Shoot Axillary Bud Morphogenesis in Kiwifruit (Actinidia deliciosa)

The annual cycle of kiwifruit [Actinidia deliciosa(A. Chev.)C. F. Liang et A. R. Ferguson var.deliciosacv. Hayward] shootaxillary bud (first-order axillary bud, FOAB) morphogenesisis described. FOABs developed quickly with the majority of budscales and leaf primordia present approx. 125 d after budbreak(dab). Mature FOABs had, on average, 23.2 bud scales and leafprimordia. Most second-order axillary structures were also presentapprox. 125 dab. During the growing season, the second-orderstructures developed into second-order axillary buds (SOABs)or remained as simple, dome-shaped meristems (SDSMs). At maturity,nearly all FOABs had four SOABs and, on average, 12.4 SDSMs.Most SDSMs were fused to the subtending leaf primordia, butsome SDSMs developed so that they were ‘free’ fromthe subtending leaf primordia. Third-order axillary meristems(third-order SDSMs) were observed in the axils of most SOABs,and, on average, there were 20.6 per FOAB. Our observationson the development of second-order axillary structures are consistentwith evocation in kiwifruit occurring earlier than the generally-acceptedtime of late summer. Actinidia deliciosa; bud morphogenesis; development; flowering; evocation     

Localization of Cell Wall Polysaccharides during Kiwifruit (Actinidia deliciosa) Ripening

The localization of pectin, cellulose, xyloglucan, and callose was compared in kiwifruit (Actinidia deliciosa [A. Chev.] C. F. Liang and A. R. Ferguson var. deliciosa "Hayward") at harvest, at the end of the first phase of softening, and when ripe. Pectin was visualized using three different methods: labeling of galacturonic acid residues, labeling of negatively charged groups, and labeling with JIM 5 (nonesterified residues) and JIM 7 (methyl-esterified) monoclonal antibodies. Labeling of pectin gave different results depending on the detection system used. Differences related to patterns of change during ripening and to spatial distribution of label intensity. Cell wall pectin was available for labeling at all stages of fruit softening, but no clear differentiation of the middle lamella region was seen, although JIM 5 binding predominated where the middle lamellae joined the intercellular spaces in unripe fruit. Negatively charged groups (cationic gold labeling) and, to a lesser extent, galacturonic acid residues (Aplysia depilans gonad lectin labeling) were preferentially located near the cell wall/plasma membrane boundary. The lack of strong binding of the JIM antibodies indicated that the reactive groups were inaccessible. Cellulose remained intact and labeled densely across the wall at all stages of fruit ripening. Distribution of xyloglucan was patchy at harvest but was scattered throughout the wall later in ripening. Alterations to labeling of xyloglucan indicated that some epitopes were differentially exposed. Plasmodesmatal regions were clearly different in composition to other wall areas, showing an absence of cellulose labeling, specific pectin labeling, and callose presence. A similar predominance of pectin labeling compared with cellulose also occurred at the middle lamella wedge near intercellular spaces.     

In Vitro Antibacterial Activity of Cysteine Protease Inhibitor from Kiwifruit (Actinidia deliciosa)

The need for replacing traditional pesticides with alternative agents for the management of agricultural pathogens is rising worldwide. In this study, a cysteine proteinase inhibitor (CPI), 11 kDa in size, was purified from green kiwifruit to homogeneity. We examined the growth inhibition of three plant pathogenic Gram-negative bacterial strains by kiwi CPI and attempted to elucidate the potential mechanism of the growth inhibition. CPI influenced the growth of phytopathogenic bacteria Agrobacterium tumefaciens (76.2 % growth inhibition using 15 μM CPI), Burkholderia cepacia (75.6 % growth inhibition) and, to a lesser extent, Erwinia carotovora (44.4 % growth inhibition) by inhibiting proteinases that are excreted by these bacteria. Identification and characterization of natural plant defense molecules is the first step toward creation of improved methods for pest control based on naturally occurring molecules.     

