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Carolyn DeMoranville and Irving Demoranville

Cold tolerance of cranberry flower buds from four cultivars was evaluated using potted sods collected from commercial cranberry beds. The plants were evaluated weekly beginning at the spring dormant stage and continuing until the buds had elongated to at least 2 cm. The potted plants were place in controlled temperature chambers at 5°C and the temperature was lowered 3°C/hr until the target temperature was reached. The plants were held at that temperature for 3 hr then slowly warmed. After 24 hr, damage was evaluated by microscopic examination of cross-sectioned buds. In the early spring, prior to leaf greening, all four cultivars were tolerant of –8°C. In the later part of the spring, cultivars with the smallest buds had greater cold tolerance than those with larger buds. Even when all cultivars appeared to be at the same developmental stage, e.g., bud swell, `Ben Lear' and `Stevens', were more sensitive than `Early Black' and `Howes'. At the 2-cm elongation stage, minimum cold tolerance of –1°C was reached for all four cultivars. New recommendations for protecting cranberry flower buds in the spring have been formulated based on this study.

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Ricardo Cesped-Ruiz* and Bingru Huang

The American cranberry often undergoes drought stress during the summer. However, the physiological response of this species to drought is not well understood. This study was designed to determine the effects of drought on two commercial cranberry cultivars of high potential yield, `Ben Lear' and `Stevens', during a vegetative stage. The plants were subjected to drought for 15 days in a greenhouse. Soil water content, leaf water content, leaf photosynthetic rate, stomatal conductance, transpiration, differential leaf-air temperature, photochemical efficiency (Fv'/Fm') and the actual PSII efficiency (deltaF/Fm') decreased in those plants subjected to drought. Drought reduced differential leaf-air temperature at day 6 of treatment and stomatal conductance and transpiration starting at day 9 and photosynthetic rate at day 13. Drought decreased leaf water content at day 14 and Fv'/Fm' and PSII efficiency at day 15. Our results indicated that cranberry plants in vegetative stage were sensitive to drought for both cultivars and stomatal conductance was the most sensitive parameter among those examined for both cultivars.

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Dana L. Baumann, Beth Ann Workmaster, and Kevin R. Kosola

Wisconsin cranberry growers report that fruit production by the cranberry cultivar `Ben Lear' (Vaccinium macrocarpon Ait.) is low in beds with poor drainage, while the cultivar `Stevens' is less sensitive to these conditions. We hypothesized that `Ben Lear' and `Stevens' would differ in their root growth and mortality response to variation in soil water potential. Rooted cuttings of each cultivar were grown in a green-house in sand-filled pots with three different soil water potentials which were regulated by a hanging water column below a fritted ceramic plate. A minirhizotron camera was used to record root growth and mortality weekly for five weeks. Root mortality was negligible (2% to 6%). Whole plant relative growth rates were greatest for both cultivars under the wettest conditions. Rooting depth was shallowest under the wettest conditions. Whole-plant relative growth rates of `Ben Lear' were higher than `Stevens' at all soil water potentials. `Stevens' plants had significantly higher root to shoot ratios and lower leaf area ratios than `Ben Lear' plants, and produced more total root length than `Ben Lear' at all soil water potentials. Shallow rooting, high leaf area ratio, and low allocation to root production by `Ben Lear' plants may lead to greater susceptibility to drought stress than `Stevens' plants in poorly drained cranberry beds.

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Beth Ann A. Workmaster, Michael Wisniewski, and Jiwan P. Palta

Infrared video thermography has recently been used to visualize ice nucleation and propagation in plants. At the UW–Madison Biotron facility, we studied the formation of ice in various parts of fruit-bearing cranberry (Vaccinium macrocarpon Ait.) uprights. The fruits were at the blush to red stages of ripening. Samples were nucleated at –1 or –2°C with ice-nucleating-active bacteria (Pseudomonas syringae). Following nucleation, samples were cooled to –6°C in ≈1 hour. The following observations were made: 1) When nucleated at a cut end, ice propagated rapidly throughout the stem and into the leaves at a tissue temperature of about –4°C. However, ice did not propagate from the stem through the pedicel to reach the fruit. During the 1 hour after ice propagation in the stem, the fruit remained supercooled. 2) Within the duration of the experiment, leaves could not be nucleated from the upper surface. Ice from the lower leaf surface did nucleate the leaf, and ice propagated from the leaf to the stem and other leaves readily. 3) Both red and blush berries could only be nucleated at the calyx end of the fruit. 4) Red berries supercooled to colder temperatures and for longer durations than the blush berries. 5) In support of our previous studies, red berries were able to tolerate some ice in their tissue. These observations suggest that: 1) The upper leaf surface and the fruit surface (other than the calyx end) are barriers to ice propagation in the cranberry plant; and 2) at later stages of fruit ripening the pedicel becomes an ice nucleation barrier from the stem to the fruit. This may contribute to the ability of the cranberry fruit to supercool.

