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Jessica M. Cortell and Bernadine C. Strik

In Spring 1993 and 1994, treatments of 0, 4, 8, and 12 floricanes per plant were established in a mature `Marion' planting. Primocanes were measured weekly for the number and length of primocanes and primocane branches. Maximum hardiness of primocanes was determined in Jan. 1994 and 1995 by controlled freezing. Yield components were measured in both the current and following season. Additional plants were harvested in summer and winter for dry-weight partitioning. Plants with no floricanes had an increased number and length of primocanes and branches than plants with floricanes in 1993, with similar trends in 1994. Primocane growth on plants without floricanes showed a 65% increase in primocane dry weight in 1993. However, in 1994, there were no significant differences among treatments. Primocane branch dry weight generally increased with decreasing floricane number. The relationship between primocane growth and the following season's yield components will be presented.

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Christine M. Bradish, Gad G. Yousef, Guoying Ma, Penelope Perkins-Veazie, and Gina E. Fernandez

of environmental protection between field and greenhouse production systems ( Kadir et al., 2006 ; Heidenreich et al., 2008 ). Most high tunnels in the United States and Canada are used for fall-fruiting primocane cultivars to extend the harvest

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Chrislyn A. Drake and John R. Clark

Primocane-fruiting blackberry (Rubus subgenus Rubus Watson) selections have recently been developed by the University of Arkansas, but proper cane-management practices for the new germplasm have not yet been determined. It was observed in previous trials that primocane-fruiting selections flowered and fruited in late July and early August in Arkansas, which is often the hottest part of the summer and earlier than desired. Therefore, this study was conducted to determine the effects of primocane tipping on cane and fruit characteristics and to determine the effect of floricane presence on primocane performance. In Fayetteville, one-year-old plants of selections APF-8 and APF-12 were used to apply the four primocane-tipping treatments in combination with the two cane management treatments (presence or absence of floricanes). In Clarksville, the same genotypes were used to apply the two cane management treatments (presence or absence of floricanes). The tipping treatments had a significant effect on primocane yield and peak harvest as well as other parameters. The cane management treatments had a significant effect on total yield, but no other effects.

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M. Pilar Bañados, Carolina Alvarez, and Alejandra Soto

To evaluate the effect of the time of primocane tipping on harvest date of `Heritage' red raspberry in the central valley of Chile (southern hemisphere), we tipped primocanes at three dates during the 1996–97 growing seasons: in Nov. 1996 (PN), Dec. 1996 (PD), and Jan. 1997 (PJ). Tipping was done manually at a 1.10-m height. Harvest date, fruit quality, and yield component was evaluated in the control and three tipping dates. A difference of 75 days on the initiation of harvest date was detected among treatments. Harvest date initiation was on 20 Jan. for the control with no tipping and for PN, 3 Mar. for PD, and 4 Apr. for PJ. Fruit of the PN treatment was smaller and lighter than the rest of the treatments; however, little differences in soluble solids, acidity, and pH were detected among treatments. Primocane lateral number was 14 for the control treatment and decreased to seven in tipped primocanes. Lateral length increased largely with tipping treatments: 7.8 cm in the control, 30 cm in PN, 29 cm in PD, and 42 cm in PJ. Fruit per lateral ranged between 6.2 in control and 12.2 in PD. Yields estimation for the fall production were 8.5 t/ha in the control, and increased to 12 t/ha estimated for the PJ treatment. The time of primocane tipping had an important effect on `Heritage' red raspberry harvest date, lateral length, and estimated yield.

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Pat Bowen and Stan Freyman

Raspberries (Rubus idaeus L.) were grown for 5 years with three floor management treatments: clean cultivation (CC) and ground covers of white clover (Trifolium repens L.) (WC) and perennial ryegrass (Lolium perenne L.) (PR). Primocane growth was strongest with WC and weakest with PR. Fruit production did not differ between WC and CC treatments and was higher than with PR. On 22 Aug. and 10 Sept. in the last year, primocanes grown with WC were taller, had more nodes and a higher dry weight, contained more N, and had retained more leaves than those grown with PR. Net CO2 assimilation per unit leaf area was higher with WC than with PR, and the difference was greater at the more proximal position. The estimated net CO2 assimilation rate per primocane was more than twice as high with WC than with PR.

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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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John R. Clark and Alejandra Salgado

‘Prime-Ark ® Traveler’ (to be U.S. plant patented as ‘APF-190T’), is the world’s first commercially released, thornless primocane-fruiting blackberry ( Rubus L. subgenus Rubus Watson) with shipping-quality fruit. This development is intended

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Marvin Pritts, Eric Hanson, Joseph Fiola, and Mary Jo Kelly

Studies were conducted over eight location-years to evaluate the effects of rowcover material, time of application, and time of removal on `Heritage' red raspberry cane growth, flowering, and fruiting. We anticipated that rowcovers would accelerate fruit maturity so that more of the crop could be harvested before the onset of cold temperatures in autumn. In seven of the eight experiments, rowcovers either increased yields or accelerated harvest. With a March application, harvest began 3 weeks earlier, and August yields of covered plants were 42 times higher than those of noncovered plants. Responses were observed with spunbonded polypropylene and polyester covers, but not with polyethylene covers. Rowcovers placed over the row before primocane emergence and removed when canes were ≈50 cm tall resulted in the greatest plant response. The use of polyester or polypropylene rowcovers with primocane-fruiting raspberries appears to be economically feasible in most years in northern climates.

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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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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.