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Primocane management systems were compared for ‘Prime-Jan’® and ‘Prime-Jim’®, primocane-fruiting blackberry (Rubus L. subgenus Rubus, Watson), grown in a field planting in Aurora, OR. Treatments studied were: 1) no manipulation of primocanes (untipped; no floricanes); 2) untipped primocanes growing in the presence of floricanes; 3) untipped primocanes grown with rowcover in late winter to early spring; and 4) primocanes “soft-tipped” at 1 m to encourage branching. Date of primocane first bloom and cane height at bloom were unaffected by cultivar and were only affected by primocane management in 2005. The number of growing degree-days to first bloom ranged from 1272 to 1390 depending on year. Primocane management did not affect ovule or drupelet number per berry or percent drupelet set. ‘Prime-Jim’ had more drupelets and greater weight per berry in 2005 than ‘Prime-Jan’. Fruit harvested earlier in the season had more ovules and drupelets than later harvested fruit in 2004. Primocanes that grew in the presence of floricanes were longer and bloomed later but did not differ in yield from untipped canes grown only for a primocane crop. Use of rowcover in 2005 advanced bloom and harvest, improving yield 73% compared with untipped control canes. Soft-tipping primocanes increased yield 114% to 150% compared with untipped canes (5.6 vs. 2.4 t·ha−1) through increasing branch and node number per cane and percentage of fruiting nodes; soft-tipping did not delay harvest. Yield/cane was negatively correlated with the number of fruiting canes/plot but positively correlated with branches/cane, total branch and cane length, number of nodes and percent fruiting nodes, fruit/cane, and berry weight. The proportion of fruiting nodes was greater on branches than on the main cane illustrating the importance of managing this type of blackberry to increase branch number for high yield.

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Field tests at two locations examined the influence of length and spacing of root propagules on blackberry plant establishment. Root propagules 10.2 cm long spaced 61 cm resulted in greater emergence, plant stand, and shoot growth than 5 cm and 2.5 cm root propagules. Differences in emergence and shoot growth between 10.2 cm progagules spaced 61 cm and 5 cm propagules spaced 61 cm were non-significant. Greenhouse tests compared four lengths of root propagules (15.2 cm, 10.2 cm, 5cm, 2.5 cm) for production of nursery plants. Percent emergence, time of emergence, and number of shoots per propagule produced from 2.5 cm propagules were comparable to results from 15.2 cm and 10.2 cm propagules.

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Decisions regarding the selection and care of trees on public lands often are delegated to public employees with limited knowledge of tree care. To provide a technical resource for the municipal employee, the Urban Forestry Notebook was developed through sponsorship by Puget Power (a major Pacific Northwest utility company), Washington State Department of Natural Resources, and the Center. The unique focus of this Notebook provided the municipal employee with information on the selection and care of 65 of the most important urban trees. It also can be used as a model by other communities who wish to improve the care of their urban trees by providing an informational resource for the public employee.

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Some raspberry and blackberry breeders are interested in using molecular markers to assist with selection. Simple Sequence Repeat markers (SSRs) have many advantages, and SSRs developed from one species can sometimes be used with related species. Six SSRs derived from the weed R. alceifolius, and 74 SSRs from R. idaeus red raspberry `Glen Moy' were tested on R. idaeus red raspberry selection NY322 from Cornell Univ., R. occidentalis `Jewel' black raspberry, Rubus spp. blackberry `Arapaho', and blackberry selection APF-12 from the Univ. of Arkansas. The two raspberry genotypes are parents of an interspecific mapping population segregating for primocane fruiting and other traits. The two blackberry genotypes are parents of a population segregating for primocane fruiting and thornlessness. Of the six R. alceifolius SSRs, two amplified a product from all genotypes. Of the 74 red raspberry SSRs, 56 (74%) amplified a product from NY322, 39 (53%) amplified a product from `Jewel', and 24 (32%) amplified a product from blackberry. Of the 56 SSRs that amplified a product from NY322, 17 failed to amplify a product from `Jewel' and, therefore, detected polymorphisms between the parents of this mapping population. Twice as many detected polymorphisms of this type between blackberry and red raspberry, since 33 SSRs amplified a product from NY322, but neither of the blackberry genotypes. Differences in PCR product sizes from these genotypes reveal additional polymorphisms. Rubus is among the most diverse genera in the plant kingdom, so it is not surprising that only 19 of the 74 raspberry-derived SSRs amplified a product from all four of the genotypes tested. These SSRs will be useful in interspecific mapping and cultivar development.

