Cool-climate wine regions will face significant impacts from climate change over the coming decades. To predict the likely effects of climate change-associated high temperatures on berry ripening, a series of field-based grape bunch heating experiments were conducted on Pinot noir (Vitis vinifera L.) berries in Marlborough, New Zealand. Pinot noir bunches were heated for 7 days at the beginning of ripening (véraison) to a diurnal temperature range of 20 °C–39 °C, while unheated control bunches experienced an ambient diurnal temperature range of 11 °C–31 °C. This heating resulted in changes to several key quality criteria. The organic acid composition was altered by heat in favour of hastened reduction in malic acid concentration for a given total sugar concentration post-véraison. The sensitivity of anthocyanin accumulation in berry skins to heating varied depending on season: major inhibition in season 1 and minor inhibition in season 2. Abscisic acid (ABA) plays a pivotal role in the initiation of berry ripening, including the onset of anthocyanin accumulation in berry skins. Seasonal variation in peak berry ABA concentration was associated with seasonal drought, suggesting that the higher ABA concentrations in the drier second season of experimentation may have masked the heating effect on anthocyanin accumulation. While perception of heat (expression of heat shock factor HsfA2) by the berries was found to occur as quickly as 4 hours after heating, changes in berry composition and the expression of genes and transcription factors regulating malic acid and anthocyanins took two or more days to respond in a manner that was mostly in proportion to the concentrations observed. The study illustrates that hot periods, with daily maximum temperatures up to 40 °C over periods of time (7 days), may have direct impacts on the ripening of Pinot noir grapes, reducing organic acid and anthocyanins.

Research to date has focused on understanding the hormonal and genetic factors regulating the transition from physiologically mature to ripe fruit. Knowledge of factors regulating the time from anthesis to fruit maturity, where the seed coat turns black and fruit becomes competent to ripen, is limited. Accumulations of nonstructural carbohydrates, organic acids, and phytohormones were profiled during fruit development of two kiwiberry (Actinidia arguta) genotypes with contrasting maturation times over two seasons. Seed maturation and rise in nonstructural carbohydrates were associated with salicylic acid (SA), abscisic acid, and their metabolites in fruit of the "Early" but not the "Late" maturing genotype. As identification of dynamic gene-metabolite interactions over time is challenging, three data integration frameworks (TimeOmics, MOFA, and MINT) were used to interrogate "omics" data and found to be complementary. SA-associated genes related to plant defense and immunity were identified as having a novel function in kiwiberry development, by promoting fruit maturation.

Drought stress and yield loss in crops will become more common due to climate change. Starch turnover is one mechanism plants use to mitigate drought stress and has been studied in leaves of various plant species. We compared the effect of drought treatment on starch turnover in flowers and leaves of tomato, a model plant and major crop. Applying a prolonged high drought treatment to tomato plants led to a significant reduction in plant growth and increased flower abortion, with a large reduction in starch concentrations in flower pistils (60 %) and mature leaves (75 %), but not sucrose. However, genes from the starch degradation pathway were not induced. SIBAM3.2 and SlBAM9 were down-regulated in pistils and young leaves. In contrast, SIBAM3.1 was significantly down-regulated in mature leaves, suggesting a different starch degradation response between source and sink tissues. SlESV1, encoding for a protein involved in restricting starch degradation, was also significantly down-regulated in pistils. To explore carbon changes during flower development and put drought stress into context, we investigated metabolite and transcriptional variations in all flower tissues from control plants. In pistils, starch concentrations were lower than in other floral tissues and lower than sucrose in pistils. Transcriptional profiles showed SlBAM3.2 and SlBAM9 were up-regulated and SlESV1 was down-regulated during pistil development. From this we concluded that lower starch concentrations in drought treated pistils were caused by decreased SIESV1 transcription allowing higher starch degradation rates, and that pistil starch turnover is critical for flowering success, fruit development and yield serving as a buffer to maintain stable sucrose concentrations during drought.

