Perennial Fruit Crops Research Articles

Assessment of irrigation situation and water requirement in perennial fruit crops in Dinh Quan district, Dong Nai province

Dinh Quan is a mountainous agricultural district in Dong Nai province, focusing on agricultural development. Estimating reference and current crop evapotranspiration, as well as irrigation water requirements, is an essential foundation for effective irrigation planning for some perennial fruit crops (mandarin, banana, and mango) to manage water resources in a reasonable and sustainable way. Applying the FAO Penman-Monteith equation combined with the CROPWAT model, reference crop evapotranspiration (ETo), current crop evapotranspiration (ETc), and irrigation water requirement (IWR) of some perennial fruit crops being cultivated mainly in Dinh Quan district (banana, mandarin, and mango) were estimated. The total amount of water required for irrigation in the year of mandarin, mango, and banana trees in the study area was determined to be 592.6 mm, 473.0 mm, and 976.4 mm, respectively, corresponding to 5,926 m3/ha, 4,730 m3/ha and 9,764 m3/ha. Based on this result, the annual irrigation water requirement of the study area was calculated to be around 46 million m3 for the cultivation of mango, banana, and mandarin, mainly in the dry season (accounting for more than 95%). With current farming practices and using water resources, if there are no effective management measures and solutions, it may lead to a shortage of water for future production, especially in the dry season.

Productivity, soil fertility and economic indicators in Centella asiatica L. production systems in semi-arid India

Centella asiatica L. urban is one of the highly traded medicinal crops in the global market and it is collected mainly from wild sources/forests. The scope for commercial cultivation of elite genotypes of C. asiatica at different nutrient levels was assessed based on resource use and economic indicators in open-field and 50% shade in India during 2016–2019. The cumulative productivity in terms of fresh biomass was significantly influenced by genotypes and nutrient levels both in open-field and 50% shade. The genotype Arka Divya genotype was superior in terms of cumulative productivity per ha (38.5 t in open-field and 33.9 t in 50% shade). Application of farmyard manure (FYM) 5 t + 125 kg nitrogen (N) through FYM registered higher cumulative yield in open (32.2 t ha−1) and 50% shade (33.1 t ha−1). The production systems in open and 50% shade maintained optimum to above optimum soil fertility and plant nutrient profile. The net return per rupee investment was higher in Arka Divya genotype at different nutrient levels in open-field (2.61–3.69) as well as 50% shade conditions (1.38–1.96). Integrated application of recommended dose of major nutrients and FYM registered higher net return per rupee investment both in open-field (3.69) and 50% shade (1.96). The elite genotypes of C. asiatica can be grown profitably in open-field or 50% shade with provision of optimum nutrition. Alternatively it can be grown as intercrop in perennial fruit or plantation crops with provision of irrigation to reduce production cost.

Winter warming stimulates vegetative growth and alters fruit quality of blackcurrant (Ribes nigrum).

The rate of global warming varies in magnitude between seasons, with warming being more pronounced in winter and spring than in summer and autumn at high latitudes. Winter warming can have profound effects on dormancy release and spring phenology of perennial fruit crops, but potential follow-on impacts on growth, fruit yield or quality have only rarely been investigated. We studied the effects of mild winter warming on spring phenology, current year shoot growth, cropping performance and fruit quality in four field-grown cultivars of blackcurrant with different chilling requirements. Plants were exposed to ambient or slightly elevated (+ 0.5°C) temperatures from early October to mid-April the following year. Winter warming had few effects on spring phenology and fruit yield, but caused significant changes in berry contents of phenolic compounds and a reduction in soluble sugars. Increased vegetative growth of warmed plants likely accounts for the changes in berry quality. The results demonstrate a persistent effect of winter warming on shoot growth, which indirectly changes fruit quality.

Insight into Carbohydrate Metabolism and Signaling in Grapevine Buds during Dormancy Progression.

