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Chuhe Chen, J. Scott Cameron, and Stephen F. Klauer

Accumulated attendance and fourth-derivative spectra were measured using intact leaf samples at mom temperature for 80 genotypes of four Fragaria species. Attendance peak wavelength and amplitude data of all samples was pooled and yielded 25 common bands for Fragaria. Of these, 14 chlorophyll bands and two phototransformed bands were consistent with French's (1972) model.

Peak wavelengths and amplitudes which represent major bands in F. chiloensis and F. × ananassa spectra were also determined separately. While peak wavelengths of the two species were identical, variation was noted in peak amplitude. The signals of the bands at Cb640, Cb649, Ca670, Ca673, Ca675-676, Ca684 and Ca693 in F. chiloensis were significantly stronger than those in F. × ananassa. Ca677 and Ca695 were stronger in F. × ananassa.

The greatest difference among Fragaria species was found in the amplitude of Ca693. The amplitude of this peak was greatest in F. chi/oensis (0.0025) and smallest in F. virginiana (-0.0005), The cultivated hybrid of these two species, F. × ananassa, was intermediate (0.0008), Preliminary evidence suggests that certain genotype-specific spectral characteristics may relate directly to observed differences in photosynthetic biology among these species.

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

Leaf-area based CO2 assimilation rate (ALA as an Indicator of genotypic differences in photosynthetic capacity is questioned on the basis of correlations found between ALA and specific leaf weight and small leaf size. To address this question of photosynthetic apparatus concentration In F. chiloensis genotypes differing significantly in ALA, visual image analysis software was used to quantify a number of leaf anatomy parameters. In 1991 and 1992, after gas exchange measurements in the field, leaf tissue was prepared In cross-sections and leaf clearings for light microscopy. Cross-sections were used to measure internal anatomical parameters and clearings for vein and stomatal densities.

Analysis of variance of 1991\92 measurements showed significant genotypic variation for leaf veination, leaf thickness, palisade cell length, cross-sectional area In mesophyll tissue and internal air space. Differences in stomatal density were observed in 1991. None of the anatomical parameters measured were correlated with ALA. This suggests that the concentration of physical apparatus Is not the major source of variation In ALA among these eight genotypes.

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Stephen F. Klauer, Chuhe Chen, and J. Scott Cameron

In 1999, yield of the split (ST) vs. conventional trellis (CT) was again compared in “Meeker” red raspberry. Field-testing was repeated at four sites in north (Lynden) and southwest (Woodland, Ridgefield, WSUV REU) Wash. A variety of widths, crossarm styles, and machine harvesters were tested in fields with varied cultural practices. Topped and tied-over canes were compared at two locations. In previous years, estimated yield potentials have been 20% to 60% greater for ST, but actual yields have only been 10% to 13% greater because of harvester damage to laterals and premature pick of green fruit. This year, Littau Harvester suggested minor machine adjustments that addressed these problems, resulting in a 19.4% yield increase for a 51-cm ST (Lynden). Lateral damage was minimized by spreading the picking heads to begin harvest, and then moving them closer after every three harvests. Excessive green fruit was controlled by reducing beater rod speed. A rough cost/benefit analysis indicates that there would be substantial economic gain (15% more $/acre in this case, assuming $0.50/lb fruit) for ST vs CT at this level of yield increase. There was no difference in harvest efficiency between treatments at WSUV. More fruit was lost to drop in the row center for ST in Lynden. Topped canes in CT and ST had reduced yields of 11 and 19% respectively compared to their tied-over counterparts. Topped ST canes had 11% greater yield than topped CT canes. ST canopies were larger, and had more leaves than CT. No differences were seen on a leaf-area basis between treatments for leaf: CO2 assimilation, fluorescence, and chlorophyll or in primocane leaf total nitrogen. Increased ST yields were recorded for a 2nd year at two locations, which supports yield sustainability for ST.

