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Two new blueberry cultivar releases from the University of Georgia (UGA) breeding program are reported to produce large size berries. ‘Titan’ (Fig.1) and ‘Krewer’ (Fig. 2) berry size is found to be twice as large as the berry size of most rabbiteye blueberry cultivars. ‘Pink Lemonade’ (recommended as a backyard cultivar) possesses unique pink fruit color and ripens late (Fig. 3). ‘Pink Lemonade’ has a very attractive and unusual appearance and draws consumers’ curiosity and attention at the marketplace. ‘Alapaha’ is known for its very early ripening, surpassing ‘Climax.’ Its blooming season is about 7 to 10 days after that of ‘Climax,’ which reduces the risk of late spring frost and freeze damage to the crop. ‘Vernon’ is another early season cultivar that has not been evaluated for production in Alabama conditions. ‘Ochlockonee’ is reported to mature about a week after ‘Tifblue’ and can extend the harvest season. An experiment was established in 2019 to evaluate cultivar vegetative growth, production potential and fruit quality characteristics in order to develop cultivar recommendations to specialty crop producers in Alabama and the southeast. Traditionally grown cultivars such as the early season ‘Climax,’ ‘Premier,’ and the late ripening ‘Powderblue’ and ‘Tifblue’ were included as controls.

 

Results

The above mentioned newly released and established blueberry cultivars were planted at the Chilton Research and Extension Center (CREC), near Clanton in central Alabama. Data to determine each cultivar bud break and flowering season were collected periodically beginning in January 2022 and continued until mid-March. A late spring freeze event occurred on March 12-13 when temperatures fell to 24 degrees F. Row covers (Figure 4) were used to protect the plants every time critically low temperatures were expected, starting as early as January 2022 until the last freeze event in mid-March. The early row cover application was due to the fact that low chill cultivars such as ‘Krewer’ and ‘Pink Lemonade’ had fulfilled their chill requirements at the end of December 2021 and had some open flowers in early January 2022 (Figure 4).

Figure 4. Row covers used to protect the blueberry cultivar experiment at the CREC, AL during January-March, 2022.

Application of row covers increased the temperature under the cover by as much as 8 degrees F and successfully protected the plants through mid-March when the strong winds of over 35 miles/hour blew away the row covers from two of the experimental rows (half of the experiment) and exposed the plants to the freezing temperatures. At this time the blueberry cultivars had between 20% (‘Tifblue’) and 100% (‘Krewer’) open flowers due to the warming trend in the beginning of March. Since blueberry plants can tolerate temperatures of 23 to 24 degrees F during the early pink bud stage, but are susceptible to cold injury at 28 degrees F at the full bloom stage, all cultivars sustained cold injury and the most advanced blueberries had a complete crop lost, especially on the two rows where the wind damage caused the row covers to be removed from the plants (Fig. 5 and 6).

Visual rating of the degree of cold injury was conducted for each blueberry plant shortly after the freeze event on March 12. The results suggest the covered rows had between 20% and 90% damaged flowers, while the damage on uncovered/unprotected rows varied between 85% and 100%.  This extensive damage resulted in a significant crop loss.

Table 1. Total yield and fruit quality attributes of selected rabbiteye blueberry cultivars grown in central Alabama CREC, 2022.

CultivarTotal yield, gMean berry weight, gSSC
Alapaha156.52.015.5
Climax58.52.116.5
Krewer229.53.515.2
Ochlockonee280.62.315.0
Powderblue137.01.715.3
Premier56.01.615.5
Tifblue355.31.615.3
Titan188.34.014.4
Vernon599.32.515.0

The first blueberry harvest occurred on June 7, 2022. Yield was measured for each individual bush. To determine berry size and SSC, a 10-berry sample was collected at each harvest date. ‘Vernon’ was the cultivar producing the highest total yield in 2022, while no crop was harvested from any of the ‘Pink Lemonade’ plants (Table 1). Due to the significant crop loss fruit quality results should be considered with caution. ‘Climax’ berries were the sweetest during 2022 season, but all blueberry cultivars produced crops with relatively high SSC, likely an effect of the low crop load. ‘Titan’ had the largest berries at 4.0 grams on average, followed by ‘Krewer’ with a mean berry weight of 3.5 grams.