Single-node Cuttings Research Articles

Time-to-event analysis to evaluate dormancy status of single-bud cuttings: an example for grapevines

BackgroundThe reduced growth of plants during the winter causes a lack in the perceptibility of the phenological events making challenging the study of dormancy. For deciduous crops, dormancy is generally determined by evaluating budbreak of single-node cuttings that are exposed to conditions suitable for growth. However, the absence of a statistical basis for analyzing and interpreting the budbreak behavior evaluated as the percent budbreak, the average time to budbreak and the time to reach 50% budbreak, has caused inconsistent and contradictory criteria to identify the dormancy status of different deciduous crops.ResultsIn this study, a method was developed to analyze the duration between sampling and budbreak of single-node cuttings and to estimate the dormancy status for grapevines (Vitis vinifera L.) based on the time-to-event distribution of the observations. This method estimates the probability curve of budbreak for each sample and classifies each curve into paradormancy, endodormancy, and ecodormancy according to the significance when compared to a sample curve estimated from cuttings collected during paradormancy and referred to as “reference.”ConclusionThe approach described in this study provided a comparison of the budbreak distribution of cuttings collected during distinct phases with a confidence of 95%. It also allowed the estimation of the date of occurrence of the dormancy stages for two grapevine cultivars ‘Cabernet Sauvignon’ and ‘Chardonnay,’ based on the variability within the sampling season rather than on fixed arbitrary criteria. This approach can also be used to analyze budbreak data of single-node cuttings from other common deciduous crops.

Physiological and Biochemical Modulations upon Root Induction in Rose Cuttings as Affected by Growing Medium

Two cut rose (Rosa hybrida) cultivars ‘Sherbet’ (easy-to-root) and ‘Alibaba’ (difficult-to-root) were propagated by single nodal cuttings on preformed media. Four commercial media such as Tosilee, Ellepot, rockwool and phenolic foam RC, and four newly-developed foam media namely Oasis PU 14-S1, Oasis TP-S1, Oasis PU-7B and Oasis PU 15-S1 were employed in this study. All media were manufactured to fit into 50-cell plug trays. The experiment was laid out in a complete randomized block design with three replications on a propagation bench with a plastic tunnel installed in a glasshouse, with (98 ± 2)% relative humidity and over 50% shading of the natural sunlight. After four weeks of experiment, growth parameters, localization of superoxide radicals, and activities of rooting biochemical markers were measured. The results suggested that the newly-developed foam media Oasis TP-S1 and Oasis PU-7B enhanced the growth, density of leaf stomata, and consisted of lesser harmful superoxide radicals in similar manner with the existing commercial media. Moreover, the Oasis TP-S1 and Oasis PU-7B media significantly enhanced the total phenol content and the activities of important enzymes involved in the phenol metabolism which plays a vital role in the formation of roots. Thus, the understanding of both physiological and biochemical changes implicated by the growing medium during the rooting of cuttings would aid in the selection of optimal growing medium for the propagation of rose cuttings.

Assessment of Genetic Diversity in Robusta Coffee Using Morphological Characters

ABSTRACTAssessing the level of genetic variation that exist in any breeding population is important as this has significant implications for selection and variety development. The objectives of the present study were to determine the variation among 71 Robusta coffee genotypes based on 21 traits and to determine the genetic relationships between the genotypes. The 71 genotypes were established in 2013 as clones raised from single node cuttings and planted in a randomized complete block design with four blocks, with five plants per genotype per block. There was variation in all the traits assessed for the different Robusta coffee genotypes as evidenced by the coefficient of variation and frequencies of the quantitative and qualitative traits, respectively. Principal Component Analysis (PCA) was performed to obtain information on the relative importance of the morphological characters assessed, and cluster analysis was used to determine relationships among the genotypes evaluated. The first and second principal components accounted for 39.2% and 18.9% of the total variability, respectively. PCA revealed that height, stem diameter, span, number of laterals per tree, diameter of laterals, and number of nodes per lateral were the principal characters to discriminate the Robusta coffee genotypes examined. Cluster analysis grouped the Robusta coffee genotypes into five clusters as revealed by the dendrogram. The diversity among the Robusta coffee genotypes in both quantitative and qualitative traits revealed by this study can be used for trait improvement through selection and hybridization.

