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  • Author or Editor: Craig K. Chandler x
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A protocol was developed for excising and culturing cotyledon explants from mature achenes of strawberry (Fragaria × ananassa Duch.). Cotyledon explants formed callus with multiple shoot buds on agar-solidified Murashige and Skoog media containing several combinations of hormones (1 μm 2,4-D; 10 μm 2,4-D; 1 μm BA + 1 μm 2,4-D; 1 μm BA + 10 μm 2,4-D; 5 μm BA; 5 μm BA + 1 μm 2,4-D; 5 μm BA + 10 μ m 2,4-D; 5 μ m BA + 5 μm NAA; 5 μ m BA + 15 μ m NAA). After three subcultures, only tissues maintained on the medium containing 5 μm BA + 5 μm NAA continued to form shoots. Tissues transferred to other media eventually died (1 μm 2,4-D; 1 μ m BA + 10 μ m 2,4-D; 5 μ m BA; 5 μ m BA + 1 μ m 2,4-D), became unorganized (1 μm BA + 1 μm 2,4-D; 5 μm BA + 10 μm 2,4-D; 5 μm BA + 15 μm NAA), or formed roots (10 μm 2,4-D). Whole plantlets were produced by transferring callus with buds to medium lacking hormones. The rapid regeneration of clonal plantlets from cotyledon explants may be useful for reducing variability in future developmental studies. Chemical names used: N-(phenylmethyl)-1H-purin-6-amine (BA); (2,4-dichlorophenoxy) acetic acid (2,4-D); and 1-naphthaleneacetic acid (NAA).

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Many horticultural crops are infected with bacterial, fungal, or viral pathogens that reduce yield and/or quality. Recovery and maintenance of pathogen eradicated crops, such as strawberry (Fragaria × ananassa Duch.), have been possible following the isolation and culture of apical meristems or meristem-tips in vitro. A laboratory exercise has been developed to provide experience in the procedures required for the isolation, surface disinfection, and in vitro establishment of meristem-tip explants excised from strawberry stolons. Stolons are obtained from greenhouse-grown strawberries (`Sweet Charlie') maintained in hanging baskets under a 14-h photoperiod. Stolons are cut into single-node segments and terminal tips. The leaf blades are removed and the nodal sections are rinsed and then surface-disinfected by successive agitation in 70% ethanol and 1.05% sodium hypochlorite, followed by three rinses in sterile deionized water. In the transfer hoods, each student attempts to isolate meristem-tips and shoot tips of various sizes under high magnification provided by a stereomicroscope. Explants are inoculated onto Murashige and Skoog basal medium (Murashige and Skoog, 1962) supplemented with 30 g/liter sucrose, 80 mg/liter adenine sulfate, 1.0 mg/liter benzyladenine, 1.0 mg/liter indole-3-acetic acid, and 0.01 mg/liter gibberellic acid (GA3) and solidified as 45°slants with 1.25 g/liter Phytagel and 3.0 g/liter TC agar. Growth responses are monitored weekly. After 6 weeks, students record the percentage of visibly contaminated cultures and number shoots produced per explant. The relationship between initial explant size and in vitro growth is also determined. Students index their cultures for the presence of cultivable bacteria and fungi using sterility test media.

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Four strawberry (Fragaria ×ananassa, Duch.) cultivars were grown in a winter strawberry fruiting study using the annual hill cultural system and polyethylene-mulched beds during two seasons. Plants were set on 15, 30, 45, and 60 cm in row-plant spacing with two rows per bed spaced at 45 cm. Increasing plant density in the fruiting field generally increased early fruit yield and sometimes total fruit yield during two seasons. Yields of cull fruit were also increased with increased plant density. Daughter plant production decreased with increased plant density. Growers should consider planting costs, fruit rot, and harvesting problems when selecting the plant density for fruit production.