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Chuhe Chen, J. Scott Cameron, and Stephen F. Klauer

Leaf water potential (LWP), relative water content (RWC), gas exchange characteristics, and specific leaf weight (SLW) were measured six hours before, during, and after water stress treatment in F. chiloensis and F. ×ananassa grown in growth chambers. The leaves of both species showed significantly lower LWP and RWC as water stress developed. F. ×ananassa had consistency lower LWP under stressed and nonstressed conditions than F. chiloensis. F. ×ananassa had higher RWC under nonstressed conditions, and its RWC decreased more rapidly under water stress than F. chiloensis. In comparison to F. ×ananassa, F. chiloensis had significantly higher CO2 assimilation rate (A), leaf conductance (LC), and SLW, but not transpiration rate (Tr), under stressed and nonstressed conditions. LC was the most sensitive gas exchange characteristic to water stress and decreased first. Later, A and stomatal conductance were reduced under more severe water stress. A very high level of Tr was detected in F. ×ananassa under the most severe water stress and did not regain after stress recovery, suggesting a permanent damage to leaf. The Tr of F. chiloensis was affected less by water stress. Severe water stress resulted in higher SLW of both species.

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Chuhe Chen, J. Scott Cameron, and Stephen F. Klauer

Leaf fluorescence characteristics, chlorophyll (Chl) content and 4th-derivative spectra were measured six times before, during, and after water stress development in F. chiloensis and F. ×ananassa grown in growth chambers. The younger strawberry leaves under water stress maintained higher Chl a, Chl b, and total Chl contents than those under nonstressed conditions, while the older ones lost Chl quickly under water stress and then died. In comparison to F. ×ananassa, F. chiloensis had significantly higher Chl a, Chl b, and total Chl contents and peak amplitudes of Cb 630 and Ca 693 in 4th-derivative spectra under stressed and nonstressed conditions. The differences in peak amplitude of Ca 693 between the two species increased under water stress. Fq was the most sensitive fluorescence characteristic to water stress and was reduced significantly under stress. Fm and Fv decreased significantly under more severe water stress. A reduction in Fv suggests that severe water stress might cause thylakoid damage and photoinhibition in the leaves, which resulted in a very depressed CO2 assimilation level. F. chiloensis had significantly higher Ft and Fq before and under water stress development (but not after stress recovery) than F. ×ananassa.

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Stephen F. Klauer, Chuhe Chen, and J. Scott Cameron

In 1998, yield of the split (ST) vs. conventional trellis was again compared in `Meeker' red raspberry with work at Vancouver focusing on advanced trellis development and technology transfer. Field testing was expanded from two to five sites in northern (Lynden) and southwestern (Woodland, Ridgefield, WSUV REU) Washington, with a total of eight trials. These tested a variety of widths (28–51 cm), crossarm styles, and machine harvesters in fields with varied cultural practices. Four trials were machine-picked, and, in Vancouver, harvest efficiency was studied. For widths >43 cm, yields were 10% to 13% greater for ST in four trials, while widths less than 43 cm showed no increase. As in previous years, estimated yield potential was 20% to 59% higher for ST in three of four trials. Differences between actual/estimated yields were due to several factors, including damage to laterals, harvest inefficiency, and poor early fruit release. Yield potential was greater (28%) for ST in a second-year trial, suggesting sustainability. In various trials, numerous data were collected including canopy and primocane measurements, aboveground biomass, light interception and leaf: area, gas exchange, chlorophyll content, fourth derivative spectra, fluorescence, N content, and tissue for anatomical analysis. Results were similar to last year. Increased light within ST causes earlier and larger canopy growth and fruit development. There was a large increase in leaf number, leaf area and berry number. Increases in yield were again associated with higher number of lateral/cane. There was no difference in leaf physiological measurements/leaf area between treatments.

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Chuhe Chen, Stephen F. Klauer, and J. Scott Cameron

Two test sites pairing perennially cold-damaged portions of fields vs. controls for a 3rd year were assessed. Winter 1997-1998 was very mild and produced less winter injury than the previous winters. We evaluated continued recovery of the raspberry canopy and cane productivity. In contrast to the last 2 years, the previously cold-damaged plots did not show higher levels of cane dieback, percentage of cane dieback, number of dead or dormant buds per cane, and percentage of dead buds at either site. Very few secondary laterals were produced at either site, which supports previous observations that raspberry compensates for winter injury with increased production of secondary laterals. For the first time, the damaged plots actually produced higher yields mainly through a significantly increased berry number per cane at both sites. Floricane leaves in the damaged plots showed higher photosynthetic rates at the green fruit stage and after harvest at site 2. Cane size was similar across sites, although the previously cold-damaged plants had higher berry numbers per lateral. It seems the newly recovered plants in the previously damaged plots had a renewed vigor, working harder to achieve a higher yield. No differences between treatments was detected in leaf nitrogen for a third year, suggesting this may not be a factor in winter injury here. A high population of weevils was observed at one injured site, suggesting a possible interaction with cold damage.