Foliar application of citric and malic acid to stock plants of rose alters the rooting of stem cuttings

BackgroundAs the world’s best-selling cut flower, there is a high demand for propagated rose plants. Auxins are the dominant growth regulator used to improve the rooting of cutting; however, their application remains a labor-intensive process, and on the other hand, side effects like poor shoot growth exist. Organic acid sprays have enhanced many physiological traits of plants which justified surveying their possible effect on the rooting process in the current study.MethodsDifferent concentrations of citric or malic acid were sprayed to stock plants of rose (Rosa x hybrida cv. ‘Sherbet’) prior to taking cuttings. Malic or citric acid (3, 6, or 9 mM) was applied five times on a 14-day interval in a commercial cut flower production greenhouse. Single-node cuttings were prepared and were rooted under mist. Data collected included rooting percentage, root count, root and shoot length and dry weight, and root-to-shoot ratio (R:S).Results and discussionThe rooting percentage was enhanced by all treatments. Citric acid enhanced root number at 6 mM level followed by 3 mM citric acid. Average root length was increased by all treatments except 3 and 6 mM malic acid. All CA treatments increased shoot length, while it remained unaffected by MA treatments. CA at 3 and 6 mM level and 6 mM MA increased shoot dry weight, but only 9 mM CA increased the root dry weight.ConclusionBoth organic acids had positive effects on rooting response of ‘Sherbet’ roses. However, the mechanism of observed responses to organic acids remains to be studied. While they enhance the physiological performance of stock plants, they can also simultaneously both enhance the rooting as well as the shoot growth of the new plantlets.

Effects of micro-environmental factors on the photoautotrophic growth of Hibiscus sagittifolius Kurz cultured in vitro

The arrow leaf abelmoschus rhizome (Hibiscus sagittifolius Kurz), or Sam Bo Chinhin Vietnamese, is a perennial suffrutex herb from which the tuber root is used as a medicine in folk remedy. This species is widely distributed and can be found on many terrains across South East Asia. With an aim to create a large number of uniform and high-quality H. sagittifolius transplants in vitro, effects of some environmental factors such as photoperiod and temperature on the photoautotrophic growth of H. sagittifoliusin vitro plants were investigated. In vitro single nodal cuttings, each with an unfolded leaf, were cultured photoautotrophically (without sucrose and vitamins) on mineral SH medium, under light intensity of 150 µmol m-2 s-1, temperature of 24oC ± 2oC, relative humidity (RH) of 55% ± 5% and three different photoperiods (8, 12 or 16 h d-1) in the first experiment. Commercial polypropylene bags (V = 1,000 ml), attached with two filter-paper membranes, were used as culture vessels. After 42 days of culture, H. sagittifolius plants under the photoperiod of 16 h d-1 had the greatestincreased fresh weight (502.3 mg/plt), increased dry weight (39.5 mg/plt) and leaf area (17.0 cm2) than those put under 8 hd-1or 12 h d-1. In addition, H. sagittifolius plants also showed statistical differences in growth when photoautotrophically cultured in different air temperature regimes, including 28/25oC (photo-/dark period), 25/25oC and 20/25oC. Increased fresh weight (775 mg/plt), increased dry weight (62 mg/plt) and leaf area (22.7 cm2) of in vitro H. sagittifolius plants were the greatest when temperature was maintained at 28 oC during photoperiod. On the contrary, the photoperiod temperature of 20oC resulted in the shortest shoot length and root length of H. sagittifoliusplants. In conclusion, this study proved that H. sagittifolius plants had the best growth when cultured on SH medium, without sucrose and vitamins supplementation, under light intensity of 150 µmol m-2 s-1, RH 55% ± 5%, photoperiod of 16 h d-1, temperature regime of 28/25oC(photo-/dark period). Citation: Nguyen Thuy Phuong Duyen, Tran Thi Van, Nguyen Le Thu Minh, Nguyen Thi Quynh, 2017. Effects of micro-environmental factors on the photoautotrophic growth of Hibiscus sagittifolius Kurz cultured in vitro. Tap chi Sinh hoc, 39(4): 496-506. DOI: 10.15625/0866-7160/v39n4.11030. *Corresponding author: qtnguyen_vn@yahoo.comReceived 7 September 2017, accepted 15 December 2017

