Kiwifruit Genotypes Research Articles

NbPTR1 confers resistance against Pseudomonas syringae pv. actinidiae in kiwifruit.

Pseudomonas syringae pv. actinidiae biovar 3 (Psa3) causes a devastating canker disease in yellow-fleshed kiwifruit (Actinidia chinensis). The effector HopZ5, which is present in all isolates of Psa3 causing global outbreaks of pandemic kiwifruit canker disease, triggers immunity in Nicotiana benthamiana and is not recognised in susceptible A. chinensis cultivars. In a search for N. benthamiana nonhost resistance genes against HopZ5, we found that the nucleotide-binding leucine-rich repeat receptor NbPTR1 recognised HopZ5. RPM1-interacting protein 4orthologues from N. benthamiana and A. chinensis formed a complex with NbPTR1 and HopZ5 activity was able to disrupt this interaction. No functional orthologues of NbPTR1 were found in A. chinensis. NbPTR1 transformed into Psa3-susceptible A. chinensis var. chinensis 'Hort16A' plants introduced HopZ5-specific resistance against Psa3. Altogether, this study suggested that expressing NbPTR1 in Psa3-susceptible kiwifruit is a viable approach to acquiring resistance to Psa3 and it provides valuable information for engineering resistance in otherwise susceptible kiwifruit genotypes.

Freezing Points of Fruit from Different Kiwifruit Genotypes at Harvest and during Cold Storage

Fruit storage is optimized at the lowest safe temperature to maximize storage life whilst avoiding chilling or freezing injury. The few published studies of freezing in kiwifruit (Actinidia spp.) have been conducted with A. chinensis var. deliciosa ‘Hayward’ fruit, with freezing temperatures reported in the range of −1.5 °C to −2.5 °C. In China, a large number of kiwifruit cultivars have been commercialized recently, with at least ten being commonly planted. In this research, freshly harvested fruits from 45 kiwifruit germplasm accessions were measured for freezing point, soluble solids content (SSC) and water content (WC). The difference in freezing point of different tissue zones within a fruit and after different periods of cold storage were determined for the fruit of three representative main cultivars: the green-fleshed ‘Hayward’, the red-fleshed A. chinensis var. chinensis ‘Donghong’, and the yellow-fleshed interspecific hybrid A. eriantha × A. chinensis ‘Jinyan’. The the freezing point of kiwifruit was found to be highly correlated with the SSC. This relationship was found irrespective of whether the measurement was made at harvest, at different places in the fruit, or after ripening during storage. These findings agree with previous reports for kiwifruit and other fruits, although it appears that the relationship may differ among kiwifruit cultivars, something not previously reported and which requires further confirmation.

Comprehensive assessment of drought resistance and recovery in kiwifruit genotypes using multivariate analysis.

As global climate change persists, ongoing warming exposes plants, including kiwifruit, to repeated cycles of drought stress and rewatering, necessitating the identification of drought-resistant genotypes for breeding purposes. To better understand the physiological mechanisms underlying drought resistance and recovery in kiwifruit, moderate (40-45% field capacity) and severe (25-30% field capacity) drought stresses were applied, followed by rewatering (80-85% field capacity) to eight kiwifruit rootstocks in this study. We then conducted a multivariate analysis of 20 indices for the assessment of drought resistance and recovery capabilities. Additionally, we identified four principal components, each playing a vital role in coping with diverse water conditions. Three optimal indicator groups were pinpointed, enhancing precision in kiwifruit drought resistance and recovery assessment and simplifying the evaluation system. Finally, MX-1 and HW were identified as representative rootstocks for future research on kiwifruit's responses to moderate and severe drought stresses. This study not only enhances our understanding of the response mechanisms of kiwifruit rootstocks to progressive drought stress and recovery but also provides theoretical guidance for reliable screening of drought-adaptive kiwifruit genotypes.

