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- Author or Editor: Craig C. Chandler x
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.
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.
Cold-stored (frigo) plants of `Irvine' and `Seascape' and non-chilled plug plants of `Sweet Charlie' and FL 87-123 were planted on August 31 on raised beds covered with white-on-black polyethylene mulch. Very little water was needed for establishment of these plants (compared to that which is normally needed for the establishment of foliated bareroot plants). `Irvine' and `Seascape' produced more runners and were later to initiate fruit production than `Sweet Charlie' and FL 87-123. `Sweet Charlie' and FL 87-123 started producing a small amount of marketable fruit in late October, while `Irvine' and `Seascape' did not produce any marketable fruit until mid and late January respectively.
Strawberries (Fragaria ×ananassa Duch.) were grown in two seasons at Dover, Fla., with polyethylene mulch and drip irrigation. Nitrogen was injected weekly at 0.28 (50), 0.56 (100), 0.84 (150), 1.12 (200), and 1.40 (250) kg N/ha per day (kg·ha-1 for season) for `Oso Grande' and `Sweet Charlie' in 1991-92 season and for `Oso Grande' and `Seascape' in 1992-1993 season. Nitrogen fertilization in 1991-1992, over the range of 0.28 to 1.40 kg N/ha per day, had no significant effect on early (November to January) strawberry yields. March (the largest production month) yield and total-season yield increased with increasing N fertilization to 0.76 and 0.54 kg N/ha per day, respectively. Nitrogen fertilization did not affect yields of strawberry in 1992-93. Fruit firmness and average fruit weight were not affected by N fertilization from 0.28 to 1.40 kg N/ha per day. Nitrogen fertilization increased whole leaf N, leaf blade N, and petiole sap nitrate-N concentrations linearly for most sampling dates in both years. Early yields were greater for `Sweet Charlie' than `Oso Grande'. Yields were greater for `Oso Grande' during March, and total-season yields were similar for both cultivars in 1991-92. `Oso Grande' had greater early, March, and total yields than `Seascape' in 1992-93.
A tissue culture protocol was developed that increased the germination percentage and decreased the lag time to germination for strawberry (Fragaria x ananassa Duch.) achenes. This technique involved cutting surface-sterilized achenes across the embryo axis then placing the shoot apex/radicle-containing sections on semisolid Murashige and Skoog medium lacking hormones. Cut achenes began germinating 5 days after culture and achieved maximum germination (97% to 100%) in less than 2 weeks, compared to whole achenes, which began to germinate 7 to 10 days after sowing and required more than 7 weeks for maximum germination (<50%). Enhanced germination of cut achenes was a general phenomenon since achenes from 231 hybrid crosses responded similarly. Following placement on culture medium, cut achenes could be stored up to 8 weeks at 4C then removed to 27C, where germination and seedling development occurred at percentages and rates comparable to freshly cut achenes. Achenes did not require stratification before cutting to exhibit increased germination. Nearly 100% of the achenes from freshly harvested red-ripe, pink and white strawberries germinated after cutting and culture, although cut achenes from white and pink berries germinated more slowly than those from red-ripe berries. Achenes from green berries, whether whole or cut, did not germinate. This method of “embryo rescue” could be used to generate more seedlings from poorly germinating hybrid crosses, would considerably decrease the time from sowing to seedling production compared to traditional means, and would produce seedlings of uniform age for subsequent field evaluation.
On standard two-row black polyethylene covered beds, `Camarosa', `Rosa Linda', and `Sweet Charlie' strawberry plants were grown at 23, 31, 38, or 46 cm within-row spacing during the 1997–98 and 1998–99 seasons at Dover, Fla. Ripe fruit were harvested twice weekly from December through March. The first 8 weeks of harvest was considered the early period; the late period consisted of all harvests after the first 8 weeks. The effect of spacing on early marketable yield was consistent across seasons and cultivars. The 23-cm spacing resulted in the highest marketable yield per unit area, followed by the 31-, 38-, and 46-cm spacing. The percentage of fruit that were small (unmarketable) was higher at the 23-cm spacing than at the wider spacings (40% vs. 35% or 36%), but spacing did not affect the percentage of fruit that were misshapen. For the late harvest period, a spacing effect on marketable yield occurred in 1998–99, but not in 1997–98. The 23-, 31-, and 38-cm spacings in 1998–99 resulted in similar late period yields, which were 15% to 21% higher than the yield resulting from the 46-cm spacing. These results indicate that marketable yields per plant during the late period were higher at the wider spacings.
The use of locally grown transplants in Florida strawberry (Fragari×ananassa Duchesne) production has increased since the release of the cultivar Sweet Charlie by the University of Florida in 1992. Previous research has shown that nursery region can influence production patterns of other strawberry cultivars through differences in photoperiod and temperature exposure. Transplants of `Sweet Charlie' strawberry (bareroot and plug plants) from sources representing northern (Canada, Massachusetts, Oregon), southern (Alabama, Florida) and mid latitude (North Carolina) transplant production regions were compared for plant vigor, production, and pest incidence at Dover, Fla. in 1995-96 and 1996-97. Total fruit production was not significantly different forplants among the plant source regions in 1995-96, but total yield from southern source plants in 1996-97 was significantly lower than northern and mid latitude plant sources. Monthly production of marketable fruits varied among the three plant source regions in December, January, and February, during which time market prices fell 46% in 1995-96 and 56% in 1996-97. Plants from northern and mid latitude sources produced significantly greater fruit yield in December than plants from southern sources. Differences among plant sources were detected for early flowering, initial crown size, incidence of foliar disease, arthropod pests, mortality, and fruit weight. Geographic location of strawberry transplant sources influenced fruiting patterns and other components that may affect profitability of `Sweet Charlie' strawberry production in west central Florida.
The objective of this study was to compare plant health and growth in Florida fruiting fields of `Sweet Charlie' plants from 10 different plant sources. Bare-root plants from Ontario, Nova Scotia, Massachusetts, Oregon, North Carolina, Alabama, and Florida and plug plants from North Carolina and Florida were compared in a RCBD of four replicates. Plants were rated for vigor, production, diseases, and pests throughout the 1995-96 season. Crown size of transplants ranged from 7 to 12 mm. Plants from northern sources exhibited angular leaf spot (Xanthomonas fragariae) and gnomonia (Gnomonia spp.) while southern-raised plants were infected with phomopsis (Phomopsis obscurans) and anthracnose (Colletoctrichum spp.). Initial ratings confirm the potential for aphids and two-spotted spider mites (Tetranychus urticae) to be introduced on transplants. Plants from northern origins flowered 10-14 days earlier than plants produced in southern regions. Total season marketable fruit production was not statistically different among the eight bare-root treatments. Monthly fruit production was significantly different among treatments for all months except February. Performance of plug plants compared to bare-root plants of the same geographic origin were inconsistent. Initial crown size, average berry size, and cull fruit production were significantly different among the plant sources. In summary, clear differences in foliar diseases and monthly fruit production were strongly associated with transplant source. A strawberry farmer may maintain more stable production throughout the year by using transplants from several geographic origins.