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T. van der Zwet, D. Stankovic, and B. Ristevski

Abstract

During the early 1900s, several plant exploration trips to the Orient were made to collect Pyrus species from Japan, China, Korea, and Manchuria to search for resistance to fire blight [Erwinia amylovora (Burr.) Winsl. et al.]. Following numerous inoculations in various tree tissues, Reimer (15) reported the four most important species, ranked in descending order of blight resistance, as follows: P. ussuriensis Maxim, P. calleryana Deche, P. betulaefolia Bunge, and P. pyrifolia (Burn.) f. Nak. Pyrus ussuriensis and P. pyrifolia were used in earlier breeding programs and are the parent species of many oriental cultivars. However, their textures and flavors have not been accepted by most Americans. P. calleryana also has been used in the USD A pear breeding program, and selections of the 3rd backcross generation appear useful only for resistance.

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Steven K. Whitesides and Robert A. Spotts

Conditions were established for inducing pear (Pyrus communis L.) blossom blast caused by Pseudomonas syringae (Ps) on detached shoots. Highest incidence of infection followed occurrence of a major exotherm in the presence of Ps suspended in water drops on blossom tissue. Eight pear cultivars were evaluated for susceptibility to blossom blast, with the red-fruited `Beurré d'Anjou' sports `Gebhart' and `Columbia' least susceptible and `Doyenné du Cornice', `Beurré d'Anjou', and `Beurré Bosc' most susceptible.

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Jonathan D. Mahoney and Mark H. Brand

. communis may provide a pathway for developing new fruits with desirable traits for both growers and consumers. Fruits of Pyrus and Aronia hybrids may be large and sweet, while still maintaining the high levels of health-promoting compounds present in

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Dennis Y. Yeo and Barbara M. Reed

Explants of three rootstock selections Pyrus calleryana Dcne `Oregon Pear Rootstock (OPR) 157', P. betulifolia Bunge `OPR 260', and P. communis L. `Old Home' × `Farmingdale 230' (`OH × F 230') were initiated from forced branches of field-grown trees. `OPR 260' and `OH × F 230' shoots cultured on Cheng medium with IBA proliferated better than those on NAA. NAA and IBA at concentrations >0.5 μm inhibited shoot multiplication. Overall, the best micropropagation medium for `OPR 260' and `OH × F 230' was Cheng medium with 8 μm BA and 0.5 μm IBA. Shoot multiplication of `OPR 157' was best on 8 μm BA and better on low NAA (0.5 μm) or no auxin than on IBA. `OH × F 230' rooted easily (>80%) with all IBA and NAA treatments. The best rooting treatment (42.9%) for `OPR 260' was 10 μm IBA in darkness for 1 week; for `OPR 157' (23.9%), it was a 15-second dip in 10 mm NAA. Only rooted plantlets survived 4 weeks of greenhouse acclimatization. Chemical names used: N6-benzyladenine (BA); indole-3-butyric acid (IBA); napthaleneacetic acid (NAA).

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Shuang Jiang, Haishan An, Xiaoqing Wang, Chunhui Shi, Jun Luo, and Yuanwen Teng

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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Yan-xin Duan, Ying Xu, Ran Wang, and Chun-hui Ma

‘Akizuki’ ( Pyrus pyrifolia Nakai), a Japanese pear, plays an important role in pear production in China because of its good quality characteristics such as large fruit, pretty shape, delicate pulp. and high soluble solid content. However, with the

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Yu Zong, Ping Sun, Xiaoyan Yue, Qingfeng Niu, and Yuanwen Teng

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

Open access

Richard L. Bell and L. Fredric Hough

Abstract

The genus Pyrus has been classified into at least 22 primary species. These can be grouped by geographical distribution and/or taxonomic relationships. The European group includes P. communis L., P. nivalis Jacq., and P. cordata, (Desv.) Schneid. The North African group contains P. longipes Coss. and Dur., P. gharbiana Trab., and P. mamorensis Trab. The west Asian group consists of P. syriaca Boiss., P. elaeagrifolia Pall., and P. amygdaliformis Vill., P. salicifolia Pall., P. glabra Boiss., P. regellii Rehd., (syn. P. bucharica and P. heterophylla Reg. & Schmalh). The medium to large fruited east Asian species are P. pyrifolia (Burm.) Nak., P. kansuensis, P. ussuriensis Max., P. hondoensis Kik. and Nak., while the Asian “pea” pear species are P. calleryana Dcne., P. betulaefolia Bung., P.fauriei Schneid., P. dimorphophylla Makino, and P. koehnei Schneid. (3, 27). A number of nonprimary species also appear in the literature, which may be either botanical varieties, subspecies, or interspecific hybrids. Among the east Asian group, P. bretschneideri Rehd. is a probable hybrid of P. betulaefolia and the cultivated forms of P. pyrifolia; P. phaeocarpa Rehd. may be a P. betulaefolia × P. ussurensis hybrid, whereas P. serrulata Rehd. is a probable interspecific hybrid involving P. pyrifolia and P. calleryana.

Open access

Mary E. Cole, Theophanes Solomos, and Miklos Faust

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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Zhengwang Jiang, Feiyan Tang, Hongwen Huang, Hongju Hu, and Qiliang Chen

The sand pear ( Pyrus pyrifolia Nakai) is one of the most important fruit tree crops in China and is extensively cultivated in central and southwest China. The species occurs naturally in southern and western China, recognized as the center of