The effects of high concentration of bicarbonate applications on kiwifruit genotypes with different ploidy levels on some growth parameters of leaves

The effects of high concentration of bicarbonate applications on kiwifruit genotypes with different ploidy levels on some growth parameters of leaves

Development of a 135K SNP genotyping array for Actinidia arguta and its applications for genetic mapping and QTL analysis in kiwifruit.

Kiwifruit (Actinidia spp) is a woody, perennial and deciduous vine. In this genus, there are multiple ploidy levels but the main cultivated cultivars are polyploid. Despite the availability of many genomic resources in kiwifruit, SNP genotyping is still a challenge given these different levels of polyploidy. Recent advances in SNP array technologies have offered a high-throughput genotyping platform for genome-wide DNA polymorphisms. In this study, we developed a high-density SNP genotyping array to facilitate genetic studies and breeding applications in kiwifruit. SNP discovery was performed by genome-wide DNA sequencing of 40 kiwifruit genotypes. The identified SNPs were stringently filtered for sequence quality, predicted conversion performance and distribution over the available Actinidia chinensis genome. A total of 134 729 unique SNPs were put on the array. The array was evaluated by genotyping 400 kiwifruit individuals. We performed a multidimensional scaling analysis to assess the diversity of kiwifruit germplasm, showing that the array was effective to distinguish kiwifruit accessions. Using a tetraploid F1 population, we constructed an integrated linkage map covering 3060.9cM across 29 linkage groups and performed QTL analysis for the sex locus that has been identified on Linkage Group 3 (LG3) in Actinidia arguta. Finally, our dataset presented evidence of tetrasomic inheritance with partial preferential pairing in A. arguta. In conclusion, we developed and evaluated a 135K SNP genotyping array for kiwifruit. It has the advantage of a comprehensive design that can be an effective tool in genetic studies and breeding applications in this high-value crop.

Evaluation of eleven kiwifruit genotypes for bicarbonate tolerance and characterization of two tolerance-contrasting genotypes

Screening bicarbonate-tolerant genotypes is an environmentally-friendly and long-term effective strategy to cope with bicarbonate-induced chlorosis in fruit crops grown on calcareous soils. We investigated eleven genotypes from four kiwifruit species (Actinidia chinensis, A. macrosperma, A. polygama, and A. valvata) for differences in bicarbonate tolerance. We also characterized the physiological and molecular differences in two contrasting genotypes of this group. In the first experiment, bicarbonate-treated plantlets were irrigated with 3.0 g L−1 CaCO3 and 5.04 g L−1 NaHCO3 in peat and perlite medium culture. Based on principal component analysis, weight-based membership function method and cluster analysis, the tested genotypes were classified into three groups: (1) tolerant, including YX, Av-1, Acd, Ap, Av-2, and QM; (2) moderately tolerant, including Av-3, Am, Av-4, and HWD; and (3) sensitive, including only QH. In the second experiment, QH (bicarbonate-sensitive) and YX (bicarbonate-tolerant) were grown in sand culture with 4.0 g L−1 CaCO3 and 0.84 g L−1 or 1.26 g L−1 NaHCO3. Compared with QH, YX showed a better ability to take up iron (Fe) by roots and to transport Fe from roots to shoots in the bicarbonate treatments, probably due to a better capacity to protect from oxidative damage and to excrete protons, and a differential expression of genes associated with Fe uptake and translocation, including HA8, IRT1, YSL3 and NRAMP3. The results can facilitate identifying potential resources for bicarbonate tolerance and breeding new rootstocks, and contribute to the elucidation of the bicarbonate tolerance mechanisms in the genus Actinidia.

Transcriptional Analysis on Resistant and Susceptible Kiwifruit Genotypes Activating Different Plant-Immunity Processes against Pseudomonas syringae pv. actinidiae.

