Search Results

You are looking at 131 - 140 of 260 items for :

  • Refine by Access: All x
Clear All
Free access

Curt R. Rom and John R. Clark

Gas exchange (assimilation, transpiration, water use efficiency, and conductance) of `Shawnee' blackberry were measured under field conditions with a portable system (ADC-IRGA with Parkinson Leaf Chamber). Gas exchange primocane pentifoliate leaflets were similar. Gas exchange rates of leaves along a cane exhibited a quadratic function of leaf position with leaves in lower-mid sections (relative position 0.3 - 0.5) having higher A, TR, WUE, gs than either basal or apical leaves. Leaves subtending fruiting laterals on fruiticanes had higher assimilation than similar age leaves on primocanes but did not differ in Tr, WUE, or gs. Primocanes had estimated dark respiration rates of 0.33mg·dm-1.hr-1, estimated light compensation at 14-20 mol.m-2.s-1, estimated light saturation at 1000-1100 mol.m-2.s-1 with maximum A rates ranging from 24-30 mg CO2.dm-1.hr-1. Measurements were made at field temperatures ranging from 24-35 C. Although temperature response was not measured, correlation indicated that Tr, WUE, and gs were more closely related to temperature than A. Similarly, Tr and WUE were more closely related to gs than A (r = 0.6 to 0.8).

Free access

Juanita Popenoe

`Heritage', `Titan', and `Boyne' red raspberries (Rubus idaeus L.) were grown for 3 years and plots were sampled annually for changes in growth. `Heritage' is a primocane- and floricane-fruiting, strongly suckering cultivar; `Boyne' is a floricane-fruiting, strongly suckering cultivar; and `Titan' is a floricane-fruiting, weakly suckering cultivar. Each year in October, plants of each cultivar were dug from two 0.5-m2 plots in each of four rows, separated into roots, crowns, canes (primocanes were harvested in October and floricanes were harvested in July), and leaves, and dried. Fruit were harvested, yields were recorded, and dry weights of subsamples were used to estimate total fruit dry weights. `Heritage' fruit included the primocane and floricane harvests. `Heritage' was more yield-efficient than `Boyne' or `Titan' in that it allocated a higher percentage of total dry weight to fruit and a lower percentage to vegetative parts. Although `Titan' had fewer canes, cane diameter and length were greater. `Boyne' allocated higher percentages of total dry weight to roots than other cultivars. The percentage of total dry weight allocated to fruit was similar for `Boyne' and `Titan' in 1992, but lower for `Boyne' in 1991. Within the cultivars tested, phenotype for suckering did not indicate productivity.

Free access

F. Takeda

Tissue-cultured raspberry plants are not exposed to low temperatures during the propagation phase, yet the primocane that grows from the crown will flower terminally after developing 20 to 25 nodes. We studied the effect of duration of chilling (hours) (CH) on days to flower (DTF) in primocanes arising from root suckers of previously cropped fall-bearing `Heritage' and `'Summit' raspberries. Growth of `Heritage' plants with 0 or low CH was either short with rosetted leaves or indeterminate. Plants with 0 CH remained vegetative for >240 days, while plants with >750 CH flowered in <4 months when the primocane had 25 to 30 nodes. These results suggested that low-temperature exposure prior to shoot emergence was necessary for flower bud initiation in `Heritage' red raspberry. In contrast, all `Summit' flowered; DTF ranged from 120 days for 0 CH plants to <70 days for plants with 1000 CH. Low-temperature treatment affected flower bud development. Plants with 0 CH developed 15 flowering laterals, while plants with >750 CH had 25 flowering laterals. Although `Summit' needs no CH to flower, low temperature treatments definitely accelerated DTF and increased the number of fruiting laterals.

Free access

Fumiomi Takeda

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.

