Humidity Tent Research Articles

Timing of Collection and Preparation of Hardwood Stem Cuttings for Propagating Hybrid Hazelnuts 1

AbstractIn previous trials we had found that dormant hybrid hazelnuts crown suckers collected in the fall after leaf drop can be successfully rooted if they are chilled at least until January before being placed in low-cost humidity tents in a greenhouse. The first objective of this experiment was to determine if cuttings could be rooted if started earlier, so as to avoid the heat stress found in the greenhouse in late spring and early summer. The second objective was to see if rooting rates could be improved by collecting non-dormant crown suckers in September and October, before leaf drop. We hypothesized that by collecting stems at a time in the fall when woody plants are translocating resources from leaves to their root systems, we could direct those resources towards growth of adventitious roots. This hypothesis proved to be wrong: stems collected in full leaf died, even with measures to avoid moisture loss from leaves. However, we found that stems collected soon after leaf abscission, in early November, could be rooted if placed in the humidity tents in late November, after only three weeks of artificial chilling at 2 C (36 F). That is much less chilling than we previously thought was needed.Index words: propagation, Corylus americana (Walter), Corylus avellana (L.), rooting, chilling requirement.Chemicals used in this study: indole-3-butyric acid (IBA).Species used in this study: hybrid hazelnuts [Corylus americana (Walter) x Corylus avellana (L.)].

Field Pretreatment of Crown Suckers for Propagating Hybrid Hazelnuts

Abstract Hybrid hazelnuts [Corylus americana (Walter) x C. avellana (L.)] are being developed for their ecological and economic value as a new crop for the Upper Midwest, but lack of economically viable propagation methods is a significant bottleneck to their wide scale adoption. Thus far, mound layering has been the primary propagation method, but layering cannot produce the numbers of plants needed for large-scale production. Rooting hardwood stem cuttings is a possible alternative. In a factorial experiment, we evaluated two pretreatments, blanching with sawdust and application of IBA, applied to rapidly growing first year collar suckers in the field five months ahead of collection for rooting. These treatments simulated mound layering, but without girdling. Sawdust by itself significantly increased both quantity and quality of subsequent rooting, but IBA pretreatment in combination with sawdust produced even better results. Stem cuttings were rooted in a growth chamber, set at 22 C (72 F) and 60% relative humidity, with PAR of 320 umol.m−2 s−1 for 16 hours per day. The lack of heat stress in the growth chamber likely also contributed to relatively high rooting relative to the humidity tents used in previous trials. Index words: Propagation, Corylus americana (Walter), Corylus avellana (L.), rooting, etiolation. Chemicals used in this study: indole-3-butyric acid (IBA). Species used in this study: hybrid hazelnuts [Corylus americana (Walter) x Corylus avellana (L.)].

Effect of bean rust [Uromyces appendiculatus (Pers.) Strauss] on photosynthetic characteristics, superoxide-dismutase activity, and lipid peroxidation of common bean (Phaseolus vulgaris L.)

The aim of the study was to investigate changes of photosynthetic efficiency, amount of photosynthetic pigments, superoxide dismutase (SOD) enzyme activity, and rate of lipid peroxidation in bean-rust interaction. The clarification of the role of the above changes involved in the defence mechanism can significantly contribute to the breeding of plant varieties with natural resistance. Consequently, the amount of chemicals used in food production can be significantly reduced. In the present study some principal physiological parameters, such as the relative chlorophyll content of the host plant, the amount of photosynthetic pigments, changes in photosynthetic efficiency, and the activity of superoxide-dismutase (SOD) in addition to rate of lipid peroxidation (LP) were measured. The experiment was conducted in a humidity tent. Significant decrease in the relative chlorophyll content and in the amount of photosynthetic pigments was measured. At both sampling times, an increase was found in superoxide-dismutase enzyme activity and in rate of lipid peroxidation due to the bean rust infection. Notably, in several cases the differences were significant. The results indicate that the above parameters have important role in the bean-rust interaction, which should be taken into consideration in resistance breeding.