Pseudomonas syringae pv. actinidiae (Psa), a bacterial pathogen, is a severe threat to kiwifruit production. To elucidate the species-specific interaction between Psa and kiwifruit, transcriptomic-profiles analyses were conducted, under Psa-infected treatment and mock-inoculated control, on shoots of resistant Maohua (MH) and susceptible Hongyang (HY) kiwifruit varieties. The plant hormone-signal transduction and plant–pathogen interaction were significantly enriched in HY compared with MH. However, the starch and sucrose metabolism, antigen processing and presentation, phagosome, and galactose metabolism were significantly enriched in MH compared with HY. Interestingly, the MAP2 in the pathogen/microbe-associated molecular patterns (PAMPs)-triggered immunity (PTI) was significantly up-regulated in MH. The genes RAR1, SUGT1, and HSP90A in the effector-triggered immunity (ETI), and the NPR1 and TGA genes involved in the salicylic acid signaling pathway as regulatory roles of ETI, were significantly up-regulated in HY. Other important genes, such as the CCRs involved in phenylpropanoid biosynthesis, were highly expressed in MH, but some genes in the Ca2+ internal flow or involved in the reactive oxygen metabolism were obviously expressed in HY. These results suggested that the PTI and cell walls involved in defense mechanisms were significant in MH against Psa infection, while the ETI was notable in HY against Psa infection. This study will help to understand kiwifruit bacterial canker disease and provide important theoretical support in kiwifruit breeding.

Dynamic Changes in Ascorbic Acid Content during Fruit Development and Ripening of Actinidia latifolia (an Ascorbate-Rich Fruit Crop) and the Associated Molecular Mechanisms.

Actinidia latifolia is one of the very few kiwifruit genotypes with extremely high ascorbic acid (AsA) content. However, a transcriptome atlas of this species is lacking. The accumulation of AsA during fruit development and ripening and the associated molecular mechanisms are still poorly understood. Herein, dynamic changes in AsA content at six different stages of A. latifolia fruit development and ripening were determined. AsA content of A. latifolia fruit reached 1108.76 ± 35.26 mg 100 g−1 FW at full maturity. A high-quality, full-length (FL) transcriptome of A. latifolia was successfully constructed for the first time using third-generation sequencing technology. The transcriptome comprises 326,926 FL non-chimeric reads, 15,505 coding sequences, 2882 transcription factors, 18,797 simple sequence repeats, 3328 long noncoding RNAs, and 231 alternative splicing events. The genes involved in AsA biosynthesis and recycling pathways were identified and compared with those in different kiwifruit genotypes. The correlation between the AsA content and expression levels of key genes in AsA biosynthesis and recycling pathways was revealed. LncRNAs that participate in AsA-related gene expression regulation were also identified. Gene expression patterns in AsA biosynthesis and metabolism exhibited a trend similar to that of AsA accumulation. Overall, this study paves the way for genetic engineering to develop kiwifruits with super-high AsA content.

Characterization and Identification of a Ripening-Related Gene AaPG18 in Actinidia arguta.

Actinidia arguta (A. arguta) is a kind of climacteric fruit that quickly softens and limits fruit shelf-life and commercial value. Therefore, it is of great significance to develop kiwifruit genotypes with an extended shelf-life of fruit. However, the ripening and softening mechanisms remain unclear in A. arguta. Here, we demonstrated that a key polygalacturonase (PG)-encoding gene AaPG18 was involved in A. arguta ripening through the degradation of the cell wall. Fruits were harvested at three developmental stages (S1, S2, and S3) for high-throughput transcriptome sequencing, based on which two candidate transcripts c109562_g1 and c111961_g1 were screened. The genome-wide identification of the PG gene family assigned c109562_g1 and c111961_g1 to correspond to AaPG4 and AaPG18, respectively. The expression profiles of candidate genes at six preharvest stages of fruit showed significantly higher expression levels of AaPG18 than AaPG4, indicating AaPG18 might be a key gene during fruit ripening processes. The subcellular localization displayed AaPG18 was located at the cytoplasmic membrane. The transient overexpression of AaPG18 in strawberry and the following morphological observation suggested AaPG18 played a key role in maintaining the stability of cell morphology. The homologous transient transformation in A. arguta “RB-4” proved the crucial function of AaPG18 in fruit ripening processes by causing the rapid redness of the fruit, which was an indicator of fruit maturity. All in all, our results identified AaPG18 as a key candidate gene involved in cell wall degeneration, which provides a basis for the subsequent exploration of the molecular mechanisms underlying the ripening and softening of A. arguta fruit.

