Interest in off-season production of red raspberry (Rubus idaeus L.) is increasing as a result of the high demand for a limited supply (Darnell et al., 2006; Knight et al., 1996; Pritts et al., 1999; Schloemann, 2001) and the resultant increase in returns for producers (Pritts et al., 1999). Several systems for off-season production of raspberry have been examined, including annual planting systems (Darnell et al., 2006; Knight et al., 1996). In these systems, long cane plants are removed from northern nurseries in early winter, shipped, and planted immediately in warm winter areas. After fruiting, plants are removed and discarded, and new plants are replanted the next winter. Yield per cane obtained in these systems is similar to first-year yields in perennial production systems but lower than yields obtained in subsequent years of perennial systems (Darnell et al., 2006). The lower yields may be the result of root loss when plants are removed from the nursery and lack of root recovery and regrowth before flowering and fruiting begin. This may limit yield potential in annual production systems, possibly by reducing the stored carbohydrate pool in roots that would normally be available to support fruit growth.
Carbohydrates play a key role in reproductive development in many plants, and stored carbohydrates are especially important in supporting flowering and early fruit development in woody perennials. In raspberry, roots and primocanes are the primary sites for carbohydrate storage during late summer and fall (Crandall, 1995). The next spring, root dry weight decreases dramatically as simultaneous growth of floricane laterals, new primocanes, and roots occur and the demand for stored carbohydrates is high (Fernandez and Pritts, 1994; Whitney, 1982). Stored root carbohydrates play an important role in supplying carbohydrates to floricanes during budbreak and early flowering (Fernandez and Pritts, 1993; Oliveira et al., 2007) and therefore can significantly impact cane yield (Rangelov et al., 1998). This is especially true when current carbohydrate availability is limited (Fernandez and Pritts, 1996). The continuous production of new primocanes also generates a sink for root carbohydrates (Whitney, 1982) until the new primocane leaves become photosynthetically competent. At this point, current photosynthate from primocanes is mobilized to the apices to support further vegetative growth and to roots for storage (Fernandez and Pritts, 1993). It is primarily through carbon mobilization from the primocanes that the root carbohydrate pool is replenished (Whitney, 1982), although mobilization from floricanes to roots has also been shown (Fernandez and Pritts, 1993).
There appears to be substantial growth competition between primocanes and floricanes. Primocane removal often increases yield compared with plants in which primocanes are maintained during the fruiting season (Dalman, 1989; Wright and Waister, 1982a). Conversely, primocane number increases significantly when floricanes (or inflorescences) are removed (Vasilakakis and Dana, 1978; Wright and Waister, 1982b). Previous work indicates there is little current photosynthate translocated from floricanes to primocanes (and vice versa) (Fernandez and Pritts, 1993), and the authors suggested that light competition, rather than carbohydrate competition, is responsible for the growth competition observed between floricanes and primocanes. However, the results were limited in scope, addressing only current photosynthate translocation from a single labeled leaflet and did not address mobilization and partitioning of stored carbohydrate from roots to floricanes and primocanes. Dalman (1989) concluded that root storage carbohydrates are important for both floricane and primocane development, and limitations in the root carbohydrate pool decreased yield or primocane growth, depending on when the limitation occurred. Thus, although there may be little direct translocation of carbohydrate from primocanes to floricanes and vice versa, there appears to be competition for root carbohydrates by both primocanes and floricanes.
As indicated, roots act as a carbohydrate source for early reproductive growth of floricanes and early vegetative growth of primocanes (Fernandez and Pritts, 1994; Whitney, 1982). Later in the growing season, roots act as a sink, obtaining carbohydrates from both floricanes and primocanes (Fernandez and Pritts, 1993). Therefore, understanding carbohydrate partitioning patterns among primocanes, floricanes, and roots is crucial for the successful implementation of an annual production system as described. The reduction in root biomass when plants are removed from the nursery would be expected to decrease the root carbohydrate pool and may alter carbohydrate dynamics in an annual production system compared with the traditional perennial system.
The objectives of the present study were to determine the influence of root carbohydrates and the presence or absence of primocanes on yield in an annual raspberry production system. Two experiments were designed to meet the objectives. In the first experiment (2003), floricanes were girdled at one of two times during bloom to determine the role and timing of root carbohydrates as a source for fruit development. Cane girdling, which interrupts assimilate translocation in the phloem, is a useful but rarely used technique for examining source–sink relations in raspberry (Prive et al., 1994). In 2004, the effects of floricane girdling during bloom in the presence or absence of primocanes was examined to further determine the role and timing of root and primocane source–sink dynamics on yield in the annual production system.
Crandall, P.C. 1995 Bramble production. The management and marketing of raspberries and blackberries Food Products Press Binghamton, NY
Darnell, R.L., Brunner, B., Alvarado, H.E., Williamson, J.G., Plaza, M. & Negron, E. 2006 Annual, off-season raspberry production in warm season climates HortTechnology 16 92 97
Fernandez, G.E. & Pritts, M.P. 1994 Growth, carbon acquisition, and source–sink relationships in ‘Titan’ red raspberry J. Amer. Soc. Hort. Sci. 119 1163 1168
Fernandez, G.E. & Pritts, M.P. 1996 Carbon supply reduction has a minimal effect influence on current year's red raspberry (Rubus idaeus L.) fruit production J. Amer. Soc. Hort. Sci. 121 473 477
Garner, D., Crisosto, C.H., Wiley, P. & Crisosto, G.M. 2003 Measurement of pH and titratable acidity 16 May 2007 <http://www.uckac.edu/postharv/PDF%20files/Guidelines/quality.pdf>.
Knight, R.J., Crane, J.H., Bryan, H.H., Klassen, W. & Schaffer, B. 1996 The potential of autumn-bearing red raspberries as an annual crop in Florida Proc. Fla. State Hort. Soc. 109 231 232
Oliveira, P.B., Silva, M.J., Ferreira, R.B., Oliveira, C.M. & Monteiro, A.A. 2007 Dry matter partitioning, carbohydrate composition, protein reserves, and fruiting in ‘Autumn Bliss’ red raspberry vary in response to pruning date and cane density HortScience 42 77 82
Pritts, M.P., Langhans, R.W., Whitlow, T.H., Kelly, M.J. & Roberts, A. 1999 Growing winter raspberries in a greenhouse HortTechnology 9 13 15
Prive, J.P., Sullivan, J.A. & Proctor, J.T.A. 1994 Carbon partitioning and translocation in primocane-fruiting red raspberry (Rubus idaeus L.) J. Amer. Soc. Hort. Sci. 119 604 609
Rangelov, B., Petkov, T. & Nesheva, M. 1998 Carbon nutrition of summer fruiting raspberry cultivars—transport of 14C—assimilates from root to fruit Bulgarian J. Agr. Sci. 4 763 766
Schloemann, S. 2001 Greenhouse raspberry production for winter sales 16 May 2007 <http://www.umass.edu/fruitadvisor/factsheets/greenhouserasp/raspberriesgh.htm>.
Vasilakakis, M.D. & Dana, M.N. 1978 Influence of primocane inflorescence removal on number of inflorescences and suckers in ‘Heritage’ red raspberry HortScience 13 700 701
Zhou, R. & Quebedeaux, B. 2003 Changes in photosynthesis and carbohydrate metabolism in mature apple leaves in response to whole plant source–sink manipulation J. Amer. Soc. Hort. Sci. 128 113 119