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When sweetpotato chlorotic stunt crinivirus (SPCSV) and sweetpotato feathery mottle potyvirus (SPFMV) infect sweetpotato [Ipomoea batatas (L.) Lam.], they interact synergistically and cause sweetpotato virus disease (SPVD), a major constraint to food productivity in east Africa. The genetic basis of resistance to these diseases was investigated in 15 sweetpotato diallel families (1352 genotypes) in Uganda, and in two families of the same diallel at the International Potato Center (CIP), Lima, Peru. Graft inoculation with SPCSV and SPFMV resulted in severe SPVD symptoms in all the families in Uganda. The distribution of SPVD scores was skewed toward highly susceptible categories (SPVD scores 4 and 5), eliminating almost all the resistant genotypes (scores 1 and 2). Likewise, when two promising diallel families (`Tanzania' × `Bikilamaliya' and `Tanzania' × `Wagabolige') were graft inoculated with SPCSV and SPFMV at CIP, severe SPVD was observed in most of the progenies. Individual inoculation of these two families with SPCSV or SPFMV, and Mendelian segregation analysis for resistant vs. susceptible categories led us to hypothesize that resistance to SPCSV and SPFMV was conditioned by two separate recessive genes inherited in a hexasomic or tetradisomic manner. Subsequent molecular marker studies yielded two genetic markers associated with resistance to SPCSV and SPFMV. The AFLP and RAPD markers linked to SPCSV and SPFMV resistance explained 70% and 72% of the variation in resistance, respectively. We propose naming these genes as spcsv1 and spfmv1. Our results also suggest that, in the presence of both of these viruses, additional genes mediate oligogenic or multigenic horizontal (quantitative) effects in the progenies studied for resistance to SPVD.

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Clingstone peach [Prunus persica (L.) Batsch cv. Allgold] trees were fertilized once with 45 or 90 kg N/ha at budbreak or twice with 22.5 or 45 kg N/ha at budbreak and after harvest. A nonfertilized control was included. Fruits from all treatments were made into puree, and objective and subjective qualities were evaluated. Puree from the N treatments and the control did not show significant differences in Color Difference Meter (CDM) `L' and hue angle, pH, titratable acidity (TA), soluble solids concentration (SSC), SSC: TA ratio, viscosity, ascorbic acid, Ca, K, phenolic and nitrates concentration. Puree from the control and 22.5 kg N/ha applied twice had significantly lower CDM `a', `b', and chroma values than from the other treatments. The split applications of N significantly reduced levels of Ca and ascorbic acid. N rate and number of applications interacted for `a' and K. When N was applied twice at 22.5 kg·ha-1, `a' and K decreased, but this response was absent when N was applied twice at 45 kg·ha-1. Puree from the nonfertilized control was rated lower by panelists for sensory quality than that from the fertilized trees. Peach puree from trees fertilized once with 45 kg N/ha at budbreak had the best overall sensory quality.

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Light is important in the production of phenolic compounds because key enzymes in phenolic biosynthesis are induced by light, and because products of photosynthesis are used in the synthesis of phenolic compounds. It is known that light intensity decreases with increasing depth in apple tree canopies. The objective of this experiment was to determine how leaf position on a limb affects the total foliar phenolic content. Leaves from `Stark Spur Supreme Red Delicious' on C6 and M26 rootstocks were collected on 28 July and 2 Aug. 1996. Each tree was divided into two sides, east and west. Each side was divided into 3 areas; exterior, middle, and interior. From each area, leaves were collected and PAR, SLW, assimilation, total N, and total phenolics were measured. Leaf position on a limb was a significant parameter for all of the measured variables. PAR, SLW, assimilation, total N, and total phenolics were highest in leaves at the exterior of the canopy. The total foliar phenolic content of the exterior canopy leaves was 20% higher than that found in the interior canopy leaves. There was a significant correlation between SLW and total phenolic content/cm2(r 2 = 0.77; P < 0.05). Assimilation may be a limiting factor in phenolics production in apple trees because of the correlation between assimilation and total phenolic content/cm2 (r2=0.56, P < 0.05).

