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  • Author or Editor: Harry Swartz x
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Abstract

Open-pollinated species, interspecific hybrid seedling populations, and selected clones propagated by softwood cuttings and tissue culture were used to further evaluate the use of dry soil to screen blueberry seedlings for drought resistance. These different propagation types of Vaccinium (subgenus Cyanococcus) were screened for drought resistance in a Galestown fine sandy loam soil. The soil was permitted to dry to progressively higher soil tension levels to a maximum of 0.8 MPa. The plants were evaluated by scoring them on a 1 to 9 shoot damage rating scale and by determining the fraction of total biomass partitioned as roots. Drought resistance in blueberries is heritable and there is a high degree of genetic diversity within and among Vaccinium spp. for resistance to water deficits. Southern species (Vaccinium darrowi Camp, V. elliottii Chapman, and V. ashei Reade) were more drought-resistant than northern species (V. corymbosum L., V. vacillans Torrey, and V. myrtilloides Michaux), which demonstrated the reliability of this soil screening method. Clones with half their germplasm from southern species were usually drought-resistant. This screening method can be used to select for shoot and root vigor and drought resistance in 6- to 7-month-old blueberry seedlings.

Open Access

Abstract

Comparative field performance of thornless blackberry plants produced by tissue-culture (TC) and standard (ST) methods (tip layers or stem cuttings) was studied to determine any effect of TC propagation on clonal phenotypic stability. In general, TC plants performed as well as, and were phenotypically similar to, ST plants. Some differences in leaf size and pattern were observed; however, the differences were related to the increased vigor of TC plants of these cultivars. Total growth of TC and ST plants of ‘Black Satin’, ‘Hull Thornless’, ‘Thornfree’, and SI-US 68-6-17 was similar. ST plants of ‘Dirksen Thornless’ and ‘Smoothstem’ failed to grow as rapidly as TC plants of these cultivars or ST plants of the other cultivars, resulting in significantly reduced 2nd-year yields. First-year growth of all TC plants was more uniform than corresponding ST plants. On the average, fruit size was smaller on TC plants; however, this was true in both years only for ‘Black Satin’. The response varied for other cultivars with TC plants of ‘Dirksen Thornless’ actually having larger fruits in one year. No consistent differences in bloom date or median harvest date due to propagation method were observed. No variant plants were observed in the field; however, one sectorial leaf chlorotic variant was observed after TC propagation but prior to field planting.

Open Access

Regeneration of adventitious shoots from in vitro-derived leaves of several Rubus genotypes was tested with various concentrations of cytokinins and auxins, different basal media, duration of dark incubation periods, temperatures and photosynthetic photon fluxes (PPF). Thidiazuron (TDZ) was significantly more effective than benzyladenine (BA), and indolebutyric acid (IBA) more effective than naphthaleneacetic acid (NAA). Leaves of `Summit' and `Sentry' raspberries and MD-ETCE-1 blackberry were most responsive (percentage of leaves responding, number of shoots formed) to 1 μM or 10 μM TDZ plus 0.5 μM or 1 μM IBA; MD-ETCE-1 leaves did not respond to BA or TDZ with either 2.7 or 5.4 μM NAA. More organogenesis occurred on MS than on half-strength MS, Anderson modified, WPM or N6 media. For the five cultivars tested (`Autumn Bliss', `Canby', `Sentry', `Summit', MD-ETCE-1), the most shoots formed when leaves were incubated at 20°C (vs. 25°C) for 1 week in the dark before they were exposed for 16 h per day to a PPF of 40 μmol·m-2·s-1. Significant differences in regeneration frequency were observed among four cultivars with the highest 71% for `Autumn Bliss' and the lowest 29% for `Summit'.

Free access

`Chandler' strawberry plants were propagated in tissue culture and grown from April to August in a protected environment to produce stolons. July-harvested daughter plants were stuck in cell packs with rooting media and placed under mist sprinklers, or cold stored at 2 °C for 42 days. Among the July transplants, some were kept in the greenhouse until field planting (14 Sept.) and others were moved into a cold room on 14 August. Daughter plant size and position on the stolon affected rooting and quality of transplants. July-harvested daughter plants that were plugged and misted after being cold stored for 42 days developed fewer roots than daughter plants plugged immediately after detaching from mother plants in July or August. In the field, transplants produced from daughter plants harvested in July and cold stored for 42 days developed more stolons than transplants from July- and August-harvested daughters that were not exposed to cold storage treatments. Larger daughter plants produced more branch crowns than did smaller daughter plants during the fall. All transplants from daughter plants harvested in July and propagated without cold treatment bloomed by November. Fruit production ranged from 521 to 703 g per plant. `Chandler' plants from daughter plants that weighed 10 g produced 10% greater yield than those that weighed <1.0 g. Plants generated from daughter plants plugged in July produced 26% more fruit than those plants plugged in August. Greenhouse soilless systems can be used to grow `Chandler' mother plants for generating runner tips and transplants for the annual plasticulture in colder climates. `Chandler' plants produced in July can yield a late fall crop under high tunnels and more fruit in the spring than August-plugged transplants