Carbohydrate levels are important regulators of the growth and yield of tree crops. Current methods for measuring foliar carbohydrate concentrations are time consuming and laborious, but rapid imaging technologies have emerged with the potential to improve the effectiveness of tree nutrient management. Carbohydrate concentrations were predicted using hyperspectral imaging (400–1000 nm) of leaves of the evergreen tree crops, avocado, and macadamia. Models were developed using partial least squares regression (PLSR) and artificial neural network (ANN) algorithms to predict carbohydrate concentrations. PLSR models had R2 values of 0.51, 0.82, 0.86, and 0.85, and ANN models had R2 values of 0.83, 0.83, 0.78, and 0.86, in predicting starch, sucrose, glucose, and fructose concentrations, respectively, in avocado leaves. PLSR models had R2 values of 0.60, 0.64, 0.91, and 0.95, and ANN models had R2 values of 0.67, 0.82, 0.98, and 0.98, in predicting the same concentrations, respectively, in macadamia leaves. ANN only outperformed PLSR when predicting starch concentrations in avocado leaves and sucrose concentrations in macadamia leaves. Performance differences were possibly associated with nonlinear relationships between carbohydrate concentrations and reflectance values. This study demonstrates that PLSR and ANN models perform well in predicting carbohydrate concentrations in evergreen tree-crop leaves.

Avocado fruits are considered unusual because of the large amounts of oil and seven-carbon (7-C) carbohydrates (mannoheptulose and perseitol) in the fruit’s flesh and skin. The fruit may be held on the tree unripe until required for marketing, and in some producing regions, this may extend past the next flowering period. This prolonged period on the tree is associated with increased oil content and decreased 7-C carbohydrates. There has been relatively less research into soluble hexose sugars and starch. In this research, the inter-relationships between fruit maturation, storage, and ripening have been investigated for both 7-C and six-carbon non-structural carbohydrates using ‘Hass’ fruit harvested from the same trees between 11 and 14 months after flowering. Significant differences were identified in both fruit flesh and skin for most compounds, affected by maturity, storage, and ripening. It is concluded that the non-structural carbohydrate composition of ‘Hass’ fruit is variable, with significant changes occurring associated with maturation, storage, and ripening. The compositions of the flesh and skin tissues are not consistently proportionate. Maturation provides the initial baseline composition from which any further change through storage or ripening can occur. The changes with maturation appear to be associated with the tree’s phenology, with tree-to-tree differences in the timing or degree of change.

Fruit quality is dependent on various factors including flavour, texture and colour. These factors are determined by the ripening process, either climacteric or non-climacteric. In grape berry, which is non-climacteric, the process is signalled by a complex set of hormone changes. Abscisic acid (ABA) is one of the key hormones involved in ripening, while sugar availability also plays a significant role in certain ripening aspects such as anthocyanin production. To understand the relative influence of hormone and sugar signalling in situ can prove problematic due to the physiological and environmental (abiotic and biotic) factors at play in vineyards. Here we report on the use of in vitro detached berry culture to investigate the comparative significance of ABA and sugar in the regulation of Pinot noir berry anthocyanin production under controlled conditions. Using a factorial experimental design, pre-véraison berries were cultured on media with various concentrations of sucrose and ABA. After 15 days of in vitro culture, the berries were analysed for changes in metabolites, hormones and gene expression. Results illustrated a stimulatory effect of sucrose and ABA on enhancing berry colour and a corresponding increase in anthocyanins. Increased ABA concentration was able to boost anthocyanin production in berries when sucrose supply was low. The sucrose and ABA effects on berry anthocyanins were primarily manifested through the up-regulation of transcription factors and other genes in the phenylpropanoid pathway, while in other parts of the pathway a down-regulation of key proanthocyanindin transcription factors and genes corresponded to sharp reduction in berry proanthocyanidins, irrespective of sucrose supply. Similarly, increased ABA was correlated with a significant reduction in berry malic acid and associated regulatory genes. These findings suggest a predominance of berry ABA over berry sugar in coordinating the physiological and genetic regulation of anthocyanins and proanthocyanins in Pinot noir grape berries.

Metabolite changes are often used to better understand the effects of experimental treatments on the physiological and metabolic processes of horticultural crops. Shade and time of day are both factors that affect the concentrations of metabolites, in particular carbohydrates. In this study we investigated the effect of reduced light on the diurnal cycling of metabolites by application of 50% shade cloth to whole vines of 'Zesy002' kiwifruit over a 28-h period. Diurnal patterns of the metabolites were also measured for a 32-h period, starting 5 h prior to the application of the shade cloth. The effects of shading on the photosynthetic rate, starch, total soluble carbohydrate and phytohormones were determined in the youngest mature leaves of shaded and non-shaded vines. Non-shaded leaves accumulated more sucrose and salicylic acid than the shaded leaves between sunrise and mid-morning; however, there were no significant differences found in the photosynthetic rate, starch, cytokinins and other stress hormone concentrations between the two treatments over the 24-h period of shading. Photosynthetic rate, starch, total soluble carbohydrates and several stress response and growth regulation phytohormones showed diurnal patterns over the 32-h period. These diurnal fluctuations in the concentration of metabolites need to be considered when sampling tissues for the assessment of metabolite processes in kiwifruit.