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A multidisciplinary effort has been initiated between the University of Arkansas and the National Center for Appropriate Technology to identify production barriers, research and outreach needs, and market opportunities for sustainable and organic fruit in the Southern region. The goals of the project are to identify barriers of the organic system through focus group meetings with producers, processors and marketers, and to develop regional research and outreach projects to overcome these obstacles. Market development, organic fertilizer knowledge and organic pest management have been identified as areas that need research and outreach activities. Long-term outcomes are expected to increase sustainable and organic fruit production, provide opportunities for growers and consumers, and encourage local economic development in the Southern region.

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The foliar phenolic content of 21 apple cultivars was evaluated. Ten leaves were sampled randomly from three positions on current-season terminal shoots. Shoots were divided as tip, middle, and basal positions. The phenolic content was determined by spectrophotometric method (390 nm) using diphenylboric acid 2-aminoethyl ester as the reagent and caffeic acid as standard. Cultivars varied significantly in phenolic content. `Stark Ultra Red' had the highest amount, and `Liberty' had the lowest amount. Significant variations in the phenolic content due to leaf position were observed. Phenolic content was highest in leaves from the tip position, and it decreased toward the basal portion of the shoot. Factors affecting the phenolic content of apple cultivars will be investigated to determine apple × insect interactions.

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Abstract

In the Cultivar and Germplasm Release article “‘Allgold’ and ‘Goldilocks’ Peaches” by J.N. Moore, Roy C. Rom, Stanley A. Brown, and William A. Sistrunk [HortScience 19(6):891–892, 1984], the captions of Figures 2 and 3 were reversed. The selection test numbers given in the text for these cultivars (‘Allgold’ = A-142; ‘Goldilocks’ = A-15) are correct.

Open Access

Abstract

‘Allgold’ and ‘Goldilocks’ are 2 new cultivars of clingstone peaches [Prunus persica (L.) Batsch.] with nonmelting flesh texture suitable for processing. Both are earlier ripening than ‘Babygold 5’ and possess good processing qualities. ‘Allgold’ is notable for its high tolerance to bacterial spot.

Open Access

Three ornamental peaches and one ornamental nectarine were released in 1992 from the Arkansas peach breeding program. `Tom Thumb' is a red-leaf dwarf peach with attractive foliage that is retained throughout summer. `Leprechaun' is a green-leaf dwarf nectarine with small but attractive, freestone fruits. `Crimson Cascade' and `Pink Cascade' are red-leaf peaches with trees of standard size that exhibit a weeping growth habit. `Crimson Cascade' produces double flowers that are dark red while `Pink Cascade' double flowers are pink. The attractive plants of these cultivars should be of value in home landscapes.

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The highly weathered, mineral, and often eroded and acidic soils of the Ozark Highlands region of northwest Arkansas generally have low soil organic matter (SOM) concentrations as a result of rapid organic matter turnover rates in the warm, moist climate. Orchard management practices that can improve SOM may also improve other soil quality-related variables for sustained production, which is an explicit goal for the National Organic Program (NOP). Therefore, beginning in Mar. 2006 and continuing for seven seasons, annual applications of municipal green compost, shredded office paper, wood chips, and mow-blow grass mulch groundcover management systems (GMS) in combination with composted poultry litter, commercial organic fertilizer, or a non-fertilized control as a nutrient source were implemented to evaluate their ability to alter near-surface soil quality in a newly established, organically managed apple orchard in the Ozark Highlands region of northwest Arkansas. The SOM concentration in the top 10 cm averaged 1.5% across all treatments at orchard establishment in 2006, but by 2012, SOM concentration had increased in all GMS and more than doubled to 5.6% under green compost. Similarly, soil bulk density in the top 6 cm, which averaged 1.34 g·cm−3 among treatment combinations in 2006, decreased in all GMS by 2012. Either green compost or shredded paper had the largest concentration of total water-stable aggregates across all aggregate size classes in the top 7.5 cm, whereas no differences among GMS were observed in the 7.5- to 15-cm soil depth. Green compost applied alone or in combination with commercial fertilizer had the largest estimated plant-available water (17.9% v/v) among all treatment combinations. Many soil quality-related variables measured in the various organic GMS had numerically greater values compared with an adjacent conventionally managed orchard on the same soils. Implementation of these GMS appears to provide apple producers in the Ozark Highlands and similar regions a tangible means of meeting NOP requirements for improving soil quality concurrent with production of certified organic crops. The findings also have implications for conventionally managed orchards, which have maintaining or improving soil quality as a management goal.

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