‘Shenandoah’ pear (Pyrus communis L.) is a new cultivar that combines spicy aromatic fruit flavor, long storage life, large fruit size, consistent yields, and moderate resistance to fire blight caused by the bacterium Erwinia amylovora (Burr.) Winsl. et al. (van der Zwet and Beer, 1999). All major cultivars of commercial importance as well as many of those available to home orchardists are susceptible to this devastating disease, which is endemic to most production regions of the northern hemisphere (van der Zwet and Beer, 1999). Long storage life, absence of core breakdown, and resistance to superficial scald are also economically important physiological traits. ‘Shenandoah’ was released by the U.S. Department of Agriculture and The Ohio State University in 2003 as a fresh market pear for commercial and home orchards.
Origin
‘Shenandoah’ is a seedling of ‘Max Red Bartlett’ and US56112-146 (Fig. 1), the cross made in 1977 by T. van der Zwet and R.C. Blake. The parentage is entirely of P. communis origin, and the original source of resistance is presumed to be the old American cultivar, Seckel, thought to be a parent of ‘Barseck’. The original seedling, designated US78304-057, was selected in 1985 by R.L. Bell at the Appalachian Fruit Research Station (AFRS). The selection was further evaluated in a nonrandomized planting of six trees propagated on ‘Bartlett’ seedling rootstock at AFRS (Bell and van der Zwet, 1993) and in randomized, replicated plantings at AFRS (10 trees) and The Ohio State University—Ohio Agricultural Research and Development Center, Wooster, OH (10 trees), where all trees were propagated on ‘Bartlett’ seedling rootstock. It is also currently being tested by eight cooperators throughout the United States for performance under diverse climatic conditions. It was jointly released as a cultivar in 2003 by the U.S. Department of Agriculture and The Ohio State University. Budwood has tested negative for viruses and pear decline phytoplasma at the National Research Support Project No. 5 at Washington State University, Prosser, WA. The cultivar is named for the nearby Shenandoah River.
Fruit are oblong–ovate–pyriform, ovate–pyriform, and obovate–acute–pyriform (Zielinski, 1955), equivalent to the International Board for Plant Genetic Resources shape ratings of 3.2, 5.2, and 5.1, respectively (Thibault et al., 1983; Fig. 2), and moderately large, averaging 72 mm in diameter, 92 in length, and weighing 235 g (Table 1). Skin color at harvest is light green with 10% to 25% red blush. The skin turns yellow–green when ripe (Fig. 2). The finish is glossy. The skin surface is usually smooth but can sometimes be uneven. The cross-sectional contour can vary from symmetrical to ribbed. The cavity is obtuse and occasionally acute. The basin is medium in depth and sloping, and the calyx is persistent and convergent. There is usually some light calyx–end tan russet under conditions at AFRS, and lenticels are slightly conspicuous. The stem is medium to long (≈25 mm), of medium thickness (≈3 mm), upright, and usually curved. Flesh texture is moderately fine, juicy, and buttery. Flesh color is creamy white. Small grit cells occur primarily around the core and under the skin, similar to ‘Bartlett’ but with overall grit content and size less than ‘Bartlett’. Core size is medium (21 mm), similar to ‘Bartlett’. Harvest maturity has been estimated to occur ≈3 weeks after ‘Bartlett’. In air storage at –1 °C, fruit will store for as long as 111 d without superficial scald or internal breakdown. When harvested firm but optimally mature, the fruit will ripen without postharvest chilling, but 10 to 12 d at 20 °C were required to reach flesh firmness acceptable for eating. The mean shelf life (number of days to soften to eating ripeness) varied from 5 to 10 d depending on harvest date. The flavor is sweet and aromatic, but acidity is also high at harvest and during the first 2 months after harvest, thereafter decreasing so that the overall character is subacid.
Table 1.Fruit descriptive and sensory traits of ‘Shenandoah’ and ‘Bartlett’z.
Trees are moderately vigorous on ‘Bartlett’ seedling rootstock and upright-spreading in growth habit, similar to ‘Conference’. Full-bloom at AFRS is midseason, similar to ‘Bartlett’. Cropping has been moderately precocious with first fruit set 3 years after planting (Table 2). Yield ratings beginning in the fourth year of growth after planting have been moderately high and greater than ‘Bartlett’. In a test planting at AFRS on ‘Bartlett’ seedling rootstock, mean cumulative yield per tree 10 years after planting was 136.7 kg for ‘Shenandoah’ versus 59.8 kg for ‘Bartlett’ (Pr > F = 0.0001). Secondary bloom is rare.
Table 2.Mean yearly and cumulative yield per tree for ‘Shenandoah’ and ‘Bartlett’z.
Fire blight resistance.
Although not immune or highly resistant to fire blight shoot (Table 3) or blossom infections (Table 4), the severity of infections is less severe than those in ‘Bartlett’.
Table 3.Response to epiphytotic and artificial fire blight infection of shoots of ‘Shenandoah’ and ‘Bartlett’.
Table 4.Frequency and severity of artificial fire blight infections in blossoms of ‘Shenandoah’ and ‘Bartlett’z.
Availability
Budwood of ‘Shenandoah’ is limited and trees are not available from either the U.S. Department of Agriculture or The Ohio State University. Pathogen-free certified budwood will be available to nurseries and researchers from NRSP No. 5 (http://nrsp5.prosser.wsu.edu). In addition, budwood has been deposited in the National Plant Germplasm System at the National Clonal Germplasm Repository, Corvallis, OR (http://ars-grin.gov/cor), where it will be available for research, including development and commercialization of new cultivars. ‘Shenandoah’ is not patented. However, when this germplasm contributes to the development of a new cultivar, selection, mutant clone, or other germplasm, it is requested that appropriate recognition be given to the source. Limited amounts of noncertified budwood will be available from Richard Leslie Bell.
Received: 07 May 2008
Accepted: 24 Jul 2008
Published Print: 01 Dec 2008
Bell,R.L. & van der Zwet,T.1993New fire blight resistant advanced selections from the USDA pear breeding programActa Hort.338415419
Norelli,J.L., Aldwinckle,H.S. & Beer,S.V.1988Virulence of Erwinia amylovora strains to Malus sp. Novole plants grown in vitro and in the greenhousePhytopathology.7812921297
van der Zwet,T. & Beer,S.V.1999Fire blight—Its nature, prevention, and control: A practical guide to integrated disease managementU.S. Department of AgricultureAgriculture Information Bulletin No. 631.
We thank Dr. D.D. Miller, the administration, and staff of The Ohio State University's Ohio Agricultural Research and Development Center for their cooperative role. We recognize the contribution of R.C. Blake in planning the cross and Wayne Zook, Greg Brenneman, John Walter, Roger Lewis, and Daniel Bullock for providing technical assistance in the evaluations. We also thank Kenneth Eastwell, William Howell, and their staff at the National Research Support Project No. 5, Washington State University, for providing virus and phytoplasm testing.
Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that also may be suitable.
