Richard H. Zimmerman

Adventitions shoot formation on excised leaves of in vitro grown shoots of apple cultivars

Leaves taken from micropropagated shoots of several apple (Malus domestica Borkh.) cultivars were cultured in vitro on Linsmaier & Skoog (LS) medium or the rice anther culture medium of Chu et al. (N6) containing various concentrations of either benzyladenine (BA) or thidiazuron (TDZ) plus naphthaleneacetic acid (NAA). Of the TDZ concentrations tested, 10 μM was most effective and it was equivalent to, or better than, 22 μM BA for both the percentage of leaves regenerating shoots and number of shoots formed per regenerating leaf in almost every experiment. Lower concentrations of NAA (1.1 and 5.4 μM) gave best results with both BA and TDZ. N6 medium gave consistently better results than LS. Lowering total salt concentration or total N concentration of LS to that of N6 did not improve the response nor did changing the NO3:NH4 ratio. The 3–4 leaves on the most distal part of the shoot were most responsive and tended to form the most adventitious shoots. Placing the leaf cultures in the dark for the first 2–3 weeks of the culture period produced the best results. Optimum results were obtained by culturing leaves from the distal part of the shoot in the dark for 2 weeks on N6 medium containing 10 μM TDZ and 1.1 or 5.4 μM NAA, then moving the cultures to 16 h daylight at a photon flux of 60 μmol s-1m-2.

The influence of cation and gelling agent concentrations on vitrification of apple cultivars in vitro

Shoot tips of ‘York’ and ‘Vermont Spur Delicious’ apples (Malus domestica Borkh.) were cultured in vitro to test the influence of K+, Mg++ and gelling agent concentrations on vitrification. These concentrations were 20.05, 14.05 and 8.05 mM K+, 1.5 and 3.0 mM Mg++, 7.0 g/l Difco Bacto agar and 1.0, 1.5 and 2.0 g/l Gelrite. The lowest K+ level produced a higher percentage of vitrified shoots, affected tissue appearance, reduced shoot number and shoot elongation and apparently altered shoot metabolic activity. Gelrite consistently produced vitrified leaves and stems, even though media gelled with 1.5 g/l Gelrite presented the same apparent gel firmness as using 7 g/l Difco Bacto agar, which did not induce vitrification. Less shoot elongation, fewer total shoots, and more usable shoots of ‘York’ were obtained on Bacto-agar, while similar but less noticeable effects were obtained with ‘Vermont Spur Delicious’. The results presented here show that vitrification can be studied in a standardized system in which the only change is substitution of one gelling agent for another.

Rooting apple cultivars in vitro: Interactions among light, temperature, phloroglucinol and auxin

Abstract‘Delicious’ apple (Malus domestica Borkh.) and several of its strains, which have been difficult to root in vitro, were successfully propagated with rooting percentages up to 100%. The combination of treatments used to achieve this result included placing the shoots on rooting medium in the dark at 30°C for the first week of the rooting stage, then moving them to a regime of 16 hr light-8 hr dark at 25°C. The rooting medium contained half strength Murashige and Skoog salts plus 1.2 μM thiamine HCl, 0.56 mM myo-inositol, 1 mM phloroglucinol (PG), 1.4 μM indolebutyric acid (IBA), 1.3 μM gibberellic acid (GA3), 87.6 mM sucrose, and 7 g l−1 Difco Bacto agar. Dark treatment applied during the proliferation stage (etiolation) was less effective than one applied at the beginning of the rooting stage. The optimum length of dark treatment during rooting was 4 to 7 days. Increasing the temperature from 25°C to 30°C improved rooting of ‘Delicious’, ‘Royal Red Delicious’, and ‘Vermont Spur Delicious’ in the absence of PG but generally had less effect in the presence of PG. Further increase in temperature to 35°C stimulated rooting of ‘Royal Red Delicious’ but reduced rooting of ‘Vermont Spur Delicious’. Transfer of the cuttings to auxin-free medium after 1 week had no effect on percentage rooting and increased the number of roots per cutting for only 1 of 4 cultivars tested and then only in the presence of PG. In general PG stimulated rooting of ‘Delicious’ and its strains, but had no effect on ‘Golden Delicious’.

Use of starch-gelled medium for tissue culture of some fruit crops

Six cultivars of apple and two of red raspberry consistently produced equal or significantly better shoot proliferation on modified Murashige and Skoog medium gelled with a mixture of corn starch and Gelrite than on the same medium gelled with agar. Two pear cultivars grown on starch-Gelrite medium produced hyperhydric shoots and almost no growth, but the addition of a polysaccharide hydric control (‘antivitrifying’) agent to the medium eliminated hyperhydricity. The resulting shoot proliferation equaled or exceeded that on the agar-gelled medium. The starch-Gelrite mixture is easy to prepare and gelling agent costs are only 10–15% of agar, or less if starch is purchased in bulk. Although the opaque gray-white medium makes it more difficult to detect internal contaminants, external contaminants are easily discerned.