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Abstract

N-(3-methyl-2-butenyl)-1H-purin-6-amine (2iP) has been used to promote multiple shoot formation in previous tissue culture studies with ericaceous plants (1, 3-7). Fordham et al. (3), however, found that (E)-2-methyl-4-(1H-purin-6-ylamino)-2-buren-1-ol (zeatin) was the most effective cytokinin for stimulating shoot proliferation of cultured Exbury azalea (Rhododendron sp.). This study was conducted to determine if highbush blueberry is similar to Exbury azalea in its response to zeatin.

Open Access

Abstract

Experiments were conducted to examine strawberry (Fragaria × anannassa Duchesne) plant renovation practices, singly and in combination, for effects on vegetative growth of greenhouse-grown, potted strawberry plants. The major results of these experiments were as follows: a) most of the plants that were both defoliated and root-pruned after fruit harvest died; b) there was a negative linear relationship between the number of leaves removed and the number of new leaves and runners produced; c) root, leaf, and total plant dry weights were negatively correlated with the severity of root pruning; and d) soil addition after fruit harvest decreased the shoot : root ratio of multiple-crown plants, but had no effect on single-crown plants.

Open Access

Abstract

Five blueberry interspecific hybrids (3 tetraploids, 1 pentaploid, and 1 hexaploid) and 2 highbush (Vaccinium corymbosum L., 2n = 4x = 48) blueberry clones were crossed in all combinations. Seeds per pollination and seed germination were the criteria used to measure the success of these crosses. The tetraploid interspecific hybrids were fully cross-fertile with the highbush clones and with each other. The pentaploid and hexaploid interspecific hybrids were only partially cross-fertile with the highbush clones and with the tetraploid interspecific hybrids; nonetheless, they still produced an adequate amount of viable seed in most combinations. Significant reciprocal differences in crossability were detected for 4 of the 5 species hybrids.

Open Access

A greenhouse hydroponic system, which uses suspended plastic troughs, was found to be an efficient system for the production of high quality strawberry (Fragaria ×ananassa) plantlets. In this system micropropagated mother plants of `Oso Grande' and `Sweet Charlie' produced an average of 84 and 80 daughters per mother plant, respectively, in 1996, at a plant density of 3 mother plants/ft2 (32 mother plants/m2). Nearly 100% of the plantlets harvested from the system were successfully rooted in plug trays, and showed no symptoms of leaf or crown diseases.

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In greenhouse and field studies, benzyladenine (BA) and gibberellic acid (GA3) applied together as a foliar spray increased runner production in dayneutral strawberries (Fragaria ×ananassa Duch.) but not when applied separately. Runner production increased linearly with increased BA concentration to 1800 mg·L–1. At high dosages, GA3-treated plants produced elongated internodes that, in the field, led to fewer daughter plants. In Florida, daughter plants derived from plants sprayed with the growth regulators increased yield by up to 10% in fruiting experiments. To induce runnering in the field and greenhouse, a treatment with BA at 1200 mg·L–1 and GA3 at 300 mg·L–1 is recommended. Chemical names used: N-(phenylmethyl)-1H-purine-6-amine (benzyladenine); gibberellic acid A3; gibberellic acids A4 and A7.

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Bare-root strawberry transplants have been conventionally used for establishment of strawberry fruiting fields. These bare-root transplants have variability in vegetative vigor that results in irregular flowering patterns. We have been experimenting with a containerized transplant system to produce uniform transplants. Increasing transplant container volume by increasing perimeter, rather than depth, has resulted in increased plant size, but also increases transplant production costs. This study evaluated three container perimeters (17, 25, 32 cm) and three container shapes (circular, elliptical, and biconvex) such that different cell perimeters had the same greatest diameter. All containers had a depth of 3.5 cm. Root imaging analysis (MacRHIZOTM) was used to measure root growth in the container as well as root growth 3 and 6 weeks after transplanting. Increasing container perimeter led to increased plant growth before and after transplanting, but did not affect fruit production. Transplant container shape did not significantly alter plant growth or fruit production. Biconvex and elliptical containers required 25% and 15% less surface area, respectively. Therefore, a biconvex shaped container can be used to increase plant density during transplant propagation, decreasing surface area needed and reducing production costs.

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