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  • Author or Editor: Curt Rom x
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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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As funding directed toward research has diminished, it has become vital seek other avenues of support to maintain long term field projects. To meet this need, the University of Arkansas Horticulture Department began the Friends of Fruit (FOF) program during 2004 engaging volunteers in conducting tree fruit field research. Volunteers were graduates of the Master Gardener program and executed tasks including data collection and plot maintenance. Objectives of this study were to evaluate the experiences and benefits to the volunteers and horticulture department, and to assess the success of the FOF program in providing assistance and support to research. All volunteers and facilitators were interviewed. Interview questions were designed to understand the motivation and level of volunteer activity, determine if training and supervision was adequate, and determine if ample recognition occurred. Volunteers sought experience and knowledge with fruit crops. Costs to volunteers included time and travel, conversely benefits included knowledge, experience and fellowship. Volunteers planned to repeat the program and were pleased with the recognition they received. Facilitators noted that volunteers had basic horticultural knowledge and the desire to learn. The program did call for improved task management and increased planning time by facilitators. The program succeeded in benefiting volunteers and horticultural research. The FOF volunteers contributed to fruit research by harvesting ≈4,000 kg of fruit samples and providing >200 hours of time.

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Apple cultivar development is an important program necessary to sustain the existing fruit industry and stimulate new production systems for Arkansas and the region. The cultivar development program has two parts. First, currently available cultivars are tested with multiple trees for multiple years. Second, about 150 advanced selections from the Arkansas apple breeding program are evaluated in trials with multiple trees (2nd test) and in replicated trials (3rd test). The goal of both programs is to identify cultivars that have potential in the local production systems and for Arkansas' markets, and to identify those cultivars which are not adapted to the region. All cultivars and advanced selections are evaluated for ∂35 qualitative and quantitative characteristics, including time of bloom, time of harvest, length of harvest season, fruit aesthetic and internal quality, environmental adaptability especially to heat and high light, and insect and disease susceptibility. Primary diseases for which cultivars and selections are screened include fireblight, cedar apple rust, powdery mildew, black rot, white rot and bitter rot. Primary insect pests include mites, codling moth, plum curculio and Japanese beetle. Cultivars are evaluated in the field, under standard management conditions for five to seven years of production before summary evaluation. The program has identified cultivars including traditional cultivars, new cultivars, and heritage cultivars adaptable to the local and regional climates and suitable for those markets.

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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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Abstract

Current season shoots of 5-year-old ‘Redhaven’ peach trees were pruned in half on 1 July, 1 Aug., or both dates (50, 80 days after growth shoot initiation). Pruning reduced current season shoot length compared to unpruned shoots, but only 1 July pruning reduced current season shoot diameter, and increased lateral shoot growth. All pruning treatments reduced flower bud number proportional to shoot length removed; however, 1 Aug. pruning increased flower bud density per node. The previous summer season pruning did not influence the amount of winter injury on 1-year-old shoots after exposure to severe winter temperatures (-27.8°C). Summer pruning did not influence number of new shoots formed the following spring.

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Abstract

The net photosynthesis (Pn) rate of intact spur leaves of greenhouse-grown ‘Golden Delicious’ apple trees were similar, regardless of the fruiting condition of the spur. Similarly, the transpiration (Tr) rate of spur leaves was independent of the spur's fruiting condition. Therefore, Pn and Tr were not correlated to the number of flowers or fruit per spur, but Pn was significantly correlated to Tr. Rates of Pn and Tr were highest during the period of full bloom until shortly after bloom. Sorbitol, soluble reducing sugars, starch fractions, and total carbohydrates of spur leaves were unaffected by the presence or absence of fruit on the spur. Fruiting did not affect the number, area, or size of spur leaves. Spur leaf area and Pn could be limiting to early fruit development.

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Abstract

Young peach trees 1) trained to a single shoot or 2) allowed to branch, were pruned by removing 50% of current growth at either or both of 2 summer dates. Another group of trees had 0%, 25%, 50%, and 75% shoot growth removed by pruning in midseason. Net photosynthesis (Pn) and transpiration (Tr) were increased within 3 days after pruning at either date. Plants pruned twice at 30-day intervals had a 2nd cycle of increased Pn and Tr, with rates returning to levels of unpruned controls within 24 days. Distribution of water soluble carbohydrates in various plant tissues was not altered by pruning. Pruning at 60 days reduced root starch, whereas pruning again at 90 days increased total root carbohydrate content. Pruning early in the season increased lateral shoot formation, and terminal bud formation was delayed by pruning. Plant dry weight was reduced by all pruning treatments, with delayed pruning and increasing pruning severity resulting in greatest reductions. Distribution of dry weight was not altered substantially by pruning, and a balance of growth was maintained between different plant parts.

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Abstract

Leaves of spurs and/or shoots of small fruiting ‘Starkrimson Delicious’ apple trees were exposed to light or shade treatments from 60 days after petal fall until fruit maturity. Shading spurs reduced spur leaf photosynthesis (Pn) and transpiration (Tr), but shading shoots had no effect on spur leaf Pn. There was no difference between fruiting and nonfruiting spur Pn and Tr. Shading shoots reduced fruit growth and delayed maturity, but shading spurs had no effect on either. Fruiting reduced—but did not eliminate—spur flowering the following year. Light conditions late in the season had no effect on flowering or spur leaf development the following spring.

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Virulence of morphologically diverse isolates of Glomerella cingulata (anamorph: Colletotrichum gloeosporioides) and Collectotrichum sp. was examined by inoculating apple fruit. Three morphologically distinct fungal pathogens were examined on Red Delicious, Golden Delicious, or Idared. Fruit were inoculated by either placing a 100 ul spore suspension (106 spores/ml) into wounds or spraying the inoculum onto wounded fruit. All fruit were incubated at 25C on 100% RH. Free moisture was maintained on spray inoculated fruit. Virulence was quantified by measuring both lesion diameter and depth every 2-5 days for 2-4 weeks after inoculation. Overall, all of the teleomorphic isolates (G. cingulata) were significantly (p=.05) more virulent than the nonchromogenic or chromogenic isolates on fruit of all three cultivars. Genetically and morphologically diverse isolates of the bitter rot pathogen(s) are being selected and used to evaluate cultivar resistance to fruit rot.

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The volatile aromas from the fruits of `Naganofuji No.2' apple (Malus domestica Mill.) were determined by gas chromatography (GC) and combined GC-mass spectrometry (GC-MS) after different temperature conditions. The fruits from CA storage were sealed in glass and the volatiles in the headspace were determined. Eleven compounds of four chemical classes from active carbon absorbed samples were measured and three of them—tormic acid pentyl ester, butanoic acid-1-methyl ethylester and 4-hydroxy-3-methyl-2-butanone, were identified at 20 °C, but not at °C. Under 20 °C condition, the contents of three volatiles increased from 1 hour and reached to their peaks at the 4th to 7th hour. The content of ethylene reached its peak at 4 hours and changed synchronically with the other volatiles during the experiment. The content of ethylene was significantly positively correlated with the contents of volatile aromas (r = 0.96-0.98, P ≤ 0.01). Under °C condition, the content of ethylene was significant lower than that of at 20°C and there was no ethylene peak produced during experiment. When the fruits were treated with ethephon (0.1 mg·L-1) at 5°C, the content of ethylene increased greatly. The highest level of ethylene was found at 4 to 7 hours and the peaks of volatiles also appeared at 7 hours or 10 hours after the treatment. It was suggested that the production of ethylene in fruits could be thought as an indicator of some volatile aromas.

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