Application of Tissue Culture Propagation to Woody Plants

During the past decade, commercial production of woody plants by tissue culture techniques has progressed from a future possibility to a rapidly expanding reality. The magnitude of this change is truly remarkable, both in terms of the number of plants produced and the number of species and cultivars now in production. Much of this expansion is now well documented in either the scientific or popular literature but must be obtained from other sources such as nursery catalogs and personal contacts.

Propagation of Fruit, Nut, and Vegetable Crops — Overview

In April, 1980, a conference on nursery production of fruit plants through tissue culture was held at Beltsville to stimulate interest among U.S. nurserymen in the potential of micropropagation for temperate tree and small fruit crops (48). At that time, use of tissue culture for propagation of fruit crops was well under way and expanding rapidly in Europe but was used very little in North America. In the succeeding five and one-half years, micropropagation of these crops has increased significantly throughout the world, both in terms of crops being propagated and in total number of plants produced. Micropropagation methods are now employed for a number of vegetable crops as well, while production of ornamental plants using this technology continues to expand and remains the largest segment of this young industry.

Propagation in vitro of some dwarf apple trees

SummarySuccessful in vitro propagation of dwarf and semi-dwarf seedling apple trees of cvs Redspur and Goldspur parentage has been accomplished. The source material was taken from 9-year-old orchar...

In vitro Culture of Temperate Fruits

In vitro culture techniques have had numerous applications to fruit crops beginning nearly 60 years ago with embryo rescue techniques for stone fruits (Tukey, 1933; see Ramming, 1990). From this beginning, the method has been applied successfully to produce commercially acceptable early-ripening peach and nectarine cultivars. The methods have been adapted to other crops as well, e.g. in breeding programs to produce both early-ripening and seedless grapes (Ramming, 1990).

Influences of uniconazole on growth, fruiting, and photosynthetic activity of tissue culture-propagated own-rooted apple trees

Abstract Tissue culture-propagated (TC) own-rooted ‘Gala’ and ‘Triple Red Delicious’ apple trees grown at three planting densities were not treated (TC control) or were treated with annual uniconazole sprays or two trunk drenches starting with the third or fourth growing season. Budded (BUD) trees on M. 7a rootstock were also included as controls. After both the fifth and sixth growing seasons, the cultivars grown and the treatments applied had more influence on the attributes measured than did planting densities. Flowering and yield were greater on ‘Gala’ trees compared with ‘Triple Red’ for the fifth, but not the sixth season. The tree propagation method did not influence flower numbers and yield of ‘Gala’ trees in either the fifth or the sixth growing season but flower numbers were greater on BUD compared with TC trees of ‘Triple Red’ for both seasons. Flowering of TC ‘Triple Red’ trees tended to be increased by uniconazole treatment. Uniconazole applied by the trunk drench method markedly retarded vegetative growth of ‘Gala’ trees during the fifth season but flowering was reduced the following season. The trunk cross-sectional area of control TC trees for both cultivars increased more than for BUD trees but uniconazole treatment slowed trunk cross-sectional area increase so that treated TC trees were maintained at nearly the same size as BUD trees. Overall, ‘Triple Red’ leaves had higher chlorophyll concentrations than ‘Gala’ leaves, but there were no differences between BUD and TC leaves for net photosynthetic rate (Pn), stomatal conductance for water (g sw ), relative chlorophyll concentration, or specific leaf weight (SLW). Uniconazole treatment increased mean seasonal Pn, g sw , relative chlorophyll, and SLW compared with controls.

Long-term evaluation of micropropagated apple trees: vegetative growth, cropping, and photosynthesis

Abstract Micropropagated apple ( Malus domestica Borkh.) trees of 20 cultivars, of both standard and spur-type growth habits, were grown for up to 14 years and measurements taken annually of size (trunk cross-sectional area), flowering and yield. For three consecutive years (1988–1990), photosynthesis, stomatal conductance, chlorophyll content and specific leaf weight were measured on three trees of each of 16 of these cultivars on at least three dates per year. The data show differences among the cultivars in vegetative vigor, age at which flowering began, fruit yields, photosynthesis and stomatal conductance. Trees did not display intraclonal variation except for one spur type, ‘Redspur Delicious’, in which the spur characteristic was variable from tree to tree. The results document growth and yield data for micropropagated trees of a broad range of apple cultivars; no other data are available in the literature for most of these cultivars.