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One year old Asian pear scion cultivars were grafted onto Pyrus calleryana rootstock utilizing two grafting methods (whip grafting and splice side grafting). Percentage survival of grafted scions was 78 and 96 via the splice side graft and the whip graft, respectfully. Shoot length and caliper 80 days after grafting did not vary between cultivars. `Yakumo' and 'Chojuro' produced a greater number of branches as compared to the remaining cultivars. `Yakumo', `Chojuro', `Seuri' and `Hosui' produced the least amount of shoot growth. Branching angle was greatest for `Seigyoku', `Chojuro' and `Yakumo' with 60, 70, and 55 degrees, respectfully. As indicated by leaf area, `Seuri' and `Hosui' produced large leaves and `Yakumo' and `Chojuro' produced small leaves.

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Some factors that affect the in vitro conservation of wild pear (Pyrus syrica) microshoot cultures were studied. Sorbitol and mannitol at 0.2 to 4.0 M reduced growth significantly and extended the subculture intervals to 5 months when cultures where kept at 15°C. Increasing sucrose to 12% in the medium was not highly effective and the subculture intervals did not exceed 3.0 months. After 2 years of maintaining cultures on slow-growth medium, cultures grew slowly when transferred to fresh control medium. Shoots started to proliferate after three subcultures (6.0 weeks apart) on medium containing 1.0 mg/L BA and 0.1 mg/L NAA. New microshoots were rooted on medium containing 2.0 mg/L IBA and rooted microshoots gave 90% survival when acclimatized ex vitro under intermittent mist.

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Abstract

In vitro shoot proliferation of Pyrus calleryana Decne. ‘Bradford’ was investigated on medium containing BA at 0, 1, 2, 10, or 20 µM in factorial combination with IBA at 0, 0.5, or 5.0 µM. Shoot proliferation increased as BA level increased but the magnitude was reduced as IBA level increased. Greatest shoot proliferation was on medium excluding IBA. Shoots were longest on medium containing 1 or 2 µM BA. Medium with 2 µM BA and 0.5 µM IBA was optimum for shoot proliferation and length. Shoot fasciation increased as BA level increased, but addition of IBA to BA reduced fasciation. Rooting of microcuttings with IBA and sucrose was unsuccessful. Chemical names used: N-(phenylmethyl)-1H purin-6-amino (BA); 1H-indole-3-butanoic acid (IBA).

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Pyrus (Rosaceae) contains ≈22 species of trees originating from Asia, northern Africa, and Europe that have been cultivated extensively as both fruit and landscape plants ( Challice, 1973 ). Pyrus calleryana was first introduced into cultivation

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differential expression of the cyclic nucleotide-gated channels gene family in pear ( Pyrus bretchneideri Rehd.) Genomics 105 39 52 10.1016/j.ygeno.2014.11.006 Colcombet, J. Hirt, H. 2008 Arabidopsis thaliana MAPKs: A complex signalling network involved in

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Edible European pears (Pyrus communis sp. communis L.) are thought to be derived from wild relatives native to the Caucasus Mountain region and eastern Europe. We collected genotype, phenotype, and geographic origin data for 145 P. communis individuals derived from seeds collected from wild relatives. These individuals are currently maintained in the USDA–ARS National Plant Germplasm System (NPGS) in Corvallis, Ore. Pear genotypes were obtained using 13 microsatellite markers. A Bayesian clustering method grouped the individual pear genotypes into 12 clusters. The subspecies of pears native to the Caucasus Mountains of Russia, Crimea, and Armenia could be genetically differentiated from the subspecies native to eastern European countries. Pears with large fruit clustered closely together and are most closely related to a group of genotypes that are intermediate to the other groups. Based on the high number of unique alleles and heterozygosity in each of the 12 clusters, we conclude that the genetic diversity of wild P. communis is not fully represented in the NPGS

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Shoot tips of ‘Almey’ crabapple [Malus baccata (L.) Borkh. × M. pumila var. niedzwetzkyana (Dieck) Schneid.] and ‘Seckel’ pear (Pyrus communis L.) were cultured on Murashige and Skoog (MS) medium containing 2 mg/liter 6-benzylamino purine (BA). The culture medium contained either TC agar or Bacto-agar at concentrations ranging from 0% to 1.2%. Optimum shoot proliferation in ‘Almey’ was obtained on media containing 0.3% of either agar. Increasing agar levels reduced shoot proliferation and shoot growth, but the reduction was especially severe with Bacto-agar. The differences in shoot proliferation between the 0.3% and 0.6% agar concentrations continued to be exhibited with Bacto-agar but not with TC agar when Mason jars, rather than 25 × 150-mm tubes, were the culture vessels. Shoot proliferation in ‘Seckel’ was best on medium containing 0.6% Bacto-agar; higher concentrations decreased shoot proliferation and shoot growth. TC agar did not influence fresh weight of ‘Seckel’ cultures, but increasing concentrations resulted in increased shoot proliferation.

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Abstract

Field and laboratory studies of host preference and resistance of Pyrus species and cultivars to the pear psylla, Psylla pyricola, were conducted in Southern Oregon from 1964–1968. Asian species were generally less attractive to oviposition than those from Asia Minor, North Africa or Europe. Attractiveness of P. pyrifolia and P. communis cultivars was higher than for P. ussuriensis.

Susceptibility of Pyrus was based on differences between total egg deposition and resulting nymphal populations. Using this nymph/egg ratio the results indicated that Asian material was more resistant than material from Asia Minor or Europe. The Asian species P. fauriei and P. calleryana exhibited both a high degree of unattractiveness to oviposition and resistance to nymphal development.

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Abstract

A natural complex hybrid, ‘Pitoma Slanopadja’, between native Pyrus amygdaliformis Vill. and cultivated P. communis L., probably ‘Beurre Giffard’, was discovered in 1954 in an orchard row fence near Cacak, Yugoslavia. Tree vigor, pubescent narrowly lanceolate leaves, large fruit buds, pronounced fruit calyx, large core, and numerous large grit cells are characteristic of P. amygdaliformis. The fruit size and ovate-pyriform shape, however, combined with a high sugar content, are very characteristic of the P. communis parent. In Yugoslavia, the tree appeared highly resistant to pear scab (Venturia pyrina Aderh.), leaf spot [Mycosphaerella sentina (Fekl.) Schroet.] and pear psylla (Psylla pyri L. and P. pyrisuga Foerst.).

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Eight cultivars and wild seedlings of pear (Pyrus spp.) from Eastern Europe were evaluated for resistance to feeding by early instar pear psylla [Cacopsylla pyricola (Foerster)] in a 24-hour assay. All were compared to a susceptible control, `Bartlett' (P. communis L.), and to a moderately resistant control, NY10352 (P. communis × P. ussuriensis Maxim. BC hybrid). Three P. communis cultivars, Bartjarka (PI 483391), Lucele (PI 483402), and Kajzerka (PI 506387), and a wild seedling (PI 506381) of undetermined species, exhibited a high degree of host resistance, measured as reduced frequency of feeding and increased either mortality or movement off of the plants.

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