Kiwifruit Plants Research Articles

Meloidogyne hapla dominates plant‐parasitic nematode communities associated with kiwifruit orchards in Portugal

AbstractKiwifruit, Actinidia spp., is an important crop worldwide and its cultivation has been increasing in Portugal. Kiwifruit plants are susceptible to plant‐parasitic nematodes (PPNs), including Meloidogyne spp. M. hapla and M. incognita have been reported to affect kiwifruit in major production regions worldwide, although information is lacking on the distribution and identity of PPNs associated with kiwifruit orchards in Portugal. Moreover, research is scarce on the drivers of PPN communities in this crop. Our primary objective was to investigate the diversity, density and distribution of PPNs within kiwifruit orchards of Portugal and to elucidate the influence of environmental factors on their community composition. Additionally, we aimed to evaluate population densities and identity of Meloidogyne spp. Nematodes were extracted from composite soil and root samples collected from orchards. Analysis of soil nematode communities suggested bacterial‐driven decomposition and high nutrient enrichment in these soils. Sixteen different genera of PPNs were detected, with Meloidogyne spp. as the dominant genus, mostly represented by a single species, M. hapla. PPN communities exhibited low richness, and β‐diversity analysis indicated a high degree of similarity among them. Additionally, their composition was significantly influenced by soil and climatic parameters. We found that 37 out of 40 kiwifruit orchards in Portugal were infested by root‐knot nematodes. The unexpectedly low species diversity, dominated by M. hapla, merits further research to establish underlying factors for its high incidence in this crop and to assess the impact of these nematodes on kiwifruit performance and productivity.

Genomes of diverse Actinidia species provide insights into cis-regulatory motifs and genes associated with critical traits

BackgroundKiwifruit, belonging to the genus Actinidia, represents a unique fruit crop characterized by its modern cultivars being genetically diverse and exhibiting remarkable variations in morphological traits and adaptability to harsh environments. However, the genetic mechanisms underlying such morphological diversity remain largely elusive.ResultsWe report the high-quality genomes of five Actinidia species, including Actinidia longicarpa, A. macrosperma, A. polygama, A. reticulata, and A. rufa. Through comparative genomics analyses, we identified three whole genome duplication events shared by the Actinidia genus and uncovered rapidly evolving gene families implicated in the development of characteristic kiwifruit traits, including vitamin C (VC) content and fruit hairiness. A range of structural variations were identified, potentially contributing to the phenotypic diversity in kiwifruit. Notably, phylogenomic analyses revealed 76 cis-regulatory elements within the Actinidia genus, predominantly associated with stress responses, metabolic processes, and development. Among these, five motifs did not exhibit similarity to known plant motifs, suggesting the presence of possible novel cis-regulatory elements in kiwifruit. Construction of a pan-genome encompassing the nine Actinidia species facilitated the identification of gene DTZ79_23g14810 specific to species exhibiting extraordinarily high VC content. Expression of DTZ79_23g14810 is significantly correlated with the dynamics of VC concentration, and its overexpression in the transgenic roots of kiwifruit plants resulted in increased VC content.ConclusionsCollectively, the genomes and pan-genome of diverse Actinidia species not only enhance our understanding of fruit development but also provide a valuable genomic resource for facilitating the genome-based breeding of kiwifruit.

Genome-wide identification of kiwifruit K+ channel Shaker family members and their response to low-K+ stress