猕猴桃高频直接再生体系的建立

为了建立猕猴桃高频再生体系,以MS为基本培养基,猕猴桃(Actinidia deliciosaQinmei)茎及叶片为外植体,研究了2,4-D、6-BA和NAA在美味猕猴桃愈伤组织形成及分化过程中的作用。方差分析结果表明,6-BA能够显著促进愈伤组织形成,6-BA和NAA可以显著促进愈伤组织形成和分化,而2,4-D抑制愈伤组织形成。附加2.0 mg/L 6-BA、1.0 mg/L NAA和600 mg/L水解酪蛋白的MS培养基是茎段培养的最佳培养基,在该培养基上,以再生的无菌苗为起始材料,一个月时叶圆盘的直接再生频率达到100%,平均每个叶圆盘产生9.33个芽,其中23.21%芽高度超过0.5 cm。     

Xyloglucan Endotransglycosylase Activity Increases during Kiwifruit (Actinidia deliciosa) Ripening (Implications for Fruit Softening)

The activity of xyloglucan endotransglycosylase (XET) was as-sayed in three tissue zones of kiwifruit (Actinidia deliciosa [A. Chev.] C.F. Liang et A.R. Ferguson var deliciosa cv Hayward) at harvest and at several softening stages following a postharvest ethylene treatment. At harvest, extractable XET activity per unit fresh weight in the inner pericarp (IP) and core tissue was 4.5 and 42 times higher, respectively, than in the outer pericarp (OP). Within 24 h of ethylene treatment there was an increase in the activity and specific activity of XET in all tissues that continued throughout softening. Activity increased most in the OP, where it showed a 12-fold rise 6 d after ethylene treatment compared with 4.5- and 2.5-fold increases in the IP and core tissues, respectively. Visible swelling of the cell wall in each tissue was observed 24 h after the first detectable rise in XET activity and was most pronounced in the OP, which showed the greatest percentage increase in XET activity. Xyloglucan, galactoglucomannan, and cell wall materials isolated and purified from kiwifruit OP were tested as donor substrates for kiwifruit XET. The enzyme showed activity against xyloglucan but was inactive against galactoglucomannan. XET was active against cell wall materials from unripe and ripe fruit, with swollen walls from the latter being the better substrate. The results indicate that XET may have a key role early in fruit ripening, loosening the cell wall in preparation for further modification by other cell wall-associated enzymes.     

Plant regeneration from protoplasts of long-term callus cultures of Actinidia deliciosa var. deliciosa cv. Hayword (Kiwifruit)

Plant regeneration of Actinidia deliciosa var. deliciosa cv. Hayword was obtained from protoplasts isolated from petiole derived long-term callus cultures. Protoplasts were cultured in liquid medium over agarose gelled medium. Regenerated green callus, plated on solid medium, could develop shoots that rooted spontaneously in hormone-less medium. The plants obtained are growing fast in soil and present a normal phenotype.Abbreviations BAP benzylaminopurine - 2,4-D 2,4-dichlorophenoxyacetic acid - DTT dithiotreitol - IAA indole-3-acetic acid - IBA indole-3-butyric acid - Kin kinetin - MES 2-(N-morpholino) ethanesulphonic acid - MS Murashige and Skoog (1962) medium - NAA naphthalene-1-acetic acid - SH Schenk and Hildebrandt (1972) medium This Research was supported by JNICT and INIC     

Cell Wall Dissolution in Ripening Kiwifruit (Actinidia deliciosa) : Solubilization of the Pectic Polymers