Effects of red and blue LEDs on in vitro growth and microtuberization of potato single-node cuttings

Effects of red and blue LEDs on in vitro growth and microtuberization of potato single-node cuttings

Regulating the rooting process of rose softwood cuttings by foliar citric and malic acid spray on stock plants

Abstract We evaluated the effects of spraying different concentrations of citric and malic acids on stock plants in the greenhouse prior to the propagation and rooting of rose (Rosa × hybrida ‘Love Letter’) cuttings. Malic and citric acids (3, 6 and 9 mM) were sprayed several times at 14-day intervals on rose plants in a commercial cut flower producing greenhouse. Single-node cuttings taken from flowering stems were rooted under misty conditions, and the rooting parameters including root count and dry root weight were measured. A distinct change was observed in rooting features in response to the applied organic acids. Malic acid significantly enhanced rooting at the intermediate concentration while retarding it at both the higher and lower concentrations. On the other hand, the effect of citric acid was best at the highest concentration applied. We conclude that in softwood cuttings taken from rose plants these organic acids can act as a potential alternative to the currently applied methods of promoting rooting.

Efficient propagation of citrus rootstocks by stem cuttings

A simple multicomponent system is described that is effective for rapid propagation of a diversity of citrus rootstock genotypes by single node cuttings, including new hybrids and cultivars that are most commonly used as rootstocks. Efficiency of this system for rooting shoot explants of six important rootstock cultivars, Swingle, Cleopatra, US-802, US-812, US-897, and US-942 is compared in a repeated study. Many of the cuttings began to grow within 2 weeks after planting into potting mix. Growth for the resultant plants of different genotypes was compared through 20 weeks, and significant differences were observed. US-802 had the highest success in establishing growing plants at 8 weeks, with 82–91% of single node cuttings successfully rooted and growing, while Cleopatra was the least efficient with a 42–45% recovery of growing plants. Comparison of plant weight for cuttings and seedlings indicated that 12 week old nucellar and true-to-type seedlings are similar in size to 12–16 week old cuttings of the same cultivars. Plants of all rootstocks, whether cuttings or seedling-propagated, were observed to approach a dry weight ratio of 80% shoot and 20% root. Pronounced differences in the number and length of roots were identified among the rootstocks, indicating large differences in root structure that might be important in relation to eventual field plant health and growth. The commercial utility of the described methods is discussed.

