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- Author or Editor: Craig 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).
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.
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.
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.
Our previous work on modifying strawberry plant morphology used either mowing to remove the leaf laminas and part of the petioles on `Camarosa', or a new reduced-risk gibberellin synthesis inhibitor, Prohexadione-Ca (ProCa), to restrict cell elongation in `Sweet Charlie'. These early studies showed promising results in acheiving desirable plant size and increasing fruit yield in annual hill plasticulture. Therefore, in the growing seasons of 2001 and 2002, we used `Camarosa' to explore the possibility of combining mowing and ProCa as a means of modifying strawberry transplant morphology in the nurseries, and studied its effect on fruit production in annual hill plasticulture. Plants were mowed and treated with 62.5 μL·L-1 of ProCa in a nursery field in Nova Scotia (45°26'N, 63°27'W). Treatments consisted of either mowing, the application of ProCa, or a combination of mowing and ProCa on one of two dates, 5 or 19 Sept. ProCa application early in the growing season had increased the production of daughter plants in the nursery. All plants were harvested in early October, and immediately transplanted in Dover, Fla. (28°00'N, 82°22'W). Fruits were collected twice weekly from late November to February or March. At time of harvest, both mowing and ProCa reduced plant height and total leaf area; plants which were treated with ProCa and mowed were the shortest. On average, treated plants had higher fruit yield as compared to untreated plants. In 2001, early fruit production in December was increased significantly in treated plants.
The demand for plug transplants by the Florida winter strawberry (Fragaria ×ananassa Duch.) industry may increase as water conservation during plant establishment becomes more important and the loss of methyl bromide fumigant makes the production of bare-root transplants more problematic. A study was conducted during the 1995-96 and 1996-97 seasons to determine the effect of container size and temperature conditioning on the plant growth and early season fruit yield of `Sweet Charlie' strawberry plants. Plants in containers of three sizes (75, 150, and 300 cm3) were grown in one of two temperature-controlled greenhouses (35 °C day/25 °C night or 25 °C day/15 °C night) for the 2 weeks just prior to transplanting into a fruiting field at Dover, Fla. Plants exposed to the 25/15 °C treatment had significantly higher average root dry weights at planting in 1995 and 1996 than did plants exposed to the 35/25 °C treatment. Plants exposed to the 25/15 °C treatment also had higher average fruit yields than the plants exposed to the 35/25 °C treatment (48% and 18% higher in 1995-96 and 1996-97, respectively). The effect of container size on plant growth and yield was variable. Plants propagated in the 150- and 300-cm3 containers tended to be larger (at planting) than the plants propagated in the 75-cm3 containers, but the larger container sizes did not result in consistently higher yields.
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.
Fresh strawberries (Fragaria ×ananassa Duch) are readily available throughout the year with several new cultivars being successfully grown in diverse environmental conditions (e.g., field and greenhouse). Consumption of strawberries with higher nutritive values and antioxidant activity may contribute to improved human wellness. Phytonutrient contents and antioxidant activity was measured as oxygen radical absorbance capacity (ORAC) were assayed in berries (`Camarosa', `Diamante', and `Gaviota') sampled in January, February to March, and April to May from fields in Plant City, Fla., and Oxnard, Calif., and from a greenhouse in Kearneysville, WV. Strawberry cultivars varied in skin color, soluble solids, total phenolics, and anthocyanins, ascorbic acid, folic acid, and ORAC activity. Response to environment was cultivar dependent. All phytonutrient constituents were lower in `Diamante' berries compared to `Camarosa' and `Gaviota'. For all cultivars, berry ORAC activity declined as TSS increased, and ORAC activity was coincident with phenolic content. ORAC activity in berries fruit harvested from plants grown in a temperature-controlled greenhouse did not change during the January to May sampling period. For `Gaviota', ORAC activity in greenhouse-produced berries was the same as that of field-produced berries. Whereas greenhouse vs. field-gown `Camarosa' and `Diamante' berries ORAC was higher and lower respectively. These findings demonstrate that the environmental conditions in greenhouses in Kearneysville, W.Va., from winter to spring are adequate for `Camarosa' and `Gaviota' color development, but not for `Diamante' strawberries. Of the three cultivars, only `Camarosa' was highly productive (1.2 kg berries per plant), even in the greenhouse. Berries were high in ascorbic acid, folic acid, phenolic acid, anthocyanins, and ORAC activity.