Perennial fruit crops enter dormancy to ensure bud tissue survival during winter. However, a faster phenological advancement caused by global warming exposes bud tissue to a higher risk of spring frost damage. Tissue dehydration and soluble sugars accumulation are connected to freezing tolerance, but non-structural carbohydrates also act as metabolic substrates and signaling molecules. A deepened understanding of sugar metabolism in the context of winter freezing resistance is required to gain insight into adaptive possibilities to cope with climate changes. In this study, the soluble sugar content was measured in a cold-tolerant grapevine hybrid throughout the winter season. Moreover, the expression of drought-responsive hexose transporters VvHT1 and VvHT5, raffinose synthase VvRS and grapevine ABA-, Stress- and Ripening protein VvMSA was analyzed. The general increase in sugars in December and January suggests that they can participate in protecting bud tissues against low temperatures. The modulation of VvHT5, VvINV and VvRS appeared consistent with the availability of the different sugar species; challenging results were obtained for VvHT1 and VvMSA, suggesting interesting hypotheses about their role in the sugar–hormone crosstalk. The multifaceted role of sugars on the intricate phenomenon, which is the response of dormant buds to changing temperature, is discussed.

Influence of Climate Change on Metabolism and Biological Characteristics in Perennial Woody Fruit Crops in the Mediterranean Environment

The changes in the state of the climate have a high impact on perennial fruit crops thus threatening food availability. Indeed, climatic factors affect several plant aspects, such as phenological stages, physiological processes, disease-pest frequency, yield, and qualitative composition of the plant tissues and derived products. To mitigate the effects of climatic parameters variability, plants implement several strategies of defense, by changing phenological trends, altering physiology, increasing carbon sequestration, and metabolites synthesis. This review was divided into two sections. The first provides data on climate change in the last years and a general consideration on their impact, mitigation, and resilience in the production of food crops. The second section reviews the consequences of climate change on the industry of two woody fruit crops models (evergreen and deciduous trees). The research focused on, citrus, olive, and loquat as evergreen trees examples; while grape, apple, pear, cherry, apricot, almond, peach, kiwi, fig, and persimmon as deciduous species. Perennial fruit crops originated by a complex of decisions valuable in a long period and involving economic and technical problems that farmers may quickly change in the case of annual crops. However, the low flexibility of woody crops is balanced by resilience in the long-life cycle.

Natural Variation in the Control of Flowering and Shoot Architecture in Diploid Fragaria Species.

In perennial fruit and berry crops of the Rosaceae family, flower initiation occurs in late summer or autumn after downregulation of a strong repressor TERMINAL FLOWER1 (TFL1), and flowering and fruiting takes place the following growing season. Rosaceous fruit trees typically form two types of axillary shoots, short flower-bearing shoots called spurs and long shoots that are, respectively, analogous to branch crowns and stolons in strawberry. However, regulation of flowering and shoot architecture differs between species, and environmental and endogenous controlling mechanisms have just started to emerge. In woodland strawberry (Fragaria vesca L.), long days maintain vegetative meristems and promote stolon formation by activating TFL1 and GIBBERELLIN 20-OXIDASE4 (GA20ox4), respectively, while silencing of these factors by short days and cool temperatures induces flowering and branch crown formation. We characterized flowering responses of 14 accessions of seven diploid Fragaria species native to diverse habitats in the northern hemisphere and selected two species with contrasting environmental responses, Fragaria bucharica Losinsk. and Fragaria nilgerrensis Schlecht. ex J. Gay for detailed studies together with Fragaria vesca. Similar to F. vesca, short days at 18°C promoted flowering in F. bucharica, and the species was induced to flower regardless of photoperiod at 11°C after silencing of TFL1. F. nilgerrensis maintained higher TFL1 expression level and likely required cooler temperatures or longer exposure to inductive treatments to flower. We also found that high expression of GA20ox4 was associated with stolon formation in all three species, and its downregulation by short days and cool temperature coincided with branch crown formation in F. vesca and F. nilgerrensis, although the latter did not flower. F. bucharica, in contrast, rarely formed branch crowns, regardless of flowering or GA20ox4 expression level. Our findings highlighted diploid Fragaria species as rich sources of genetic variation controlling flowering and plant architecture, with potential applications in breeding of Rosaceous crops.