Effect of Auxins and Associated Metabolic Changes on Cuttings of Hybrid Aspen

In the present study, an attempt was made to induce rooting from single-node cuttings of hybrid aspen (Populus tremula L. × P. tremuloides Michx.) with different concentrations of Indole-3-acetic acid (IAA), Indole-3-Butytric acid (IBA) and 1-Naphthylacetic acid (NAA). Among the three auxins used, 0.54 mM NAA showed more effective induction on rooting as compared to IAA and IBA at the whole level. Thereafter, 0.54 mM NAA was used further for the anatomical and biochemical investigation. The results showed that it took 12 days from the differentiation of primordium to the appearance of young adventitious roots under NAA application. It was found that endogenous IAA, Zeatin riboside (ZR) and Gibberellic Acid (GA3) levels increased, but Abscisic acid (ABA) decreased in cuttings with NAA treatment. In contrast to the endogenous IAA level, NAA resulted in a decrease in IAA-oxidase (IAAO) activity. Similarly, the decreased peroxidase (POD) activity, consistent with down-regulation of expressed levels of POD1 and POD2, was observed in NAA-treated cuttings. Moreover, NAA resulted in a higher activity in polyphenol oxidase (PPO) compared with control cuttings. Collectively, the study highlighted that 0.54 mM NAA is efficient on rooting in hybrid aspen, and its effect on metabolic changes during rooting was discussed, which can provide valuable information for propagating hybrid aspen.

<i>In vitro</i> induction of tetraploids from <i>Exacum ritigalensis</i> (Gentianaceae)

Exacum ritigalensis (Gentianaceae) (Sinhalese: Binara or Ginihiriya) has a potential to develop as a potted plant by improving the size of the flowers and inflorescence. The aim of the study was to establish an efficient and effec-tive system for the production of tetraploid plants through colchicine treatment. Single nodal cuttings (0.5 cm) from aseptic plantlets were established on Murashige and Skoog basal medium (MS) supplemented with 2 mgL-1BAP and different colchicine concentrations (0, 10, 20, 30, 40 and 50 mg-1). They were kept in different durations (0, 7, 14 21 and 28 days) and transferred into 10ml of MS basal medium containing 2 mgL-1 BAP. After one month, they were transferred to MS medium containing 2mgL-1Indole-3-butyric acid (IBA) for rooting. Then root tips were collected from treated plants to observe chromosome number. Afterwards the selected diploid and tetra-ploid plants were acclimatized and transferred to field to observe the morphological characters. Factorial Com-plete Randomized Design (FCRD) with 10 replicates was used for each treatment and statistical analysis was car-ried out using Duncan’s Multiple Range Test of SAS program (9.1.3).The highest percentage of tetraploid plant-lets (26.6%) was observed from nodal cuttings treated with MS basal medium with 2mgL-1 BAP + 30mgL-1 colchi-cine for seven days. The chromosome number of diploid and tetraploid E. ritigalensis determined as 28 and 56 respectively. Cells of the tetraploid plants were comparatively larger cells than diploids plants. The stomata size of the tetraploid (2.96*2.27 μm2) were larger than those of the diploids (1.94*1.48μm2). Leaf shape of diploids was lanceolate while it was ovate or narrowly elliptic in tetraploids. Flower petals of diploid plants were overlapping along their entire length while in tetraploids flower petals were not overlapping. The plants height was significantly higher in diploid (67.00±9 cm) than in tetraploid (38.00±4 cm). Newly produced polyploids of E. ritigalensis have a potential to popularize as a potted plant in the floriculture trade.

Base temperature as a function of genotype: a foundation for modeling phenology of temperate fruit species

