Craig K. Chandler

Effect of High Tunnels on the Growth, Yields, and Soluble Solids of Strawberry Cultivars in Florida

Two studies were conducted to compare the effects of high tunnel and open-field production on the growth, fruit earliness, yield, and soluble solid content of Florida strawberry cultivars. Three strawberry cultivars and two production systems were tested inside high tunnels and in open fields. The cultivars were ‘Strawberry Festival’, ‘Winter Dawn’, and ‘Florida Elyana’. Production systems and cultivars significantly affected strawberry early and total yields, but the interaction between both factors was not significant. Early yields increased by up to 54% inside high tunnels in comparison with those from open fields. Strawberry total marketable yields maximized inside high tunnels in comparison with open fields, with up to 63% fruit weight increments. Fruit yields after freezing events and soluble solid contents were also increased inside high tunnels. Using high tunnels in Florida for strawberry production might benefit growers by improving earliness and providing a competitive edge in the market, reducing sprinkler irrigation use for freeze protection, hence lowering fruit damage and fuel or electricity costs, and the incidence of foliar and fruit diseases.

Strawberry fruit resistance to simulated handling

ABSTRACT: Harvest operations are currently the main source of mechanical injury of strawberry( Fragaria x ananassa Duch. ). Experiments were designed to simulate conditions encountered duringcommercial handling. Individual fruits were subjected to impact or compression forces with similarenergy to determine the sensitivity to mechanical injury. Bruise volume was used as the measurementof injury. Bruise severity increased as a function of impact energy for both impact types. However,dropped fruits had larger bruise volume than fruits submitted to pendulum impactor at the sameenergy level. Doubling the impact energy (0.040 to 0.083 J) increased bruise volume by 7 times (13 to91 mm 3 ). Fruits dropped from 380 mm (0.075 J) showed 71% greater bruise volume than those droppedfrom either 130 mm (0.025 J) or 200 mm (0.040 J). Compressed fruits showed higher bruise volume thanother tests. Some cultivars are more susceptible to compression forces than others. ‘Sweet Charlie’berries showed bruise volume 40% higher than the others cultivars when subjected to compression.Fruits subjected to impact showed bruise volume lower than the compressed fruits, indicating thepossibility to be handled and graded in a packing line.Key words:

Influence of Nitrogen Fertilization Rates on the Performance of Strawberry Cultivars

Two sets of studies were conducted to examine the response of “Strawberry Festival” and “Winter Dawn” strawberries (Fragaria x ananassa Duch.) to different nitrogen (N) rates. The first set of studies consisted of two trials conducted during the 2005–06 and 2006–07 growing seasons. N rates were 0.5, 0.7, and 0.9 kg/ha per day (75, 105, and 135 kg/ha per season). The second set of studies was conducted during the 2006–07 and 2007–08 growing seasons. Nitrogen rates were 0.9, 1.4, and 2.0 kg/ha per day (75, 210, and 300 kg/ha per season) using the same cultivars. During the first set of studies, canopies of “Strawberry Festival” were 30% and 10% wider than “Winter Dawn” at 6 and 12 weeks, whereas N rates linearly increased canopy diameters of both cultivars. There was a significant cultivar by N rate interaction for total marketable fruit weight. Increasing N rates from 0.5 to 0.9 kg/ha per day linearly improved total marketable fruit weights of “Strawberry Festival,” but not those of “Winter Dawn.” For the second set of studies, N rates only influenced strawberry plant canopy diameters, but not early and total marketable fruit weight and number. There were no differences between the total marketable fruit weights of both cultivars. The data showed that the response of different strawberry cultivars depends on the range of N rates used for fertilization.

Evaluation of strawberry cultivars in Florida.

Field studies were conducted over two seasons to examine the performance of strawberry cultivars. During the 2007–2008 season, the cultivars tested were ‘Winter Dawn’, ‘Florida Elyana’, ‘Florida Radiance’, ‘Ruby Gem’, ‘Strawberry Festival’, ‘Treasure’, and ‘Camarosa’; whereas in the 2008–2009 season, ‘Winter Dawn’, ‘Florida Elyana’, ‘Florida Radiance’, ‘Strawberry Festival’, ‘Treasure’, ‘FL 05–73’, and ‘FL 05–107’ were planted. During both growing seasons, ‘Strawberry Festival’ consistently produced the highest early and total fruit numbers among all tested cultivars. Similarly, the same cultivar had the highest early fruit weight. With regards to total fruit weight, ‘Florida Radiance’, ‘Treasure’, and ‘Strawberry Festival’ resulted in the highest values among all cultivars tested during both seasons. There was no consistency on specific cultivars producing the largest early fruit, while ‘Florida Radiance’ and ‘Florida Elyana’ had the largest total weight per fruit during both seasons. These results indicated that ‘Strawberry Festival’ is an adequate choice as a main cultivar for production under Floridas conditions, which could be complemented during low production periods with other promising and late producing cultivars such as ‘Florida Radiance’ and ‘Treasure’.

Fruit Quality Measures from a Historical Trial of University of Florida Strawberry Cultivars

The strawberry breeding program of the University of Florida develops varieties that are highly adapted to west-central Florida, where approximately 8,800 acres of strawberries were grown during the 2009–10 season. In order to gain insight into breeding progress over time, two advanced selections and ten released cultivars, from Florida Belle (1975) to Florida Radiance (2008), were compared for various fruit quality traits. Cultivars and selections were arranged in a randomized complete block design at each of two locations (Balm, FL and Dover, FL). Fruit size varied dramatically with a minimum average weight of 16.2 g for ‘Dover’ (1979) and a maximum of 30.8 g for ‘Elyana’ (2008). Regression of average fruit weight on year of release showed an average gain in fruit size of 0.26 g/yr (R2 = 0.44). Improvements in fruit uniformity were also apparent, but gains for internal flesh color were not sustained. There was wide seasonal variability in sugars (sucrose, glucose, fructose, Brix) and acids (citric, malic, and titratable acidity); March tended to produce fruit with lower sugars. Sugars were highest in February while acids were highest in January. Also, correlations were found between sugars and volatiles having fruity and strawberry characters. Comparison of chemical data with sensory data from related studies indicates that instrumental measures, particularly for SSC/TA, could aid in breeding for improved flavor.