Background‘Hongyang’ kiwifruit (Actinidia chinensis cv ‘Hongyang’) is a high-quality variety of A. chinensis with the advantages of high yield, early ripening, and high stress tolerance. Studies have confirmed that the Shaker K+ genes family is involved in plant uptake and distribution of potassium (K+).ResultsTwenty-eight Shaker genes were identified and analyzed from the ‘Hongyang’ kiwifruit (A. chinensis cv ‘Hongyang’) genome. Subcellular localization results showed that more than one-third of the AcShaker genes were on the cell membrane. Phylogenetic analysis indicated that the AcShaker genes were divided into six subfamilies (I-VI). Conservative model, gene structure, and structural domain analyses showed that AcShaker genes of the same subfamily have similar sequence features and structure. The promoter cis-elements of the AcShaker genes were classified into hormone-associated cis-elements and environmentally stress-associated cis-elements. The results of chromosomal localization and duplicated gene analysis demonstrated that AcShaker genes were distributed on 18 chromosomes, and segmental duplication was the prime mode of gene duplication in the AcShaker family. GO enrichment analysis manifested that the ion-conducting pathway of the AcShaker family plays a crucial role in regulating plant growth and development and adversity stress. Compared with the transcriptome data of the control group, all AcShaker genes were expressed under low-K+stress, and the expression differences of three genes (AcShaker15, AcShaker17, and AcShaker22) were highly significant. The qRT-PCR results showed a high correlation with the transcriptome data, which indicated that these three differentially expressed genes could regulate low-K+ stress and reduce K+ damage in kiwifruit plants, thus improving the resistance to low-K+ stress. Comparison between the salt stress and control transcriptomic data revealed that the expression of AcShaker11 and AcShaker18 genes was significantly different and lower under salt stress, indicating that both genes could be involved in salt stress resistance in kiwifruit.ConclusionThe results showed that 28 AcShaker genes were identified and all expressed under low K+ stress, among which AcShaker22 was differentially and significantly upregulated. The AcShaker22 gene can be used as a candidate gene to cultivate new varieties of kiwifruit resistant to low K+ and provide a reference for exploring more properties and functions of the AcShaker genes.

Genotype-associated core bacteria enhance host resistance against kiwifruit bacterial canker.

Both the phyllosphere and rhizosphere are inhabited by different kinds of microorganisms that are closely related to plant growth and health. However, it is not clear whether disease-resistant cultivars shape the microbiome to facilitate disease resistance. In this study, significant differences were found in the aboveground and belowground bacterial communities of disease-resistant and disease-susceptible cultivars grown in the same kiwifruit orchard. The phyllosphere of the resistant cultivar 'Wanjin' showed greater enrichment of Pseudomonas spp. and Sphingomonas spp. than the susceptible cultivar 'Donghong'. The rhizosphere microbes of 'Wanjin' were less affected by field location, with significantly greater bacterial abundance than those of 'Donghong' and more bacteria with potential biocontrol properties. Pseudomonas syringae pv. actinidiae (Psa) infection significantly affected the microbiome of the phyllosphere of kiwifruit plants, especially that of 'Donghong'. Resistant and susceptible kiwifruit cultivars exhibit distinct beneficial microbial recruitment strategies under Psa challenge. The phyllosphere of 'Donghong' in Jinzhai was enriched with Sphingomonas spp. and Pantoea spp. under Psa infection, while the rhizosphere of 'Wanjin' was enriched with Sphingomonas spp. and Novosphingobium spp. We further identified five key biomarkers within the microbial community associated with Psa infection. Inoculation experiments showed that Lysobacter sp. R34, Stenotrophomonas sp. R31, Pseudomonas sp. R10 and RS54, which were isolated from belowground compartments of 'Wanjin', could positively affect plant performance under Psa challenge. The combination use of Pseudomonas sp. R10 and Stenotrophomonas sp. R31 significantly improve the management of kiwifruit canker. Our findings provided novel insights into soil-microbe-plant interactions and the role of microbes in plant disease resistance and susceptibility.

