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Kim D. Patten and John Wang

The relationships between canopy density of three perennial weed species (Potentilla pacifica Howell, Aster subspicatus Nees, and Lotus corniculatus L.) and `Mcfarlin' and `Stevens' cranberry (Vaccinium macrocarpon Ait.) yield and fruit quality were evaluated. Yield was more severely affected by weed interferences than fruit size or color. Best-fit regression equations for the effects of weed density on yield, fruit size, and color were linear or quadratic polynomials with a strong linear component. For each bog, the slope of the linear relationship between yield and weed density was more negative as the mean yield of weed-free controls increased. `Stevens' fruit size and yield were more sensitive and fruit color was less sensitive to changes in P. pacifica population density than those of `McFarlin'.

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Michael A. Norman, Kim D. Patten and Sarangamat Gurusiddaiah

Three indicator species [rye (Secale cereale L.), radish (Raphanus sativus L.), and alfalfa (Medicago sativa L.)] and nonrooted cuttings of `Stevens' cranberry (Vaccinium macrocarpon Ait.) vines were grown in pots to establish the dose response levels for a sand-applied phytotoxin(s) from a crude extract of Pseudomonas syringae (strain 3366) culture. At 114 ppm [milligrams phytotoxin(s)/kilograms sand], the material was noninhibitory, whereas 1140 ppm reduced root and shoot growth significantly in all four species. In subsequent experiments, a 10-ppm dose controlled corn spurry (Spergula arvensis L.) and fireweed (Epilobium angustifolium L.) seedlings, while 103 ppm reduced root or shoot growth of cuttings of the perennial weeds birdsfoot trefoil (Lotus corniculatus L.) and silverleaf (Potentilla pacifica Howell). Root and shoot growth of partially rooted `McFarlin' cranberry vines was reduced at 103 and 563 ppm, respectively. The phytotoxin(s) could potentially control germinating annual weeds in newly established `Stevens' cranberry bogs.

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Glenn C. Wright, Kim D. Patten and Malcolm C. Drew

`Tifblue' and `Brightwell' rabbiteye blueberry (Vaccinium ashei Reade) and `Sharpblue' southern highbush blueberry (primarily V. corymbosum) were treated with 0, 25, and 100 mm Na+ as Na2SO4 or NaCl, and 0, 1, 3, and 10 mm supplemental Ca2+ in sand culture in the greenhouse. For rabbiteye plants salinized with Na2SO4, leaf Na+ concentrations increased 54-fold and the percentage of total plant Na+ found in the leaves increased from 9% to 63% with increasing external Na+. Calcium supplementation reduced the Na+ concentrations in leaves by up to 20%. Leaf Ca2+ concentrations increased with Ca2+ supplementation, but accounted for a decreasing percentage of the total Ca2+ found in the plant, since root Ca2+ concentrations were much higher. Root Na+ concentrations increased with increasing Na+ treatments to a smaller extent than in the leaves and were also reduced by Ca2+ supplements. Potassium concentrations in leaves and roots decreased with increasing Na+ treatment levels, particularly in roots, where K+ concentration was about half at 100 mm Na+ (as Na2SO4.) Leaf Na+ concentrations were up to two times greater when Na was supplied as NaCl compared to Na2SO4. For plants salinized with NaCl, leaf Na+ levels increased to 1.1% and did not decrease when supplemental Ca2+ was applied. Leaf Cl- concentrations also increased greatly with NaCl, reaching >1.0% (dry weight basis.). Root Cl- concentrations also increased with increasing salinity and were not affected by Ca2+ supplements. Ca2+ supplementation led only to a greater Ca2+ concentration in leaves and roots, but this did not alter Na+ concentrations. Nutrient concentrations in `Sharpblue' leaves, stems, and roots were greater than those of the rabbiteye cultivars, but were influenced by salinity and Ca2+ in essentially the same way. Excess Na+, Cl-, or both, together with lowered K+, were likely the cause of extensive leaf necrosis and may be indicative of a lack of a mechanism to control Na+ influx into blueberry leaves.