Preliminary selection studies in the kiwifruit breeding program in Turkey: characteristics of some selected kiwifruit genotypes

Preliminary selection studies in the kiwifruit breeding program in Turkey: characteristics of some selected kiwifruit genotypes

Optimizing Seed Germination and Seedling Growth in Different Kiwifruit Genotypes

The presence of dormant embryos in seeds and nonuniformity in seedling growth are the main limiting factors for kiwifruit propagation. Studies on the germination of hybrid genotypes are limited, especially at different ploidy levels. Low germination percentages and nonuniformity in seedling growth are two of the limiting factors of kiwifruit breeding, especially new and imported germplasm. The effect of cold moist stratification and growing substances on seed germination and seedling growth, respectively, on different kiwifruit seed populations were evaluated in this study. The effect of cold moist stratification (3, 4 and 5 weeks at 4 °C) and growing substrate composition (peat, perlite and coco peat) on seed germination and seedling growth of different Actinidia genotypes were assessed. In general, increasing stratification period duration often increased germination speed and uniformity. It was also found that increasing the ratio of peat moss improved the vegetative growth parameters of all kiwifruit seedlings. Stratification treatment, light and temperature fluctuation and consequently suitable substrate can accelerate and increase the production of seedlings and reduce seedling losses. It was also found that peat–perlite (1:1) medium was the best medium for kiwifruit seedling growth.

Full-length transcriptome profiling reveals insight into the cold response of two kiwifruit genotypes (A. arguta) with contrasting freezing tolerances

BackgroundKiwifruit (Actinidia Lindl.) is considered an important fruit species worldwide. Due to its temperate origin, this species is highly vulnerable to freezing injury while under low-temperature stress. To obtain further knowledge of the mechanism underlying freezing tolerance, we carried out a hybrid transcriptome analysis of two A. arguta (Actinidi arguta) genotypes, KL and RB, whose freezing tolerance is high and low, respectively. Both genotypes were subjected to − 25 °C for 0 h, 1 h, and 4 h.ResultsSMRT (single-molecule real-time) RNA-seq data were assembled using the de novo method, producing 24,306 unigenes with an N50 value of 1834 bp. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of DEGs showed that they were involved in the ‘starch and sucrose metabolism’, the ‘mitogen-activated protein kinase (MAPK) signaling pathway’, the ‘phosphatidylinositol signaling system’, the ‘inositol phosphate metabolism’, and the ‘plant hormone signal transduction’. In particular, for ‘starch and sucrose metabolism’, we identified 3 key genes involved in cellulose degradation, trehalose synthesis, and starch degradation processes. Moreover, the activities of beta-GC (beta-glucosidase), TPS (trehalose-6-phosphate synthase), and BAM (beta-amylase), encoded by the abovementioned 3 key genes, were enhanced by cold stress. Three transcription factors (TFs) belonging to the AP2/ERF, bHLH (basic helix-loop-helix), and MYB families were involved in the low-temperature response. Furthermore, weighted gene coexpression network analysis (WGCNA) indicated that beta-GC, TPS5, and BAM3.1 were the key genes involved in the cold response and were highly coexpressed together with the CBF3, MYC2, and MYB44 genes.ConclusionsCold stress led various changes in kiwifruit, the ‘phosphatidylinositol signaling system’, ‘inositol phosphate metabolism’, ‘MAPK signaling pathway’, ‘plant hormone signal transduction’, and ‘starch and sucrose metabolism’ processes were significantly affected by low temperature. Moreover, starch and sucrose metabolism may be the key pathway for tolerant kiwifruit to resist low temperature damages. These results increase our understanding of the complex mechanisms involved in the freezing tolerance of kiwifruit under cold stress and reveal a series of candidate genes for use in breeding new cultivars with enhanced freezing tolerance.

