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M.M. Stahler, F.J. Lawrence, and R.R. Martin

More than 300 red raspberry cultivars and selections were screened for raspberry (Rubus idaeus L.) bushy dwarf virus (RBDV), tobacco streak virus (TSV), and tomato ringspot virus (TomRSV) using enzyme-linked immunosorbent assay in three naturally infected breeding program selection plots at Corvallis, Ore. All genotypes tested negative for TSV and TomRSV. The RBDV incidence in primocane-fruiting cultivars and selections was 67%; in floricane-fruiting genotypes, it was 34%. The pattern of RBDV infection in the field showed no discernible trend. The high incidence may have been due to use of infected parents, propagation of infected genotypes, and pollen transmission. `Willamette', considered to be immune to the common strain of RBDV, along with 14 clones that had been in the field 10 years or longer, tested negative. The high incidence of RBDV in the breeding plots may provide an opportunity to identify resistant parents for breeding programs. An early seedling screening method for RBDV susceptibility is desirable to eliminate highly susceptible genotypes from the program and maintain a lower incidence of RBDV within the breeding plots.

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Kim S. Lewers and Courtney A. Weber

Researchers developing new cultivars of red raspberry (Rubus idaeus subsp. idaeus L.) and black raspberry (R. occidentalis L.) observe progeny of breeding populations for several seasons to identify those that perform reliably. If a portion of any breeding population could be eliminated based on a qualitative character or molecular marker, resources used for that portion could be used for other progeny. Our objective is to identify such molecular markers for red raspberry and black raspberry. A black raspberry × red raspberry cross was made to develop a map of each parent, and an F2 population was generated to join the maps. Simple sequence repeat (SSR) markers derived from red raspberry and strawberry were used. The level of homozygosity for the red raspberry was 40%, and the level for the black raspberry was 80%. Severe segregation skewing was observed in the F2 generation and indicates problems with transmission. Our findings help quantify the relative levels of homozygosity previously reported for red raspberry and black raspberry. In addition, the severe skewing observed in the F2 generation provides a molecular perspective to the fertility problems previously reported for the black raspberry × red raspberry hybrids (purple raspberry). Since black raspberry is highly homozygous, purple raspberry has transmission and fertility problems, and black raspberry breeders have reported a frustratingly low level of diversity in this subgroup, development of a black raspberry map is expected to require twice the markers as for a red raspberry map, emphasizing the need for a black raspberry sequence from which to develop molecular markers.

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Stephen F. Klauer, Chuhe Chen, Paul W. Foote, and J. Scott Cameron

On four dates during the 1991 growing season, gas exchange rates were measured on the same middle leaflets every 3 h from 7am-10pm from deflowered (DF) and fruiting (F) red raspberry (Rubus idaeus L. cv. “Meeker”) canes. Concurrently, the adjacent side leaflets were sampled for anatomical starch determination. The dates corresponded to the late anthesis/early green fruit, early red fruit, late red fruit, and post fruit maturity stages of the growing season. For all dates, CO2 assimilation (A) was highest from 7-10am, lowest at 4pm, and increased at 7pm. Overall A peaked during fruit development. Leaves of F canes had greater A than leaves of DF canes during fruit development, but rates were similar after fruit maturity.

Starch accumulation in leaf cross-sections generally followed the diurnal pattern observed for A. Starch appeared heaviest from 7am-lpm and often showed an increase from 7-10pm. Leaves from DF canes generally had a greater accumulation of starch. Seasonally, leaf starch from F canes appeared greatest at late anthesis, decreased during fruit development and was very low post fruit maturity. Leaf starch in DF canes appeared greatest at the late anthesis and late red fruit stages.

DF leaves had greater dry weight accumulation than F leaves during the red fruit stages. A Western blot showed that Rubisco levels as a percentage of total soluble protein were higher during fruit development and decreased after fruit maturity.