Thinning Methods to Regulate Sweet Cherry Crops—A Review

In perennial fruit crops, bearing can be influenced by various factors, including environmental conditions, germplasm, rootstocks, and cultivation methods. Cherries, one of the most important and popular fruit species from the temperate climate zone, achieve high prices on the market. New agricultural technologies and environmental factors force a change in the approach to cherry cultivation. Old-type cherry orchards, with their high demand for water, nutrients, and manual work, are replaced by orchards of self-pollinating cherry cultivars grown on dwarf rootstocks. These changes make it necessary to search for ways to regulate fruiting, in particular to thin buds, flower, and fruit. In light of environmental regulations and consumer pressure, thinning methods are being sought that either do not involve the use of chemicals or that use eco-friendly chemical agents. This review examines recent progress in understanding the effect of thinning methods on the physiology, tree growth, and fruit quality of cherries; discusses horticultural practices aimed to ensure regular cropping and their influence on fruit quality; and provides suggestions for future research.

Breeding an underutilized fruit crop: a long-term program for Hylocereus.

This review describes three decades of introduction, agro-technology development, breeding and selection of Hylocereus species, known as pitaya or dragon fruit, as an example of a holistic program aimed to develop the horticultural potential of a perennial underutilized fruit crop. Interspecific homoploid and interploid crosses and embryo rescue procedures produced improved hybrids, some of which have been released to farmers. Molecular tools and morphological and phenological comparisons between the parental species and the resulting hybrids provided valuable information on dominant/recessive traits and on genetic relationships that could be exploited for further hybridizations. In addition, Hylocereus were crossed with species of the closely related genus Selenicereus, producing valuable intergeneric hybrids. In situ chromosome doubling resulted in the production of autopolyploid lines, from which an understanding of the effect of increased ploidy on fruit traits and metabolomic profiles was obtained. Gamete-derived lines were produced, adding to our biobank homozygote lines that were subsequently used for further hybridization. Spontaneous chromosome doubling occurred in haploid gamete-derived Hylocereus monacanthus lines and in interspecific interploid Hylocereus megalanthus × H. undatus hybrids obtained from an embryo rescue procedure, resulting in plants with double the expected ploidy. Challenging technical problems were addressed by the development of protocols for DNA isolation, flow cytometry, in situ chromosome doubling, androgenesis, gynogenesis and embryo rescue following interspecific and interploidy crosses. Current research leading to the development of genomics and molecular tools, including a draft genome of H. undatus, is also presented. Perspectives for further development of Hylocereus species and hybrids are discussed.

Development of LR-PCA Based Fusion Approach to Detect the Changes in Mango Fruit Crop by Using Landsat 8 OLI Images

Change detection (CD) is the process of detecting changes from multi-temporal satellite images that have undergone spatial changes due to natural phenomena and/or human-induced activities. Mango is a major fruit crop in India, but detection of changes in mango crops remains a challenging task because the reason that many perennial crops have similar reflectance profiles. Therefore, a potent change detection technique is required for different applications such as the rate of deforestation, urban developments, damage evaluation, and resource monitoring. Compared to annual and seasonal crops, relatively few studies have been conducted on change detection in perennial fruit crops. In this study, a novel change detection technique (i.e., LR-PCA) is developed using the fusion of log-ratio (LR) and principal component analysis (PCA) images derived from bi-temporal soil adjusted vegetation index (SAVI) images to extract meaningful information and detect temporal changes in the mango fruit crop areas with high change detection accuracy. The proposed approach comprised two steps: (1) SAVI images from 2015 and 2019 were used to retrieve the log-ratio (LR) and principal component (PC) images, respectively, and both the images were fused by applying the pixel-by-pixel fusion approach. (2) Fused images were classified into three classes: “positive change”, “no change”, and “negative change” using a derived threshold value. The results show that the LR-PCA method of change detection yields a high change detection accuracy of 92% in comparison with the other change detection methods viz. vegetation image differencing, image ratioing, PCA, and log-ratio. To validate the adaptability of the proposed algorithm, experiments with two sets of bi-temporal SAVI indices images belonging to the Sitapur district of Uttar Pradesh State determine that the proposed change detection method performs well as compared to the existing individual methods for detection of changes in mango fruit crop. The proposed method is expected to be useful for detecting changes in the area of perennial crops. In the future, an accurate and efficient change detection analysis may be helpful for developing a real-time mango fruit crop monitoring system at the national level.

