‘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
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
More than 4500 accessions of eight genera including Pyrus at the National Clonal Germplasm Repository, Corvallis, Ore., require testing for cold hardiness. Since pear xylem deep supercools (7), differential thermal analysis (DTA) would be a suitable test if large numbers of samples could be examined simultaneously. The object of this study was to produce a method of multichannel DTA for defining cold hardiness of pear accessions. Visual browning was also examined to confirm cold hardiness values.
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.
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.
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
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).
High levels of decadienoate esters were found in the iso-octane soluble fraction extracted directly from pureed canned fruit of ‘Harvest Queen’, HW-606, ‘Bartlett’, 5 sports of ‘Bartlett’, ‘Surecrop’, and ‘Laxtons Progress’ pear (Pyrus communis L.). These cultivars, with the exception of ‘Surecrop’, had a Bartlett-like aroma. The decadienoate equivalents observed in 19 other cultivars ranged from none to one-half the high group. Higher levels of decadienoate esters were also detected by high pressure liquid chromatography (HPLC) in essences of canned fruit of ‘Bartlett’, ‘Harvest Queen’, and HW-606 with a Bartlett-like aroma than in canned fruit of 3 cultivars with aroma unlike ‘Bartlett’, including ‘Harrow Delight’, HW-607, and ‘Kieffer’. Cultivars with Bartlett-like aroma seem to be characterized by high decadienoate ester level, but high decadienoate ester levels are not necessarily indicative of Bartlett-like aroma. Decadienoate esters were not detected in essences extracted from actively growing or dormant shoots of ‘Bartlett’. Thus, early screening of seedlings for Bartlett-like aroma on basis of decadienoate extraction of the shoot or leaves cannot be effective.
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
The United States produced 407,000 t of ‘Bartlett’ pears ( Pyrus communis L.) in 2012 [ U.S. Department of Agriculture (USDA), 2013] . California produces ≈32% of all pears in the nation and exports between 20% and 30% of the fresh crop each year