Comparative Metabolomic and Transcriptomic Studies Reveal Key Metabolism Pathways Contributing to Freezing Tolerance Under Cold Stress in Kiwifruit.

Cold stress poses a serious treat to cultivated kiwifruit since this plant generally has a weak ability to tolerate freezing tolerance temperatures. Surprisingly, however, the underlying mechanism of kiwifruit’s freezing tolerance remains largely unexplored and unknown, especially regarding the key pathways involved in conferring this key tolerance trait. Here, we studied the metabolome and transcriptome profiles of the freezing-tolerant genotype KL (Actinidia arguta) and freezing-sensitive genotype RB (A. arguta), to identify the main pathways and important metabolites related to their freezing tolerance. A total of 565 metabolites were detected by a wide-targeting metabolomics method. Under (−25°C) cold stress, KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway annotations showed that the flavonoid metabolic pathways were specifically upregulated in KL, which increased its ability to scavenge for reactive oxygen species (ROS). The transcriptome changes identified in KL were accompanied by the specific upregulation of a codeinone reductase gene, a chalcone isomerase gene, and an anthocyanin 5-aromatic acyltransferase gene. Nucleotides metabolism and phenolic acids metabolism pathways were specifically upregulated in RB, which indicated that RB had a higher energy metabolism and weaker dormancy ability. Since the LPCs (LysoPC), LPEs (LysoPE) and free fatty acids were accumulated simultaneously in both genotypes, these could serve as biomarkers of cold-induced frost damages. These key metabolism components evidently participated in the regulation of freezing tolerance of both kiwifruit genotypes. In conclusion, the results of this study demonstrated the inherent differences in the composition and activity of metabolites between KL and RB under cold stress conditions.

Fruit From Two Kiwifruit Genotypes With Contrasting Softening Rates Show Differences in the Xyloglucan and Pectin Domains of the Cell Wall.

Fruit softening is controlled by hormonal and developmental cues, causing an upregulation of cell wall-associated enzymes that break down the complex sugar matrices in the cell wall. The regulation of this process is complex, with different genotypes demonstrating quite different softening patterns, even when they are closely related. Currently, little is known about the relationship between cell wall structure and the rate of fruit softening. To address this question, the softening of two Actinidia chinensis var. chinensis (kiwifruit) genotypes (a fast ‘AC-F’ and a slow ‘AC-S’ softening genotype) was examined using a range of compositional, biochemical, structural, and molecular techniques. Throughout softening, the cell wall structure of the two genotypes was fundamentally different at identical firmness stages. In the hemicellulose domain, xyloglucanase enzyme activity was higher in ‘AC-F’ at the firm unripe stage, a finding supported by differential expression of xyloglucan transglycosylase/hydrolase genes during softening. In the pectin domain, differences in pectin solubilization and location of methyl-esterified homogalacturonan in the cell wall between ‘AC-S’ and ‘AC-F’ were shown. Side chain analyses and molecular weight elution profiles of polyuronides and xyloglucans of cell wall extracts revealed fundamental differences between the genotypes, pointing towards a weakening of the structural integrity of cell walls in the fast softening ‘AC-F’ genotype even at the firm, unripe stage. As a consequence, the polysaccharides in the cell walls of ‘AC-F’ may be easier to access and hence more susceptible to enzymatic degradation than in ‘AC-S’, resulting in faster softening. Together these results suggest that the different rates of softening between ‘AC-F’ and ‘AC-S’ are not due to changes in enzyme activities alone, but that fundamental differences in the cell wall structure are likely to influence the rates of softening through differential modification and accessibility of specific cell wall polysaccharides during ripening.