As agricultural intensification affects global environmental change, a redesign of our food production systems towards practices that replace external inputs with inbuilt ecosystem services is needed. Specifically, human-induced changes to biogeochemical flows of nitrogen (N) cycling exceed the proposed planetary boundaries, highlighting a priority area for reducing nutrient inputs in agricultural production systems. A new understanding of nutrient interactions in the complete agroecosystem will allow us to better predict and mitigate the consequences of anthropogenic environmental changes compared with a reductionist approach. Here, we review for the first time system-level nutrient interactions, particularly N, in perennial horticulture using high-producing kiwifruit and apple crops grown in New Zealand as a basis to identify critical knowledge gaps and prioritize new research. The major points identified are (1) current nutrient guidelines are from the 1980s to the early 2000s and do not take into account substantial production changes since that time; (2) few studies construct complete nutrient budgets of all sources and losses; (3) nutrient loss estimates are generally low relative to those from other agricultural land uses; (4) there is a lack of studies which address nutrient interactions between above- and below-ground food webs in perennial horticultural crops; (5) there is contradictory literature where fertilizer has been found both to increase and to decrease plant chemical signaling and defense mechanisms. New tools are emerging to improve orchard nutrient management, including advances in fertilizer application techniques, new methods to monitor plant and soil nutrients, and utilizing genetic variability to breed cultivars with improved nutrient use efficiency. To reduce adverse nutrient effects on the environment, new research is needed, addressing the relationships between carbon and nutrients and nutrient demands in modern fruit cultivars and growing systems; the nutrient balance for perennial horticultural crops considering all inputs and outputs; and interactions of the above- and below-ground nutrient flows in orchard food webs.

Bilberry (Vaccinium myrtillus) is a commercially important wild berry species, which accumulates high amounts of polyphenols, particularly anthocyanins, in the skin and flesh. Whilst a number of studies have quantified these phytochemicals in intact ripe bilberry fruit, we extend the current knowledge by investigating the spatial distribution of anthocyanin-associated polyphenols in fruit tissue, and study their links with primary metabolism during ripening. To address this, we used LC-MS and mass spectrometry imaging to measure and map primary and secondary metabolites in fruit. Correlation analysis showed that five sugars displayed strong positive correlations with anthocyanin accumulation, whereas all amino acids were negatively correlated. The accumulation patterns of polyphenols correlated in fruit skin and flesh, but altered with development. Finally, spatial segmentation analysis revealed that the chemical signatures of ripening first appear at defined regions under the skin and rapidly expand to encompass the entire fruit at the eating-ripe stage.

This work aims to understand how Vitis vinifera (Chardonnay) vines prioritise the export and distribution of recently fixed photoassimilate between root tissue, fruit, and defence, following the elicitation of a defence response. Jasmonic acid (JA) and its methyl ester, MeJA, are endogenous plant hormones, known collectively as jasmonates, that have signalling roles in plant defence and consequently are often used to prime plant defence systems. Here, we use exogenous jasmonate application to mature source leaves of Chardonnay grapevines to elucidate the prioritisation strategy of carbon allocation between plant defence and growth. Our results demonstrate that jasmonate application to Chardonnay leaves can elicit a defence response to Botrytis cinerea, but the effect was localised to the jasmonate-treated area. We found no evidence of a systemic defence response in non-treated mature leaves or young growing tissue. JA application reduced the photosynthetic rate of the treated leaf and reduced the export rate of recently fixed carbon-11 from the leaf. Following JA application, a greater proportion of available recently fixed carbon was allocated to the roots, suggesting an increase in sink strength of the roots. Relative sink strength of the berries did not change; however, an increase in berry sugar was observed seven days after JA treatment. We conclude that the data provide evidence for a "high sugar resistance" model in the mature treated leaves of the vine, since the export of carbon was reduced to ensure an elevated defence response in the treated leaf. The increase in berry sugar concentration seven days after treatment can be explained by the initial prioritisation of a greater portion of the exported carbon to storage in the roots, making it available for remobilisation to the berries once the challenge to defence had passed.

