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George J. Hochmuth, Earl E. Albregts, and Craig K. Chandler

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.

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Eric B. Bish, Daniel J. Cantliffe, and Craig K. Chandler

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.

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Eric B. Bish, Daniel J. Cantliffe, and Craig K. Chandler

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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Eric B. Bish, Daniel J. Cantliffe, and Craig K. Chandler

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.

Free access

Adam Dale, Don C. Elfving, and Craig K. Chandler

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.

Open access

Craig K. Chandler and Arlen D. Draper

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.

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Céline Jouquand, Craig Chandler, Anne Plotto, and Kevin Goodner

The aim of this study was to understand the flavor components of eating quality of several strawberry (Fragaria ×ananassa Duch.) genotypes grown in Florida over two harvest seasons. Five selections and one cultivar of the University of Florida Breeding program as well as two new cultivars from Australia (Rubygem and Sugarbaby) harvested on different dates from the same grower were evaluated by sensory evaluation. Festival, the main strawberry cultivar grown in Florida, had low ratings for flavor and sweetness in January and March. Selection FL 00-51 and ‘Rubygem’ had relatively high and consistent ratings for flavor and sweetness compared with the other selections. Genotypes with low flavor ratings were always judged as “not sweet enough” by the panelists, thus linking flavor to sweetness preference. Instrumental analysis confirmed that typically these selections had low soluble solids content (SSC) and/or high titratable acidity (TA), thus explaining their lack of sweetness. Volatile compounds that varied only quantitatively did not seem to influence the flavor rating except for ‘Sugarbaby’. This cultivar contained between seven and 40 times less total ester content than the other selections and was disliked by panelists despite its high sugar content and perceived sweetness. It was perceived as having an artificial peach- or blueberry-like flavor. A principal component analysis was performed with chemical parameters (SSC, TA, and volatile content) and selections over the two harvest seasons. Chemical composition was mainly influenced by harvest date, except for FL 00-51. This selection maintained high volatile content and SSC throughout the seasons, explaining consistently high flavor ratings.

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George Hochmuth, Dan Cantliffe, Craig Chandler, Craig Stanley, Eric Bish, Eric Waldo, Dan Legard, and John Duval

Experiments were conducted in two seasons in Dover, Fla. (central Florida), with bare-root and containerized (plug) strawberry (Fragaria ×ananassa) transplants to evaluate transplant establishment-period water use, plant growth, and flowering responses in the 3-week transplant establishment period. Strawberry plug plants were established with 290 gal/acre water applied only with the transplant at planting time, while 200,000 gal/acre from microjet or 1 million gal/acre of water from sprinkler irrigation were used to establish bare-root transplants. Root, shoot, and crown dry matter of plug plants rapidly increased during the establishment period, while there was a decline in leaf area and root and crown mass of bare-root plants, even with sprinkler or microjet irrigation. Water applied with the bare-root transplant only at planting was not enough to keep the plant alive during the establishment period. Large plug plants, but not irrigated bare-root plants, began flowering at 3 weeks after planting. Plug plants were used to successfully establish strawberry crops with low water inputs.

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George Hochmuth, Dan Cantliffe, Craig Chandler, Craig Stanley, Eric Bish, Eric Waldo, Dan Legard, and John Duval

Strawberry (Fragaria ×ananassa) crops were transplanted in two seasons in central Florida with bare-root and containerized (plug) plants under three transplant establishment-period irrigation methods to evaluate crop fruiting responses and production economics associated with the various establishment systems. Irrigation was not required to establish plug transplants in the field. Early (first 2 months) fruit yield with nonirrigated plug plants was greater than early yield with sprinkler-irrigated bare-root plants (the current commercial system) in one of two seasons and equal in a second season. Total-season yields were similar in each season between the two establishment systems. Large or medium plug plants led to greatest early fruit yields in one season while large plug plants resulted in greatest early yield in a second season. Total yield was greatest with medium plants in one season and large plants in another season. The extra cost for the plug plant system was $1853/acre. In one out of two seasons there was increased net income amounting to $1142/acre due to greater early yield associated with the plug plant cultural system. Strawberry plug transplants showed promise for earlier and more profitable crops in addition to substantial savings in water used for plant establishment in the field. The ability to establish strawberry crops without irrigation will be important in areas where growers are required to reduce farm water consumption.

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Craig K. Chandler, Daniel E. Legard, Timothy E. Crocker, and Charles A. Sims