Organic blackberry ( Rubus L. subgenus Rubus , Watson) production is an important niche market in Oregon, which produces a significant portion of the organic and conventional crop in the United States [ U.S. Department of Agriculture (USDA), 2010
Emily K. Dixon, Bernadine C. Strik, and David R. Bryla
Herbert D. Stiles and Paul J. Semtner
Blackberry drupelet development is influenced by a number of agents (Ellis et al., 1991; Moore and Skirvin, 1990). We have observed poor drupelet-setting and `nubbins' that were not attributable to common pests, such as tarnished plant bug or diseases. In seeking causes for such problems during 1986, we discovered tiny (diptera) larvae in unopened flower buds and newly opened blossoms of wild-growing and domestic blackberries. Pistils and stamens of infested buds and blossoms showed signs of necrosis; injuries seemed worse in buds that contained more larvae. We confirmed relationships among bloom-time symptoms, drupelet setting, and fruit weight by tagging symptomatic and asymptomatic postanthesis blossoms on 22 May 1989. One week before the normal harvest season, symptomatic berries averaged 38 mg and asymptomatic berries averaged 208 mg. Twelve symptomatic blossoms (27%) produced no drupelets, 19 (43%) produced one to 10 drupelets, and no symptomatic blossom yielded a normal berry. We devised or adapted larval collection and rearing apparatuses and procedures to obtain adult midges that were needed for taxonomic speciation of this new blackberry pest. During 1994, SEL identified resultant specimens as Contarinia agrimoniae Felt. This genus previously had not been recorded from Rubus buds, and little is known of C. agrimoniae habits, life cycle, etc. Additional studies are needed to identify procedures for management of C. agrimoniae.
Blair Buckley III, James N. Moore, and John R. Clark
Rosette, incited by Cercosporella rubi (G. Wint.) Plakidas, is the most severe disease of blackberries in the southern United States. Sixteen blackberry cultivars and breeding selections were evaluated in a field test over a 3-year period for incidence and severity of rosette. Test plots were planted in a randomized complete block design with four replications. A plot consisted of a 3-m hedgerow of blackberry canes. Each test plot row was bordered on each side by a row of the rosette-susceptible cultivar Shawnee. Disease ratings were conducted on five random floricanes in each plot. Disease severity was rated with a 1 to 8 scale (1 = 0% floricane nodes with rosettes, 2 = 0% to 10%, 3 = 10% to 25%, 4 = 25% to 50%, 5 =50% to 75%, 6 = 75% to 90%, 7 = 90% to 100%, 8 = 100%). `Shawnee' and `Rosborough' had high incidence and severity. Cultivars and selections with moderate-high incidence and low-moderate severity were `Brazos', `Cheyenne', `Choctaw', A-1260, A-1442, A-1560, and A-1585. Cultivars and selections with zero-low incidence and severity were `Arapaho', `Humble', `Navaho', A-1374, A-1594, A-1616, and A-1617.
In Sept.1993, `Navaho' blackberries were planted in raised beds in a converted bermudagrass hay meadow. Tall fescue was planted between the beds. There are three plants per plot and nine replications with 1.3 m between plants, 3 m between plots, and 5 m between rows. Each row is one replication. The plots are 3 m wide and 3.9 m long. Weed management treatments were applied in a randomized complete-block design, and included: alfalfa (Medicago sativa) cover crop, rye (Secale cereale) cover crop, herbicide (simazine and oryzalin) and hoeing, mowing volunteer vegetation, and hardwood sawdust mulch 8 to 10 cm deep. In Spring 1994 and 1995, data were taken on weed populations in each of the plots. In early 1995, the blackberry plants were measured. Data taken included cane number, cane length, and cane diameter. Early results indicate that the best blackberry plant growth occurred when rows were maintained with no mulch or vegetation by application of herbicides and hoeing. However, these plots sustained significant soil erosion, which may result in decreased plant productivity over time.
Chrislyn A. Drake and John R. Clark
Little research has been done to determine the chilling requirement for southern blackberry cultivars. However, field observations from areas where low amounts of chilling occur indicate that `Navaho' requires more hours of chilling than does `Arapaho'. The objective of the study was to determine a method for measuring chilling requirement using whole plants of two blackberry cultivars, Arapaho and Navaho. One-year-old bare-root plants of `Arapaho' and `Navaho' were field-dug and placed in a cold chamber at 3 °C. Ten single-plant replications of each cultivar were removed at 100-hour intervals up to 1000 hours. The plants were then potted and placed in a greenhouse (daily minimum temperature 15 °C) in a completely randomized design. Budbreak was recorded on a weekly basis. Data for budbreak was analyzed as a two-factor factorial (two cultivars and 10 chilling treatments) by SAS and means separated by lsd (P = 0.05). Data indicated that the chilling requirement for `Arapaho' is between 400 and 500 hours. This is evident as a 6-fold increase, which was the largest increase between two chilling treatments, occurred between 400 and 500 hours. For `Navaho', the largest increase (also 6-fold) occurred between 800 and 900 hours, which indicated a chilling requirement for `Navaho' of 800 to 900 hours. These data support previous observations and indicate the method used was successful in determining chilling requirement for blackberries.
