James N. Moore, who began the University of Arkansas fruit breeding program in 1964, filed the first plant patent for a cultivar from the program in 1982, `Reliance' grape. Before that, he released six nonpatented cultivars. `Reliance' was anticipated to be more adapted to the midwestern U.S. than Arkansas and the South, and Moore was interested in program support outside Arkansas for those that would benefit from this development. He found that nurseries and producers were receptive to the idea of patented cultivars and paying per plant royalties on new developments. In 1984, eight nurseries were licensed to propagate `Reliance'. Since that time the fruit breeding program has released 40 cultivars, of which 25 have been plant patented. Licensing for the patented cultivars has been on a nonexclusive basis with nurseries in the U.S., and exclusive agreements for defined territories have been exercised outside the U.S. Total license agreements in early 2006 total >300. Trademarking was first used in 2003 for the first primocane-fruiting blackberry cultivars. Breeding agreements were put in place 2003 as a way to generate program support and move germplasm developments into additional commercial channels. Testing agreements have been expanded outside the U.S., with fees paid to test genotypes and provide first option for exclusive licensing. Proprietary releases have been of benefit to the University of Arkansas and intellectual property protection of new developments should continue to be used.
Fertility and soil preparation practices for blackberries from numerous states were reviewed to determine common recommendations. Soil pH was uniformly suggested to be 6.0–6.5, with the use of dolomitic lime commonly preferred for pH adjustment. Organic matter additions were often recommended, using cover crops or animal manures the year before planting. Additionally, the incorporation of P and K the fall before planting was commonly suggested, with rates of application dependent on soil test levels. Nitrogen applications were recommended each year, with rates increasing to the maximum suggested in years 2 or 3. Ammonium nitrate was always the preferred N source. Rates ranged from 28 to 56 kg N/ha for the first year to 67 to 90 kg N/ha for mature plantings, with rates largely dependent on soil type, with sandy soils receiving the higher rates. Application of K was usually recommended for every other year, based on soil test levels.
Eastern U.S. blackberries are heterogeneous tetraploids. Some traits have been quite difficult to improve, and the example of erect-caned, thornless cultivar development is a good example. Thornlessness was associated with semi-erect canes, poor seed germination, and other undesirable traits, thus extending the amount of time to achieve an erect-caned, thornless cultivar. The first release of this type was `Navaho' in 1989. Primocane fruiting is a trait that would not likely be considered intractable, but did not gain substantial attention until the late 1980s. Subsequent work in primocane fruiting has shown substantial progress in a relatively short time of breeding emphasis for this trait. Fruit size gains have been substantial, and even though this trait might be considered intractable, progress has been significant in the last 40 years. Excellent postharvest handling and flavor are additional traits which one might consider intractable. Substantial progress has been made in improving fruit quality for shipping, providing for an expansion in fruit shipped to distant markets. These and other improvements are expanding opportunities for blackberry growers worldwide.
Primocane-fruiting blackberry breeding was initiated in the early 1990s at the University of Arkansas. The source of this trait is the diploid genotype ‘Hillquist’. Introductions from this effort are the cultivars Prime-Jim® and Prime-Jan®. These genotypes are intended for home-garden use as a result of lack of quality for commercial production. Several traits have been identified that are high priorities in primocane blackberry breeding advancement, including heat tolerance of flowers and fruits, fruit quality, thornlessness, and time of fruit ripening. Progress in addressing these limitations through breeding has been positive and the outlook for further improvement of this type of blackberry is promising.
Eastern U.S. blackberries (Rubus subgenus Rubus) have advanced in recent years in production and quality of cultivar choices. Mainly a pick-your-own and local sales item of the early 1990s and before, the increased presence of blackberries in retail grocery stores in the last 10 years has broadened the market for this small fruit. Cultivars that can be shipped and have extended shelf life have been the cornerstone of this expansion. Also, off-season production in Mexico has provided fruit for retail marketing during most months of the year. Further advances in production, marketing, and consumption can be achieved with the continuation of improved cultivar development and expansion of production technology.