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  • Author or Editor: R. Bourne x
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The southern highbush blueberry (Vaccinium spp.) `Blueridge', `Cape Fear', `Cooper', `Georgiagem', `Gulf Coast', and `O'Neal'; the rabbiteye (V. ashei Reade) `Climax'; and the highbush (V. corymbosum L.) `Bluecrop' were evaluated for ovary damage following exposure of flower buds to 0 to 30C in a programmable freezer in Dec. 1993 and Jan. and Feb. 1994. The plants sampled were growing at the Univ. of Arkansas Fruit Substation, Clarksville. Damage was based on oxidative browning of the ovaries following an incubation period after removal from the freezer. With the exception of `Climax', a minimum temperature of –15C was required before bud damage was sufficient enough to differentiate among cultivars. All southern highbush cultivars and `Bluecrop' had superior hardiness compared to `Climax' at –15C in December, –20C in January, and –15C in February. Maximum hardiness of all cultivars was found in January. The hardier southern highbush cultivars were `Cape Fear' and `Blue Ridge'. Less hardy cultivars were `Gulf Coast, `Cooper', `Georgiagem', and `O'Neal', although the date of sampling affected the ranking of these clones for hardiness, especially for the February sample date. `Bluecrop' was not consistently hardier than the hardier southern highbush cultivars, except at the February sample date.

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The growth and productivity of `Redhaven'/Lovell peach during the first 3 years in a replant site was evaluated after planting in one of five preplant treatments. Treatments (trt) were 1) nontreated control (CK), 2) killed fescue (F), 3) soybean rotation (L), 4) summer solarization (SOL), and 5) methyl bromide fumigation (FUM). An orchard was removed from the experimental site in Spring 1991 before establishments of treatments. In June 1991, a tall fescue (K-31), soybeans, or mustard, and cabbage were sown in trt plots 2, 3, and 4, respectively. In July, trt 4 was covered with clear, 4-mil plastic sheeting for 90 days. In October, trt 5 was fumigated with methyl bromide under a 4-mil plastic sheet. Trees were planted in Spring 1992. Soil characteristics, weed populations, and tree growth and productivity were measured in the first three seasons after planting. FUM significantly reduced weed density into the third season. SOL plots had the highest weed density in years 2 and 3. TCSA, yield, and yield efficiency of FUM trees were significantly larger than CK. Trees in F or SOL had significantly lower yields.

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`Redhaven' trees on 10 rootstocks planted in 1984 were annually evaluated for growth and cropping as part of the NC-140 national cooperative rootstock troial. All trees on Citation have died, 60 % of trees on GF-43 have died and only a single tree of Lovell, Halford, and GF-677 have died. Trees on Damas GF-1869 and GF-655.2 had significantly more root suckers than other trees. Redhaven own-root, Halford and GF-677 were largest in height, spread, canopy volume or TCSA while the smallest trees were GF-43, Damas, and GF-655.2. Damas, GF-43 and GF-655.2 bloomed 3-4 days before trees on Lovell. Fruit on Redhaven own-root matured 4 days before fruit on Lovell while fruit on Halford, GF-677 and GF-43 ripened 2 days later than Lovell. Trees on Halford had the highest annual yield and accumulated yield while GF-655.2, Damas and GF-43 had the lowest yields. Redhaven own-root and Halford had the highest yield efficiencies (kg/cm2TCSA). Trees on Lovell consistently produced the largest individual fruit size.

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Summer pruning effects on processing peach on fruit quality, light penetration and interception, and % defects was studied in 2 trials. In study A, pillar-trained trees were pruned with the following treatments: a control, summer pruning at stage II fruit growth, summer pruning post-harvest or, pruning twice (all trees dormant pruned). In the first year, pruning prior to harvest significantly increased blush and flesh firmness but reduced soluble solids content (SSC). In the second year, summer pruning reduced yield per tree and fruit drop (weight and % of total) but did not affect fruit size, blush, or SSC. After 2 years, trees pruned post-harvest or twice had significantly smaller height, spread and trunk diameter.1 In study B, 2 cultivars of central leader trained trees were pruned at stage II fruit growth in the following treatments: a control, canopy thinning, and hedging. Thinning pruning improved light penetration and hedging reduced light interception. Thinning pruning reduced % of fungal rotted fruit but did not affect fruit quality.

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The effects of supplemental Ca on salinity tolerance were tested using a Brassica rapa L. landrace, `Sani', which is salt-sensitive. Plants were grown in a continuous aerated hydroponic system with 0.25-strength Hoagland solutions containing 125 mM NaCl plus 0, 2.5, 5.0 or 10 mM CaCl 2. The effects of Ca treatment were significant in reducing Na accumulation in roots, Na+ transport from roots to shoots and in enhancing K and Ca accumulation and transport. The Ca addition also enhanced the selectivities of both K and Ca over Na of accumulation at roots and of transport to shoots. However, supplemental Ca did not alleviate the growth reduction caused by the NaCl salinity. These results suggest that the growth inhibition of salt-treated B. rapa `Sani' is mainly caused by factors other than Na, K, and Ca contents in plants.

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Ethrel sprays were applied at 50 or 100 ppm at approximately 40%, 70% leaf fall (10/16/89 or 10/24/89, respectively) or at both times on `Redhaven' and `Allgold' peaches. Bud hardiness was determined biweekly by differential thermal analysis (DTA). Stage and percentage of bloom open during the bloom period were subjectively estimated.

Spraying trees with 100ppm Ethrel at 50% leaf fall significantly increased bud hardiness at mid-winter compared to other treatments. After a mid-winter freeze (-21.7 C on 12/21/89), there was no significant difference between % bud survival of any treatments. But, trees treated with 50 or 100ppm Ethrel had 10-20% better bud survival than other treatments. Buds of the 2 cultivars had statistically similar hardiness although DTA analysis indicated that Redhaven had a .5-.8 C lower freezing point than Allgold in mid winter. This trend was reversed close to bloom with Allgold having .7 C lower freezing point than Redhaven. The time of full bloom was significantly delayed by treating trees with 100ppm at 40% leaf fall or 50ppm at both 40 and 70% leaf fall the previous autumn.

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