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Abstract

Young highbush blueberry seedlings (Vaccinium corymbosum L.) from 26 crosses of a partial diallel were inoculated with Phytophthora cinnamomi Rands by dipping the roots into a mycelial slurry. The seedlings were grown 90 days in sand in the greenhouse and rated for resistance to root rot damage. Of the 2412 inoculated seedlings, 214 (8.9%) were resistant. The 2 parental clones that produced the largest percentage of resistant seedlings were US 141 and G-164; within their progenies, each produced an average of 18% resistant seedlings. Mean squares for general (GCA) and specific combining ability (SCA) were significant at the 1% and 5% levels, respectively. The mean square estimate for GCA was about 5 times higher than that for SCA, While both additive and nonadditive effects are important, rapid improvement can be made by phenotypic selection. Resistance to P. cinnamomi in blueberry progenies studied appears to be partially recessive and quantitatively inherited. Inoculation of young seedlings by root dipping in a mycelial slurry of P. cinnamomi and growing the seedlings in sand provided rapid identification of resistant plants.

Open Access

The effects of carbon dioxide enrichment on growth, photosynthesis, and postharvest characteristics of `Meijikatar' potted roses were determined. Plants were grown in 350, 700, or 1050 μl CO2/liter until they reached 50% flower bud coloration and then were placed into dark storage for 5 days at 4 or 16C. Plants grown in 700 or 1050 μl CO2/liter reached the harvest stage earlier and were taller at harvest than plants produced in 350 μl CO2/liter, but there were no differences in the number of flowers and flower buds per plant among CO2 treatments. Plants grown in early spring were taller and had more flowers and flower buds than plants grown in late winter. Shoot and root growth of plants grown in 700 or 1050 μl CO2/liter were higher than in plants produced in 350 μl CO2/liter, with plants grown in early spring showing greater increases than plants grown in late winter. Immediately after storage, plants grown in 350 μl CO2/liter and stored at 4C had the fewest etiolated shoots, while plants grown in 1050 μl CO2/liter and stored at 16C had the most. Five days after removal from storage, chlorophyll concentration of upper and lower leaves had been reduced by ≈50% from the day of harvest. Carbon dioxide enrichment had no effect on postharvest leaf chlorosis, but plants grown in early spring and stored at 16C had the most leaf chlorosis while plants grown in late winter and stored at 4C had the least leaf chlorosis.

Free access

Stenospermocarpic seedlessness from Vitis vinifera L. is being introgressed into muscadine grape (Vitis rotundifolia Michx.) germplasm through the use of a cross-fertile hybrid of the two species. Recently, a sequence-tagged site (STS) molecular marker, p3_VvAGL11, has been developed which enables detection of the dominant allele controlling stenospermocarpic seedlessness in V. vinifera. This marker was evaluated in six Euvitis Planch. × Muscadinia Planch. hybrid progenies to determine its association with seedlessness in this material. The presence of the 214-bp seedlessness-associated p3_VvAGL11 allele in seedling vines resulted in a nearly 3-fold reduction in mean seed fresh weight (MSFW) and significantly reduced mean seed weight per berry (MSWB), percent berry weight composed of seed (BWCS), and mean berry weight (MBW). When the lack of lignified seed was used as the determinant of seedlessness, the p3_VvAGL11 marker was able to correctly judge seedlessness in ≈85% of the progeny. Analysis of seedlessness in the progenies was hampered by poor vigor and fruiting ability of the hybrid seedlings. The p3_VvAGL11 marker shows potential to speed the introduction of the stenospermocarpic seedlessness into Muscadinia germplasm by identifying seedless progeny at the seedling stage.

