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Muscadine Grape Breeding Program: Cultivars

General Information

Dry (or Stem) Scar

Unlike bunch grapes, muscadines are usually picked as single berries rather than in clusters. In nature, muscadine 'Golden Isles' berries showing the tearing typical of a cultivar with wet stem scars.berries often abscise from the cluster (shatter) at maturity. Unfortunately, many cultivars tend to have stem scars that remain open in the center, or the skin tears around the scar. This is known as having a wet scar. This is deleterious as it provides an entrance into the berry for mold, and the juice can leak from the scar and get the berries sticky. For the fresh market, it is important to have as few wet scars as possible. No cultivar is perfect, but some cultivars are better than others at producing a dry scar, and these are favored for fresh market, especially where berries will be stored for a period before the sale. We evaluate this trait by evaluating the percentage of berries with dry scars each year, with a higher percentage being better than a low percentage.


Flower Type

Muscadine flowers can be either male, female, or self-fertile (or perfect). In nature, vines are either female or male, and only the female vines set fruit. Before there were self-fertile flowers, vineyards were planted with the female fruiting cultivars, and male plants were interspersed to pollinate the female vines. Thus, production was reduced because the male vines produce no fruit.

Fortunately, a few vines that had self-fertile flowers were discovered, and through breeding, this trait was introduced into new cultivars with good berry quality. This meant that self-fertile vines could be used to pollinate the female cultivars, and berries could be harvested from the entire vineyard.

Currently, most vineyards consist of a mix of female and self-fertile vines. Usually, the female vines have a lower and more inconsistent yield than the self-fertile vines, but have a larger berry size. However, with self-fertile cultivars with large berry size being developed, the planting of female cultivars will likely decline in the future.

Muscadine flowers (from left): Male, Perfect and Female

Male flowers have extended stamens and are missing the female pistil. Female flowers have shorter reflexed stamens with nonfunctional pollen. Perfect flowers have functional pistils along with extended stamens with functional pollen.

Female flowersFemale cultivars often have reduced yields. This is sometimes because the calyptera dries down and does not fall off the pistil. Notice how these are brown and still attached as compared to the female flower above showing a green healthy calyptera excising from the pistil. This prevents pollen from reaching the stigma and thus the flower isn't pollinated.


Soluble Solids

For our uses, percent soluble solids is a measure of the sugar content of the grape juice. The higher the sugar content the sweeter the juice, so in general we want a higher percent soluble solids.

Soluble solids percentage will differ based on cultivar, berry ripeness, crop load, and environment. We measure percent soluble solids by taking a sample of 10 berries and squeezing the juice onto an electronic refractometer. Our readings are the average of several years, and we try to measure at the time the berries would be just ready to pick. I have found that you want a soluble solids percentage of at least 14 or 15 to have a good flavor, and berries at 17%+ are noticeably very sweet.


Variety Protection

Like many inventions, new cultivars of plants can be patented. For more information on plant patents, visit the U.S. Patent and Trademark Office Plant Patent Web site.

If a cultivar is patented, you may not propagate the cultivar without permission of the patent holder. Plant patents last for 20 years from the date of filing the patent, after that time the patent is expired and propagation is allowable. Most of the muscadine vines listed on this Web site that are patented originated with Ison's Nursery. The patent on some of these cultivars has expired, and others are still in force. Check the date of the patent as the pages are not updated very often. Cultivars with a patent are usually only available via Ison's Nursery, while unpatented cultivars may be available at several nurseries.