Comprehensive study of Malus genus resources for the creation of adaptive grades

The breeding renewal of the apple assortment in the conditions of southern fruit growing in Russia on the basis of domestic achievements is due to the acceleration of the breeding process associated with an in-depth study of the existing gene pool of culture, the widespread use of the samples most valuable in terms of the quality of the products obtained to create commercially demanded grades of regional breeding. The aim of the study is to isolate, on the basis of a long-term comprehensive study in the conditions of the Western Ciscaucasia, valuable specimens of the genusMalusto enhance the efficiency and accelerate the process of creating adaptive and high-quality grades of regional breeding. The work was carried out using generally accepted and modern programs and methods of variety study and selection of perennial fruit crops (apple trees). The long-term results of the study for 2010-2020 are summarized. in the conditions of the Kuban zone of the North Caucasian region of gardening of collection specimens of apple trees. Established that the increase in high-temperature stressors, the deficit in August of precipitation (28.2 mm) in recent years (2010-2020) has a negative impact on the growth, development and ripening of fruits, the laying of generative buds of the next year’s harvest. The weather conditions that have developed in the region, which are not sufficiently favorable for apple plants, make it possible to select drought-resistant, high-yielding, stably fruiting grades with commercially valuable fruits. Highlighted with high productivity potential diploids: 12/1-21-60, 12/2-20-22, 12/2-20-75 and triploids: 12/2-21-35, 12/2-20-56 (average yield 28.06-34.08 t/ha; total – up to 374.88 t/ha). Diploids were distinguished by large-fruited: Orpheus and 12/1-21-60 (average fruit weight 202.3-204.5 g, maximum – 224.8-278.8 g) and triploid varieties and elite forms (from the family of Idared × Balcgard 0247E): 12/2-21-35, 12/2-20-56, 12/1-21-27 (average fruit weight 201.4-317.9 g, maximum – 286.5-387.2 g).

Detection and Characterization of Stressed Sweet Cherry Tissues Using Machine Learning

Recent technological developments in the primary sector and machine learning algorithms allow the combined application of many promising solutions in precision agriculture. For example, the YOLOv5 (You Only Look Once) and ResNet Deep Learning architecture provide high-precision real-time identifications of objects. The advent of datasets from different perspectives provides multiple benefits, such as spheric view of objects, increased information, and inference results from multiple objects detection per image. However, it also raises crucial obstacles such as total identifications (ground truths) and processing concerns that can lead to devastating consequences, including false-positive detections with other erroneous conclusions or even the inability to extract results. This paper introduces experimental results from the machine learning algorithm (Yolov5) on a novel dataset based on perennial fruit crops, such as sweet cherries, aiming to enhance precision agriculture resiliency. Detection is oriented on two points of interest: (a) Infected leaves and (b) Infected branches. It is noteworthy that infected leaves or branches indicate stress, which may be due to either a stress/disease (e.g., Armillaria for sweet cherries trees, etc.) or other factors (e.g., water shortage, etc). Correspondingly, the foliage of a tree shows symptoms, while this indicates the stages of the disease.

Purification of Total RNAs and Small RNAs from Fruit Tree Leaf Tissues.

Perennial fruit crops are susceptible to many viral pathogens, which often lead to declines in quality and yield. For the production of good quality and virus-free propagation materials, conventional molecular detection methods combining high throughput sequencing technology have been widely applied to virus detection and discovery in fruit trees. Recovery of high-quality RNAs from fruit tree leaf tissues, the critical step for the subsequent molecular analysis, is often complicated by the presence of high levels of RNases and problematic biomolecules. Therefore, the universal extraction methods often require modification according to different properties of various tissues. In this chapter, we provide a set of methods that have been used successfully to isolate total RNAs and small RNAs from various fruit tree leaf tissues and as examples, presented in detail of a modified TRIzol method for total RNAs purification from mulberry (Morus alba L.) leaf tissues and an alternative small RNAs purification protocol using mirVana™ miRNA isolation kit (Ambion/Life Technologies) for some fruit tree leaf tissues. The protocols described here aim to provide examples of what have worked successfully for a range of fruit trees and may be successful for a given sample in the future.

