Primocane-fruiting blackberries released by the University of Arkansas (Clark et al., 2005; Clark and Perkins-Veazie, 2011) offer an alternative or addition to the other types of high-value, fresh-market blackberries available, especially in production systems for season extension (Strik and Thompson, 2009).
Annual, primocane-fruiting, erect blackberries can be grown for a double crop (floricane in early summer plus primocane in late summer through fall) or a single crop (primocane only). Drake and Clark (2003) showed that double cropping did not reduce the yield of the primocane crop in Arkansas. Worldwide, primocane-fruiting blackberries are primarily being tested and grown for an annual, primocane crop.
Primocane-fruiting blackberries initiate flower buds after a short period of growth and may initiate flower buds independently of photoperiod and temperature (Lopez-Medina et al., 1999). In field-grown primocane-fruiting raspberry (Rubus idaeus L.), fruiting season can be modified by advancing or delaying primocane growth using rowcovers (Pritts et al., 1992) and can be easily manipulated to produce fruit at most times of the year in warm climates and/or tunnels to target high-priced niche markets (Darnell et al., 2006; Oliveira et al., 1996, 1998).
Cultural practices may be used to manipulate the fruiting season of primocane-fruiting blackberries. Use of spun-bound rowcover from late winter through early spring advanced flowering and fruiting in Oregon (Strik et al., 2008) but had no impact in North Carolina (Fernandez and Ballington, 2010). In plants in which primocanes were mowed back to ground level when height averaged ≈0.5 m, fruit production was delayed by ≈4 weeks (Thompson et al., 2009). Producing primocane-fruiting blackberry in an unheated tunnel extended the harvest season ≈3 weeks later in the fall in Oregon’s temperate climate (Thompson et al., 2009).
Research in primocane-fruiting raspberry showed that primocane tipping had some effect on fruiting season and yield. “Hard tipping” (removal of 0.3 m) ‘Heritage’ primocanes to 1 m delayed fruiting (Jordan and Ince, 1986; Richter et al., 1989). Oliveira et al. (1998) found that summer tipping advanced harvest in primocane-fruiting raspberry compared with plants that were recut to ground level, but they did not have an untipped control for comparison. Tipping canes later in the season reduced yield. In primocane-fruiting blackberry, the effects of “soft-tipping” (removal of 2 to 5 cm) individual primocanes on yield and berry size depended on when the tipping was done (Drake and Clark, 2003). They suggested that other tipping treatments and studies in a milder climate than that of Arkansas would be beneficial to development of a production system for this new crop. Soft-tipping the primocane at 1 m induced branching and increased flower and fruit number and yield threefold without affecting fruiting season in Oregon (Strik et al., 2008). A double tip, where branches are further shortened, has been shown to increase yield compared with untipped canes (Thompson et al., 2009). A better understanding of the impact of primocane management on cane architecture and yield components may advance production systems of genotypes in various climates.
The objectives of this study were to determine the impact of primocane tipping in summer, the presence of floricanes, and the use of rowcover on the fruiting season, yield, fruit size, cane architecture, and yield components of primocane-fruiting blackberry.
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