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Fumiomi Takeda and Jorge Soria

unit model for predicting bloom dates in Rubus HortScience 43 2000 2004 Brennan, R.M. McNicol, R. Raffle, S. 1999 Factors affecting out-of-season Rubus production Acta Hort. 505 115 120 Brittingham-Brant, M. Demchak, K. Frazier, M. Guiser, S

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Daniela Salvini, Silvia Fineschi, Roberta Pastorelli, Federico Sebastiani, and Giovanni G. Vendramin

Twenty populations of the species aggregate Rubus fruticosus were collected throughout European natural forests and analyzed by chloroplast microsatellites (SSR). Results showed high genetic diversity (h T = 0.73) and haplotipic richness (17 haplotypes were detected), and the presence of several unique alleles. The value of genetic differentiation between populations was low for unordered alleles (G ST = 0.29) and for ordered alleles (N ST = 0.30), revealing the absence of phylogeographic structure of the haplotypic diversity. This can be mainly ascribed to the mechanisms of seed dispersal, mostly mediated by animal ingestion, which are responsible for a efficient gene flow through seeds. Rubus L. species are characterized by the ability to colonizing disturbed, but also intact forest communities, rapidly propagating though suckering and hybridizing with native species. Our results suggest that efficient seed dispersal can counterbalance the effects of vegetative propagation, maintaining a high genetic diversity.

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Maxine M. Thompson

The U.S. Dept. of Agriculture, Agricultural Research Service, National Clonal Germplasm Repository (NCGR), Corvallis, Ore., maintains Rubus germplasm representing worldwide diversity of the genus. Chromosome numbers were counted for 201 plants representing 124 taxa (species and varieties). There are new reports for 42 taxa, confirmation for 72 previously reported, and 10 counts for plants unidentified to species. The basic chromosome number was seven, and ploidy levels ranged from 2x to 12x.

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Derek N. Peacock and Kim E. Hummer

We contrasted the effect of liquid nitrogen (LN2), sulfuric acid (H2SO4), and a nontreated control on the germination of six Rubus species. We also were interested in determining if LN2 could be an effective mechanical scarifying agent for these species. Seeds of each species were treated with three 3-minute dips in LN2 with alternating 10-minute thaws, with H2SO4 for 30 minutes, or left untreated. The percent germination of R. multibracteatus A. Leveille & Vaniot, R. parviflorus Nutt., R. eustephanos Focke ex Diels, R. leucodermis Douglas ex Torrey & A. Gray, R. ursinus Cham. & Schldl., and R. chamaemorus L. treated with LN2 was not significantly different than the control. Germinated seedlings from the LN2 treatment of each species showed normal development upon planting, indicating that long-term cryogenic preservation of these Rubus species seeds may be possible. The H2SO4 treatment significantly increased the rate and percentage of germination in R. parviflorus, R. eustephanos, R. leucodermis, and R. ursinus over that of the control and the LN2 treatment. The alternative LN2 application techniques that have been attempted thus far have not significantly improved Rubus seed germination compared with that of the control.

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Derek N. Peacock and Kim E. Hummer

Many Rubus species have a seedcoat imposed exogenous dormancy. Our objective was to contrast the effect of liquid nitrogen (LN2), sulfuric acid (H2SO4), and an untreated control on seed germination of R. multibracteatus A. Leveille & Vaniot and R. parviflorus Nutt. and to determine if LN2 could be used as a mechanical scarifying agent for these species. Three replicates of 100 seeds of each species were treated with either three 3-min dips in LN2 with corresponding 10 min thaws or for 30 min with H2SO4 or were left untreated. The LN2 pretreatment did not significantly reduce the viability of R. multibracteatus or R. parviflorus as compared to the control. A random sample of germinated R. multibracteatus from the LN2 pretreatment showed normal seedling development upon planting. The H2SO4 pretreatment significantly increased germination percentages as compared to the control or LN2 pretreatment as well as for R. ursinus Cham. & Schldl. and R. eustephanus Focke ex Diels. The LN2 treatment did not significantly improve germination over the control group and therefore was not an effective scarifying agent as applied to R. multibracteatus or R. parviflorus. However, these two Rubus species were not damaged by repeated dips in LN2. Alternative LN2 pretreatments are being examined for their potential to improve Rubus germination further.