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Glenn C. Wright, Kim D. Patten and Malcolm C. Drew

`Tifblue' rabbiteye blueberry (Vaccinium ashei Reade) and `Sharpblue' southern highbush blueberry (primarily V. corymbosum) were treated with 0, 25, or 100 Mm Na+ as Na2SO4 or NaC1, and 0, 1, 3, or 10 Mm supplemental Ca2+ in sand culture in the greenhouse. Greatest stomatal conductance (gs) and net assimilation (A) occurred in unsalinized `Tifblue' plants not given additional Ca2+. Stomatal conductance, A, transpiration (E), and xylem water potential(Ψ)of `Tifblue' and `Sharpblue' plants were all lowered as salinity increased, and these effects were more pronounced with NaCl than with Na2SO4. After 63 days, for plants given 100 Mm Na+ as NaCl, gs and net assimilation rate were reduced to only 10% of the unsalinized controls, while for plants salinized with 100 mm Na+ as Na2SO4, gs and A were 35% and 43%, respectively, of unsalinized controls. Leaf necrosis was more extensive on `Sharpblue' plants given NaCl than on `Tifblue' plants. Neither Ca2+ nor Na+ treatments led to severe chlorosis; reductions in leaf chlorophyll content were mainly due to necrosis. The Na+- induced reduction in gas exchange was associated with negative Ψw Ca2+ deficiency, or a combination of these factors. Additional factors leading to inhibition of gas exchange in NaCl- stressed plants include Cl- toxicity and leaf necrosis. Calcium supplements were unable to ameliorate NaCl damage in `Tifblue' or `Sharpblue' plants, possibly because of the inability of Ca2+ to counter Cl- entry and toxicity. In contrast, additional Ca2+ improved gs, A, Ψw, and leaf chlorophyll content of `Tifblue' plants that received Na2SO4. For plants treated with 25 mm Na+ as Na2SO4 and 1 mm Ca2+, gs was 1.5 to 2.5 times higher than in plants without added Ca2+. Low (1 mm) concentrations of Ca2+ were more effective in ameliorating the effects of 100 mm Na+ as Na2SO4. than were 3 or 10 mm Ca2+ supplements, possibly because higher Ca2+ concentrations damaged the metabolism of the calcifuge blueberry.

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Glenn C. Wright, Kim D. Patten and Malcolm C. Drew

`Tifblue' and `Brightwell' rabbiteye blueberries (Vaccinium ashei Reade.) were subjected to 0, 25, or 100 mM Na+, as Na2SO4 or NaCl, and 0, 1, 3, or 10 mM supplemental Ca2+, primarily as CaSO4, in an irrigated sand culture in the greenhouse. Additionally, the effect of NaCl on `Sharpblue' southern highbush blueberry (primarily V. corymbosum L.) was examined. For unsalinized plants, fastest growth occurred in plants not receiving supplemental Ca2+. Root and shoot growth were depressed as salinity increased in plants lacking additional Ca2+. With 100 mM Na+ as Na2SO4. `Tifblue' root and shoot dry weight increases were only 37% and 25%, respectively, of the increase of unsalinized controls, while with 100 mM Na+ as NaCl, the corresponding shoot and root dry weight increases were only 38% and 43%, respectively. `Brightwell' plants reacted similarly to `Tifblue' in salinity treatments with Na2SO4 and NaCl, but `Sharpblue' plants were more severely affected by 100 mM NaCl than were the rabbiteye cultivars. In no case did addition of Ca2+ have any ameliorative effect on either the dry weight of roots of plants exposed to 25 or 100 mM NaCl or on the shoot growth of plants exposed to NaCl. The inability of Ca2+ to counter Cl- entry or toxicity may account for the lack of amelioration. In contrast, additional Ca2+ did improve shoot growth of plants exposed to Na2SO4. For `Tifblue' plants supplied with 25 mM Na+ as Na2SO4, growth increased by almost 25% in the presence of 10 mM Ca2+, while for `Tifblue' plants treated with 100 mM Na+ as Na2SO4, growth was more than three times greater in plants supplied with 1 mM Ca than in those not given any Ca2+. Growth increase was primarily due to increased leaf area and number. Low (1 mM) concentrations of Ca2+ were more effective in ameliorating the effects of 100 mM Na+ as Na2SO4 than were 3- and 10-mM Ca2+ supplements, possibly because higher Ca2+ additions lead to metabolic damage in these calcifuge Vaccinium species.

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Edward L. Proebsting, David Ophardt, William E. Howell, Gaylord I. Mink and Kim D. Patten

Thirty-five `Bing' sweet cherry (Prunus avium L.) clones were collected, primarily from old commercial orchards in central Washington; propagated on P. mahaleb L. rootstock; and their horticultural performance was evaluated. Nine of the 35 clones were not infected with the common pollen-borne ilarviruses prunus necrotic ringspot virus and prune dwarf virus—four of the clones after decades of exposure in commercial orchards. As a group, the nine virus-free clones produced larger trees with earlier fruit maturity and less rain cracking, but softer fruit, than did the 26 infected clones. These data challenge the general assumption that the presence of one or both of these ilarviruses is always detrimental. This assumption has driven development of many valuable virus certification programs and the adoption of virus-free trees as the standard for commercial fruit growing in most states.