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Neil C. Bell, Bernadine C. Strik, and Lloyd W. Martin

Primocanes of `Marion' trailing blackberry plants (Rubus spp.) were suppressed by cutting them off at ground level in either late April, May, June, or July 1991 and 1992. A control was included in which primocanes were not cut. Four canes per plant were trained in either August or February, with all other canes being removed and measured. Yield data were collected in 1992 and 1993, after which yield components were measured. Cane diameter was greatest for unsuppressed plants and declined with later primocane removal date. Cane length was greatest for unsuppressed and April-suppressed plants. Internode length decreased and main cane percent budbreak increased with later suppression date. Cane number and total main cane length per plant were increased in April-, May-, and June-suppressed plants in 1992 and for April- and June-suppressed plants in 1993. Consequently, yield of April-suppressed plants exceeded that of unsuppressed plants in 1992. Yield of April-, May-, and June-suppressed plants exceeded that of unsuppressed plants in 1993. August-trained plants yielded 46% more than February-trained plants, primarily because of higher percent budbreak on main canes. August-trained plants also produced longer canes with more nodes and a greater number of fruit per main cane lateral.

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P. Perkins-Veazie, J.K. Collins, and J.R. Clark

Fruit at three stages of ripeness were harvested from four erect blackberry (Rubus spp.) cultivars, `Navaho', `Choctaw', `Cheyenne', and `Shawnee', for 2 years to evaluate fresh-market shelf life during 7 days of storage at 2C, 95% relative humidity. Ethylene production was highest from dull black fruit and varied widely among cultivars, ranging from 7.3 to 51.1 pmol·kg–1·s–1 for `Navaho' and `Choctaw' fruit, respectively. Weight loss ranged from 0.8% (`Shawnee') to 3.3% (`Navaho') after storage. Mottled (50% black) fruit of all cultivars were higher in fruit firmness and titratable acidity and had lower soluble solids and anthocyanin concentrations than fruit at other stages of maturity. Cultivars did not differ in total anthocyanin concentration, but dull black fruit had a higher anthocyanin concentration than shiny black fruit. Dull black `Choctaw', `Shawnee', and `Cheyenne' fruit were softer and had more leakage and decay than shiny black fruit. Both shiny and dull black `Navaho' fruit had less leakage than fruit of other cultivars. All cultivars at the shiny black stage were considered marketable after 7 days at 2C because fruit were firm with little decay or leakage. However, red discoloration appeared more frequently on shiny black than on dull black fruit. Mottled fruit of erect cultivars should not be harvested, while shiny black fruit of `Cheyenne', `Shawnee', and `Choctaw' might be suited for regional markets. Either shiny black or dull black `Navaho' fruit could be shipped to distant markets.

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Michele R. Warmund, Fumiomi Takeda, and Glen A. Davis

`Hull Thornless' and `Black Satin' blackberry (Rubus spp.) canes were collected from Sept. 1989 through Mar. 1990 to determine the hardiness and supercooling characteristics of buds at various stages of development. Anatomical studies were also conducted to examine the location of ice voids in buds frozen to -5 or -30C. Differentiation of the terminal flower occurred in `Black Satin' buds by 6 Nov., whereas `Hull Thornless' buds remained vegetative until early spring. As many as nine floral primordia were observed in both cultivars by 12 Mar. The hardiness of the two cultivars was similar until February. Thereafter, `Black Satin' buds were more susceptible to cold injury than those of `Hull Thornless'. Flora1 and undifferentiated buds of both cultivars exhibited one to four low temperature exotherms (LTEs) from 9 Oct. to 12 Mar. in differential thermal analysis (DTA) experiments. The stage of flora1 development did not influence the bud's capacity to supercool. The number of LTEs was not related to the stage of floral development or to the number of floral primordia. Extracellular voids resulting from ice formation in the bud axis and scales were observed in samples subjected to -5 or -30C.

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Tina M. Rivera, Martin F. Quigley, and Joseph C. Scheerens

The commercial and ornamental potential of three apple-berry polyculture systems was ascertained by monitoring the above-ground performance of component species in plots of `GoldRush' apple (Malus ×domestica Borkh.) trees on M.7 rootstock cropped with either blackberry (Rubus spp. L. `Navaho'), edible honeysuckle (Lonicera caerulea L. `Blue Belle' and `Blue Velvet'), or jostaberry (Ribes nidigrolaria Bauer `Josta') as understory plants. Polyculture plots and corresponding monoculture controls were established in 1999, with berry plants at recommended (R) or close [(C), half-recommended] spacings. Blackberries and jostaberries planted in monoculture at recommended spacings [i.e., control (R) plots] amassed dry weights >1 kg/plant by Fall 2001; the dry weight of edible honeysuckle from comparable plots was slightly >0.3 kg/plant. In 2001, blackberry yield (3.1 kg/plant) and fruit weight (3.4 g) were typical of `Navaho' plantings of similar age, whereas jostaberry was only moderately productive (yield = 286 g/plant; fruit weight = 1.4 g). Edible honeysuckle productivity (yield = 13 g/plant, fruit weight = 0.5 g) was minimal, due to disparate flowering phenology between cultivars. `GoldRush' apple growth and productivity (yield = 25 kg/tree; fruit weight = 158 g) was consistent with values expected for trees of similar age. Blackberry plant dry weights were reduced by 20% to 33% when planted at close spacing, whereas blackberry yields were reduced 35% to 38% when grown in polyculture with apple. Both polyculture and plant spacing significantly reduced jostaberry dry weights (i.e., 12% and 24%, respectively) relative to the control, but neither significantly affected jostaberry yield. Conversely, both close-spaced planting and the presence of an apple tree improved the yield of edible honeysuckle. Apple performance was not affected by the presence of an edible honeysuckle understory, but apple growth factors were reduced in blackberry and jostaberry polycultures by as much as 65%. Apple bloom, fruit set, and yield were also significantly reduced in apple-blackberry and apple-jostaberry plots, with fruit numbers/tree averaging <5 in all except the apple-blackberry (C) treatment. None of the polyculture treatments studied were suitable for profitable fruit production. However, each of the polyculture constituents exhibited unique, beneficial attributes with respect to their use as components within an edible landscape.

