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crops, but its mode of action as a bloom thinner is unknown. Among the many fungal diseases that require grower intervention in the mid-Atlantic, cedar apple rust ( G. juniperi - virginiana ) and quince rust ( G. clavipes ) are formidable barriers to

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Abstract

‘Freedom’ is a productive, large, red apple, Malus domestica Borkh. that is very resistant to apple scab [Venturia inaequalis (Cke) Wint.], moderately resistant to apple powdery mildew [Podosphaera leucotricha (E. & E.) Salm], resistant to cedar apple rust (Gymnosporangium juniperi-virginianae Schw.), and to fire blight [Erwinia amylovora (Burrill) Winslow et al.]. It has been grown for 23 years without any disease-controlling sprays, and no losses have occurred in New York State. This apple was tested under the number NY 58553-1.

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-point lesions, chlorotic lesions, necrotic lesions, nonsporulating, cupped or convoluted leaves. Seedlings that produced conidia and exhibited signs of sporulation were considered susceptible. Cedar apple rust susceptibility was determined based on the

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., 2006 ). Malus orientalis germplasm possesses traits that are of potential interest to breeding programs ( Aldwinckle et al., 2002 ). We previously identified 20 individuals that exhibited resistance to apple scab, fire blight, and cedar apple rust

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( Argyrotaenia velutinana ), oblique-banded leaf roller ( Choristoneura rosaceana ), and fruit-tree leaf roller ( Archips argyrospila ) injury, and evidence of cedar apple rust, powdery mildew, apple scab, sooty blotch/flyspeck, bitter rot, and black rot

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Abstract

‘Liberty,’ which was tested under the number NY55140-19 is a good quality red apple that can be grown without fungicidal sprays in New York State (3). It is highly resistant to Venturia inaequalis (Cke.) Wint., apple scab, and to Gymnosporangium juniperivirginianae (Schw.), cedar apple rust and resistant to Podosphaera leucotricha (E. & E) Salm, apple powdery mildew, and Erwinia amylovora (Burrill) Bergey et al, fire blight.

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Abstract

The polymorphism in nine enzyme systems in apple (Malus domestica Borkh.) was analyzed using horizontal starch gel electrophoresis. The systems studied included aspartate aminotransferase, diaphorase, glucosephosphate isomerase, isocitrate dehydrogenase, phosphoglucomutase, and triosephosphate isomerase. The products of at least 27 loci could be distinguished in these systems, 19 of which displayed polymorphism. Joint segregation analysis in populations derived from crosses between highly heterozygous cultivars revealed four multilocus linkage groups: Aat-c–Idh-1, Dia-2–Mdh-4, Gpi-c2-Aat–p, and (Dia-5, Pgm-p1)–(Mdh-2, Tpi-c2). Although several of the populations investigated had been prescreened for resistance to apple scab, cedar-apple rust, or fire blight, no correlation could be established between the inheritance of an allozyme and a resistant phenotype. The high frequency of duplicate loci encountered is in accordance with the postulated tetraploid nature of the genome.

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Malus sieversii, the main progenitor of domesticated apple, is native to areas in Central Asia. To better represent Malus wild germplasm in the USDA–ARS germplasm collections, maintained in Geneva, N.Y., a cooperative project was initiated with the Republic if Kazakhstan to collect and assess that country's wild populations of M. sieversii and to develop more secure in situ reserves to complement ex situ holdings in the United States and Kazakhstan. To date, four exploration trips to the region have included participants from the United States, Kazakhstan, Canada, New Zealand, and South Africa. Four Kazkh scientists have toured USDA–ARS sites, exchanged information, and collected germplasm in the United States greenhouse screens of 1600 have revealed potentially new sources of resistance to apple scab, cedar apple rust, and fire blight. An isozyme analysis of maternal half-sib families from four regions suggests the populations of M. sieversii collected represent a single panmictic population, with over 85% of total genetic variation due to differences among families. The most recent collections in 1995 were directed towards more ecologically diverse regions, including a site (Tarbagatai) at the most northern limit for M. sieversii equivalent to northern Minnesota in the United States. Some trees in this region produced fruit nearly 70 mm in diameter with excellent aroma, firmness, and color. This germplasm is being systematically characterized for horticultural traits, pest and disease resistance, and molecular markers.

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The apple cultivar Enterprise is a product of the Purdue–Rutgers–Illinois (PRI) disease-resistant apple breeding program. It has field immunity to apple scab, has a high level of resistance to cedar apple rust and fire blight, and is moderately resistant to apple powdery mildew. This resistance to these diseases makes the production of this cultivar desirable, especially on the popular fire blight-susceptible M.26 rootstock. Compared to many other scab-resistant cultivars, `Enterprise' has performed well in the mid-Atlantic area. However, this cultivar has been reported to be susceptible to low-Ca disorders when grown in New Jersey and Virginia. The mid-Atlantic area is notorious for the production of fruit with high levels of corking and bitter pit. This may be due to factors such as vigorous tree growth and low transpirational flow, which may be weather-related. Circumstantial evidence based on the production of clean `Enterprise' at Biglerville, Pa., where moderately high rates of CaCl2 have been applied in cover sprays, indicate that this disorder may be a Ca deficiency symptom. A replicated trial of many scab-resistant cultivars was established in 1990, 1991, and 1992. Due to the common incidence of low-Ca disorders, CaCl2 has been added to the cover spray program that is applied for insect control. Low-Ca disorders have never been seen in fruit produced at Biglerville, and the cover spray program applied 67 and 73 kg·ha–1 of CaCl2 (77% to 80% CaCl2, flake) in 1993 and 1994, respectively.

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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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