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- Author or Editor: Craig Chandler x
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.
During the past 10 years, the Florida strawberry growers, through the Florida Strawberry Growers Association, have made a serious commitment to fund university research on strawberries. They have purchased equipment and donated monies for facilities at Dover. They have also helped support a new faculty position in breeding and genetics. During this same period, the University of Florida has made an equally strong commitment to support strawberry research and extension. These commitments are beginning to pay significant dividends for industry and the University. Cultural and pest management information has been generated that is saving the industy money, and the breeding program is developing new cultivars that will keep the industry competitive in the marketplace. The University has benefitted through the acquisition of new facilities, equipment, and faculty and graduate student support.
During the 1992-93 fruiting season, strawberries were fertigated weekly with 0.28, 0.56, 0.84, 1.12, or 1.40 kg N/ha/day from ammonium nitrate. K was applied uniformly at 0.84 kg/ha/day by fertigation. Irrigation maintained soil moisture tension in the beds between -10 and -15 kPa. Fruit yields responded positively to N fertilization with yields maximized at 0.56 kg N/ha/day. Leaf N and petiole sap nitrate N concentrations increased with N rate with leaf-N for the plants receiving 0.28 kg N/ha/day remaining below 25 g·kg-1 most of the season. Sufficiency ranges for petiole sap nitrate-N quick testing were developed.
Containerized strawberry transplants offer an alternative to problematic bare-root transplants, which often have variability in flowering and vegetative vigor. Containerized transplants were propagated in three different container cell sizes (75, 150, and 300 cm3) and grown at two different temperature regimes for 2 weeks prior to planting (25/15 and 35/25°C day/night). Bare-root transplants from Massachusetts and Florida were graded into small, medium, and large plants based on crown size (8, 12, and 16 mm respectively). Plug transplants grown at 25/15°C had greater root dry weights than transplants grown at 35/25°C. Root imaging analysis (MacRHIZO) showed that the differences in dry weight were due to root area, not root tissue density. Crown dry weight increased with increasing cell size. Plug transplants grown at 25/15°C flowered earlier and had greater production than any other treatment. The 75 cm3 cell size grown at 35/25°C produced greater December strawberry production than larger cell sizes at the same temperature regime; however, the 75 cm3 cell size had decreased January strawberry production while the larger cell sizes had increased production. Larger plug cell sizes had significantly greater production than smaller plugs throughout the season, whereas larger bare-roots had greater production only early in the season. Containerized plug transplants therefore offers a viable alternative to problematic bare-root transplants.
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.
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.
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.