruit (Artocarpus altilis) is a tropical fruit tree primarily grown as a staple crop for food security in Oceania. Significant wind damage has driven an interest in developing its dwarf phenotype. The presence of any dwarf breadfruit variety remains unknown. Little is known regarding the growth of the species on rootstocks. Here, we examined the phenotype of breadfruit plants growing on marang (Artocarpus odoratissimus) rootstocks within 18 months after grafting; we identified a rootstock-induced dwarf trait in the species. This dwarf phenotype was characterized by shorter stems, reduced stem thickness and fewer branches, with 73% shorter internode length, 51% fewer and 40% smaller leaves compared to standard size breadfruit plants. The height of breadfruit plants on marang rootstocks was reduced by 49% in 9 months, and 59% in 18 months after grafting. The results suggest marang rootstocks can be applied to breadfruit breeding program for tree vigor control. Further biochemical characterization showed plants on marang rootstocks displayed leaves without change of total chlorophyll content, but with lower total soluble sugars, and stems with reduced activity of plasma membrane H+-ATPase, a well-known primary proton pump essential for nutrient transport. The significance of the two parameters in rootstock dwarfing is discussed

Breadfruit (Artocarpus altilis) gibberellin 2-oxidase genes in stem elongation and abiotic stress response

Breadfruit (Artocarpus altilis) is a traditional staple tree crop in the Oceania. Susceptibility to windstorm damage is a primary constraint on breadfruit cultivation. Significant tree loss due to intense tropical windstorm in the past decades has driven a widespread interest in developing breadfruit with dwarf stature. Gibberellin (GA) is one of the most important determinants of plant height. GA 2-oxidase is a key enzyme regulating the flux of GA through deactivating biologically active GAs in plants. As a first step toward understanding the molecular mechanism of growth regulation in the species, we isolated a cohort of four full-length GA2-oxidase cDNAs, AaGA2ox1- AaGA2ox4 from breadfruit. Sequence analysis indicated the deduced proteins encoded by these AaGA2oxs clustered together under the C GA2ox group. Transcripts of AaGA2ox1, AaGA2ox2 and AaGA2ox3 were detected in all plant organs, but exhibited highest level in source leaves and stems. In contrast, transcript of AaGA2ox4 was predominantly expressed in roots and flowers, and displayed very low expression in leaves and stems. AaGA2ox1, AaGA2ox2 and AaGA2ox3, but not AaGA2ox4 were subjected to GA feedback regulation where application of exogenous GA or gibberellin biosynthesis inhibitor, paclobutrazol was shown to manipulate the first internode elongation of breadfruit. Treatments of drought or high salinity increased the expression of AaGA2ox1, AaGA2ox2 and AaGA2ox4. But AaGA2ox3 was down-regulated under salt stress. The function of AaGA2oxs is discussed with particular reference to their role in stem elongation and involvement in abiotic stress response in breadfruit

Smallholder farmer perceptions of postharvest loss and its determinants in Fijian tomato value chains

The Fiji Islands, like many small Pacific island nations, are thought to incur high rates of postharvest loss. Little work has been undertaken to quantify the amount of loss within Pacific horticultural value chains, or identify the key determinants. This study sought to quantify postharvest loss within Fijian smallholder tomato value chains and to examine the relative importance of current on-farm practices as possible contributors to this loss. A semi-structured survey of 115 smallholder tomato farmers in Sigatoka Valley and eastern Viti Levu was undertaken, covering socio-economic and demographic parameters, production and postharvest handling practice, and postharvest loss based on farmer recall. On-farm postharvest loss for smallholder farmer tomato value chains was between 26.1% in Sigatoka Valley and 27.6% in eastern Viti Levu. This finding was consistent with quantification of postharvest loss in Fijian tomato chains by direct determination, but is relatively high when compared to smallholder tomato value chain loss in Sub-Saharan Africa. When Fijian tomato value chains were segregated according to specific postharvest handling practice, the contributors to postharvest loss were often associated with on-farm decision-making. Those value chains that only harvested once a week, or in the early morning (before 7 am) or mid-day onwards, stored harvest product in the field for more than three hours, did not sort or grade prior to on-farm ripening, or used packing sheds that had relatively open designs, all had consistently higher levels of postharvest loss. The prevalence of specific postharvest handling practice in both locations is further reported. While this study highlights the impact of current on-farm postharvest handling practices on tomato value chain loss, what remain unclear are the underlying drivers associated with current postharvest handling behaviour and the decision-making that shapes quality and logistic control activities

Expression of Gibberellin metabolism genes and signalling components in dwarf phenotype of Breadfruit (Artocarpus altilis) plants growing on Marang (Artocarpus odoratissimus) rootstocks

Breadfruit () 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 () 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, , and increase in expression of a GA catabolic genes, , 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, . 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