Primocane-fruiting (PF) is the ability of bramble plants to produce fruit on the tips of first year canes. The PF trait was recognized in red raspberry plants over 200 years ago. In the last 50 years, PF red raspberry cultivars such as 'Heritage', 'Autumn Bliss', 'Amity', 'Summit' , and 'Caroline' have become popular for home and commercial fruit production . The more recent releases of 'Prime-Jim', 'Prime-Jan', and 'Prime-Ark-45'PF blackberries has allowed season extension of fruit using new production systems.
In fact, PF berry plants have significantly changed worldwide production and the availability of these fruits to consumers year-round.
The PF trait also occurs in black raspberry. The first black raspberry cultivar, 'Ohio Everbearer' was selected from a wild plant growing near the shore of Lake Erie and was released in 1832. By 1920, at least 19 other cultivars were named, including 'Grigg's Daily Bearing', 'Miller's Daily Bearing', and 'Lum's Autumn Black'. Because most of these cultivars produced small poor quality fruit, they fell out of favor until 1973 when 'Black Knight' was introduced.
Over time, PF black raspberry germplasm was lost until a recent renewed interest in studying this trait. The most recently released PF cultivar is 'Explorer', but it is limited by poor pollen fertility. However, the release of this cultivar has rekindled the collection and evaluation of wild black raspberry germplasm throughout the United States. Because some plants erratically produce primocane fruit on the tips of some branches of all or just a few branches on plant canes, thorough evaluation of germplasm is necessary. Also, some plants express PF in some, but not all years. As with red raspberry and blackberry, environment may also affect the expression of PF in black raspberry. Currently, the USDA-ARS/Oregon State University cooperative breeding program and a private breeding program in Longmont, Colorado are leading the effort to find cultivars that strongly express the PF trait. One of the most advanced selections, PT-2A4 is in trial at several locations across the U.S. and purportedly produces larger fruit with smaller seeds than that of 'Explorer'. Also, experiments are in progress to determine if cane tipping (to produce more branching and delay harvest) is advantageous and to evaluate disease susceptibility of plants.
Until a modern, promising PF black raspberry cultivar is released, the older summer fruiting cultivars are commercially available such as 'Black Hawk', 'Jewel', 'Bristol', 'Munger', and 'Mac Black'. Cultivars with anthracnose resistance ('Black Hawk' and 'Jewel') most likely perform better than others during rainy growing seasons. While the flavor of these black raspberries is unique, fruit size remains small when grown in Missouri and plants growth may be suppressed due to warm summer temperatures. The rediscovery of black raspberry and renewed interest in breeding for this trait promises to rejuvenate the culture of this crop. As improved cultivars are released and production acreage is expanded, it may be possible for consumers to purchase delectable black raspberries at local grocery stores throughout the year.
REVISED: October 11, 2011