Nine-year-old 'Black Satin' blackberry (Rubus subgenus Rubus) plants were dormant pruned to three floricanes with three, six, nine, or twelve 12-node lateral branches (≈108, 216, 324, or 432 axillary buds per plant) to determine the effect of lateral branch number on budbreak, fruit cluster number, fruit number per cluster, fruit weight, total soluble solids (TSS), and yield. Percent budbreak of primary and secondary axillary buds was reduced as the lateral branch number increased. Pruning did not affect fruit weight (6.4 g) or TSS (9.5%). Yield per lateral branch was reduced as lateral branch number increased. A plant with three floricanes, each with 12 lateral branches, produced 21 kg of fruit. The results indicate that pruning lateral branches to a manageable length may be advantageous for eastern thornless blackberry trained on a divided canopy trellis.
Small fruits, such as strawberries and blueberries, are rich in phytonutrients and regarded to have high human health-functional bioactivities. In this workshop, 1) the horticultural and environmental factors affecting antioxidant levels in small fruit, 2) fruit volatiles as related to postharvest shelf life and quality, 3) changes in non-volatile fruit constituents, and 4) olfactometric analyses and consumer perception of these value-added fruit constituents will be discussed. In addition, novel detection methods for fruit- and microbial-derived aromas to address the food safety issues will be discussed.
Easter thornless blackberries (ETB) are highly productive and commercially grow” in several areas of the country. Fruit are acceptable for the fresh market and the processor. Mature plants of ETB cultivars develop 3 or 4 primocanes annually. On these primocanes as many as 15 lateral shoots may develop from axillary buds. In 1992, the effects of lateral shoot numbers on axillary bud break, fruit cluster numbers, berry size, and yield were determined. `Black Satin' (9-yr-old) vines were dormant pruned to three floricanes with 3, 6, 9, or 12 l2-node lateral shoots (108. 216, 324, or 432 axillary buds per plant). In all plants, about 77% of primary axillary buds broke and grew into fruiting laterals. However, percentage bud break of secondary axillary buds was reduced as the lateral shoots per floricane increased. Pruning severity affected neither berry size (6.4 gm) or SSC (9.5%). Yield per lateral shoot was reduced as lateral shoot number increased. For higher fruit production in ETB, the number of primocanes as well as the lateral shoot numbers per plant must increase.
NAA at 0.25% to 1.0% applied in late May on the basal portion of thornless blackberry (Rubus, subgenus Eubatus) primocanes inhibited lateral shoot growth in the treated area and reduced the number of primocanes. However, regrowth occurred near or below ground from axillary buds not contacted by NAA. Rates of (0.25% and 0.12570 NAA did not affect the terminal or lateral growth above the treated area. The reduced number of basal lateral shoots facilitated machine harvesting. Chemical name used: napthaleneacetic acid (NAA).
Fumiomi Takeda and John Phillips
Using the rotating cross-arm (RCA) trellis and cane training system, lateral canes of trailing ‘Siskiyou’ blackberry (genus Rubus subgenus Rubus) were kept vertically or rotated down to horizontal so that plant canopy was close to the ground. In winter, the plots were either covered with a non-woven rowcover (RC) or left uncovered. Cane injury was least in plants with lateral canes oriented horizontally and covered. Cane injury was high in plants with lateral canes oriented vertically in winter, whether covered or not, and among plants with lateral canes laid close to the ground but not covered. Among ‘Siskiyou’ plants that had lateral canes oriented horizontally, 280 flower clusters and 6.0 kg fruit/plant were produced on plants that had a RC in the winter compared with only 72 flower clusters and 1.7 kg fruit/plant for plants that were not covered in winter, in 2009. Fewer flower clusters developed and the yield was ≤2 kg/plant on plants with lateral canes oriented vertically. Yield differences between the most and least productive treatments were low in 2010 because of milder winter conditions and snowfall during the coldest periods that fully or partially covered the lateral canes oriented horizontally and close to the ground. The RC treatment had no effect on cane injury or yield when lateral canes were oriented vertically. The findings suggested that ‘Siskiyou’ blackberry can be grown in the eastern United States, where winter injury has frequently caused a crop failure, by positioning the lateral canes close to the ground and covering plants with a RC.
Fumiomi Takeda and Wojciech Janisiewicz
Restrictions on pesticide usage and the occurrence of fungicide resistant strains of postharvest pathogens have necessitated research for alternative methods of disease control. Psuedomonas cepacia was tested for control of Botrytis fruit rot in strawberry. Results of field applications of P. cepacia were variable. A compound isolated from P. cepacia, identified as pyrrolnitrin, was as effective as Benlate/captan (2,000 ppm) sprays in field applications. Postharvest pyrrolnitrin (100 ppm) dip inhibited growth of pathogens for three days at room temperature. A pyrrolnitrin dip followed by storage at 1°C for five days extended the shelf-life for another five days. Preharvest pyrrolnitrin sprays to `Bristol' black raspberry delayed rot development by 4 to 5 days. Captan (2,000 ppm) treatment provided no protection. In vitro tests showed that B. cinerea isolated from the fruit had developed resistance to captan. These results suggest that the use of a naturally-produced compound might afford another opportunity to reduce postharvest rots without the use of synthetic fungicides.
Fumiomi Takeda and David Handley
A combination of simple cultural practices, a modified rotatable crossarm (RCA) trellis system, and covering plants with insulation material in winter overcame the lack of cold hardiness in trailing blackberries that have been established at Kearneysville, W.Va. After tying canes to trellis wires and rotating the cross-arms to below horizontal, tied canes were close to the ground, allowing them to be covered with protective materials, such as floating rowcover and polyethylene plastic during winter. Covers were removed in early spring and the canes remained in the horizontal orientation until bloom, which promoted flowering laterals to grow upright. After bloom, the cross-arm was rotated beyond vertical to position the fruit on one side of the row and improve harvest efficiency. In Jan. and Feb. 2005, the daily minimum temperatures under the FRC+PE covers were about 3 °C higher than in the open. The covers also provided protection against the wind. Tissue damage in protected trailing blackberries was significantly less than for unprotected plants. `Siskiyou' plants in covered plots produced 3 to 5 times more fruit than plants in the open. Harvesting of `Siskiyou' fruit occurred during the red raspberry harvest season or 2 to 3 weeks earlier than for eastern blackberries. Our findings suggest that trailing blackberries can grow satisfactorily and produce fruit if the adverse effect of low temperatures and winds is mitigated with our trellis system and winter protection method. If practical cultural techniques for improving their winter survival become available, there is a potential for early-season high-quality blackberry production in the mid-Atlantic coast region.