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Six experiments were conducted using three cultivars to investigate the impact of water electrical conductivity (EC) and the addition of nutrients to vase solutions on postharvest quality of cut rose (Rosa hybrids) stems. Postharvest quality of cut ‘Freedom’ rose stems was evaluated using solutions containing either distilled water with sodium chloride (DW+NaCl) or DW+NaCl with the addition of a commercial floral preservative (holding solution containing carbohydrates and biocide) to generate a range of EC values (Expts. 1 and 2). The third experiment compared the effect of different EC levels from the salts NaCl, sodium sulfate (Na2SO4), and calcium chloride (CaCl2). The fourth experiment investigated EC’s impact on rose stems with the addition of two rose cultivars (Charlotte and Classy). When ‘Freedom’ stems were subjected to DW+NaCl, the longest vase life was achieved with 0.5 dS·m–1. The addition of holding solution not only extended vase life but also counteracted the negative effects of high EC with maximum vase life occurring at 1.0 dS·m–1. Furthermore, stems in the holding solution experienced significantly less bent neck and the flowers opened more fully than those in DW. Stems placed in DW with a holding solution also experienced more petal bluing, pigment loss, necrotic edges, and wilting than those held in DW alone. This effect was likely due to increased vase life. Salt solutions containing Na2SO4 and CaCl2 resulted in extended vase life at 1.0 dS·m–1, but increasing salt levels decreased overall vase life. As EC increased, regardless of salt type, water uptake also increased up to a maximum at 0.5 or 1.0 dS·m–1 and then continually declined. Maximum vase life was observed at 1.5 dS·m–1 for cut ‘Charlotte’ stems, and at 1.0 dS·m–1 for ‘Classy’ with the addition of a holding solution. Physiological effects were different based on cultivar, as observed with Charlotte and Freedom flowers that opened further and had less petal browning than Classy flowers. ‘Freedom’ had the greatest pigment loss, but this effect decreased with increasing EC. Further correlational analysis showed that in water-only solutions, initial and final EC accounted for 44% and 41% of the variation in vase life data, respectively, whereas initial pH accounted for 24% of variation. However, the presence of carbohydrates and biocides from the holding solution was found to have a greater effect on overall vase life compared with water pH or EC. Finally, in Expts. 5 and 6, cut ‘Freedom’ stems were subjected to DW solutions containing 0.1, 1, 10, or 100 mg·L–1 boron, copper, iron, potassium, magnesium, manganese, or zinc. None of these solutions increased vase life. Conversely, 10 or 100 mg·L–1 boron and 100 mg·L–1 copper solutions reduced vase life. Finally, the addition of NaCl to a maximum of 0.83 dS·m–1 increased the vase life in all solutions. These analyses highlight the importance of water quality and its elemental constituents on the vase life of cut rose stems and that the use of a holding solution can overcome the negative effects of high EC water.

Open Access

Sixty clones (four clones from each of 15 provenances) were micropropagated and planted in replicated plots in lowland and upland sites in Carbondale, IL in 1991. Data were collected on tree growth, including basal caliper, height, branching, crown volume, dates of bud break, bud set, and leaf fall. There were significant and strong positive genotypic and phenotypic correlations between tree height and basal caliper throughout the three years of growth. During 1993, bud break was not significantly correlated with any growth parameters. After three years in the field, tree height was significantly negatively correlated with the amount of callus that had formed after one month during the in vitro micropropagation phase. However, all shoots that formed in vitro were of axillary origin.

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Clonal micropropagation studies with silver maple (Acer saccharinum L.) included experiments with various shoot. explant types, cytokinins, and stock plant maturation levels. These trials led to successful explant establishment, axillary shoot proliferation, rooting of microshoots, and establishment of plantlets in the greenhouse. Overall, the best cytokinin tested was the phenylurea derivative TDZ. Shoot proliferation on juvenile explants was poor with kinetin, 2iP, and BA. Only zeatin at 10 μm was comparable to TDZ. TDZ at 10 nm was optimal for both juvenile and adult nodal explants. Juvenile explants that were held in vitro for 4 months commonly had at least 60 axillary shoots that could be subculture or excised for rooting. Microshoots rooted within 2 weeks. Following rooting, silver maple plantlets could be transplanted into a growing medium and placed directly onto a greenhouse bench. Studies were also conducted on rooting stem cuttings (macropropagation). Single nodes from juvenile plants rooted under intermittent mist, regardless of auxin application; however, shoot-tip cuttings from adult trees rooted best when auxin in ethanol solution was applied. Chemical names used: N- phenyl- N' -1,2,3 -thiadiazol-5-ylurea (thidiazuron, TDZ), N- (2-furanylmethyl)-1H-purin-6-amine (kinetin), isopentenyladenine (2iP), benzyladenine (BA), (E)-2-methyl-4-(1H-purin-6-ylamino)-2-buten-1-ol (zeatin).