Molecular Responses to Drought and Waterlogging Stresses of Kiwifruit (Actinidia chinensis var. deliciosa) Potted Vines

Environmental extremes, such as drought and flooding, are becoming increasingly common, resulting in significant crop losses. The aim of the present study was to understand the molecular response induced by drought and waterlogging conditions, and to link these responses to the physiological adaptation of plants. For this purpose, leaf RNA expression was analyzed in potted kiwifruit plants by Illumina Next Generation Sequences. Stressed plants showed an impairment of all physiological parameters (leaf-gas exchange and stem-water potential) with a more evident effect in waterlogging condition than in drought condition. However, the impact on the transcriptome in waterlogged plants was less intense than in drought stress. Drought affected several metabolic pathways, among which “plant hormone signal transduction”, “protein processing in endoplasmic reticulum”, and “mitogen-activated protein kinase signaling pathway” were the most representative in terms of number of genes involved. The genes involved in the biosynthesis of phenylpropanoids were positively influenced by both drought and waterlogging. Finally, waterlogging stimulated secondary metabolisms by upregulating the genes responsible for the biosynthesis of terpenoids and flavonoids, such as stilbenoids. The obtained results show that the two contrasting stress conditions share several common physiological responses and molecular mechanisms.

Comparative genomic analyses provide insight into the pathogenicity of three Pseudomonas syringae pv. actinidiae strains from Anhui Province, China

BackgroundPseudomonas syringae pv. actinidiae (Psa) is an important bacterial plant pathogen that causes severe damage to the kiwifruit industry worldwide. Three Psa strains were recently obtained from different kiwifruit orchards in Anhui Province, China. The present study mainly focused on the variations in virulence and genome characteristics of these strains based on the pathogenicity assays and comparative genomic analyses.ResultsThree strains were identified as biovar 3 (Psa3), along with strain QSY6 showing higher virulence than JZY2 and YXH1 in pathogenicity assays. The whole genome assembly revealed that each of the three strains had a circular chromosome and a complete plasmid. The chromosome sizes ranged from 6.5 to 6.6 Mb with a GC content of approximately 58.39 to 58.46%, and a predicted number of protein-coding sequences ranging from 5,884 to 6,019. The three strains clustered tightly with 8 Psa3 reference strains in terms of average nucleotide identity (ANI), whole-genome-based phylogenetic analysis, and pangenome analysis, while they were evolutionarily distinct from other biovars (Psa1 and Psa5). Variations were observed in the repertoire of effectors of the type III secretion system among all 15 strains. Moreover, synteny analysis of the three sequenced strains revealed eight genomic regions containing 308 genes exclusively present in the highly virulent strain QSY6. Further investigation of these genes showed that 16 virulence-related genes highlight several key factors, such as effector delivery systems (type III secretion systems) and adherence (type IV pilus), which might be crucial for the virulence of QSY6.ConclusionThree Psa strains were identified and showed variant virulence in kiwifruit plant. Complete genome sequences and comparative genomic analyses further provided a theoretical basis for the potential pathogenic factors responsible for kiwifruit bacterial canker.

Enhancing precision of root-zone soil moisture content prediction in a kiwifruit orchard using UAV multi-spectral image features and ensemble learning

Accurate and real-time monitoring of soil moisture content (SMC) is of utmost importance for effective field irrigation and maximizing crop water productivity. However, a comprehensive investigation into the inversion study for determining suitable combinations of unmanned aerial vehicle (UAV) image features and enhancing the precision of SMC model prediction has yet to be fully validated within a kiwifruit orchard setting. This study addresses this gap by employing a pre-processing method and an optimal band combination algorithm to assess the impact of various combinations of kiwifruit canopy reflectance and fraction vegetation coverage (FVC) features on the sensitivity of root-zone SMC. Furthermore, an optimal ensemble learning (EL) framework was developed to monitor SMC at various root-zone depths (0–10 cm [SMC10], 0–20 cm [SMC20], 0–30 cm [SMC30], 0–40 cm [SMC40], 0–50 cm [SMC50], 0–60 cm [SMC60]). The key findings of this research highlight the successful derivation of 10 wavebands and FVC features, exhibiting a strong correlation with SMC at different root depths. The gradient boosting (GBDT) model demonstrated the exceptional accuracy in estimating SMC10, with an impressive R2 value of 0.963 ± 0.030 and low RMSE values of 0.238 ± 0.111. Similarly, the eXtreme Gradient Boosting (XGBoost) model outperformed in estimating SMC20 to SMC60, with R2 and RMSE values of 0.963 ± 0.024 and 0.117 ± 0.053, respectively. Additionally, the utilization of the optimal EL model allows for digital mapping of SMC at different depths across fruit growth stages, showcasing superior adaptability for SMC30 to SMC60 (with R2 and RMSE of 0.782 ± 0.090 and 0.037 ± 0.011) compared to SMC10 and SMC20 (with R2 and RMSE of 0.765 ± 0.097 and 0.056 ± 0.024). These results underscore the potential of the EL estimation framework in characterizing the spatial distribution of root-zone SMC at the individual kiwifruit plant level.