Effect of Salt stress on growth, physiological and biochemical characters of Four kiwifruit genotypes

Salt stress negatively impacted growth and physiological processes in plants, and the effects involved oxidative damages within cell and cell organelles. In this study, four different genotypes (CG, KM, XX, and ZM-H) of Actinidia germplasm resources were exposed to CK, 0.3 %, and 0.6 % NaCl concentrations for 15 days. We measured the growth, physiological and biochemical indicators in leaves, shoots, and roots. The relative lateral branch length (RLBL), plant fresh weight (PFW), plant dry weight (PDW), and plant relative water contents (PRWC) were decreased in all genotypes under salinity stress. Whereas, the Salt damage index (SDI, sodium ions (Na+) and chloride ions (Cl−) increased in all kiwifruit genotypes under high salt conditions. On the contrary, the potassium ion (K+) and K+/Na+ ratio was decreased in all genotypes under higher salt conditions. For organic osmolytes, Proline increased and total soluble sugars (TSS) decreased in all genotypes under high salt. The enzymatic activities of APX, GST, and GR were increased in all kiwifruit genotypes when subjected to higher levels of NaCl stress. The salt tolerance of different kiwifruit genotypes was assessed by principal component analysis (PCA), and the order of salt tolerance was as following: ZM-H > CG > XX > KM. Hence, the ZM-H from A. valvata Dunn. possessed strong tolerance against salt stress and could be an important germplasm resource for the salt tolerance rootstock breeding program of kiwifruit.

Effect of cytokinins and sucrose concentration on the efficiency of micropropagation of ‘Zes006’ Actinidia chinensis var. chinensis, a red-fleshed kiwifruit cultivar

The effect of N6(3-hydroxybenzyl)adenine (meta-Topolin—mT) was compared with that of N6-benzylaminopurine (BAP) and zeatin at the proliferation stage of micropropagation of red-fleshed Actinidia chinensis var. chinensis ‘Zes006’ in two separate experiments. Shoot number, shoot weight, leaf number and leaf area were significantly higher in mT-supplemented media compared with BAP or zeatin. When transferred to rooting media, plantlets that were propagated in mT-supplemented media readily produced roots, enabling easy acclimation to the greenhouse, whereas none of the plantlets propagated in BAP- or zeatin-supplemented media produced roots. Using 12 pairs of Simple Sequence Repeat primers designed for A. chinensis var. chinensis, a very low rate of somaclonal variation was detected at some loci in plantlets produced in zeatin- (1.04%), BAP- (0.4%) as well as in mT- (0.2%) supplemented media. Overall, mT in equimolar concentrations was the better cytokinin for tissue culture of ‘Zes006’ kiwifruit and may well be applicable to many other kiwifruit genotypes. Supplementation of media with meta-Topolin for in vitro propagation of the red-fleshed kiwifruit cultivar ‘Zes006’ enhanced better shoot proliferation, giving healthy plantlets that were easier to acclimatize to the greenhouse environment compared with media supplemented with 6-benzylaminopurine or zeatin. It also induced a lower rate of somaclonal variation, as detected by SSR markers.