Free access

The effect of altered red/far-red light environment on subsequent field performance of strawberry plug plants was tested. Two wavelength-selective plastic films were compared to neutral shade and full-sun control for conditioning `Chandler' strawberry plug plants before transplanting to a winter production system. The following year, plug plants of `Chandler', `Sweet Charlie', and `Allstar' were conditioned under the same treatments, with the addition of a continuous incandescent light and a short-day photoperiod, and plant performance was followed in the winter production system in Florida, a cold-climate annual hill system in Maryland, and in a low-input greenhouse production system. During the first year, the red light-filtering film slightly advanced fruiting in Florida. However, during the second year, the effect of the red light-filtering film was not significant, and a short-day treatment resulted in a greater reduction in runnering and increased early crown and flower development. For June-bearing strawberry plants maintained above 20 °C, altering the red/far-red environment did not consistently advance flowering.

Free access

Abstract

A phenotypic and sexual analysis of Fragaria vesca ‘Albo-Marginata’ determined that the leaf variegation was of chimeral origin. Stable periclinal chimeras were established in vitro from runner tips. Plants were transferred to proliferation media containing 0.5 μm IBA, 0.3 μm GA3, and BA at either 0, 1.3, 4.4, or 13.2 μm. Whereas the histogens of field-grown runner plants remained stable, more than 90% of the plantlets propagated in vitro varied from the original explants. Most variants were albino or were green, but some were mericlinal chimeras. Histological evidence indicated that many shoots were adventitious, arising from basal callus tissue or petioles. Chemical names used: 1H-indole-3-butanoic acid (IBA); gibberellic acid (GA3); N-(phenylmethyl)-1H-purin-6-amine (BA).

Open Access

Abstract

Removal of bud scales hastened bud burst of several early and late blooming apple cultivars. Descaling was most effective during the onset and end of rest. During deep rest, bud scale removal was effective only when applied 2 weeks before forcing conditions. Extracts of bud scales inhibited apple bud break in vitro. Abscisic acid (ABA) may have been responsible for part or all of this bioactivity, since ABA occurred in bud scale diffusates and could replace or reinforce the bud scales in vitro. Wound-produced ethylene was not involved in the bud scale removal response.

Open Access

The net carbon exchange rate (NCER) of Fragaria species, synthetic octoploids [SO (interspecific hybrids)], F1 (SO × cultivar), and first outcross [OC1 (F1 × cultivar)] hybrids were evaluated in both field and greenhouse conditions. Plants were grown in a field trial at the Elora Research Station in Ontario, Canada, for one season and then plants were dug and moved into a greenhouse where the trial was repeated during the next season. Single leaf photosynthesis measurements and light response curves were generated at different stages of plant development. Photosynthetic capacity of the species was related to the ecological background of the species with sun-adapted species having higher rates compared with the shade-adapted species. The Fragaria species and introgressed hybrids (F1 and OC1) had significantly higher NCERs compared with the cultivars with rates 28% and 23% higher, respectively. Species and hybrids also appear to have increased adaptability to both high and low light conditions. These increases in NCER may be a heterotic effect because NCER of the hybrids were consistently higher compared with the midparent values and in some cases, they were higher than the high parent. These results suggest that the introgression of lower-ploidy Fragaria species into the cultivated strawberry (Fragaria ×ananassa) may lead to increased NCER and light adaptability.

Free access

Abstract

Thornless blackberry plants were trained on 2 trellis types to determine the effect of primocane-floricane separation on plant productivity. Plants grown on a divided canopy had less shaded primocanes and more productive floricanes than those grown on a single canopy. Light interception was correlated positively to an increase in number of fruit per raceme and soluble solid/acid ratio. Dormant pruning had no effect on light interception or yield.

Open Access