To complete each phase of the growing season, plants must accumulate thermal time at lower base temperature (Tb). Little information exists on Tb variation between either fruit species or cultivars of the same species. We therefore aimed to determine the lower base temperature for contrasting genotypes in precocity of peach, plum, grape, pear, and kiwi. Twigs 25-35 cm long for the following cultivars: peach, Tropic Beauty (TB) and Eragil (ER); plum, Gulf Blaze (GB) and Letícia (LE); grape, Chardonnay (CH) and Cabernet Sauvignon (CS); pear, Smith (SM) and Packham’s (PA); and kiwi, Golden King (GK) and Hayward (HA) were collected in orchards in Veranópolis, RS Estate, on 06/13/2014, with 0 h at temperatures ? 7.2°C (chilling hours; HC) in the field. Intact twigs packed in black plastic film were subjected to 1,008 HC at 0°C in incubators to overcome dormancy and then transferred to temperatures of 2, 4, 6, 8, 10, and 12°C on single-node cuttings planted in phenolic foam to define effective heat temperature for the genotypes. Over 110 d, budburst of the buds was evaluated in 2-3-d intervals in the green-tip stage. The resulting inverse data of number of days to budburst (1/days to budburst) was inserted into regression curves to estimate Tb for each genotype. Historical phonological series comprised of 10 years for the analyzed cultivars and meteorological data of the cultivation sites were used to determine thermal time (degree-days) for the fruit trees during the growing season, considering different phenological phases. Temperate fruit species exhibited different Tb behaviors: Tb was lower for early cultivars (TB and GB = 2.2°C; CH = 2.1°C; SM = 4.4°C; GK = 4.3°C) and higher for late cultivars (ER = 6.3°C; LE = 6.2°C; CS = 4.3°C; HA and PA = 8.2°C) for all cultures. The Tb f fruit cultivars related directly with genotype chilling requirements: the higher the chilling requirement, the higher the Tb of the cultivar. Cultivars of the same fruit species yielded a sum of degree-days almost equal to finalize the growing season, regardless of the degree of precocity (TB = 1720; ER = 1801; GB = 1680; LE = 1718; CH = 2310; CS = 2369; SM = 2096; PA = 2003 GD; GK = 2775; HA = 2691). Regarding phenological phases, 82% of the assessed cases responded more to thermal time (degree-days) than to chronological time (d) to complete phenological steps. Differences in Tb between genotypes are a relevant factor for improving the accuracy and applicability of phenology models in agriculture.

Clonal propagation of Pterocarpus santalinoides L'Hér. ex DC.: the effect of substrate, cutting type, genotype and auxin

Pterocarpus santalinoides is a multipurpose tree species, native to Africa and South America. However, excessive pruning for fodder is jeopardising its seed production leading to poor regeneration in the Sahel region. Efficient vegetative propagation techniques may overcome this concern. To address this issue, four experiments were conducted to determine the effects of substrate (Experiment 1), cutting type (Experiments 2 and 3), genotype (Experiment 4) and auxins (Experiments 1, 2, and 4) on rooting ability in a non-mist propagating unit in Mali. Among the four tested substrates, no significant differences were found in rooting parameters, including the percentage of rooted cuttings, the number of roots and secondary roots per rooted cutting, and the length of the longest root per rooted cutting. Semi-hardwood cuttings rooted significantly better than softwood cuttings with a higher percentage of rooted cuttings (31.7 ± 6.5% vs. 9.2 ± 2.7%), greater number of roots (8.2 ± 4.8 vs 1.5 ± 0.7), greater number of secondary roots (16.7 ± 4.2 vs 4.6 ± 1.8) and longer root length (17.8 ± 12.0 cm vs 2.3 ± 1.0 cm) per rooted cutting. In addition, one-node cuttings cut below the second and third nodes, respectively, had the highest rooting success (88% and 90%, respectively) followed by cuttings cut below the fourth node (68%) and the first node (62%). Significant differences in the percentage of rooted cuttings were found among 12 randomly selected genotypes with rooting varying from 2% to 75%.The results also showed that auxin application, especially IBA, had a significant effect on rooting success, the number of roots and secondary roots per rooted cutting. Single-node cuttings, and cuttings of 10 cm length with multiple softwood and semi-hardwood nodes, can be used with or without auxin treatment for successful clonal propagation of P. santalinoides. The results of the present study indicated that P. santalinoides is amenable to clonal propagation using low-cost propagators and sand-based rooting media.