Optimizing IBA Concentration and Stem and Segment Size for Rooting of Hybrid Hazelnuts from Hardwood Stem Cuttings

Abstract Germplasm improvement of woody crops through plant breeding depends on effective methods of vegetative propagation, both for evaluation of candidate germplasm and for dissemination of improved varieties. Hybrid hazelnuts [Corylus americana (Walter) x C. avellana (L.)] are being developed as a new crop for the Upper Midwest for their ecological and economic value, but lack of economically viable propagation methods is a significant bottleneck to their wide scale adoption. This paper describes two trials to optimize propagation from hardwood stem cuttings in low-cost humidity tents, using dormant crown suckers collected in the fall. We found that: 1) 2 g.L−1 (2,000 ppm) indole-3-butyric acid (IBA) in a 50% ethanol solution is the best concentration for rooting cuttings of a range of sizes and 2) rooting declines with increasing basal diameter of stems, but increases with increasing length of stem. The thicker cortex of large diameter stems may present a physical barrier to emergence of adventitious roots. Conversely, longer stems have larger stores of carbohydrates, which are essential both for keeping the stems alive until roots can be developed, and for providing the building blocks for growing those roots. Index words: Propagation, Corylus americana (Walter), Corylus avellana (L.), rooting, indole-3-butyric acid. Chemicals used in this study: indole-3-butyric acid (IBA). Species used in this study: hybrid hazelnuts [Corylus americana (Walter) x Corylus avellana (L.)].

The Effects of Relative Humidity and Substrate Moisture on Rooting of Hybrid Hazelnuts from Hardwood Stem Cuttings1

Abstract Hybrid hazelnuts (Corylus americana Walter x C. avellana L.) are currently being bred for use as a cold-hardy perennial crop that could produce profits for Midwestern farms while supporting agroecosystem sustainability. However, asexual propagation techniques for producing germplasm for breeding and dissemination purposes have proven difficult. This study was one of a series attempting to develop a protocol for hardwood stem cutting propagation. This study assessed the impact that relative humidity (RH) and substrate moisture has on rooting of hardwood stem cuttings propagated in low-cost humidity tents. Hardwood stem cuttings retrieved from 14 hybrid hazelnut genotypes were planted into enclosed humidity tents, each housing 64 cuttings. Treatments were RH thresholds of 30%, 50%, 70%, and 90%, which were maintained by daily monitoring and watering to saturate the substrate when a tent's RH fell below its specified RH threshold. Cuttings propagated in 50% and 70% RH tents showed the highest rates of rooting at 16% and 12% respectively, whereas only 7% of cuttings rooted at 90% RH and 3% at 30% RH. By showing that intermediate RH levels and watering regimes are optimal for rooting, these results suggest daily monitoring is not necessary for hardwood stem cutting propagation of hybrid hazelnuts. Index words: propagation, relative humidity, substrate moisture, hardwood stem cuttings, hazelnuts, adventitious rooting. Chemicals used in this study: IBA (indole-3-butyric acid). Species used in this study: hybrid hazelnuts (Corylus americana Walter x C. avellana L.).

Comparative Growth Analysis and Acclimatization of Tissue Culture Derived Cocoyam (Xanthosoma sagittifolium L. Schott) Plantlets

The current study was carried out to compare the external leaf structure of tissue culture-derived and conventionally-propagated Cocoyam [ Xanthosoma sagittifolium (L) Schott] plantlets and to develop an efficient acclimatization protocol for these plantlets. Acclimatization studies were carried out during winter and summer to ascertain seasonal influence relative to plant survival upon transfer from in vitro to natural conditions. Results indicated that, cocoyam leaves have few stomates on both abaxial and adaxial surfaces with fewer on the adaxial surface. High levels of epicuticular wax (EW) found in vitro may have contributed to reduced transpiration rates. The reduced amounts of EW on acclimatized plants could be attributed to the rapid cell enlargement in expanding leaves, more rapid than the rate of wax formation. Acclimatization using humidity tent decreased leaf wilting

Effects of inoculum concentration, temperature, plant age and interrupted wetness on infection of lentil (Lens culinaris) byBotrytisspp. Conidia