Adoption and perception of cover crop implementation for tropical fruit growers

Cover cropping is a sustainable strategy for increasing soil nutrients and organic matter, and improving overall soil health. This practice is heavily promoted for annual vegetable growers; however, there is less widespread acknowledgement for cover crops as a management strategy in perennial settings. Research is limited in this field, specifically when considering cover cropping for tropical fruit groves. The current study analyzes data from surveys distributed to Miami-Dade County (MDC) tropical fruit producers to quantify their perceptions on incorporating cover crops in their fruit production systems. Two surveys were formulated and distributed virtually to understand farmer familiarity/interest in cover cropping and to uncover factors that impact likelihood of cover crop adoption. Logistic regression analysis of cover crop adoption revealed that having previous experience with cover crops, valuing cover crop importance, perceiving the practice as economically viable, and farm acreage were all positive predictors of cover crop adoption. When questioned about specific tropical leguminous cover crop species, sunn hemp (<i>Crotalaria juncea</i> L.) and velvet bean (<i>Mucuna pruriens</i> [L.] DC), farmers expressed ~5% greater interest in incorporating sunn hemp into their production systems. Quantitative and qualitative data revealed that 90% of surveyed farmers were interested in learning more about cover crops and 85% were likely to attend demonstrative workshops to discern if implementing cover crops would be right for their operation. Overall, the findings suggest that MDC fruit producers are interested in incorporating cover cropping practices with 80% of respondents indicating they would like to improve conservation practices within their production systems. Applying cover crops can potentially improve soil quality and reduce erosion in the MDC agricultural area and in other regions where perennial fruit crop production is prominent. Additionally, implementation of cover cropping as a substitute to reduce usage of synthetic fertilizers has positive implications to decrease nutrient loads in the imperiled ecosystems of Florida Bay and the Everglades.

Additive and synergistic effects of arbuscular mycorrhizal fungi, insect pollination and nutrient availability in a perennial fruit crop

Managing ecosystem services might reduce the dependence of modern agriculture on external inputs and increase the sustainability of agricultural production. Insect pollinators and arbuscular mycorrhizal fungi (AMF) provide vital ecosystem services for crop production, but it has not been tested whether their effects on crop yield interact and how their effects are influenced by nutrient availability. Here we manipulated insect pollination, AMF inoculation and fertilizer application (four levels) in a randomized complete block design with potted raspberry (Rubus idaeus L.) to assess the interacting effects of these variables on crop yield. AMF inoculation increased the per-plant flower number by 33% and the fruit number by 35%, independently from insect pollination and fertilizer application. Single berry weight furthermore increased more strongly with fertilizer application rates in AMF inoculated plants than in non-inoculated plants. As a consequence, AMF inoculation boosted raspberry yield by 43% compared to non-inoculated plants. AMF inoculation increased pollinator visitation rate per plant under intermediate fertilizer levels, suggesting additional indirect effects of AMF inoculation on yield. Fruit yield of pollinated plants increased more strongly with fertilizer application rate than the yield of plants from which pollinators had been excluded. At maximum nutrient availability, the combined benefits of both ecosystem services resulted in a 135% higher yield than that of fertilizer-only treatments. Our results suggest that the benefits of ecosystem services on yield can be additive or synergistic to the effects of conventional management practices. Intensive, high-input farming systems that do not consider the potential adverse effects of management on ecosystem service providing species might risk becoming limited by delivery of ecosystem services. Proactively managing ecosystem services, on the other hand, has the potential to increase crop yield at the same level of external inputs.

Severe Stunting Symptoms upon Nepovirus Infection Are Reminiscent of a Chronic Hypersensitive-like Response in a Perennial Woody Fruit Crop.