Plant metabolomics within field-based food production systems is challenging owing to environmental variability and the complex architecture and metabolic growth cycles of plants. Kiwifruit cultivars of Actinidia chinensis are vigorous perennial vines grown as clones in highly structured orchard environments, intensively managed to maximize fruit yield and quality. To understand the metabolic responses of vines to orchard management practices, we needed to better understand the various sources of metabolic variability encountered in the orchard. Triplicate composite leaf, internode and fruit (mature and immature) samples were collected from each of six Actinidia chinensis var. deliciosa 'Hayward' and A. chinensis var. chinensis 'Zesy002' kiwifruit vines at three times during the growing season and measured by LC-MS. In general, there was more variation in metabolite concentrations within vines than between vines, with 'Hayward' showing a greater percentage of within-vine variability than 'Zesy002' (c. 90 vs. 70% respectively). In specific tissues, the sampler, infection by Pseudomonas syringae var. actinidiae and the rootstock also influenced metabolite variability. A similar pattern of metabolic variability was observed from quantitative analysis of specific carbohydrates and phytohormones. High within-vine metabolic variability indicates that it is more important to obtain sufficient replicate samples than to sample from multiple vines. These data provide an objective basis for optimizing metabolite sampling strategies within kiwifruit orchards.

The commonly accepted kiwifruit harvest index based solely on soluble solids content (SSC) has lost its original significance owing to the increased sophistication of marketing coupled with the commercialisation of new cultivars, many with yellow flesh when ripe. The precision of novel harvest indices may be improved by a molecular understanding of fruit maturation changes in commonly monitored fruit attributes, including SSC, flesh colour and firmness. Transcriptional changes in the early-maturing Actinidia chinensis var. chinensis ‘Zesy002’ and later maturing A. chinensis var. deliciosa ‘Hayward’, grown at a single site, have been quantified weekly in the period leading up to and past the commercial harvest period. Transcriptomic data highlighted numerous maturation related changes in the fruit, and differences between the two cultivars. Examples of gene changes of relevance for non-structural carbohydrates included the large sub-unit 4 of ADP-glucose pyrophosphorylase (APL4) indicative of starch synthesis, BETA AMYLASE 3.2 (BAM3.2) for starch breakdown and the sugar transporter (SWEET9a). The association between STAYGREEN2 (SGR2) with flesh degreening was strong in ‘Zesy002’, although a later increase in ‘Hayward’ to levels similar to those in ‘Zesy002’ was not accompanied by an equivalent flesh colour change. In ‘Zesy002’ there were numerous individual cell wall gene changes associated with the change to rapid softening, including EXPANSIN7 (EXP7), POLYGALACTURONASE1 (PG1), PECTATE LYASE (PL), PECTIN METHYL ESTERASE (PME) and XYLOGLUCAN TRANSGLYCOSYLASE/ HYDROLASE (XTH). However, among these genes, it is possible to see similar changes in ‘Hayward’ which were not associated with a marked change in softening rate, including for EXP7 and PG1. The most obvious start points for changes in transcription of these genes were the seed coat colour change, the cessation of growth, and the change to ripening (rapid softening and starch breakdown). The findings are discussed with respect to fruit maturation and the possible use of gene markers as harvest indices.

Consumer acceptance of fruit is determined by size, flavour and ripeness. In this study we investigated how altering the carbohydrate supply to Actinidia chinensis var. chinensis 'Zesy002' kiwifruit altered the balance between growth and accumulation of metabolites. Canes were phloem girdled and fruit thinned to a leaf-to-fruit ratio (L:F) of either 2 (Low carbohydrate) or 6 (High carbohydrate) at either 38 (Early) or 86 (Late) days after anthesis (DAA) and compared with ungirdled control canes with a L:F of 3. Fruit growth, metabolite accumulation, cytokinin concentrations and maturation were monitored and the sensory attributes of ripe fruit were assessed. The final weight of Early-High and Late-High carbohydrate fruit was 38% and 16% greater compared with control fruit. High carbohydrate fruit had increased starch, soluble sugar and cytokinin concentrations and fruit began to mature earlier and those with a Low carbohydrate had decreased concentrations and matured later compared with control fruit. Control fruit were described by consumers as more acidic and under-ripe compared with those from Early-High carbohydrate canes, but as sweeter than those from Low carbohydrate canes. This study showed that carbohydrate supply can have a major impact on the growth, sugar accumulation and maturity of 'Zesy002' fruit sinks.