Greenhouse experiments confirmed that both Botrytis cinerea and B. fabae could infect lentil and cause Botrytis grey mould symptoms. Experiments were conducted under controlled environments to determine the effects of temperature, leaf wetness duration, plant age and inoculum concentration on infection of lentil by B. cinerea. Optimum conditions for infection and sporulation were defined at 15–25°C, with limited sporulation at 10°C but no sporulation at 5°C or 30°C. Sporulation occurred 6–7 days after inoculation when leaf wetness was constantly maintained using humidity tents. Absence of leaf wetness for up to 4 weeks following inoculation did not reduce the disease severity, but reduced the time to sporulation to 3 days after leaf wetness was returned. Increasing the age at which plants were inoculated, from 6 to 18 weeks, had no significant effect on disease severity. Senescent and mature plant material acted as a focus for infection and sporulation. Increasing inoculum concentration from 5×104 conidia/mL to 5×106 conidia/mL significantly increased the number of plants infected, independent of genotype resistance. No disease developed at the lowest concentration of 5×102 conidia/mL.

First Report of Downy Mildew on Greenhouse and Landscape Coleus Caused by a Peronospora sp. in Louisiana and New York.

In May 2005, two commercial greenhouse flower growers, one in Louisiana (LA) and one in New York (NY), submitted coleus, Solenostemon scutellarioides (L.) Codd, plants for diagnosis after observing stunted growth, inward curling and twisting of leaves, and leaf abscission on multiple cultivars. Downy mildew-like growth was observable with hand lens or a microscope on the abaxial leaf surfaces of affected plants. Irregular necrotic spotting was present on some, but not all, plants on which sporulation was evident. Microscopic examination of LA material led to tentative identification of the pathogen as Peronospora lamii A. Braun (2). The pale brown conidia ranged from 17 to 26 × 15 to 26 μm (average 23 × 19 μm). Conidiophores ranged from 345 to 561 × 9 to 15 μm. No oospores were found. Additional coleus plants with downy mildew were subsequently found in three retail nurseries in LA in early summer. In NY, infected coleus plants were observed in landscapes in Farmington, Rochester, Ithaca, and in two commercial greenhouses between August and October 2005. NY samples sent to the USDA/APHIS in Beltsville, MD were examined, and the fungus was found to have morphology consistent with P. lamii. Two pathogenicity trials were conducted in NY. Conidia were rubbed from an infected coleus leaf onto the leaves of six healthy potted coleus plants of five cultivars and two basil plants that were placed in a shaded plastic tent in the greenhouse where temperatures ranged from 17 to 22°C. A household humidifier was used to supply mist inside the tent for 5 h per day. Six noninoculated plants of each coleus cultivar and two basil plants, placed in the same environment, served as controls. Downy mildew sporulation and some curling and twisting of leaves were observed 14 days after inoculation on all inoculated plants for three of the five cultivars (Florida Rustic Orange, Aurora Peach, and Aurora Mocha). Cvs. Florida Sun Rose and Lava showed no symptoms or signs of downy mildew. An irregularly shaped brown lesion developed on one inoculated basil leaf, and downy mildew sporulation was evident on the abaxial surface 35 days after inoculation. All noninoculated control plants remained disease free. In a second trial, conidia were rinsed from infected coleus leaves and sprayed onto the abaxial leaf surfaces of three coleus cv. Aurora Mocha plants. Three noninoculated plants served as controls and all were placed in a humidity tent. Leaf twisting and downy mildew sporulation were observed 13 days later on all inoculated plants, and control plants showed no sporulation or symptoms. A downy mildew causing disease of greenhouse-grown basil in Europe, originally identified as P. lamii on the basis of morphology, has recently been reported to be taxonomically distinguishable from P. lamii when tested by molecular methods (1). ITS sequences of coleus downy mildew from NY and LA were nearly identical (99% homology) to those of basil downy mildew from Switzerland and Italy (1). To our knowledge, this is the first report of downy mildew occurrence on coleus.

Germination and Growth of Four Species of Ericaceous Plants

The germination of ericaceous plant species is often variable and not well-defined. We have had some difficulty in obtaining good germination and significant establishment and growth after transplanting. Four different moisture regimes and two different media were used for the germination of Kalmia latifolia, Oxydendrum arboreum, Rhododendron maximum, and Vaccinium corymbosum seeds. Seeds were surface-sown on peat or peat + bark (1:4) media. Pots were then placed under either one of two different misting regimes, set in a tray of water, or set in a tray of water under a humidity tent. Germination was higher and more consistent for all species sown on peat and occurred sooner for seeds under the humidity tent. Rhododendron and Kalmia under the humidity tent grew more rapid than with other treatments. Increases in germination under the humidity tent were due more in part to higher temperatures than to the minimal increase of humidity inside the tent. Germination was poor for seeds under the high-mist treatment, presumably because there was too much moisture. Germination of Vaccinium and Oxydendrum was low for all treatments.

