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Background Breadfruit (Artocarpus altilis) is a traditional staple tree crop throughout the tropics. Through interspecific grafting, a dwarf phenotype with over 50% reduction in plant height was identified when marang (Artocarpus odoratissimus) rootstocks were used. However, the molecular mechanism underlying the rootstock-induced breadfruit dwarfing is poorly understood. Results An RNA-sequencing study of breadfruit scions at 22 months after grafting identified 5409 differentially expressed genes (DEGs) of which 2069 were upregulated and 3339 were downregulated in scion stems on marang rootstocks compared to those on self-graft. The DEGs were predominantly enriched for biological processes involved in carbon metabolism, cell wall organization, plant hormone signal transduction and redox homeostasis. The down-regulation of genes encoding vacuolar acid invertases and alkaline/neutral invertases, was consistent with the decreased activity of both enzymes, accompanying with a higher sucrose but lower glucose and fructose levels in the tissues. Key genes of biosynthetic pathways for amino acids, lipids and cell wall were down regulated, reflecting reduction of sucrose utilisation for stem growth on dwarfing rootstocks. Genes encoding sugar transporters, amino acid transporters, choline transporters, along with large number of potassium channels and aquaporin family members were down-regulated in scion stems on marang rootstocks. Lower activity of plasma membrane H+-ATPase, together with the predominance of genes encoding expansins, wall-associated receptor kinases and key enzymes for biosynthesis and re-modelling of cellulose, xyloglucans and pectins in down-regulated DGEs suggested impairment of cell expansion. Signalling pathways of auxin and gibberellin, along with strigolacton and brassinosteroid biosynthetic genes dominated the down-regulated DEGs. Phenylpropanoid pathway was enriched, with key lignin biosynthetic genes down-regulated, and flavonoid biosynthetic genes upregulated in scions on marang rootstocks. Signalling pathways of salicylic acid, jasmonic acid, ethylene and MAPK cascade were significantly enriched in the upregulated DEGs. Conclusions Rootstock-induced disruption in pathways regulating nutrient transport, sucrose utilisation, cell wall biosynthesis and networks of hormone transduction are proposed to impair cell expansion and stem elongation, leading to dwarf phenotype in breadfruit scions. The information provides opportunity to develop screening strategy for rootstock breeding and selection for breadfruit dwarfing.
Yuchan Zhou; Steven J. R. Underhill. Differential transcription pathways associated with rootstock-induced dwarfing in breadfruit (Artocarpus altilis) scions. BMC Plant Biology 2021, 21, 1 -21.
AMA StyleYuchan Zhou, Steven J. R. Underhill. Differential transcription pathways associated with rootstock-induced dwarfing in breadfruit (Artocarpus altilis) scions. BMC Plant Biology. 2021; 21 (1):1-21.
Chicago/Turabian StyleYuchan Zhou; Steven J. R. Underhill. 2021. "Differential transcription pathways associated with rootstock-induced dwarfing in breadfruit (Artocarpus altilis) scions." BMC Plant Biology 21, no. 1: 1-21.
The Kingdom of Tonga has one of the highest rates of diet-related non-communicable diseases (NCDs) in the world. Initiatives to promote pro-health dietary behaviour are possibly being compromised by poor or inconsistent consumer accessibility to affordable and safe fresh fruits and vegetables, referred to as the agriculture–nutrition–income nexus. While donors increasingly focus on nutrition-sensitive agriculture across the Pacific, there is little contemporary information concerning Tonga’s domestic horticultural distribution and market system, particularly in regards to food loss. This study surveyed 292 municipal and road-side vendors on Tongatapu and ‘Utu Vava’u Islands, with the aim of mapping and analyzing horticultural markets and farm supply, transport logistics, and quantifying postharvest practice and market loss. Tonga’s domestic horticultural market structure consists of a central municipal market and on Tongatapu Island, a supplementary network of urban and rural based road-side vendors. There is limited inter-island trade, with most farms located within 25 km of the central municipal market. Mean postharvest horticultural loss was very low, at 1.4% to 5.3%, with road-side vendors more vulnerable to loss. This level of loss was thought to reflect short intra-island transport distance, the type of crops being traded, and rapid market throughput, rather than a level of value chain efficiency. Vendors regulated market supply volume and price discounting and were the principal strategies to mitigate postharvest loss. While low levels of postharvest loss, short transport logistics, and fast market throughput are consistent with a relatively efficient horticulture market system, vendor practice may be impeding fresh fruit and vegetable accessibility.