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Deborah L. Allan, Bruce D. Cook, and Carl J. Rosen

The effect of N form and solution pH on the carboxylic and phenolic acid content of cranberry (Vaccinium macrocarpon Ait. cv. Searles) shoots and roots was determined in a greenhouse experiment. The predominant carboxylic acids measured were malate and citrate. Protocatechuic acid was the dominant phenolic acid detected. Total organic acid concentrations were unaffected by N form supplied. In shoots, higher total concentrations of organic acids were found at pH 4.5 than at 6.5 in the shoot, but there was little pH effect in the roots.

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Mary Jane Else, Hilary A. Sandler, and Scott Schluter

A system of mapping weed infestations in cranberries (Vaccinium macrocarpon Ait.) was developed that enables growers to incorporate integrated pest management practices into their weed control program. This system provides growers with information on the location of weeds and the area of weed patches, but differs from other weed mapping systems in that information on control priorities is included on the maps. Weed management efforts can then be directed to the most economically damaging weeds first. The mapping system also provides growers with a permanent record that can be used to communicate with staff and to evaluate weed management strategies.

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Zhanao Deng, Brent K. Harbaugh, and Natalia A. Peres

initiated a caladium breeding program at its Gulf Coast Research and Education Center in Bradenton, FL, in 1976. Since then, this breeding program has led in development and release of new cultivars for the caladium industry. ‘Cranberry Star’ ( Fig. 1 ) is

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J. M. Hart, Arthur Poole, Kris L. Wilder, and B. C. Strik

Cranberries (Vaccinium macrocarpon Ait.) require low rates of N fertilizer compared to many horticultural and agronomic crops. Excess N promotes vegetative growth at the expense of yield. Growers desire information about N fertilization to achieve optimum yields without overgrowth, Little information has been published about N rate and timing influence on cranberries in south coastal Oregon. An N rate and timing field experiment with Crowley and Stevens cultivars was established to answer grower questions. N was applied at 0, 18, 36 and 54 kg/ha in various combinations at popcorn (white bud), hook, fruitset, early bud, and late bud. Yield, yield components, (fruit set, number of flowering and total uprights, berry size, flowers per upright and the proportion of uprights that flower), vegetative growth and anthocyanin content were measured. After 2 years of treatments, N rate or timing had little influence on yield or yield components in the previously heavily fertilized Crowley bed. In the previously lightly fertilized Stevens bed, N rate increased yield, vine growth, and the number of flowering uprights, N timing also influenced the number of flowering uprights. The total number of uprights was influenced by the interaction of N rate and timing.

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Richard Novy, Nicholi Vorsa, and Kim Patten

The cranberry cultivar `HcFarlin', selected from a natural bog in Massachusetts in 1874, has become the most widely grown cultivar in the Northwestern U.S.A. Washington state growers have noted variable productivity among `McFarlin' bogs. The determination of whether there is a genetic basis for the variability has been made difficult by a paucity of reliable morphological descriptors in cranberry. A random amplified polymorphic DNA (RAPD) analysis of 45 clones sampled from 12 WA `McFarlin' bogs identified 17 unique RAPD profiles. Cluster analysis identified 7 groups having various numbers of distinct, but related individuals. Eight clones were found to have RAPD profiles identical to the cultivar `Howes' indicating varietal misclassification had occurred in some bogs. One group of clones that originated from bogs classified as “Good” or “True” Mcfarlin' by growers had RAPD profiles similar to those of representatives from WI and MA `Mcfarlin' bogs. RAPD analysis has shown that `McFarlin' is represented by several genotypes, suggesting that the observed variability in production may have a genetic component.

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James R. Altwies II, Beth Ann Workmaster, Joy E. Altwies, Jiwan Palta, and Teryl R. Roper

It is commonplace in Wisconsin for cranberry growers to flood their beds to form thick ice during winter to protect the uprights from dangerously low winter air temperatures. However, the specifics of ice thickness and zone temperature within and below the ice vs. surface air temperature have not been studied. We have developed several models using finite element analysis, a process by which a complex system is divided into finite segments and analyzed individually. All pieces are then recombined into the complete system so a comprehensive picture of the activity of the freezing cranberry bed may be visualized. It was determined that cold surface air temperatures of -25 °C and thin ice of 15 cm, soil and gap air temperatures do not drop lower then -5 °C, which is congruent with data collected from the field. Models on sand beds and peat beds did not show enough difference to be of concern. Temperatures within the ice, where the uprights would be encased, reached -15 °C under the cold air regime, which has been proven to be well within the survival range of the dormant buds.