Raymond H. Thomas, Floyd M. Woods*, William A. Dozier Jr., Robert C. Ebel, Monte Nesbitt, Brian S. Wilkins, and David G. Himelrick
Blackberries are an excellent source of natural antioxidants. Fully ripened fruit of `Apache', `Arapaho', `Chester', `Loch Ness', `Navaho', and `Triple Crown' thornless blackberries were evaluated for their physicochemical and antioxidative activity. Differences in initial pH, titratable acidity (TA), total soluble solids (TSS), TSS/TA ratio and soluble sugars (reducing sugar, sucrose, and total sugars) differed among cultivars. Differences among cultivars with respect to reduced ascorbic acid (AA) were established, but there were no differences in either oxidized ascorbic acid (DHA) or total ascorbic acid (TAA) content. Antioxidant activity was determined by ABTS radical cation procedure for fractionated crude fruit extracts and the cultivars varied in the parameters evaluated. Hydrophilic antioxidant activity (HAA) was not different among cultivars evaluated. In contrast, lipophilic antioxidant activity (LAA) and total antioxidant activity (TAA) differed. The results obtained in this study indicate that Alabama-grown blackberries vary in their quality indices and are an excellent source of natural antioxidants. Information compiled will assist in marketing, handling, postharvest storage of these fruit and serve as a guide to partial fulfillment of recommended daily dietary requirements.
Michele R. Warmund and Joan Krumme
The time of rest completion of `Apache', `Arapaho', `Chickasaw', `Darrow', `Kiowa', `Navaho', and `Shawnee' blackberry (Rubus subgenus Rubus Watson) buds was compared and various models for estimating chilling were evaluated. `Kiowa' and `Arapaho' buds had the shortest rest periods, while those for `Shawnee', `Navaho', and `Chickasaw' buds were intermediate. `Apache' and `Darrow' buds had the longest rest periods. The model that accounted for the variation in percent budbreak among cultivars and temperatures during two dormant periods had the following two components: 1) a chilling inception temperature of –2.2 °C and 2) weighted chilling hours that accumulated after the chilling inception temperature. The chilling hours in this model were weighted as follows: 0 to 9.1 °C = 1; 9.2 to 12.4 °C = 0.5; 12.5 to 15.9 °C = 0; 16 to 18 °C = –0.5; >18 °C = –1. This study also elucidated that a blackberry model with a chilling inception temperature of –2.2 °C estimated chilling more accurately than one with chilling inception just after the maximum negative accumulation of chill units as used in the Utah chilling model. Also, temperatures between 0 and 2.4 °C must be weighted more heavily in a blackberry model than in the Utah peach model to accurately estimate chilling and rest completion.
Jose Lopez-Medina and James N. Moore
Root cuttings of A-1836, APF-13, and NC194 primocane-fruiting (PF) blackberry (Rubus subgenus Rubus) genotypes were dug from the field on 31 July 1997 and stored in plastic bags at 2 °C for 32 days. On 1 Sept. freshly dug root cuttings, along with the cold-treated ones, were planted in pots, which were kept in a lath house for 4 weeks and then moved to a heated greenhouse under natural daylength. Cold-treatment hastened emergence of all genotypes. Transition from vegetative to floral phase was first observed in cold-treated A-1836 and APF-13 at the fifth node, with floral appendages clearly evident in both genotypes at the seventh node 45 days after planting (DAP). Bloom started on 26 Nov. and 5 Dec. 1997 and the first fruits were picked on 10 and 25 Jan. 1998 in cold-treated APF-13 and A-1836, respectively. Plants of cold-treated NC194 and of all non-cold-treated genotypes remained stunted with rosetted leaves, showing no signs of floral initiation until 150 DAP. These findings show that exposure to chilling prior to shoot emergence greatly promotes flowering in PF blackberries, and may have application in greenhouse culture of blackberry.
K.S. Lewers, S.M.N. Styan, S.C. Hokanson, and N.V. Bassil
mapping population, and Sam Garrett, Dr. Courtney Weber, Dr. John Clark, and Eric Stafne for raspberry and blackberry leaf tissue. In addition, we would like to thank Dr. Tad Sonstegard and Tina Sphon for genotyping, and the Beltsville Agricultural
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.