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  • Journal of the American Society for Horticultural Science x
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The genus Pyrus (pears) consists of important fruit trees, and ≈20 primary species are generally accepted by most taxonomists ( Challice and Westwood, 1973 ). Based on their geographic distribution, Pyrus species are divided into oriental and

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imperative for better management ( Atangana et al., 2010 ; Boccacci et al., 2013 ). Pyrus betulaefolia , as the most popular pear rootstock in China and other east Asian countries for its good adaptability to versatile environments ( Okubo and Sakuratani

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Pear ( Pyrus L.) is an important commercial fruit crop widely cultivated around the world. Since the 1980s, with the introduction and breeding of improved cultivars, the planting area of early-maturing chinese sand pear cultivars has gradually

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Abstract

Respiration of flower-buds of Pyrus communis L., a late blooming species, and P. calleryana, an early blooming species, was investigated throughout the winter. Respiration of P. calleryana Decne at 5°C was twice as high as that of P. communis, whereas the respiration rates were similar at 25°. A large portion (60–70%) of the respiration at 5° was cyanide resistant in P. calleryana and much less in P. communis. The combination of inhibitors, cyanide (KCN) and salicylhydroxamic acid (SHAM), still only partially inhibited respiration. The residual respiration was much higher for P. calleryana than for P. communis. The nature of the residual respiration is not known.

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Edible european pears (Pyrus communis L. ssp. communis) are derived from wild relatives native to the Caucasus Mountain region and eastern Europe. Microsatellite markers (13 loci) were used to determine the relationships among 145 wild and cultivated individuals of P. communis maintained in the National Plant Germplasm System (NPGS). A Bayesian clustering method grouped the individual pear genotypes into 12 clusters. Pyrus communis ssp. caucasica (Fed.) Browicz, native to the Caucasus Mountains of Russia, Crimea, and Armenia, can be genetically differentiated from P. communis ssp. pyraster L. native to eastern European countries. The domesticated pears cluster closely together and are most closely related to a group of genotypes that are intermediate to the P. communis ssp. pyraster and the P. communis ssp. caucasica groups. Based on the high number of unique alleles and heterozygosity in each of the 12 clusters, we conclude that genetic diversity of wild P. communis is not fully represented at the NPGS. Additional diversity may be present in seed accessions stored in the NPGS and more pear diversity could be captured through supplementary collection trips to eastern Europe, the Caucasus Mountains, and the surrounding countries.

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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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Abstract

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 8.8 µm BA. Media were solidified with either Bacto-agar, Phytagar, or TC agar at concentrations varying from 0.3% to 1.2%. Explant nutrient levels were influenced both by agar brand and concentration. The trends in nutrient composition, although not identical, tended to be similar for both genera. Increasing agar concentrations resulted in increased P, Fe, Zn, and Al in the explant and reduced Ca, Mg, and Mn levels. Although striking variations in many elements occur both in agar brands and in explants cultured on media containing similar concentrations of different agar brands, variations in shoot proliferation and growth of explants cannot be explained on the basis of variations in individual elements. From the nutritional standpoint, the alterations in the elemental composition of the basal medium by the addition of specific agars best explain variations induced by different agar brands. Chemical names used: N-(phenylmethyl)-1H-purin-6-amine (BA).

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Abstract

Deep supercooling was found in the stem tissues of all the Pyrus species studied. There was more than 1 low temperature exotherm resulting from the freezing of supercooled water in stem tissue, and these exotherms were associated with the tissue injury. The supercooled water in the stems of P. nivalis Jacq., P. cordata (Desv.) Schneider and P. elaeagrifolia Pall, was found in both xylem and bark tissues. The supercooling characteristics of vegetative and flower buds are also described. The hardiest and least hardy species found were P. caucasica Fed. and P. pashia D. Don., respectively.

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A total of 118 Pyrus sp. (pear) and cultivars native mainly to east Asia were subjected to randomly amplified polymorphic DNA (RAPD) analysis to evaluate genetic variation and relationships among the accessions. Two hundred fifty RAPD markers were scored from 20 decamer primers. RAPD markers specific to species were identified. Clustering analysis revealed two divisions: one comprising cultivars of P. communis L., and the other including all accessions of Pyrus native to east Asia. The grouping of the species and cultivars by RAPD data largely agrees with morphological pear taxonomy. However, some noted incongruence existed between two classification methods. Pyrus calleryana Dcne. clustered together with P. koehnei Schneid., P. fauriei Schneid. and P. dimorphophylla Makino. Pyrus betulaefolia Bge. clustered with P. ×hopeiensis Yu and P. ×phaeocarpa Rehd. A noncultivated clone of P. aromatica Kikuchi et Nakai grouped with P. aromatica cultivars. Pyrus hondoensis Nakai et Kikuchi and cultivars of P. ussuriensis Max. formed a single group. Some accessions from Korea (named Korean pear) had species-specific RAPD markers and comprised an independent group. Most of the Chinese white pears clustered together with most of the Chinese sand pears. Based on the present results, the new nomenclature P. pyrifolia var. sinensis (Lindley) Teng et Tanabe for Chinese white pear was suggested. Most accessions of Japanese pears fell into one main group, whereas pear cultivars from Kochi Prefecture of Japan subclustered with some Chinese sand pears and one accession from Korea. Our results infer that some local Japanese pear cultivar populations may have been derived from cultivars native to Kochi Prefecture in Shikoku region, and that the latter may have been introduced from ancient China and/or Korea.

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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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