Evaluation of cold plasma activated water composite reagent on kiwifruit plants with bacterial canker and the external qualities of kiwifruit after spray treatment

This study aimed to investigate the efficacy of cold plasma activated water (PAW) and its complex solution (PKC) in conjunction with kasugamycin copper oxychloride wettable powder (KC) against kiwifruit bacterial canker (KBC) caused by Pseudomonas syringae pv. actinidiae (PSA). Through morphological identification and 16S rDNA sequence analysis, Pantoea agglomerans was identified as the pathogen responsible for KBC in the 'Bairui' orchard. Results indicated that PKC exhibited the highest effectiveness in controlling KBC, particularly on mildly (II) infested plants, with a remarkable reduction of 63.64 % in PKC II disease index and a control efficiency of 38.64 %. Additionally, the application of PKC significantly increased fruit yield, improved fruit weight, and enhanced fruit morphology, resulting in a more uniform and refined fruit shape. Analysis of fruit skin conformational parameters revealed that KBC-affected fruit exhibited reduced hardness and brittleness, increased toughness, and thinner skin. These findings are pivotal for developing effective strategies to further prevent and manage KBC outbreaks. In future studies, further investigations could focus on elucidating the mechanism of action of PAW in complex solution with copper-based pesticides and the potential mechanism of inactivation of PSA.

Feasibility analysis of photovoltaic systems for kiwifruit irrigation: A case study in Shaanxi province, China

AbstractAlthough photovoltaic (PV) irrigation systems are widely used in China, feasibility assessment of these systems is important because of differences in the distribution characteristics of solar resources and crops. In this study, kiwifruit planting in Shaanxi province was considered, and a calculation model for PV irrigation system evaluation was developed. Based on the geographical distribution of kiwifruit planting, as well as the spatial and temporal distributions of solar energy in Shaanxi province, the application potential of PV irrigation for kiwifruit was investigated comprehensively from the perspectives of technology, economy and irrigation feasibility. The results showed that the proportion of the PV module scale to the irrigation scale in all the kiwifruit planting areas in Shaanxi province was far less than 1.5%, and there were no technical obstacles. In Baoji, Weinan, Hanzhong and Ankang, the annual cost of the PV irrigation system was greater than that of the diesel pump irrigation system. Regarding irrigation feasibility, farmlands with a slope of 0%–8.75% were considered highly suitable for installing a PV irrigation system. The results revealed 32,269 ha of farmland appropriate for PV irrigation among the 66,371 ha of kiwifruit in Shaanxi province.

Advancement of kiwifruit cultivation in Nepal: Top working techniques

In recent years, there have been notable advancements in the cultivation techniques of kiwifruit, a fruit that is both popular and economically important. One particular practice that has gained recognition is top-working, which involves grafting new scions onto existing rootstocks. This horticultural technique has shown promise in improving yield, disease resistance, and overall productivity in orchards. This comprehensive review paper examines the different methods used in top working for kiwifruit cultivation, explores the factors that influence its success, and discusses the benefits and challenges associated with this practice. This review provides an overview of various techniques used for the top-working kiwifruit plants in Nepal. The success of top-working depends on factors such as timing, compatibility between scion and rootstock, grafting materials, and proper grafting techniques. This review paper also ranges over the importance of kiwifruit cultivation for Nepalese farmers, problems faced by them, persistent constraints in the country, and the future promise that kiwifruit cultivation holds for the economic advancement of the nation.