Previous studies have shown the conversion of the perennial kiwifruit (Actinidia spp.) to continuously flowering allows rapid cycling of generations. These plants are smaller, flower earlier and do not undergo dormancy. They provide a model system to rapidly test gene function in flowers and fruit, and allows for continuous production of fruit rather than seasonal production. In this study, the fruit of continuously flowering, CENTRORADIALIS (CEN) gene-edited, yellow-fleshed 'Hort16A' kiwifruit lines were assessed for a range of fruit quality characters. The fruit were smaller and often misshapen, but maturation and ripening occurred on a similar timeline to those of orchard-grown fruit. A single edited CEN line with balanced vegetative-floral production and fruit maturation was selected to assess the effects of growing conditions on fruit maturation and ripening. By lowering the temperature of the plants during maturation, starch breakdown and fruit softening were induced and degreening slowed. This result shows that despite the gene-edited plants flowering continuously and not experiencing a period of winter dormancy, the fruit they produce can complete a full cycle of development and ripening, and these fruit may be manipulated in a predictable manner through temperature within the controlled growing environment.

Following cell division, fruit growth is characterized by both expansion through increases in cell volume and biomass accumulation in cells. Fruit growth is limited by carbon starvation; however, the mechanism controlling fruit growth under restricted carbohydrate supply is poorly understood. In a previous study using red-fleshed kiwifruit, we showed that long-term carbon starvation had detrimental effects on carbohydrate, anthocyanin metabolism, and fruit growth. To elucidate the mechanisms underlying the reduction in fruit growth during kiwifruit development, we integrated phytohormone profiling with transcriptomic and developmental datasets for fruit under high or low carbohydrate supplies. Phytohormone profiling of the outer pericarp tissue of kiwifruit showed a 6-fold reduction in total cytokinin concentrations in carbon-starved fruit, whilst other hormones were less affected. Principal component analysis visualised that cytokinin composition was distinct between fruit at 16 weeks after mid bloom, based on their carbohydrate supply status. Cytokinin biosynthetic genes (IPT, CYP735A) were significantly downregulated under carbon starvation, in agreement with the metabolite data. Several genes that code for expansins, proteins involved in cell wall loosening, were also downregulated under carbon starvation. In contrast to other fleshy fruits, our results suggest that cytokinins not only promote cell division, but also drive fruit cell expansion and growth in kiwifruit.

New Zealand and French stone fruit industries desire new long-storing, sweet-tasting apricot cultivars. The climacteric nature of apricots (a high ethylene production that stimulates softening via cell wall degradation) shortens their storage life. Breeders in France (FR) and New Zealand (NZ) have some apricot populations producing fruit with unusually low climacteric behavior and with a large range of total soluble solids (TSS). Trials in FR and NZ shared the same research protocols, for optimal comparison and verification. Up to 60 genotypes representative of fruit diversity in each country were studied in June-July 2016 in FR and January-February 2017 in NZ, with four cultivars in common. For each genotype, six fruits, selected according to firmness, were characterized for fruit quality traits on the day of harvest. Measurements were intact fruit: compression firmness, near infrared spectroscopy (NIRS), ethylene production, skin color, and penetrometer; and fruit tissue samples: TSS, titratable acidity (TA), and individual sugar and organic acid contents. A large diversity was observed for firmness, from 4 to 55 N in NZ and 1 to 36 N in FR. Ethylene production ranged from 0 to 740 nmol h(-1) kg(-1) in NZ and 0 to 4257 nmol h(-1) kg(-1) in FR, and discriminated between known lowand high-ethylene cultivars. Conversely, the variability was larger in NZ than in FR for biochemical content: TSS ranged from 8 to 24 degrees Brix in NZ and 10 to 22 degrees Brix in FR and TA from 85 to 514 meq kg(-1) in NZ and 24 to 350 meq kg(-1) in FR. NIRS has the ability to discriminate across countries. The fruit genetic variability opens new opportunities for breeding programs.

International markets are increasingly demanding fruit with high visual, taste and textural appeal. High sensory appeal of fruit products is widely recognized to result in repeat purchasing by the consumer, and premium returns to the producer. Hence, precision management of canopies is increasingly being implemented in modern orchard systems in New Zealand to reduce variable fruit quality in the supply chain. In a study using four commercial apple cultivars: 'Braeburn', 'Royal Gala', 'Scilate', and 'Scifresh', increases in fruit total non-structural carbohydrate concentration and fruit dry matter concentration were of the greatest magnitude 30-85 days after anthesis, but did not greatly change from day 85 until commercial harvest. By 50 days after anthesis, fruit instrumental firmness for each cultivar was similar to 4 to 5 kg f, declining to similar to 2 to 2.5 kg f by commercial harvest. Fruit dry matter concentration ( i.e., taste potential) and flesh firmness (i.e., textural potential) at harvest appeared to be influenced in early fruit development. We discuss how both fruit yield and quality can be increased further in modern orchard systems through management practices (pruning and crop loading) and decisions (orchard and training system design) that work with the underlying physiology of trees to maximise early season fruit development.