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Penelope Perkins-Veazie, Julie K. Collins, John R. Clark, and Lawrence Risse

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Gina E. Fernandez and John R. Clark

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Neil C. Bell, Bernadine C. Strik, and Lloyd W. Martin

Primocanes of `Marion' trailing blackberry plants were suppressed by cutting them off at ground level in either late April, May, June, or July 1991 and 1992. An unsuppressed control was included in which primocanes were not cut. A single cane was removed from each replication of the five primocane suppression dates at monthly intervals from mid-November to mid-February 1991-92, and from mid-November to mid-January 1992-93. One-node samples were exposed to controlled freezing at temperatures of 4, -6, -9, -12, -15, and -18C in November through February. In December and January, the-6 temperature was replaced with-21C. After 5 days at room temperature following freezing, growing point, budbase, vascular, and pith tissues were evaluated for tissue browning on a 1 to 5 scale. The LT50 developed for each suppression date was compared to the control. July-suppressed plants were generally hardiest for all tissues. June-suppressed plants were somewhat less hardy than July-suppressed plants, while April-, May- and unsuppressed plants were comparable and least hardy. Cane tissues of July-suppressed and unsuppressed plants had a higher level of soluble carbohydrates than other suppression dates.

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Hermen Malik and Douglas D. Archbold

The potential for plant growth regulator (PGR) manipulation of `Chester Thornless' blackberry (fibus spp.) primocane growth was evaluated. PGR treatments included combinations of soil-applied uniconazole at 1, 5, 25, and 125 mg/plant and GA, foliar-applied one or two times at 100 ppm 3 and 4 weeks after a 25-mg/plant uniconazole application. Also, GA and BA were applied at 100 ppm alone or in combination one, two, or three times. Increasing rates of uniconazole reduced primocane length, leaflet count, and leaf, cane, and root dry weights. GA, applications reduced primocane length and increased branch elongation but failed to reverse the effects of uniconazole at 25 mg/plant, except those on branch length, leaflet count, and primocane dry weight. Only applications of BA + GA, increased both branch production and elongation and dry weights of some component tissues, while BA alone generally had no effects. Chemical names used: (E)-1-(p-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-ol (uniconazole); N-(phenylmethyl)-1H-purin-6-amine (benzyladenine, BA); gibberellic acid (GA).

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P. Perkins-Veazie, J.K. Collins, and J.R. Clark

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Jessica M. Cortell and Bernadine C. Strik

In Spring 1993 and 1994, mature trailing `Marion' blackberry (Rubus L. subgenus Rubus Watson) plants were pruned to 0, 4, 8, and 12 floricanes. In 1994, yield per cane was higher for plants with 4 floricanes compared to plants with 8 or 12 floricanes. In Summer 1993, there was a trend for lower primocane dry mass with a higher floricane number and a significant reduction in primocane branch dry mass with an increase in floricane number. Total plant, fruit, floricane, and lateral dry mass increased linearly with floricane number. Results were similar for floricane components in Summer 1994; however, there were no treatment effects on primocane or branch dry mass and there was a significant linear increase in crown dry mass with floricane number. By Winter 1994-95, there were no treatment effects on primocane or crown dry mass. Plants without floricanes produced more primocanes per plant than plants with floricanes in 1993 but not in 1994. Plants without floricanes produced primocanes that had a significantly lower percent budbreak the following year (1994) than plants with floricanes. Primocanes produced by plants without floricanes had more nodes per branch and a greater average branch cane length than those from plants with floricanes the previous season. The number of nodes per primocane tended to decrease with an increase in floricane number per plant in 1994 and 1995. There was no significant effect of floricane number per plant the previous season on fruit per lateral, fruit mass, or yield per plant the following season in either treatment year (1993 + 1994). However, in 1994, plants without floricanes the previous year had the lowest yield per cane. Topping primocanes at 30 cm in 1993 and 1994 had few significant effects on yield components the following season. Thus, `Marion' blackberry can compensate for reduced fruiting cane number through an increased percent budbreak on remaining canes. While there were differences in primocane dry mass among treatments after harvest in 1993, there were no differences by mid-winter in either 1993 or 1994. Although plants grown without floricanes in 1993 had more primocanes, these canes had a lower percent budbreak the following season. Consequently, in this study we did not see increased yield in plants grown without floricanes the previous season. This was perhaps because primocanes were not trained as they grew, a practice that improves light exposure to the canes and may increase flower bud initiation.