Virus infection of plants can result in various degrees of detrimental impacts and disparate symptom types and severities. Although great strides have been made in our understanding of the virus–host interactions in herbaceous model plants, the mechanisms underlying symptom development are poorly understood in perennial fruit crops. Grapevine fanleaf virus (GFLV) causes variable symptoms in most vineyards worldwide. To better understand GFLV-grapevine interactions in relation to symptom development, field and greenhouse trials were conducted with a grapevine genotype that exhibits distinct symptoms in response to a severe and a mild strain of GFLV. After validation of the infection status of the experimental vines by high-throughput sequencing, the transcriptomic and metabolomic profiles in plants infected with the two viral strains were tested and compared by RNA-Seq and LC-MS, respectively, in the differentiating grapevine genotype. In vines infected with the severe GFLV strain, 1023 genes, among which some are implicated in the regulation of the hypersensitive-type response, were specifically deregulated, and a higher accumulation of resveratrol and phytohormones was observed. Interestingly, some experimental vines restricted the virus to the rootstock and remained symptomless. Our results suggest that GFLV induces a strain- and cultivar-specific defense reaction similar to a hypersensitive reaction. This type of defense leads to a severe stunting phenotype in some grapevines, whereas others are resistant. This work is the first evidence of a hypersensitive-like reaction in grapevine during virus infection.

Chromosome-level genome assemblies of five Prunus species and genome-wide association studies for key agronomic traits in peach

Prunus species include many important perennial fruit crops, such as peach, plum, apricot, and related wild species. Here, we report de novo genome assemblies for five species, including the cultivated species peach (Prunus persica), plum (Prunus salicina), and apricot (Prunus armeniaca), and the wild peach species Tibetan peach (Prunus mira) and Chinese wild peach (Prunus davidiana). The genomes ranged from 240 to 276 Mb in size, with contig N50 values of 2.27−8.30 Mb and 25,333−27,826 protein-coding gene models. As the phylogenetic tree shows, plum diverged from its common ancestor with peach, wild peach species, and apricot ~7 million years ago (MYA). We analyzed whole-genome resequencing data of 417 peach accessions, called 3,749,618 high-quality SNPs, 577,154 small indels, 31,800 deletions, duplications, and inversions, and 32,338 insertions, and performed a structural variant-based genome-wide association study (GWAS) of key agricultural traits. From our GWAS data, we identified a locus associated with a fruit shape corresponding to the OVATE transcription factor, where a large inversion event correlates with higher OVATE expression in flat-shaped accessions. Furthermore, a GWAS revealed a NAC transcription factor associated with fruit developmental timing that is linked to a tandem repeat variant and elevated NAC expression in early-ripening accessions. We also identified a locus encoding microRNA172d, where insertion of a transposable element into its promoter was found in double-flower accessions. Thus, our efforts have suggested roles for OVATE, a NAC transcription factor, and microRNA172d in fruit shape, fruit development period, and floral morphology, respectively, that can be connected to traits in other crops, thereby demonstrating the importance of parallel evolution in the diversification of several commercially important domesticated species. In general, these genomic resources will facilitate functional genomics, evolutionary research, and agronomic improvement of these five and other Prunus species. We believe that structural variant-based GWASs can also be used in other plants, animal species, and humans and be combined with deep sequencing GWASs to precisely identify candidate genes and genetic architecture components.

Effect of light on growth and chlorophyll development in kiwifruit ex vitro and in vitro

Light is one of the most important environmental factors that strongly mediates plant physiological and morphological development. Few studies have investigated the effect of light on perennial fruit crops, which have long generation times and are large in size, that complicates the evaluation of plant responses to light in controlled environments. This study assessed the impact of light intensity on chlorophyll (Chl) variation in 41 kiwifruit cultivars during the growing season, and examined the physiological, morphological and gene expression changes of kiwifruit plantlets in vitro under different light qualities treatments, such as white light, red light (RL), blue light (BL) and a mixture of RL and BL with different ratios. The Chl content in 24.4% of kiwifruit varieties increased continuously with increasing sunlight intensity from April to August; but 34.15% of varieties remained unchanged and 41.5% of varieties decreased in July and August when kiwifruit plants were exposed to maximum solar radiation density and duration. The controlling experiment of light qualities showed that blue light was effective for the induction and accumulation of kiwifruit Chl contents and carbon nitrogen ratio (C/N ratio), as well as the numbers of guard cell plastids, whereas red light induced plant vegetative growth and increased starch and sucrose content in leaves. Furthermore, blue light induced higher expression of key genes for Chl biosynthesis than red light. These results indicate that kiwifruit plants exhibit strong morphological plasticity induced by light, and the development of kiwifruit can be induced by culturing the plants in vitro under a combination of BL and RL.