Steven Underhill; Soane Patolo; Yuchan Zhou; Sarah Burkhart. The Agriculture–Nutrition–Income Nexus in Tonga: Is Postharvest Loss Undermining Horticulture Market Efficiency in Tonga? Horticulturae 2020, 6, 61 .
AMA StyleSteven Underhill, Soane Patolo, Yuchan Zhou, Sarah Burkhart. The Agriculture–Nutrition–Income Nexus in Tonga: Is Postharvest Loss Undermining Horticulture Market Efficiency in Tonga? Horticulturae. 2020; 6 (4):61.
Chicago/Turabian StyleSteven Underhill; Soane Patolo; Yuchan Zhou; Sarah Burkhart. 2020. "The Agriculture–Nutrition–Income Nexus in Tonga: Is Postharvest Loss Undermining Horticulture Market Efficiency in Tonga?" Horticulturae 6, no. 4: 61.
Honiara’s fresh horticultural markets are a critical component of the food distribution system in Guadalcanal, Solomon Islands. Most of the population that reside in Honiara are now dependent on the municipal horticultural market and a network of smaller road-side markets to source their fresh fruits and vegetables. Potentially poor postharvest supply chain practice could be leading to high levels of postharvest loss in Honiara markets, undermining domestic food security. This study reports on a preliminary assessment of postharvest horticultural market loss and associated supply chain logistics at the Honiara municipal market and five road-side markets on Guadalcanal Island. Using vendor recall to quantify loss, we surveyed a total of 198 vendors between November 2017 and March 2018. We found that postharvest loss in the Honiara municipal market was 7.9 to 9.5%, and that road-side markets incurred 2.6 to 7.0% loss. Based on mean postharvest market loss and the incidence of individual vendor loss, Honiara’s road-side market system appears to be more effective in managing postharvest loss, compared to the municipal market. Postharvest loss was poorly correlated to transport distance, possibly due to the inter-island and remote intra-island chains avoiding high-perishable crops. Spatial mapping of postharvest loss highlighted a cohort of villages in the western and southern parts of the main horticultural production region (i.e., eastern Guadalcanal) with atypically high levels of postharvest loss. The potential importance of market-operations, packaging type, and mode of transport on postharvest market loss, is further discussed.
Steven Underhill; Leeroy Joshua; Yuchan Zhou. A Preliminary Assessment of Horticultural Postharvest Market Loss in the Solomon Islands. Horticulturae 2019, 5, 5 .
AMA StyleSteven Underhill, Leeroy Joshua, Yuchan Zhou. A Preliminary Assessment of Horticultural Postharvest Market Loss in the Solomon Islands. Horticulturae. 2019; 5 (1):5.
Chicago/Turabian StyleSteven Underhill; Leeroy Joshua; Yuchan Zhou. 2019. "A Preliminary Assessment of Horticultural Postharvest Market Loss in the Solomon Islands." Horticulturae 5, no. 1: 5.
Here we discuss the novel application of handheld infrared thermal imagery as a learning tool to help smallholder farmers improve postharvest temperature management. Farmers in the Fiji Islands were trained in using a handheld thermal camera to view a series of on-farm demonstrations highlighting the consequence of poor postharvest practice. We observed that smallholder farmers accurately interpreted thermal imagery and the implication of poor practices. Our results showed thermal imagery has the potential to better communicate fundamental concepts of postharvest management. The availability of a range of iPhone, iPad, and Android platforms also means this technology can be widely accessible.
Steven J. R. Underhill; Yuchan Zhou; Salesh Kumar. Infrared Thermal Imaging: A Practical Educational Tool to Improve Smallholder Farmer Postharvest Practice in the Fiji. Journal of Agricultural & Food Information 2017, 7, 1 -6.
AMA StyleSteven J. R. Underhill, Yuchan Zhou, Salesh Kumar. Infrared Thermal Imaging: A Practical Educational Tool to Improve Smallholder Farmer Postharvest Practice in the Fiji. Journal of Agricultural & Food Information. 2017; 7 (2):1-6.
Chicago/Turabian StyleSteven J. R. Underhill; Yuchan Zhou; Salesh Kumar. 2017. "Infrared Thermal Imaging: A Practical Educational Tool to Improve Smallholder Farmer Postharvest Practice in the Fiji." Journal of Agricultural & Food Information 7, no. 2: 1-6.