Pectic polysaccharides solubilized in vivo during ripening, were isolated using phenol, acetic acid, and water (PAW) from the outer pericarp of kiwifruit (Actinidia deliciosa [A. Chev.] C.F. Liang and A.R. Ferguson var deliciosa `Hayward') before and after postharvest ethylene treatment. Insoluble polysaccharides of the cell wall materials (CWMs) were solubilized in vitro by chemical extraction with 0.05 molar cyclohexane-trans-1,2-diamine tetraacetate (CDTA), 0.05 molar Na₂CO₃, 6 molar guanidinium thiocyanate, and 4 molar KOH. The Na₂CO₃-soluble fraction decreased by 26%, and the CDTA-soluble fraction increased by 54% 1 day after ethylene treatment. Concomitantly, an increase in the pectic polymer content of the PAW-soluble fraction occurred without loss of galactose from the cell wall. The molecular weight of the PAW-soluble pectic fraction 1 day after ethylene treatment was similar to that of the Na₂CO₃-soluble fraction before ethylene treatment. Four days after ethylene treatment, 60% of cell wall polyuronide was solubilized, and 50% of the galactose was lost from the CWM, but the degree of galactosylation and molecular weight of pectic polymers remaining in the CWMs did not decrease. The exception was the CDTA-soluble fraction which showed an apparent decrease in molecular weight during ripening. Concurrently, the PAW-soluble pectic fraction showed a 20-fold reduction in molecular weight. The results suggest that considerable solubilization of the pectic polymers occurred during ripening without changes to their primary structure or degree of polymerization. Following solubilization, the polymers then became susceptible to depolymerization and degalactosidation. Pectolytic enzymes such as endopolygalacturonase and β-galactosidase were therefore implicated in the degradation of solubilized cell wall pectic polymers but not the initial solubilization of the bulk of the pectic polymers in vivo.     

NMR and DSC Water Study During Osmotic Dehydration of Actinidia deliciosa and Actinidia chinensis Kiwifruit

This study investigated mass transfer and water state changes promoted by osmotic dehydration on two kiwifruit species, Actinidia deliciosa and Actinidia chinensis. Osmotic treatment was performed in a 61.5% w/v sucrose solution at three different temperatures (25, 35 and 45 °C), with treatment time from 0 to 300 min. Treatment time positively influenced kiwifruit water loss and solid gain while temperature significantly affected only water loss. Peleg’s model highlighted that the main response differences between the two species occurred during the initial phase of the osmotic treatment. Thermal properties and relaxation time measurements offered a complementary view concerning the effects of osmotic dehydration on kiwifruit. DSC parameters appeared to be sensitive to water and solid exchange between fruit and osmotic solution. LF-NMR proton T₂ revealed the consequences of the water–solid exchange on the cell compartments, namely vacuole, cytoplasm plus extracellular space and cell wall. During the osmotic treatment, the initial freezing temperature and the freezable water content decrease was dependent on time and treatment temperature, showing a similar tendency for both the kiwifruit species. They evidenced the same treatment response also concerning the reduction of vacuole and the increase of cytoplasm plus extracellular space T₂ values.     

Magnesium deficiency of kiwifruit (Actinidia deliciosa)

Magnesium deficiency was associated with large yield reductions in a five-year-old commercial kiwifruit (Actinidia deliciosa) orchard. The effect on yield resulted primarily from a reduction in fruit numbers, there being no difference in mean fruit weight between fruit harvested from affected and unaffected vines. Magnesium deficiency had no deleterious effect on postharvest storage characteristics of fruit stored at 0.5–1°C for 18 weeks; fruit from deficient vines were firmer but had slightly lower soluble solids than fruit from control vines. Although deficiency symptoms were first observed on the basal leaves of the non-fruiting shoots mid season, indications of the impending deficiency could be established very early in the season using foliar analysis. Magnesium concentrations in youngest fully expanded leaves (YFEL) on the affected vines were less than 2.0 g kg⁻¹ DM four weeks after budbreak and remained below this value for the rest of the season; concentrations in YFEL on unaffected vines did not decrease below this value and gradually increased after fruitset to 4.5 g kg⁻¹ DM at harvest. To avert potential production losses, it is suggested that soluble magnesium fertilizers (containing at least 200 kg ha⁻¹ Mg) should be broadcast early in the season if foliar magnesium concentrations less than 2.0 gkg⁻¹ DM are measured four–six weeks after budbreak.     