Genome-wide identification and expression pattern analysis of the kiwifruit GRAS transcription factor family in response to salt stress

BackgroundGRAS is a family of plant-specific transcription factors (TFs) that play a vital role in plant growth and development and response to adversity stress. However, systematic studies of the GRAS TF family in kiwifruit have not been reported.ResultsIn this study, we used a bioinformatics approach to identify eighty-six AcGRAS TFs located on twenty-six chromosomes and phylogenetic analysis classified them into ten subfamilies. It was found that the gene structure is relatively conserved for these genes and that fragmental duplication is the prime force for the evolution of AcGRAS genes. However, the promoter region of the AcGRAS genes mainly contains cis-acting elements related to hormones and environmental stresses, similar to the results of GO and KEGG enrichment analysis, suggesting that hormone signaling pathways of the AcGRAS family play a vital role in regulating plant growth and development and adversity stress. Protein interaction network analysis showed that the AcGRAS51 protein is a relational protein linking DELLA, SCR, and SHR subfamily proteins. The results demonstrated that 81 genes were expressed in kiwifruit AcGRAS under salt stress, including 17 differentially expressed genes, 13 upregulated, and four downregulated. This indicates that the upregulated AcGRAS55, AcGRAS69, AcGRAS86 and other GRAS genes can reduce the salt damage caused by kiwifruit plants by positively regulating salt stress, thus improving the salt tolerance of the plants.ConclusionsThese results provide a theoretical basis for future exploration of the characteristics and functions of more AcGRAS genes. This study provides a basis for further research on kiwifruit breeding for resistance to salt stress. RT-qPCR analysis showed that the expression of 3 AcGRAS genes was elevated under salt stress, indicating that AcGRAS exhibited a specific expression pattern under salt stress conditions.

Exogenous γ-aminobutyric acid enhances heat tolerance of kiwifruit plants by protecting photosynthetic system and promoting heat shock proteins expression

Kiwifruit plants are highly susceptible to increased atmospheric temperature, and the extreme high temperature often causes the loss of production and quality of the fruit. The γ-aminobutyric acid (GABA) has been widely proved to play important roles in plants in response to abiotic stresses, showing an important potential for application in agricultural industry to overcome environmental challenges. However, application of GABA in kiwifruit plants to resist external stresses has not been reported yet. This study found that pre-irrigation of kiwifruit plants with 0.5 mM GABA was effective in alleviating the heat damage on them. GABA treatment led to better antioxidant capacity and reduced ROS production in kiwifruit plants under high temperature. Moreover, exogenous GABA protected the photosynthetic system of kiwifruit plants when exposed to high temperature. Particularly, we found that endogenous ABA, Glu, Pro metabolisms were participated in the GABA-mediated heat resistance of kiwifruit plants. Furthermore, GABA treatment induced higher expression of AdHsps in kiwifruit plants, being partly responsible for their better performance under heat stress. In summary, this research first demonstrated that exogenous GABA treatment plays a positive role in kiwifruit plants to response to extreme heat stress.

Rapid and Visual Detection of Actinidia Chlorotic Ringspot-Associated Virus Using One-Step Reverse-Transcription Recombinase Polymerase Amplification Combined with Lateral Flow Dipstick Assay.

Actinidia chlorotic ringspot-associated virus (AcCRaV) occurs widely in major kiwifruit producing areas of China and is often accompanied by coinfecting viruses, affecting the growth, yield, and quality of kiwifruit. Therefore, a rapid and sensitive detection method is crucial for diagnosing and developing effective AcCRaV management strategies. In this study, a one-step reverse-transcription recombinase polymerase amplification combined with a lateral flow dipstick (RT-RPA-LFD) assay was developed for rapid detection of AcCRaV. Specific primers and a probe were designed based on the conserved region of the coat protein gene sequence of AcCRaV. The one-step RT-RPA reaction can be performed at 35 and 40°C within 10 to 30 min, and the amplification results can be read directly on the LFD within 5 min. The detection limit of the one-step RT-RPA-LFD assay was 10-8 ng (about 20 viral copies), which was equal with one-step RT-qPCR and 100 times more sensitive than one-step RT-PCR. Moreover, the one-step RT-RPA-LFD assay was successfully applied to detect AcCRaV from crude extracts, and the entire detection process can be completed within 40 min. These results indicate that the RT-RPA-LFD assay is a simple, rapid, and sensitive strategy that can be used for accurate diagnosis of AcCRaV-infected kiwifruit plants in the field. To our knowledge, this is the first study applying the one-step RT-RPA-LFD assay to detect a kiwifruit virus.