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During 1987, we selected the six fastest-growing seedlings or clones from each of 15 provenances that represented the natural distribution range of silver maple (Acer saccharinum L.). Shoots from all 90 trees were cut into nodal segments, rooted as cuttings, and maintained as clonal stock plants in the greenhouse. Rooting was generally excellent and more than half of the clones rooted ≥90%. At the same time, explants were obtained from these field-grown trees and many were established in vitro as aseptic cultures by first pretreating with benomyl and rifampicin. Single-node explants from the greenhouse-grown clonal stock plants were also established and multiplied in vitro. There was a significant effect of clone within provenance on all in vitro growth characteristics. All clones proliferated axillary shoots, but not all at the same rates. Although statistically significant, low correlation coefficients indicated that micropropagation results were not good predictors of nursery performance of the populations from which the clones were selected, nor of the climatic conditions at the site of origin of the trees. The micropropagation system reported herein, therefore, should be applicable to a wide variety of silver maple genotypes. Chemical name used: methyl [1-[butylamino)carbonyl]-1H-benzimidazol-2-yl]carbamate(benomyl).

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Growing southern highbush blueberries in milled pine bark beds ≈15 cm deep has become a popular fruit production system in Georgia and Florida. One of the primary limiting economic factors in this system is the cost of the growing media, which can exceed $10,000 U.S. per ha. In an effort to discover low-cost substitutes for milled pine bark, available waste or low-cost organic materials were screened for there suitability as growing media for southern highbush blueberries. Cotton gin waste, pecan shells, hardwood “flume” dirt, milled composted urban yard waste, composted urban tree trimmings, pine telephone pole peelings, and pine fence post peelings were evaluated. Only pine derived materials had a suitable pH (<5.3). Fresh pine telephone pole peelings (≈25% bark to 75% elongated fibers of cambial wood) and pine fence post peelings (≈75% bark to 25% elongated fibers of cambial wood) were evaluated for several seasons in containers and field trials. The growth index of blueberries in these materials was slightly less or equal to milled pine bark. Surprisingly, nitrogen deficiency was slight or not a problem. The results indicate that pine pole and post peelings may offer an excellent, low-cost substitute for milled pine bark for blueberry production.

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We investigated the response 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 regimes, 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 morphological abnormalities in floral structures were evident in 41% and 98% of the MT- and HT-grown plants, respectively. The viability (stainability) of pollen from LT- and MT-grown Prime-Jan™ flowers exceeded 70%; that of Prime-Jim™ pollen was significantly reduced (<40%) by the MT regime. Pollen in-vitro germinability was negatively influenced by temperature but was unaffected by cultivar. LT-grown pollen held at 23.9 °C retained 63% of its original germinability over a 32-hour period; the germinability of LT-grown pollen held at 35.0 °C was decreased by 97% from its original level after 16 hours. Virtually all flowers cultured under HT conditions were male-sterile, exhibiting structural and/or sporogenous class abnormalities including petaloidy, malformation of tapetal cells, and microspores or failure of dehiscence. The duration of stigma receptivity, pistil density, and drupelet set were also negatively influenced by increasing 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. Herein, flowering and fruiting parameters and presumably the yield potential of Prime-Jan™ and Prime-Jim™ were adversely affected by increased temperature. However, assessment of their adaptative response to heat stress under field conditions awaits experimentation.

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Since 1997, populations of Japanese beetle have settled into some of the major urban areas of Arkansas, especially Little Rock and Northwest Arkansas, due to transported turf and nursery material. Experimental trials at the University of Arkansas Agricultural Research and Extension Center, Fayetteville have sustained significant damage due to the increasing Japanese beetle population. Plantings of blackberries and blueberries were rated for feeding damage. Significant differences were observed among genotypes of both crops. Mean damage ratings varied from 0.6 to 4.0 for the blackberries and 1.2 to 3.5 for the blueberries. As evidenced by the mean damage ratings, some resistance or tolerance is present within these populations and may be exploited for improvement.

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