The aim of this study was to determine the effects of date of summer pruning and cane densities on growth and fruiting characteristics of the raspberry (Rubus idaeus) plant. Three summer-pruning dates (early, middle, and late July) and four cane densities (8, 16, 24, and 32 canes/m row) were imposed to the greenhouse-grown primocane-fruiting raspberry `Autumn Bliss' in 2 consecutive years (1994 and 1995). A higher light microclimate and CO2 assimilation rate were measured within the canopy at the lowest density. Some compensation in CO2 assimilation rates were observed in the upper leaves of the high-density treatments, probably in response to low light. Delayed pruning decreased yield per cane and per row. The highest yields per cane were always observed at the lowest cane density. Densities of 16 and 24 canes/m produced the highest fruit yield. Light conditions appeared to be the most important environmental factor affecting plant productivity. Fruit were a weaker sink than roots; therefore, the role of carbohydrate reserves should be investigated.
Pedro B. Oliveira, Cristina M. Oliveira and António A. Monteiro
Pedro Brás de Oliveira, Maria José Silva, Ricardo B. Ferreira, Cristina M. Oliveira and António A. Monteiro
In a 2-year experiment (1994 and 1995), plants of primocane-fruiting red raspberry cultivar ‘Autumn Bliss’ grown in a plastic greenhouse were destructively harvested at different growth stages to determine the effect of pruning date and cane density on dry matter distribution, carbohydrate concentration, and soluble protein concentration in different plant parts. Three summer-pruning dates (early, mid, and late July) and four cane densities (8, 16, 24, and 32 canes/m row) were imposed. Relative root biomass decreased from pruning to first flower stage and remained constant thereafter for all pruning dates. Earlier pruning dates corresponded to earlier fruit production, but yield was significantly reduced on later pruning dates and higher cane densities. Sucrose concentration was higher in fine roots than in suberized roots and had a slight decrease during flowering and the beginning of harvest. Soluble protein concentrations did not differ significantly between pruning dates. Reserve carbohydrates in the root system were unaffected by pruning and cane density, and were rapidly used during active vegetative growth, began to recover just after bloom, and were fully recovered at the end of the season. Our experiment suggested that in red raspberry plants grown under poor environmental conditions, current yield is reduced but there is enough carbohydrate accumulation to support next year's growth.
Pedro B. Oliveira, Cristina M. Oliveira, Luís Lopes-da-Fonseca and António A. Monteiro
The spring shoots of `Autumn Bliss' red raspberry (Rubus idaeus L. var. idaeus; primocane-fruiting type) were cut on 2, 16, 31 July and 15 and 30 Aug. with the objective of delaying fruit harvest into the off-season under mild winter climatic conditions. Cutting shoots in August delayed fruit harvest until February and April of the following year, but shoot growth was weak and fruit yield low (4.8 and 2.1 g/cane). July cuttings delayed harvest until October to January with acceptable fruit yield (63.5, 52.8, and 26.5 g/cane for 2, 16, and 31 July, respectively). The differences in cane height and total node and fruiting node count between the three cutting dates of July were small, but there was a constant decrease in leaf area per cane from the first to the third date and a sharp decrease in fruit yield from the second to the third date. Vegetative shoot growth was less affected than yield when summer cutting was delayed until the end of July to induce a later harvest. Fruit quality always reached acceptable standards. This study confirms the practicability of using summer-cutting of primocane-fruiting red raspberries to induce off-season fruit production under protected cultivation in mild winter climates.