Fruit Set in Avocado: Pollen Limitation, Pollen Load Size, and Selective Fruit Abortion

Avocado is a woody perennial fruit crop originating in Central America and Mexico domesticated and cultivated in the Americas since pre-Columbian times, currently cultivated in subtropical, tropical, and Mediterranean climates worldwide, with increasing importance in international trade. Avocado shows an exuberant flower production that, however, results in a very low fruit set reflected in a massive abscission of flowers and fruitlets. Several factors are involved in this behavior, and, in this work, we have focused on pollination limitation. The results obtained show that pollen deposition takes place at the female and male stages during the avocado flowering season and that the percentage of flowers with pollen on the stigma varies along the flowering season, probably due to changes in temperature that affect not only the floral behavior but also pollinator activity. However, no embryo or endosperm development took place when pollination occurred during the male flowering phase. Thus, the low number of pollen grains landing on the stigmas of female stage flowers observed under natural pollination conditions might not be enough to ensure a good yield. The production of an excess of flowers and subsequent flower drop of most of the flowers provides the opportunity of a selective fruitlet drop depending on the genotype of the embryo since fruits derived from outcrossing showed higher chances of reaching maturity. Moreover, an important competition for resources occurs among developing fruits and new vegetative growth, conferring importance to the time of flower fertilization for effective fruit set.

Simulating organ biomass variability and carbohydrate distribution in perennial fruit crops: a comparison between the common assimilate pool and phloem carbohydrate transport models

AbstractVariability in fruit quality greatly impedes the profitability of an orchard. Modelling can help find the causes of quality variability. However, studies suggest that the common assimilate pool model is inadequate in terms of describing variability in organ biomass. The aim of the current study was to compare the performances of the common assimilate pool and phloem carbohydrate transport models in simulating phloem carbohydrate concentration and organ biomass variability within the whole-plant functional–structural grapevine (Vitis vinifera) model that we developed previously. A statistical approach was developed for calibrating the model with a detailed potted experiment that entails three levels of leaf area per vine during the fruit ripening period. Global sensitivity analysis illustrated that carbohydrate allocation changed with the amount of leaf area as well as the limiting factors for organ biomass development. Under a homogeneous canopy architecture where all grape bunches were equally close to the carbohydrate sources, the common assimilate pool and phloem transport models produced very similar results. However, under a heterogeneous canopy architecture with variable distance between bunches and carbohydrate sources, the coefficient of variation for fruit biomass rose from 0.01 to 0.17 as crop load increased. These results indicate that carbohydrate allocation to fruits is affected by both the size of crop load and fruit distribution, which is not adequately described by the common assimilate pool model. The new grapevine model can also simulate dynamic canopy growth and be adapted to help optimize canopy architecture and quality variability of other perennial fruit crops.

Developing perennial fruit crop models in APSIM Next Generation using grapevine as an example

AbstractA new model for grapevines (Vitis vinifera) is the first perennial fruit crop model using the Agricultural Production System sIMulator (APSIM) Next Generation framework. Modules for phenology, light interception, carbohydrate allocation, yield formation and berry composition were adapted or added into APSIM Next Generation to represent the nature of fruit-bearing vines. The simulated grapevine phenological cycle starts with the dormancy phase triggered by a critical photoperiod in autumn, and then goes through the subsequent phenophases sequentially and finally returns to dormancy for a new cycle. The canopy microclimate module within APSIM Next Generation was extended to allow for row crop light interception. The carbohydrate arbitrator was enhanced to consider both sink strength and sink priority to reflect carbohydrate reserve as a concurrent competing sink. Weather conditions and source–sink ratio at critical developmental stages were used to determine potential grapevine yield components, e.g. bunch number, berry number and berry fresh weight. The model was calibrated and tested extensively using four detailed data sets. The model captured the variations in the timing of measured budburst, flowering and véraison over 15 seasons across New Zealand for five different varieties. The calculated seasonal dynamics of light interception by the row and alley were consistent with field observations. The model also reproduced the dynamics of dry matter and carbohydrate reserve of different organs, and the wide variation in yield components caused by seasonal weather conditions and pruning regimes. The modelling framework developed in this work can also be used for other perennial fruit crops.