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Séverine Morel, Richard E. Harrison, Donald D. Muir, and E. Anthony Hunter

Fruit from three red raspberry (Rubus idaeus L.) cultivars—`Glen Clova', `Glen Lyon', and `Glen Moy'—were harvested from four sites on two harvest dates and evaluated fresh or following storage at -20 °C to determine the relative importance of genotype, harvest date, location and freezing effects on 19 sensory attributes using a trained sensory panel. Freezing and cultivar × freezing interaction effects were relatively large while site, harvest date, and other interactions were of minor importance. The cultivar × freezing interaction was caused by differential responses among cultivars for the sensory attributes purple, juicy, sweet, and raspberry aroma with less discrimination among cultivars postfreezing. `Glen Clova' fresh fruit received the highest values for juicy, fruity, sweet, and raspberry aroma; `Glen Moy' fresh fruit received the highest values for purple; `Glen Lyon' fresh fruit received the lowest values for juicy, postfreezing, `Glen Lyon' received the highest values for purple and sweet and all three cultivars were similar for the other attributes. These data suggest that selection for improved postfreezing sensory characteristics should not rely solely on fresh fruit evaluations although further study of a more genetically diverse group of genotypes would be beneficial. The significant cultivar and minimal harvest date and location effects suggest that these fruit sensory analysis methods should be useful in selecting raspberry genotypes with superior fruit quality.

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Shiow Y. Wang and Hsin-Shan Lin

Fruit and leaves from different cultivars of thornless blackberry (Rubus sp.), red raspberry (Rubus idaeus L.), black raspberry (Rubus occidentalis L.), and strawberry (Fragaria × ananassa D.) plants were analyzed for total antioxidant capacity (oxygen radical absorbance capacity, ORAC) and total phenolic content. In addition, fruit were analyzed for total anthocyanin content. Compared to fruit, leaves were found to have higher ORAC values. In fruit, ORAC values ranged from 7.8 to 33.7 μmol Trolox equivalents (TE)/g of fresh berries, while in leaves, ORAC values ranged from 20.8 to 45.6 μmol TE/g of fresh leaves. Fruit harvested at different stages of maturity were analyzed in blackberries, raspberries, and strawberries. Blackberries and strawberries had their highest ORAC values during the green stages, while raspberries generally had the highest ORAC activity at the ripe stage (with exception of cv. Jewel, a black raspberry). Total anthocyanin content increased with maturity for all three fruit. There was a linear correlation existed between total phenolic content and ORAC activity for fruit and leaves. For ripe berries, there was also a linear relationship between ORAC values and anthocyanin content. Of the ripe fruit and leaves tested, raspberry plants appeared to be the richest source for antioxidants.

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David C. Percival, John T. A. Proctor, and J. Alan Sullivan

A study examining the influence of trickle irrigation (TI), IRT-76 plastic film (PF) and straw mulch (SM) on the establishment of Rubus idaeus L. cv. `Heritage' micro-propagated raspberries was initiated at Cambridge, Ontario in 1993. Environmental, nutritional, vegetative and reproductive data were collected. Soil temperature and soil water status were greatly affected by TI, PF and SM. TI lowered soil NO3-N and increased soil NH4-N and Mg. PF increased soil NO3-N and NH4-N. Foliar N decreased by 10% with TI and increased by 8% with PF. Foliar P and Ca increased by 45 and 6% respectively, with TI. Node number was not influenced by TI, PF or SM. PF however, increased cane height, cane diameter, dry weight and leaf area by 14, 17, 77 and 11% respectively, and TI increased cane diameter by 13%. Although TI increased the number of fruiting laterals by 63%, there was no effect of TI, PF or SM on harvested berry number or weight.

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J.A. Sullivan, Weikai Yan, and J.P. Privé

Primocane-fruiting (PF) red raspberry (Rubus idaeus L.) cultivars are being grown in many regions as their popularity increases. However, testing of this perennial fruit crop is expensive and requires many years. Large genotype (G) × environment (E) interactions can make identification of superior genotypes difficult. The G/G × E (GGE) biplot can be used to measure cultivar performance and group locations into mega-environments. The GGE biplot was applied to yield trial data of three PF red raspberry cultivars Autumn Bliss, Heritage, and Redwing grown in 17 environments (year-location combinations). The 17 environments encompassed six locations in Ontario and Quebec, Canada between 1989 and 1996. `Autumn Bliss' produced the highest yields in 11 of 17 environments. `Heritage' was usually the lowest yielding cultivar. Two mega-environments were identified based on the performance of `Autumn Bliss' and `Redwing'. Some environmental variables were likely to be responsible for the discriminating ability of the test environments as they were correlated with the primary effects. The GGE biplot was an effective analysis to determine mega-environments and the cultivars best adapted to each.