Gamma irradiation of in-vitro proliferated cultures of rose (Rosa hybrida) for induction of novel mutants

In-vitro mutations were induced in two Hybrid Tea rose (Rosa hybrida L.) cultivars Pusa Mohit and Raktima for induction of novel traits. Single node cuttings were used to proliferate cultures under in-vitro and were irradiated with different doses of g-rays (0, 5, 10, 15, 20 or 25 Gy) using a 60Co source. The g-irradiated microshoots were then cultured aseptically on to rooting medium containing 0.5 × MS basal medium supplemented with 2.69 µM a- naphthalene acetic acid (NAA) plus 2.46 µM 6-benzylaminopurine (BAP) plus 40 g/l sucrose and 0.8% (w/v) agar- agar for rooting. Decreased root lengths, numbers of roots per shoot were observed at 25 Gy. In-vitro proliferated cultures and non-irradiated (control) plants were transferred to plastic pots 1 month after acclimatization under laboratory conditions and examined for their morphological traits. Marked vegetative abnormalities with respect to leaf shape, leaf lamina, fused leaves, albinism or leaves with less chlorophyll, variegated leaves with stunted growth etc. were observed between the mutated and control populations. Four new variants with altered or novel flower colour, form, shape and size were isolated and numbered as PM 1, PM 2 (from cv. Pusa Mohit) and RK 1, RK 2 (from cv. Raktima) as compared to the original cultivars. These variants were multiplied on a large-scale through micropropagation and evaluated for their stability. This study developed a mutagenesis protocol that could be used to develop novel flower colour mutants in rose.

Micropropagation of Endangered and Decorative Species Dianthus pinifolius Sibth. et Sm.

The aim of this study was to establish an efficient protocol for the in vitro propagation of the endangered, endemic and decorative species Dianthus pinifolius Sibth. et Sm. The effects of different concentrations of 6-benzylaminopurine (BAP) and naphtalenacetic acid (NAA), and different explant types (single-node cuttings, terminal buds and shoot cuttings) on shoot multiplication were examined on Murashige and Skoog (MS) and half-strength MS media. The best results were obtained for shoot cuttings on the MS medium supplemented with 0.5 mg/L BAP and 0.1 mg/L NAA, achieving a maximum rate of regeneration (100%) and a total of 15.4 newly-developed shoots per explant. The highest rooting rate (96.7%) was obtained on MS medium containing 1 mg/L NAA, while the acclimatization of the microplants obtained to ex vitro conditions was successful (88.9%).

BUD DORMANCY INTENSITY IN PEACH TREE CULTIVARS BY BIOLOGICAL AND TETRAZOLIUM TEST

ABSTRACT Temperate climate fruit trees often exhibit uneven budding and flowering, due to the low number of chilling hours that determine the occurrence of dormancy and its depth. The objective of this study was to determine the depth of bud dormancy in peach tree cultivars and evaluate the efficiency of the tetrazolium test for dormancy and comparing with biological test. Branches of the cultivars Aurora 1, Chimarrita, Chiripá, Coral, Eldorado, Granada, Leonense, Maciel, Marli, Premier, and Vanguard were collected between May and August 2008 at two locations: Curitiba and Lapa. The evaluation of dormancy was performed using a biological test of single node cuttings through the parameters: average time for bud burst, velocity of bud burst, final rate of bud burst and rate of vigorous bud burst. For the tetrazolium test, 300 mg of buds was used and the color intensity readings were obtained using a spectrophotometer. The peach tree cultivars evaluated differ in the intensity of dormancy in late fall. The most intense endodormancy cultivars found were: Chiripá, Leonense and Eldorado cultivars, and the weaker cultivars found were: Aurora 1 and Maciel. The tetrazolium test was efficient at estimating the intensity of dormancy in peach trees when the occurrence of cold was suitable for installation endodormancy. At a location with the lowest occurrence of cold (Curitiba), the tetrazolium test did not simulated successfully the biological test results.