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Maxine M. Thompson

Chromosome numbers were counted for 90 Rubus cultivars and selections maintained at the U.S. Dept. of Agriculture, Agricultural Research Service, National Clonal Germplasm Repository, Corvallis, Ore. To my knowledge, 37 of the counts are new, including five that are corrections of previously published counts, 30 that are confirmations of numbers that were previously published but assumed from their parentage rather than actually counted, and 23 that are confirmations of previous counts. The basic number was 7, and 2n numbers ranged from 2x to 14x, including odd-ploids and aneuploids.

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Bernadine C. Strik, John R. Clark, Chad E. Finn, and M. Pilar Bañados

example, ‘Eldorado’ ( Rubus allegheniensis × R. frondosus ) introduced in the mid-1850s in the United States ( Hall, 1990 ; Moore, 1984 ). Blackberries are often classified according to their cane architecture into three types: erect, semierect, and

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Chad Finn, Kirsten Wennstrom, and Kim Hummer

Populations of 40 Rubus sp., representing the Malachobatus, Idaeobatus, Eubatus, and Anoplobatus, were planted in the field in 1994. To get a preliminary idea of how successful crosses between these species and standard cultivars would be, 58 crosses were attempted between standard cultivars and randomly selected genotypes of the 14 species that produced a significant number of flowers in 1995. Diploid species were crossed with `Tulameen' and `Meeker' raspberry and the tetraploid species with `Cherokee' and `Chester' blackberry. Twenty-two crosses produced seed lots ranging from 8 to 630 seeds. Crosses were successful with R. caesius, R. caucasicus, R. coreanus, R. georgicus, R. parvifolius, R. rosifolius, and R. sumatranus. Crosses were not successful with R. eustephanos, R. insularis, R. innominatus, R. lambertianus, R. sachalinensis, R. setchuenensis, R. swinhoei, and R. tsangorum. In vitro seed germination was attempted with all crosses. Larger seed lots were also germinated using standard procedures for Rubus. There is a great deal of variability in leaf morphology of the young seedlings within a cross that suggests that some or all of the seedlings are true hybrids. Seedlings that are not true hybrids could result from contaminant pollen or, as in R. armeniacus, pseudogamous embryo formation. Crossing results from 1995 and 1996, including crosses attempted and seed numbers per cross, will be presented along with, for the 1995 crosses, the number of germinated seedlings and our assessment of whether they appear to be true hybrids.

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Angela K. Anderson and Chad E. Finn

The superb flavor of trailing blackberry cultivars, such as `Marion', is derived from Rubus ursinus Cham. & Schlecht. Wild R. ursinus offer a range of horticulturally desirable traits to breeders, from high fruit quality to improved cold hardiness. Current cultivars are derived from relatively few sources of R. ursinus, selected primarily for fruiting characteristics. A replicated field trial of 460 clones, representing 20 populations from southern British Columbia, Washington, and Oregon, was established in 1994. Observations during the planting year have indicated that monitoring variability in the following reproductive traits will be useful in assessing diversity; budbreak, flowering, and fruiting date; lateral length; proportion of reproductive laterals; gender; flower and fruit number; and fruit size. In particular, there are clones that exhibit large fruit size (4 to 5 g), high flower number per lateral, and uniform fruit set. Analysis of these data will contribute to determination of relative genetic distances among the populations and enhance the understanding of the diversity available in R. ursinus.

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Maxine M. Thompson and Kim E. Hummer

Chromosome numbers were determined for the Rubus species and cultivars held at the USDA/ARS National Clonal Germplasm Repository, Corvallis, Ore. Counts were made on a total of 205 taxa; 81 of which were new, 124 were corrections, and a few were corrections of previous reports. The numbers ranged from 2n = 2x = 14 to 2x = 98, and included odd-ploids and aneuploids. Knowledge of the chromosome number of a plant is important for its use in breeding because of potential sterility problems that may arise due to unbalanced gametes. The value of these particular counts are that they are vouchered by a permanent, living plant collection that is available to the scientific user community.