Free access

Norman A. Gundersheim and Marvin P. Pritts

A factorial arrangement of 48 treatments was used to evaluate the effects of cane density, time of cane density adjustment, primocane tipping, and cane or branch length on yield components in `Royalty' purple raspberry [(Rubus occidentals × R. idaeus) × R. idaeus] over 2 years. Yield was positively related to cane density and length, while fruit size and fruit count per lateral were negatively related to cane and branch length. When branches on tipped canes were shortened in late winter, more buds became fruitful at the proximal end of the branch, but fruiting laterals did not have more flowers or fruit. Fruiting laterals were longer on shortened canes, resulting in a decrease in the fruit: wood ratio. Plants performed similarly whether floricane density was adjusted in late winter orprimocane density was adjusted in late spring. Although potential yield was higher when primocanes were tipped in late spring, harvesting was more difficult because of branch orientation, and the incidence of cane blight infection was higher. Our study suggests that maintaining at least 12 canes per meter of row, avoiding primocane tipping, retaining full cane length, and providing adequate light, moisture, and nutrient levels can result in high yields of large fruit.

Free access

Joseph Naraguma and John R. Clark

Applications of N to blackberry plantings are a common practice in Arkansas, but fertilizer recommendations are largely based on those of other states. The need for information on fertility of a new blackberry from the Arkansas breeding program motivated this study. A three-year-old `Arapaho' blackberry planting at the University of Arkansas Fruit Substation was used for this study. Treatments which began in 1994 and continued through 1996 were: 1) control—no N applied, 2) 56 Kg N/ha applied in a single application in early spring, 3) 112 Kg N/ha applied in a single early spring application, and 4) 112 Kg/ha applied in a split application with one-half applied in the early spring and one-half applied immediately after harvest. Fruit was harvested from the plots in June and total yield and average berry weight determined. Foliar samples were collected in August and elemental analysis conducted. Primocanes in each plot were counted at the end of the growing season. Over the three years, there was no significant treatment effect on yield, berry weight, or primocane number. A trend toward higher primocane number where N was applied was seen, however. Foliar levels of N, P, K, Ca, S, and Mn were affected by either N rate or time of application. The foliar N levels were influenced by N rate and the split application gave the highest concentration. Calcium was higher when no N was applied, Mn was greater at higher N rates while the control had the lowest foliar N level in each year.

Open access

P. C. Crandall and J. D. Chamberlain

Abstract

Factors that are usually associated with the slowing of primocane growth during late summer hastened the appearance of floral primordia in red raspberry axillary buds. Of the factors tested, water stress was most effective in advancing floral primordia appearance. Small diam canes had buds more advanced than thick canes. July applications of succinic acid-2,2-dimethylhy dr azide (SADH) at 2000 and 4000 ppm and (2-chloroethyl)phosphonic acid (ethephon) at 500 ppm increased the number of blossom primordia present during early October. Growth regulators had no significant effect on yields.

Open access

J. R. Morris and C. A. Sims

Abstract

The response of 4 erect blackberry cultivars to 2 levels of soil moisture and 2 hedge pruning heights was evaluated. Supplemental irrigation increased yield on all cultivars, but was most effective for the highest-yielding cultivar, ‘Cherokee,’ during the first harvest season (6.03 T/ha for irrigated plots compared to 4.22 T/ha for nonirrigated plots). Increased lateral branching and yield, with no effect on fruit quality, resulted when the new primocanes were pruned mechanically to a height of 90 cm compared to 120 cm. ‘Cherokee’ and ‘Comanche’ berries had superior color compared with that of other cultivars. Irrigation resulted in a slight reduction in percentage of soluble solids and pH.

Open access

Miltiadis D. Vasilakakis, B. Esther Struckmeyer, and Malcolm N. Dana

Abstract

Flower bud initiation in mature overwintering canes of ‘Heritage’ red raspberry (Rubus idaeus L.), a primocane-fruiting cultivar, began below the last inflorescence on the current year's growth in October and was completed by the end of December. Flower buds beyond the stage of initiation were not observed in noncold treated canes. However, in cold treated canes gradual basipetal flower bud development beyond initiation was observed. In non-cold treated overwintering canes of ‘Latham’, a June-bearing cultivar, flower bud induction and initiation occurred but no further development was observed.

Free access

John R. Clark

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.