Root demography in kiwifruit (Actinidia deliciosa)

A rhizotron was used to study fine-root demography in mature vines of kiwifruit (Actinidia deliciosa). The vines were grown in a deep, well drained, silt loam and received normal orchard management. Roots were measured from 10 to 160cm depth at biweekly intervals for 2 years. After an initial phase of rapid colonisation of the repacked soil behind the rhizotron windows, the total length of visible roots per vine remained quite steady. This apparent stability of the total belied fast and sustained localized turnover of the fine roots at all soil depths. Fifty-one per cent of the roots survived ≤28d, 69% died at an age ≤56d and only 8% survived >252d. For each year, the cumulative length of roots grown was equivalent to about 2·75 times the maximum net length of roots visible. These may be the largest annual rates of root turnover yet reported. This has important ramifications for the carbon balance, mineral nutrition and water relations of the plant.     

Pollen Development in Actinidia deliciosa var. deliciosa: Histochemistry of the Microspore Mother Cell Walls

The development of the microspore mother cell walls in Actinidiadeliciosa (kiwifruit) has been studied using light and electronmicroscopy. The microspore mother cell wall is similar, histochemically,and structurally in anthers from both functionally staminateand functionally pistillate flowers. Deposition, which beginsduring early prophase I, produces an electron-dense multilaminatedwall layer (layer a) and by the end of meiosis I a thick electron-lucentlayer (layer b) to the inside of this multilayered wall. Thereasons for histochemical differences and similarities betweenthese layers are discussed. The original primary wall persistsuntil the late uninucleate microspore stage. Layer (b), whichis probably mainly callose, dissolves at the late tetrad/earlymicrospore stage while layer (a), which probably also containsother polysaccharides, persists and dissolves concurrently withthe primary wall. Actinidia deliciosa, kiwifruit, microspore mother cell wall, callose, histochemistry, light microscopy, electron microscopy, male sterility     

Anatomy and Histochemistry of the Root System of the Kiwifruit Vine, Actinidia deliciosa var. deliciosa.

The kiwifruit vine is a species which has been newly introducedinto cultivation and little is known of its comparative physiologyand anatomy. In this study we found that fibrous, 'magnolioid'roots, which have undergone secondary vascular development butwhich retain the cortex and develop a suberized epidermis, comprisethe greater part of the root system (95% of total length). Newlyinitiated roots with primary development conform to norms establishedin other woody plant species. However, the structural roots,like the fibrous roots, also retain a cortex and phellodermwhich is initiated by hypodermal cells within the cortex andnot by the pericycle which is the common progenitor tissue inother species. This phellogen produces new cells centrifugallyonly. The cortex is a relatively small component of the structuralroot and the bulk of the tissue is vascular in origin, as inthe roots of other plant species. The endodermis is retainedand continues to divide periclinally to accommodate the increasein circumference with growth.Copyright 1993, 1999 Academic Press Actinidia deliciosa, root anatomy, ontogony, histochemistry, exodermis, endodermis     

A genome-specific repeat sequence from kiwifruit (Actinidia deliciosa var. deliciosa)

Summary Six members of a family of moderately repetitive DNA sequences from kiwifruit (Actinidia deliciosa var. deliciosa) have been cloned and characterized. The repeat family is composed of elements that have a unit length of 463 bp, are highly methylated, occur in tandem arrays of at least 50 kb in length, and constitute about 0.5% of the kiwifruit genome. Individual elements diverge in nucleotide sequence by up to 5%, which suggests that the repeat sequence is evolving rapidly. Homologous sequences were found in A. deliciosa var. chlorocarpa. The repeat sequence was not found under low stringency hybridization conditions in the diploid A. chinensis, the species most closely related to the hexaploid kiwifruit, or in eight other Actinidia species. However, homologous repeats were detected in a tetraploid species, A. chrysantha. The results provide the first molecular evidence to suggest that kiwifruit may be an allopolyploid species.     