English

Prunus africana (Kanda stick) is a valuable medicinal tree classified as priority species for domestication in Cameroon. To measure the ability for developing axillary buds and multiple shoots in relation with the origin and state of explants, some biochemical parameters were assessed in eight types of single-node cuttings. These cuttings were treated with different concentrations of kinetin (kin) indole butyric acid (IBA) and thidiazuron (TDZ) and cultured in Murashige and Skoog (MS) medium. The glutelin content (1.13 ± 0.201 µg/mg FW) was higher compared to those of total albumin, globulin and prolamin and most representative at mature vegetative apical stage (MVA). The highest (15.60 ± 1.966 µg/mg FW) and lower (2.82 ± 0.072 µg/mg FW) amount of phenol compound was observed in the mature dormant stages and immature vegetative distal stage (IVD), respectively. Regarding the peroxidases, highest activity (0.453 ± 0.055 OD/mg/ FW.5 min -1 ) was obtained in mature dormant apical stage. Apart from IVA state, there was no reactive explant cultured in vitro. The high percentage of budding and proliferation of budding (100%) and rooting (100%) were achieved with 12 μM Kin and 24 μM IBA, respectively. In the presence of 24 μM TDZ, multiple shoot was induced with a maximum of 5 shoots/explants. Micropropagation success of P. africana is influenced by cytokinin, physiological and biochemical status of single node cutting. Key words : Biochemical profile, Prunus africana, budding, multiple shoots, rooting.

Long-term response on growth, antioxidant enzymes, and secondary metabolites in salicylic acid pre-treated Uncaria tomentosa microplants.

To obtain micro propagated Uncaria tomentosa plantlets with enhanced secondary metabolites production, long-term responses to salicylic acid (SA) pre-treatments at 1 and 100µM were evaluated after propagation of the plantlets in a SA-free medium. SA pre-treatments of single node cuttings OF U. tomentosa produced long-term responses in microplants grown for 75 days in a SA-free medium. Reduction in survival rate, root formation, and stem elongation were observed only with 100µM SA pre-treatments with respect to the control (0+DMSO).Both pre-treatments enhanced H2O2 and inhibited superoxide dismutase and catalase activities, while guaiacol peroxidase was increased only with 1µM SA. Also, both pre-treatments increased total monoterpenoid oxindole alkaloids by ca. 55% (16.5mgg(-1) DW), including isopteropodine, speciophylline, mitraphylline, isomitraphylline, rhynchopylline, and isorhynchopylline; and flavonoids by ca. 21% (914μgg(-1) DW), whereas phenolic compounds were increased 80% (599μgg(-1) DW) at 1µM and 8.2% (359μgg(-1) DW) at 100µM SA. Pre-treatment with 1µM SA of U.tomentosa microplants preserved the survival rate and increased oxindole alkaloids, flavonoids, and phenolic compounds in correlation with H2O2 and peroxidase activity enhancements, offering biotechnological advantages over non-treated microplants.

Stress-induced development of inflorescence necrosis and bunch-stem necrosis in Vitis vinifera L. in response to environmental und nutritional effects

Inflorescences and mature clusters, respectively, of field-grown Muller-Thugau grapevines ( Vitis vinifera L.) were immersed in aqueous solutions of the glutamine synthetase (GS) inhibitor phosphinothricin (PPT). Typical symptoms of inflorescence necrosis developed after immersion in 1 or 10 mM PPT, but not in the 0.1 mM treatment. No necrotic symptoms could be induced in mature clusters. In addition, single-node cuttings of field-grown Muller-Thurgau and Pinot noir vines with one cluster, with or without adjacent leaf, were incubated in various solutions with or without PPT at several phenological stages. Necrotic symptoms occurred in all treatments including the H 2 O control. However, at early stages of development the symptoms appeared earlier than at later stages, and elevated PPT concentrations reduced the development of necrotic manifestations. The addition of NH,NO, to the solution enhanced the appearance of symptoms both in the presence and absence of PPT, while KNO 3 did not. In incubation solutions without PPT, metallic cations like Mg 2+ , Ca 2+ and K + reduced the incidence of bunch-stem necrosis. When cuttings were exposed to different environmental conditions, there was no significant light effect, but wind decreased the incidence of both inflorescence necrosis and bunch-stem necrosis. A leaf, attached to the cluster, or the addition of sucrose to the solution effectively delayed the development of necrotic manifestations. These results indicate that GS is present in rachis, flower and berry tissues and that the buildup of toxic NH 4+ levels is involved in the development of both inflorescence necrosis and bunch-stem necrosis. However, NO 3 - reduction and primary N assimilation appear not to contribute significantly to NH 4+ accumulation. This buildup may rather be a secondary effect related to senescence of the tissue due to carbon depletion.