Chitosan- and gallic acid-based (NPF) displayed antibacterial activity against three Pseudomonas spp. plant pathogens and boosted systemic acquired resistance in kiwifruit and olive plants.

Pseudomonas syringae pv. actinidiae (Psa), P. syringae pv. tomato (Pst) and P. savastanoi pv. savastanoi (Psav) are bacterial plant pathogens with worldwide impact that are mainly managed by the preventive application of cupric salts. These are dangerous for ecosystems and have favoured the selection of resistant strains, so they are candidates to be replaced in the next few years. Thus, there is an urgent need to find efficient and bio-based solutions to mitigate these bacterial plant diseases. Nanotechnology could represent an innovative way to control plant diseases, providing alternative solutions to the agrochemicals traditionally employed, thanks to the formulation of the so-called third-generation and nanotechnology-based agrochemicals. In this work, a novel nanostructured formulation (NPF) composed of cellulose nanocrystals (CNC) as carrier, high amylose starch (HAS) as excipient, and chitosan (CH) and gallic acid (GA) as antimicrobials, was tested at 2% in vitro and in vivo with respect to the three different Pseudomonas plant pathogens. In vitro agar assays demonstrated that the NPF inhibited ≤80% Psa, Pst and Psav. Moreover, the NPF did not decrease biofilm synthesis and it did not influence bacterial cells flocculation and adhesion. On plants, the NPF displayed complete biocompatibility and boosted the transcript levels of the major systemic acquired resistance responsive genes in kiwifruit and olive plants. This works provides novel and valuable information regarding the several modes-of-action of the novel NPF, which could potentially be useful to mitigate Psa, Pst and Psav infections even in organic agriculture. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Transcriptome Analysis Reveals the Molecular Mechanism and Responsive Genes of Waterlogging Stress in Actinidia deliciosa Planch Kiwifruit Plants

Waterlogging stress is one of the major natural issues resulting in stunted growth and loss of agricultural productivity. Cultivated kiwifruits are popular for their rich vitamin C content and unique flavor among consumers, while commonly sensitive to waterlogging stress. The wild kiwifruit plants are usually obliged to survive in harsh environments. Here, we carried out a transcriptome analysis by high-throughput RNA sequencing using the root tissues of Actinidia deliciosa (a wild resource with stress-tolerant phenotype) after waterlogging for 0 d, 3 d, and 7 d. Based on the RNA sequencing data, a high number of differentially expressed genes (DEGs) were identified in roots under waterlogging treatment, which were significantly enriched into four biological processes, including stress response, metabolic processes, molecular transport, and mitotic organization, by gene ontology (GO) simplify enrichment analysis. Among these DEGs, the hypoxia-related genes AdADH1 and AdADH2 were correlated well with the contents of acetaldehyde and ethanol, and three transcription factors Acc26216, Acc08443, and Acc16908 were highly correlated with both AdADH1/2 genes and contents of acetaldehyde and ethanol. In addition, we found that there might be an evident difference among the promoter sequences of ADH genes from A. deliciosa and A. chinensis. Taken together, our results provide additional information on the waterlogging response in wild kiwifruit plants.

