Patrick Conner, University of Georgia – Tifton Campus 

‘RubyCrisp’ is a new muscadine cultivar released from the University of Georgia muscadine breeding program. ‘RubyCrisp’ was selected from a cross of ‘Supreme’x‘Tara’ and was tested as Ga 8-1-338 in replicated trials in Tifton, GA. Single vine replicates were planted in randomized order in 2012. Vines were spaced 3.0 m between plants within the row, and 4.5 m between rows. Vines were trained to a single wire trellis with a single trunk and two cordons per vine. Vines were annually spur pruned by hand and fertilized with 560 kg•ha-1 of 10N-4.4P-8.3K. Drip irrigation was used and diseases and insects were controlled according to commercial guidelines.

‘RubyCrisp’ vines are self-fertile and do not need a pollinizer. Total yields of ‘RubyCrisp’ were excellent and consistently ranked among the highest yielding cultivars in all years of the trial (Table 1). Usable yield was reduced by both rot and pedicel scar split, but usable yield remained among the highest of the tested cultivars. Berry rot in ‘RubyCrisp’ appears higher than typical black cultivars but lower than bronze-colored cultivars (Table 1). Percentage pedicel scar split was higher than the recent commercial cultivar releases Hall and Paulk. Overall percentage of dry scar was lower than ‘Hall’, ‘Paulk’, and ‘Supreme’ (Table 1).  Berry firmness was similar to ‘Paulk’, less than ‘Supreme’ and more than ‘Fry’ at harvest (Table 2). However, after 11 d of storage berry firmness was less than both ‘Paulk’ and ‘Supreme’ and similar to ‘Fry’. The ability to pick berries with a dry scar and firmness in storage are vital traits for a commercial packing berry, and the low percentage of dry scar and softening during storage of ‘RubyCrisp’ make it unfavorable for this use.

Average first harvest of ‘RubyCrisp’ was 21 Aug. (Table 1), which was similar to the midseason check cultivars Supreme, Fry, and Paulk. Normal harvest seasons extended into the first week of September. Berry size of ‘RubyCrisp’ was similar to ‘Supreme’ and ‘Paulk’, and larger than the other check cultivars (Table 1).  Percent soluble solids was higher than all other cultivars except ‘Lane’ (Table 1) and flavor was sweet with relatively low muscadine aroma. Textural analysis of ‘RubyCrisp’ indicate that the berries had a very firm flesh (4.5 N maximal force) and tender skins (11.4 mJ berry puncture work). The firm flesh and tender skin of ‘RubyCrisp’ make it distinctly different from the other tested muscadine cultivars and more similar to texture of V. vinifera table grape cultivars. In addition,‘RubyCrisp’ berries are non-slipskin and the berry skins have a neutral flavor, favoring the flesh and skins to be eaten together. ‘RubyCrisp’ berries are attractive with a distinctive red color (Figs. 1, 2) and have a good flavor.

‘RubyCrisp’ combines several rare traits for a muscadine cultivar which have led it to be a popular selection at field days and grower events.  The red coloration of the berries is very distinguishing and pleasing to most consumers.  In addition, the tender skins and crisp flesh of ‘RubyCrisp’ is similar to a V. vinifera fresh-market grape and adds to the originality of this cultivar.  Berries show good sweetness, but muscadine aroma and flavor is low.  This is pleasing to some people who dislike muscadine flavor, but unfavorable to others that do like the characteristic flavor of a traditional muscadine.  Unfortunately, the tender skin of ‘RubyCrisp’ berries make it difficult to commercially pick without suffering relatively large losses due to berry split.  Heavy rainfall during harvest season can also lead to fruit cracking.  However, the unique fruit quality traits of ‘RubyCrisp’ warrant its release as a home-garden and pick-your-own cultivar.  Given the large berry size and high production potential of ‘RubyCrisp’, growers may need to limit vine fruitfulness, especially on young vines, by increasing the distance between fruiting spurs or thinning the crop so that the vine is not weakened by maturing excessive crops.  Limited data is available to determine the cold hardiness of ‘RubyCrisp’ vines, and large plantings should not be made in the northern muscadine regions until more data is available. ‘RubyCrisp’ has been licensed to Ison’s Nursery and Bottom’s Nursery. 

Table 1. Yield, flower and fruit attributes of ‘RubyCrisp’ and standard muscadine cultivars in Tifton, GA in the third through fifth years of growth (2014-2016).

Cultivar Flower typez Berry color Avg. day of first harvest Total yield Tifton (kg) Usable yield (kg)y Percent berry rotx Percent dry pedicel scarw Berry wt. (g) Berry diam. (mm) Percent soluble solids of all harvests  
RubyCrisp Red Aug. 21 abv 25.2 a 19.6 ab 8.4 bc 48.7 d 15.2 a 30.2 a 16.1 a 
Fry Bronze Aug. 19 b 11.4 c 8.5 d 12.6 ab 49.4 d 12.2 b 27.9 b 14.5 b 
Hall Bronze Aug. 2 c 19.3 ab 15.7 bc 16.6 a 90.9 a 10.1 c 26.0 c 14.9b 
Lane Black Aug. 4 c 15.5 bc 11.7 cd 4.0 c 52.2 cd 9.2 c 25.4 c 15.5 ab 
Paulk Black Aug. 19 b 22.9 a 21.0 a 4.7 c 84.9 a 15.0 a 30.2 a 14.9 b 
Supreme Black Aug. 24 a 20.7 ab 17.7 ab 3.4 c 59.3 c 15.0 a 30.0 a 14.5 b 
Significance   <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 0.017 
z(H) hermaphrodite, (F) female 
yUsable yield is total yield minus weight of rotted berries and berries with pedicel scar splitting. 
xPercentage of berries with visible signs of decay or fungal pathogens. 
wPercentage of berries with no splitting or tearing at the pedicel scar after picking. 
vMean separation within columns by Duncan’s multiple range test, P<0.05, with n = 4. 

Table 2.  Change in firmness (g•mm-1) of ‘Paulk’ and test cultivars at harvest and after cold storage (0-1 °C, 90% to 95% relative humidity).z 

Cultivar Firmness (g•mm-1)y Firmness (g•mm-1)y 
 Day 0 Day 10 + 1 
RubyCrisp 222 b 176 c 
Paulk 240 ab 203 b 
Fry 199 c 178 c 
Supreme 248 a 222 a 
Significance <0.001 <0.001 
zBerries were evaluated at harvest, packaged in ventilated clamshell containers, and placed in cold storage for 10 days.  Berries were then brought out of cold storage allowed to warm for 24 h at room temperature (21 °C) and evaluated 1 d post-removal. 
yValues are means with n=4.  Each replication consisted of 25 berries measured for firmness using a Bioworks FirmTech II.  Mean separation within columns by Duncan’s multiple range test, P<0.05.
Figure 1.  RubyCrisp™ berries on the vine. 
Figure 2.  ‘Fry’, RubyCrisp™, and ‘Supreme’ berries in pint clamshells. 
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