Importance of in vitro storage root development for the successful transfer of micropropagated asparagus plants to greenhouse conditions

Abstract The importance of in vitro storage root development for the growth and survival of micropropagated asparagus (Asparagus officinalis L.) plants under greenhouse conditions was assessed in four genotypes (‘CRD047’, ‘CRD100’, ‘CRD101’, and ‘CRD222’). Plants with greater development of in vitro storage roots exhibited higher survival rates and took less time for the initiation of new shoot growth during acclimatisation in a humidity tent immediately following transfer out of culture. They also had higher survival rates and greater shoot growth on an open greenhouse bench 9 weeks following transfer from in vitro culture. An ideal micropropagated asparagus plant for greenhouse establishment consists of an in vitro minicrown supporting 4–6 shoots and 3–4 storage roots (3–4 cm long). Such plants typically develop on a high-sucrose rooting medium.

An Inexpensive Humidity Tent for Screening Plants against Disease

An Inexpensive Humidity Tent for Screening Plants against Disease

RAPID MICROPROPAGATION OF COCOYAM (XANTHOSOMA SAGITTIFOLIUM SCHOTT)

Shoot tips, approximately 3-5mm, were isolated from corms of young greenhouse-grown plants of cocoyam, cultivar South Dade White. After preliminary evaluations, the initiation media evaluated were B5 basal salts supplemented with 0.05 μM NAA with 5μM BAP, 20μM BAP or 2μM TDZ. The above media were in the form of liquid medium in flasks on a rotary shaker, liquid medium with filter paper bridges, stationary liquid medium without filter paper and solidified medium with 0.4% agar. TDZ stimulated greater growth with multiple shoot formation. Liquid media either in the shaker or stationary form were more effective in terms of growth. Shoots were subsequently evaluated for multiplication with 1μM TDZ and 5μM BAP with 0.05μM NAA producing greater shoot numbers. Over 30 plants have subsequently been rooted and acclimatized under mist or humidity tent.

Micropropagation of Telopea speciosissima R. Br. (Proteaceae). 2: Rhizogenesis and acclimatisation to ex vitro conditions

Conditions affecting rhizogenesis in vitro and ex vitro and subsequent acclimatisation of Telopea speciosissima (waratah) were investigated. Clonal selections were successfully rooted in vitro in agar, on filter paper bridges or using crushed quartz-sand, the last substrate resulting in superior growth of roots. The in vitro substrates were impregnated with half-strength MS, 7.5 gl-1 sucrose and various concentrations of IBA. For the quartz-sand, an IBA concentration of 50 μM was optimal, 70% of microcuttings were rooted. No plantlets rooted in vitro were acclimatised to ex vitro conditions (using mist, fog or humidity tent regimes). Microcuttings (25–45 mm in length) were rooted ex vitro in a fog humidity regime (droplet size 20%) of the mixture, measured after the medium was saturated and then drained for 24h. Plantlets must be left under the high humidity regime until shoot growth resumes (four to eight weeks) otherwise plant mortality increase significantly. In vitro-produced leaves abscised between eight and 12 weeks after transfer to ex vitro conditions, indicating that these structures did not acclimatise ex vitro.

Use of humidity tents and antitranspirants in the acclimatization of tissue-cultured plants to the greenhouse

Film-type antitranspirants and a humidity tent were tested on tissue-cultured chrysanthemum and carnation plants in order to determine the most effective way to increase the vigor and survival of the plants at the time of transfer to a greenhouse. Phytotoxicity necessitated applying most antitranspirants at concentrations lower than that recommended by the manufacturers. Plants grown in the humidity tent were significantly larger and more vigorous than plants in any other treatment. Although a silicone formulation had the greatest effect in reducing transpiration and water stress in transferred plants, it had the adverse effect of stunting plant growth. All other treatments with antitranspirants were ineffective in improving vigor and survival of plants compared to controls.