Modelling chlorophyll fluorescence of kiwi fruit (Actinidia deliciosa)

Kiwi fruit displays chlorophyll fluorescence. A physical model was developed to reproduce the observed original fluorescence for the whole fruit, from the emission of the different parts of the kiwi fruit. The spectral distribution of fluorescence in each part of the fruit, was corrected to eliminate distortions due to light re-absorption and it was analyzed in relation to photosystem II-photosystem I ratio. Kiwi fruit also displays variable chlorophyll-fluorescence, similar to that observed from leaves. The maximum quantum efficiency of photosystem II photochemistry (F(v)/F(m)), the quantum efficiency of photosystem II (Φ(PSII)), and the photochemical and non-photochemical quenching coefficients (q(P) and q(NP) respectively) were determined and discussed in terms of the model developed. The study was extended by determining the photosynthetic parameters as a function of the storage time, at both 4 °C and room temperature for 25 days.     

Pollen-pistil interaction in kiwifruit (Actinidia deliciosa; Actinidiaceae)

The pollen-pistil interaction has been examined in kiwifruit (Actinidia deliciosa). In this species a large number of seeds are produced in each fruit and a great many pollen grains germinate and grow to reach the ovules. This growth is assisted by an abundant secretion that is present all along the pistilar tract. At anthesis, the stigma is covered by a secretion where the pollen grains germinate and grow. The stylar transmitting tissue is initially rich in starch reserves, but the starch gradually disappears and, concomitantly, an abundant secretion that stains for carbohydrates appears in all of the intercellular spaces. Pollen tube growth relies on this secretion since it is depleted after pollen tube passage, while in unpollinated flowers it remains unaltered throughout the flower life-span. In the ovary a similar situation occurs. The placental surface, where the pollen tubes grow before reaching the ovules, is covered by a number of obturators. At anthesis, these obturators are rich in starch reserves and have an abundant secretion on their outer surface. As time passes, starch disappears while the secretion increases. It is in this secretion that the pollen tubes grow on their way toward the ovules. These observations are discussed in terms of the support given by the pistil to pollen tube growth to achieve the highly successful reproductive performance of this species.     

The Effect of Drought and Vapour Pressure Deficit on Gas Exchange of Young Kiwifruit (Actinidia deliciosavar.deliciosa) Vines

To evaluate the effect of drought and vapour pressure deficit (VPD) on stomatal behaviour and gas exchange parameters, young kiwifruit vines (Actinidia deliciosavar.deliciosacv. Hayward) were exposed to alternating periods of drought and drought-relief over two growing seasons. Vines were grown either in the field or in containers. Stomatal conductance of fully-expanded leaves rapidly decreased as pre-dawn leaf water potential was reduced below a threshold value of -0.3MPa. Stomatal conductance reached minimum values of 10–20mmol m^-2s^-1. Transpiration rate was similarly sensitive to changes in leaf water status, whereas more severe drought levels were necessary to affect photosynthesis significantly. Net daily carbon gains were estimated at 4.7 and 2.7gm^-2for irrigated and droughted vines, respectively. Gas exchange parameters recovered to values of irrigated vines within a few hours after relief of stress. Rate of recovery depended on the level of stress reached during the previous drought period. There was a steady decline in stomatal conductance when VPD was increased from 0.8 to 2.5kPa in both irrigated and droughted vines. The VPD at which stomatal conductance reached 50% of maximum values was 2.1–2.2kPa for both treatments. We conclude that stomata were highly sensitive to changes in soil water status and that midday depression of photosynthesis measured in kiwifruit vines was related to water deficits arising in the leaf because of both transpirational losses and to the direct effect of increasing VPD.     

Anti-hyperglycemic activity of kiwifruit leaf (Actinidia deliciosa) in mice

The methanol extract of kiwifruit leaf suppressed the postprandial blood glucose level after an oral administration of soluble starch or sucrose in mice. The mechanism of action is proposed to be due to the alpha-amylase-inhibiting activity in the 90% aqueous methanol fraction and alpha-glucosidase-inhibiting activity in the n-buthanol fraction, based on the results of in vitro experiments.     