Effect of Rootstock on Rooting and Early Yield of Stenting-propagated Cut Roses

The study was conducted to investigate the effect of rootstock on growth and early yield of stenting-propagated cut roses (Rosa hybrida Hort.) 'Pink Aurora' and 'Yellow King'. The scions, prepared as single-node cuttings, each with a five-leaflet leaf, were grafted onto cuttings of Rosa indica 'Major', Rosa multiflora 'Chille Wonye No. 1', Rosa multiflora 'K-1', or Rosa multiflora 'Burr' as the rootstock. The rootstock cuttings were removed of all leaves and buds before grafting. The base of scion and the top of rootstock were held together and simultaneously cut at a <TEX>$45^{\circ}$</TEX> angle for ease of grafting. Scion-rootstock unions were stuck in rockwool cubes and placed on a misted glasshouse bench for rooting before being transplanted into a rockwool slabs for cultivation. Rooting was the greatest in the 'Pink Aurora' and 'Yellow King' grafted on the rootstock Rosa indica 'Major'. In 'Pink Aurora', stem length, stem diameter, five-leaflet leaves per stem, and stem fresh weight of the harvested cut flowers were not affected by the rootstock. The greatest total yield of 'Pink Aurora' was obtained in plants grafted onto the Rosa indica 'Major' rootstock. Overall growth of 'Yellow King' was the greatest in plants grafted onto Rosa multiflora 'Burr' rootstock, although total yield was not affected by the rootstock. These results suggest that Rosa indica 'Major' is the most effective rootstock not only for rooting, but also for early yield and growth for stenting propagation of these cut roses.

Effects of shoot girdling and/or periodic leaf removal on inflorescence primordia initiation and development inVitis vinifera L. cv. Sauvignon Blanc

Background and Aims Inflorescence primordia (IP) development starts in the buds of leaf axils approximately 12 months before flowering. Primordia initiation progresses acropetally as the shoot develops, although little is known about the timing of initiation at different node positions up the developing shoot. Girdling and/or leaf removal treatments were used to investigate the timing of development and structure of grapevine inflorescences at different positions along the shoot. Methods and Results Individual shoots were either girdled at their base shortly after fruitset or left intact. Leaves were then removed from those shoots on four occasions from the time of girdling to natural leaf fall in the autumn. Dormant latent buds from treatment shoots (shoot node positions one to ten) were grown as single-node cuttings (SNCs) in a glasshouse, and the inflorescence number per SNC and their architecture were scored on developing shoots. Girdling fully leafed shoots increased the proportion of SNC basal inflorescences with an outer arm but had no effect on the number of inflorescences per SNC. Girdled shoots that had their leaves removed at 0 or 4 weeks post-fruitset had a decrease in inflorescence number per SNC and outer arm development from nodes six and eight, respectively. Conclusions Inflorescence initiation before node positions six and eight was complete by the time girdling and leaf removal treatments were applied, and initiation at nodes six and eight occurred at 0 and 4 weeks post-fruitset. The development of the apical IP and the outer arm of the basal IP appears to occur at the same time. Significance of the Study This study presents novel information regarding the timing of IP initiation at different positions along the developing shoot, including the initiation and development of the outer arm. Also, the formation of an outer arm is shown to be sensitive to girdling and/or leaf removal.