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Stephen F. Klauer, J. Scott Cameron, and Chuhe Chen

With the advent of new rotary-head mechanical harvesters, it is now possible to machine-harvest a wider raspberry canopy. In Spring 1996, a trial was established in a grower's field in Lynden, Wash., comparing raspberries trained to two top wires with a 70-cm spread (split trellis) to the conventional single top wire system. Within the split trellis, increases in leaf number per cane (97%), and leaf area per cane (55%) were not reflected in a concomitant increase in total leaf dry weight per cane (35%). Leaf dry weight per fruit weight was 11% less within the split trellis. These data suggest that the canopy is more efficient with this type of trellis. Increases in estimated yield per cane (49%) and projected yield per acre (50%) associated with the split trellis were due to increases in berry number per cane (47%). Fruit number per meter of lateral was 35% greater within the split trellis. Greatest enhancements to yield components were in the upper parts of the canopy where canes were tied over. Since there were no differences in lateral numbers or lateral lengths between the two systems, this increased productivity was due to increased floral expression, enhanced fruit set, increases through Spring bud initiation or any combination thereof. In both trellis systems, the longest laterals occurred on the middle third of the cane and decreased in length progressively towards the tip of the cane. Primocane lengths were shorter (20%) and diameters were smaller (10%) and more uniform in the split trellis system.

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Chuhe Chen, J. Scott Cameron, and Stephen F. Klauer

Two sets of field experiments have been set up in Lynden, Wash., to evaluate cold damage to red raspberry `Meeker'. The locations represent newly established crops (fi eld 1) and a field that suffered reoccurring cold damages in recent years (fi eld 2), respectively. Temperature and moisture HOBOs were set up in the check and colddamaged treatments of both of the fields to record the air and soil temperatures and air moisture. The cold-damaged treatments in both fields had significantly higher cane dieback and dead buds. Cold injury significantly reduced berry yield in field 1, but not in field 2, through an steep drop in berry number per cane, mainly due to a significant reduction in lateral number/cane. Cold damage reduced primary lateral number/cane, and increased secondary lateral number/cane in both fields. Secondary laterals were shorter in length and had lower berry number/lateral than the primary ones. It proved that cold damage also delayed initiation and development of secondary laterals, and resulted in more yield loss to the plant. The cold-damaged fruiting cane had lower gas exchange rates, leaf and stomatal conductance, and transpiration rates during fruit development in both fields. It also significantly reduced fluorescence parameters Fo, Fm, Fv, T1/2, and Fq of the cold injury treatment in field 1. On a few cold days this spring, the HOBOs recorded a lower daily low temperature in the cold damaged area than in the check area.

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J. Scott Cameron, Chuhe Chen, and Stephen F. Klauer

Limited twospotted spider mite feeding significantly reduced the CO2 assimilation rate of red raspberry leaves and damaged the photosynthetic apparatus prior to visible damage to the leaf. The impact of miticides on the photosynthetic biology of raspberry and strawberry leaves was tested in growth chambers, greenhouses, and the field, with similar results across environments. In general, miticides appear to reduce the photosynthetic capacity of the leaves for 10 to 14 days, with reductions of ≈30% occurring within the first several days. Chlorophyll fluorescence and fourth-derivative spectroscopy of intact leaf lamina showed changes in the structure and function of the photosynthetic apparatus in response to chemical treatment. High temperature reduced physiological processes in strawberry plants grown at two diurnal regimes (30/24C, 21/15C); however, the relative degree of reduction in photosynthetic activity due to miticide application was similar for both. A preliminary screening of mite-resistant and -susceptible red raspberry genotypes after prolonged infestation suggested varying levels of physiological tolerance of mite damage, which are not well-correlated with visual appearance.