The allopolyploid origin of kiwifruit,Actinidia deliciosa (Actinidiaceae)

The genetic origin of kiwifruit (Actinidia deliciosa var.deliciosa) was studied using phylogenetic analysis of DNA sequences derived from the polygalacturonase gene. Results indicate that hexaploid kiwifruit had an allopolyploid origin with the diploidA. chinensis contributing one genome (genome A) and another (as yet unidentified) diploid species contributing a second genome (genome B). The results leave open the question of whether a third, distinct species contributed to the hexaploid kiwifruit genome. A tetraploid race ofA. chinensis is also suggested to be allopolyploid containing genomes A and B.     

Effects of Temperature and Leaf Position on Leaf Area Expansion of Kiwifruit (Actinidia deliciosa) Shoots: Development of a Modelling Framework

This paper describes mathematically the effects of temperatureand position on the expansion of leaves along a kiwifruit (Actinidiadeliciosa) shoot, taking into account shoot morphology. Theleaves were grouped into three zones along the shoot: initialcluster leaves (first zone); the rest of the leaves that werepreformed during the previous season (second zone); and leavesthat were initiated during the current season (third zone).After opening of the initial cluster, the leaves appeared atconstant rates for each of the two temperature treatments considered.The expansion of individual leaves was modelled by a growthfunction with the parameters: final area; duration of the growthwindow; centre of the growth window (timing of expansion); andlower asymptote. Within the first two zones, the pattern ofleaf expansion was affected by nodal position, with basal leaveshaving higher initial rates of expansion than distal leaves.The timing of expansion was linear with respect to the nodalposition within each of the zones, with the slope independentof temperature for the first zone. The slopes of the timingof expansion for the second and third zones depended on temperatureand were correlated for each temperature treatment. Final leafarea was a function of leaf position in the first zone and afunction of timing of leaf expansion for distal leaves startingfrom leaf 10. Temperature had no effect on final leaf area inthe first zone. For the rest of the leaves, temperature affectedfinal leaf area indirectly, through the timing of leaf expansion.The effect of temperature on the growth window of individualleaves within the first zone was less than that for the restof the leaves. However, simulated values for the total leafarea of shoots using the average shoot growth window showedgood agreement with experimental values.Copyright 2001 Annalsof Botany Company Actinidia deliciosa‘Hayward’, shoot development, individual leaf area, temperature effect, positional effects, modelling     

Purification and characterisation of a galactoglucomannan from kiwifruit (Actinidia deliciosa)

A galactoglucomannan (GGM) has been purified from the primary cell walls of ripe kiwifruit. A combination of barium hydroxide precipitation, anion exchange- and gel-permeation chromatography gave a chemically homogeneous polymer with a 1:2:2 galactose-glucose-mannose ratio and a molecular weight range of 16-42 kDa. Complete hydrolysis of the polymer with endo-1,4-beta-mannanase (EC 3.2.1.78) from Aspergillus niger gave a mixture of oligosaccharides, three of which (II, III, IV) accounted for more than 80% of the GGM. Structural characterisation of these oligosaccharides and the original polysaccharide was achieved by linkage analysis, 1D and 2D NMR spectrometry and enzymatic hydrolysis. Oligosaccharide II beta-D-Glcp-(1-->4)-beta-D-Manp-(1-->, III beta-D-Glcp-(1-->4)-[alpha-D-Galp-(1-->6)]-beta-D-Manp-(1-->, and IV beta-D-Glcp-(1-->4)-[beta-D-Galp-(1-->2)-alpha-D-Galp-(1-->6)]-beta-D-Manp-(1-->4)-beta-D-Glcp-(1-->4)-beta-D-Manp-(1-->, appeared in the molar ratio of 2:1:1. A trace amount of mannobiose (I) was detected, indicating that some of the mannosyl residues were contiguous. It is concluded that the predominant structural feature of kiwifruit GGM is a backbone of alternating beta-(1-->4)-linked D-glucopyranosyl and D-mannopyranosyl residues, with approximately one third of the latter carrying side-chains at 0-6 of single alpha-D-Galp-(1--> residues (50% of the branches) or the disaccharide beta-D-Galp-(1-->2)-alpha-D-Galp-(1--> (50% of the branches), the substituted residues being separated by three or five unsubstituted monosaccharide units.