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Joseph C. Neal, Marvin P. Pritts, and Andrew F. Senesac

Five greenhouse and two Geld experiments were conducted to evaluate tissue culture-propagated (TC) raspberry (Rubus idaeus cv. Heritage) sensitivity to preemergent herbicides. Plant performance was measured by plant vigor, above-ground fresh weight, root development, and primocane number. Simazine and oryzalin caused significant injury to newly planted TC raspberry plants in greenhouse and field experiments. The severity of injury was generally linear with respect to herbicide rate, but no appreciable differences in injury were observed between the granular and spray applications. Napropamide wettable powder caused some foliar injury, but plants recovered within one growing season and growth was equal or superior to the hand-weeded controls. The granular formulation of napropamide produced similar results, but did not cause the initial foliar burn. Pre-plant dipping of roots into a slurry of activated carbon did not prevent simazine or oryzalin injury, but injury was reduced when herbicide applications were delayed. Simazine applied 4 weeks after planting was not Injurious, and oqzalin applied 2 or 4 weeks after planting caused some foliar injury, hut no reduction in plant fresh weight. Delayed treatments of napropamide increased foliar injury. Herbicide tolerance of tissue-cultured plantlets appeared to be less than that of conventionally propagated plants. Chemical names used: N,N-diethyl-2-(1-napthalenyloxy)propanamide (napropamide), 4-(dipropylamino)-3,5-dinitrobenzenesulfonamide (oryzalin), 6-chloro-N,N'diethyl-1,3,5-triazine-2,4-diamine (simazine).

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Stenhen F. Klauer, J. Scott Cameron, and Paul W. Foote

Results from previous cultural and physiological studies of red raspberry suggest that primocanes compete with floricanes for light, nutrients and/or photoassimilates. This study was undertaken to determine whether this competition might be reflected in the actual translocation of photoassimilates between the two types of canes. In 1993, pairs of greenhouse grown, potted red raspberry (Rubus idaeus L.) plants contaming one or two floricanes and numerous primocanes were labeled with 14CO2 on four dates corresponding with early anthesis, green fruit, red fruit and post fruit maturity stages of the growing season. For each experiment, either a floricane or a primocane was exposed to 92.5μCi 14CO2 within a sealed bag. After 24 hours, the bag was removed and the presence of label was monitored for up to 11 days. Activity was determined using liquid scintillation. At all developmental stages 14C moved from the labeled floricane to primocanes that were from 2.5 cm to 1.5 m tall and to the roots. Movement was quickest and relatively greatest at early anthesis, dccreascd during fruiting, and was still occuring at 2 months after fruit maturity. Small amounts of label were detected in roots of labeled primocanes at all stages, but trace amounts were present in fruit and other primocanes only at post fruit maturity.

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Pedro B. Oliveira, Cristina M. Oliveira, Luís Lopes-da-Fonseca, and António A. Monteiro

The spring shoots of `Autumn Bliss' red raspberry (Rubus idaeus L. var. idaeus; primocane-fruiting type) were cut on 2, 16, 31 July and 15 and 30 Aug. with the objective of delaying fruit harvest into the off-season under mild winter climatic conditions. Cutting shoots in August delayed fruit harvest until February and April of the following year, but shoot growth was weak and fruit yield low (4.8 and 2.1 g/cane). July cuttings delayed harvest until October to January with acceptable fruit yield (63.5, 52.8, and 26.5 g/cane for 2, 16, and 31 July, respectively). The differences in cane height and total node and fruiting node count between the three cutting dates of July were small, but there was a constant decrease in leaf area per cane from the first to the third date and a sharp decrease in fruit yield from the second to the third date. Vegetative shoot growth was less affected than yield when summer cutting was delayed until the end of July to induce a later harvest. Fruit quality always reached acceptable standards. This study confirms the practicability of using summer-cutting of primocane-fruiting red raspberries to induce off-season fruit production under protected cultivation in mild winter climates.