Genomic architecture of resistance to latania scale (H. lataniae) in kiwifruit (A. chinensis var. chinensis)

BackgroundLatania scale (Hemiberlesia lataniae Signoret) is an armoured scale insect known to cause damage to kiwifruit plants and fruit, which ultimately reduces crop values and creates post-harvest export and quarantine issues. Resistance to H. lataniae does exist in some commercial cultivars of kiwifruit. However, some of the commercial cultivars bred in New Zealand have not inherited alleles for resistance to H. lataniae carried by their parents. To elucidate the architecture of resistance in the parents and develop molecular markers to assist breeding, these experiments analysed the inheritance of resistance to H. lataniae from families related to commercial cultivars.ResultsThe first experiment identified a 15.97 Mb genomic region of interest for resistance to H. lataniae in rtGBS data of 3.23 to 19.20 Mb on chromosome 10. A larger population was then QTL mapped, which confirmed the region of interest as the sole locus contributing to H. lataniae resistance. inDel markers mapping the region of low recombination under the QTL peak further narrowed the region associated with H. lataniae resistance to a 5.73 Mb region.ConclusionsThe kiwifruit populations and genomic methods used in this study identify the same non-recombinant region of chromosome 10 which confers resistance of A. chinensis var. chinensis to H. lataniae. The markers developed to target the H. lataniae resistance loci will reduce the amount of costly and time-consuming phenotyping required for breeding H. lataniae scale resistance into new kiwifruit cultivars.

Identification and functional analyses of the transcription factors AcWRKY117 and AcWRKY29 involved in waterlogging response in kiwifruit plant

Waterlogging is becoming an increasingly significant problem for crop production and food security. As one of the largest transcription factor (TFs) families in plant crops, WRKYs are reported to be involved in various abiotic stress responses, including waterlogging resistance. However, little is known about the molecular regulation of WRKYs responding to waterlogging stress in kiwifruit plant (Actinidia chinensis). Based on the transcriptome and genome database, a total of 112 AcWRKYs, which were divided into seven subgroups, had been identified in A. chinensis cv. Donghong. Transcript levels of 7 out of these 112 AcWRKYs showed closely correlation with increasing of acetaldehyde and ethanol contents resulted from the high expression of AcPDCs and AcADHs during waterlogging response of the roots. AcWRKY117 and AcWRKY29, which were clustered into group I and II-e respectively, had been verified to trans-activate the expression of AcPDC2 based on the results of dual luciferase assays. Both AcWRKY117 and AcWRKY29 could bind to the w-box (5′-TGACC (A/T)-3′) motif located in target promoter of AcPDC2. Furthermore, contents of acetaldehyde and ethanol in both 35S::AcWRKY117 and 35S::AcWRKY29 overexpression kiwifruit calli had been significantly increased. These were consisted with the significant higher transcript levels of AcPDCs and AcADHs, as well as AcERF74 and AcERF75 which trans-activate the activity of AcADH1 promoter, in the transgenic kiwifruit calli. Moreover, the expression pattern of AcWRKY117 had been dramatically induced in 35S::AcWRKY29 transgenic lines, and vice verse. Taken together, our results provide molecular evidence for WRKYs regulation on waterlogging response in kiwifruit.

Comparison of comprehensive performance of kiwifruit production in China, Iran, and Italy based on emergy and carbon emissions

Extensive kiwifruit farming patterns worldwide are generating increasing environmental stress and thus hindering their sustainability. Comprehensive performance, based on resource efficiency and resource structure, pollutant emissions’ impact and carbon emission, is still not clear for this planting system. Therefore, this study proposes a comprehensive evaluation of kiwifruit planting systems by combining emergy analysis with carbon emission accounting method. The proposed approach not only considers the resource efficiency and resource structure of this planting system, as well as its carbon emission intensity, but also describe tradeoffs among emergy sustainability, pollutant emissions’ impacts and carbon emission intensity using the proposed index - Co-benefit index (CBI). Finally, four kiwifruit planting systems from China (Kiwifruit planting system in Sichuan province (SCPS) and Kiwifruit planting system in Shaanxi (SXPS)), Italy (Kiwifruit planting system in Italy (ITPS)) and Iran (Kiwifruit planting system in Iran (IRPS)), as case studies, are investigated using the presented approach. The study results show that (1) carbon emission intensity (CO2-eq/kg product) embodies trends of SXPS (0.16) > ITPS (0.15) > SCPS (0.12) > IRPS (0.11); (2) pollutant emissions’ impact intensity follows the trends of SXPS (2.54E+14) > ITPS (1.58E+14) > SCPS (8.29E+13) > IRPS (2.56E+13) in units of sej/t product; (3) environmental sustainability reveals trends of IRPS > ITPS > SXPS > SCPS mainly due to different environmental load rates. Generally, the four systems are not sustainable in the long term due to their high dependence on nonrenewable resources (especially labor and services (L&S) and chemical fertilizers); (4) results of Co-benefit index reflect the trends of IRPS > SCPS > ITPS > SXPS accordingly. Some targeted measures are proposed for SCPS, SXPS and ITPS. Considering low sustainability level, it is urgent for the four kiwifruit planting systems to further improve their utilization rate of chemical fertilizer and resource structure in the future.