Growth and physiological responses of four kiwifruit genotypes to salt stress and resistance evaluation

In this study, four genotypes (Acva-1, Acva-2, Acva-3 and ZM-2) of Actinidia germplasm resources were grown in different NaCI concentrations (0, 0.4, 0.8 and 1.2 g L–1). The growth, physiological and biochemical indicators were measured, and a graded scale was developed as the salt damage index (SDI) according to different damage symptoms in leaves. The results showed SDI increased gradually, and average number and length of new shoot decreased significantly. Three antioxidant enzymes (superoxide dismutase, peroxidase and catalase) and two osmotic adjustment substances (soluble sugar and proline) showed different changes in old and new leaves of four genotypes. SPAD values exhibited a decreased trend in the whole except in the new leaves of Acva-2. Malonaldehyde contents increased and root activity decreased with the increasing salt concentrations. Principal component analysis was used to assess the salt tolerance, and the results showed Acva-3, from Actinidia valvata Dunn., had the strongest tolerance to salt, and could be a potential resistant resource to the salt-tolerance dedicated rootstock breeding of kiwifruit.

Flavonoid-Rich Extract of Actinidia macrosperma (A Wild Kiwifruit) Inhibits Angiotensin-Converting Enzyme In Vitro.

Increasing interest in flavonoids in kiwifruit is due to the health-promoting properties of these bioactives. Inhibition of the angiotensin-converting enzyme (ACE) is one of the main therapeutic targets in controlling hypertension. The present study investigated the ACE inhibitory activity of flavonoid-rich extracts obtained from different kiwifruit genotypes. The flavonoid-rich extracts were prepared from fruits of Actinidia macrosperma, Actinidia deliciosa cv Hayward (Green kiwifruit), and Actinidia chinensis cv Hort 16A (Gold kiwifruit) by steeping the lyophilized fruit samples in 70% aqueous acetone, followed by partitioning the crude extracts with hexane. The composition of each extract was analyzed using ultrahigh-performance liquid chromatography-mass spectrometry (UPLC-MS/MS). The ACE inhibitory activity of the fruit extracts was performed using a fluorescence-based biochemical assay. The subclass flavonol was the most abundant group of flavonoids detected in all the extracts tested from three different kiwifruit cultivars. Quercetin-3-O-galactoside, quercetin-3-O-glucoside, quercetin-3-O-rhamnoside, quercetin-3-O-rutinoside, quercetin-3-O-arabinoglucoside, catechin, epigallocatechin gallate, epigallocatechin, chlorogenic, ferulic, isoferulic, and caffeic acid were prominent phenolics found in A. macrosperma kiwifruit. Overall, the flavonoid-rich extract from A. macrosperma showed a significantly (p < 0.05) high percentage of inhibition (IC50 = 0.49 mg/mL), and enzyme kinetic studies suggested that it inhibits ACE activity in vitro. The kiwifruit extracts tested were found to be moderately effective as ACE inhibitors in vitro when compared to the other plant extracts reported in the literature. Further studies should be carried out to identify the active compounds from A. macrosperma and to validate the findings using experimental animal models of hypertension.

Analysis of Antioxidant Enzyme Activity Involved in Ascorbate-glutathione Cycle in Green-flesh Kiwifruits

To compare the activities of enzymes related to ascorbate-glutathione cycle (AsA-GSH cycle) in different varieties, the fruits of five green-fleshed kiwifruit varieties were used as materials and activities of ascorbate peroxidase (APX), monodehydroascorbic acid (MDHA), dehydroascorbate reductase (DHAR) were measured by ultraviolet spectrophotometry. Results showed that ‘Cuiyu’ had higher MDHAR activities. The higher enzyme activity is responsible for the higher accumulation of AsA in kiwifruit. All of these results indicated that there were significant differences in the activities of enzymes in 5 kiwifruit genotypes.

Ascorbic Acid Content in Five Yellow-Flesh Kiwifruit Genotypes

In this study, the content of ascorbic acid (AsA) in five kinds of yellow-flesh kiwifruit genotypes was determined by high performance liquid chromatography. Content of AsA and GSH involved in AsA-GSH cycle were compared in different yellow flesh kiwifruit genotypes. The results indicated that the AsA levels changed vary remarkably in different yellow flesh kiwifruit genotypes, and the AsA levels in ‘Fengyue’ and ‘Guihai 4’ were higher.