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We investigated the responses of staminate and pistillate floral components of Prime-Jan and Prime-Jim primocane-fruiting blackberry (Rubus L. subgenus Rubus Watson) to three different growth chamber temperature regimens, 35.0/23.9 °C (HT), 29.4/18.3 °C (MT), and 23.9/12.8 °C (LT). Temperature was negatively related to flower size, and morphologically abnormal floral structures were evident in 41% and 98% of the MT- and HT-grown plants, respectively. Anthers of LT- and MT-grown plants dehisced. The viability of pollen (as deduced through staining) from Prime-Jan grown at LT or MT exceeded 70%, whereas that of Prime-Jim pollen was significantly reduced (<40%) by the MT regimen. In vitro pollen germinability (typically <50%) was negatively influenced by temperature but was unaffected by cultivar. Pollen useful life was diminished under HT conditions; LT-grown pollen held at 23.9 °C retained 63% of its original germinability over a 32-h period, while the germinability of that held at 35.0 °C for 16 hours decreased by 97%. Virtually all flowers cultured under HT conditions were male sterile, exhibiting structural or sporogenous class abnormalities including petaloidy and malformation of tapetal cells or microspores; HT anthers that were present, failed to dehisce. Stigma receptivity, pistil density, and drupelet set were also negatively influenced by increased temperature; values for these parameters of floral competency among control plants were reduced by 51%, 39%, and 76%, respectively, in flowers cultured under HT conditions. In this study, flowering and fruiting parameters, and presumably the yield potential of Prime-Jan and Prime-Jim, were adversely affected by increased temperature. However, their adaptive response to heat stress under field conditions awaits assessment.

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Floral initiation (FI) was studied both in greenhouse- and field-grown plants of primocane-fruiting (PF) blackberries recently developed by the Univ. of Arkansas. Root cuttings of A-1836 and APF-13 were dug from the field and planted in a greenhouse on 1 Mar. 1997. NC 194 was included only in the field study. Terminal apices were sampled weekly starting at 0 (just before emergence) nodes of growth on 21 Mar. Floral primordia were first seen at five and six nodes of growth in greenhouse-grown A-1836 and APF-13, respectively, 35-42 days after root cuttings were planted (DAP). Under field conditions, the same event was not observed until 21 May when A-1836 and APF-13 reached at least 20 nodes; NC 194 did not show evidence of floral parts until 10 July. Once FI occurred, floral differentiation proceeded uninterrupted until completion. Blooming occurred 32-35 and 40-45 days after FI in APF-13 and A-1836, respectively; NC 194 bloomed in late August. The first fruits of APF-13 were harvested 120 DAP. These findings demonstrate that PF blackberries form flower buds soon after a short period of vegetative growth. This information should be useful for implementing horticultural practices, such as programming of the harvest date.

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The flowering morphology of the erect, thorny, primocane-fruiting blackberry (Rubus L. subgenus Rubus, Watson) cultivars ‘Prime-Jan’ and ‘Prime-Jim’ were studied in 2005 and 2006 in Aurora, OR. Primocanes that were “soft-tipped” in early summer to 1 m were compared with untipped primocanes. In both years, soft-tipped primocanes developed two- to threefold more branches and almost twice the number of flowers as untipped canes. ‘Prime-Jan’ and ‘Prime-Jim’ began blooming on the branches of soft-tipped canes in mid-July, whereas untipped primocanes began to bloom in late July in 2005 and 2006. Within a primocane inflorescence, the terminal or distal flower was always the first to open followed by terminal flowers from axes located on the basal portion of the inflorescence. Flowers then opened acropetally within the inflorescence, with the exception of the most basal flower, which was typically the last to open. The blooming pattern within an inflorescence was similar for soft-tipped and untipped primocanes. Days from anthesis to black fruit for soft-tipped and untipped primocanes averaged 45 to 51 d in both years, depending on cultivar.

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