Development, Management and Utilization of a Kiwifruit (Actinidia spp.) In Vitro Collection: A New Zealand Perspective.

The New Zealand Institute for Plant and Food Research Limited (PFR) supports a large kiwifruit breeding program that includes more than twenty Actinidia species. Almost all the kiwifruit accessions are held as field collections across a range of locations, though not all plants are at multiple locations. An in vitro collection of kiwifruit in New Zealand was established upon the arrival of Pseudomonas syringae pv. Actinadiae-biovar 3 in 2010. The value of an in vitro collection has been emphasized by restrictions on importation of new plants into New Zealand and increasing awareness of the array of biotic and abiotic threats to field collections. The PFR in vitro collection currently holds about 450 genotypes from various species, mostly A. chinensis var. chinensis and A. chinensis var. deliciosa. These collections and the in vitro facilities are used for germplasm conservation, identification of disease-free plants, reference collections and making plants available to users. Management of such a diverse collection requires appropriate protocols, excellent documentation, training, sample tracking and databasing and true-to-type testing, as well as specialized facilities and resources. This review also discusses the New Zealand biosecurity and compliance regime governing kiwifruit plant movement, and how protocols employed by the facility aid the movement of pathogen-free plants within and from New Zealand.

The Pollen Donor Affects Seed Development, Taste, and Flavor Quality in 'Hayward' Kiwifruit.

To investigate how different species or ploidy level of pollen donors affects the fruit quality of kiwifruit, flowers of 'Hayward' kiwifruit (a hexaploid Actinidia deliciosa cultivar, 6x) were hand-pollinated with pollen from ten different male donors. Kiwifruit plants pollinated with four distant species-M7 (2x, A. kolomikta), M8 (4x, A. arguta), M9 (4x, A. melanandra), and M10 (2x, A. eriantha)-had a low fruit-setting rate and therefore were not investigated further. Of the other six treatments, kiwifruit plants pollinated with M4 (4x, A. chinensis), M5 (6x, A. deliciosa) M6 (6x, A. deliciosa) had a larger fruit size and weight than those pollinated with M1 (2x, A. chinensis) and M2 (2x, A. chinensis). However, pollination with M1 (2x) and M2 (2x) resulted in seedless fruits, having few small and aborted seeds. Notably, these seedless fruits had higher fructose, glucose, and total sugar and lower citric acid content. This resulted in a higher sugar to acid ratio compared to fruits from plants pollinated with M3 (4x, A. chinensis), M4 (4x), M5 (6x), and M6 (6x). Most volatile compounds increased in the M1 (2x)- and M2 (2x)-pollinated fruit. A combination of principal component analysis (PCA), electronic tongue, and electronic nose suggested that the different pollen donors significantly affected the kiwifruit's overall taste and volatiles. Specifically, two diploid donors had the most positive contribution. This was in agreement with the findings from the sensory evaluation. In conclusion, the present study showed that the pollen donor affected the seed development, taste, and flavor quality of 'Hayward' kiwifruit. This provides useful information for improving the fruit quality and breeding of seedless kiwifruit.