Performance and Phenology of Wild Black Raspberry (Rubus Occidentalis L.) Germplasm in a Common Garden
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Genet Resour Crop Evol (2016) 63:653–673 DOI 10.1007/s10722-015-0274-y RESEARCH ARTICLE Performance and phenology of wild black raspberry (Rubus occidentalis L.) germplasm in a common garden Michael Dossett . Chad E. Finn Received: 16 January 2015 / Accepted: 2 June 2015 / Published online: 17 June 2015 Ó Springer Science+Business Media Dordrecht (outside the USA) 2015 Abstract A lack of genetic diversity in cultivated vigor, and apparent field tolerance to Verticillium black raspberry (Rubus occidentalis L.) germplasm wilt. For nearly every trait examined, wild black has been widely recognized as a major factor limiting raspberry germplasm exhibited a range of variation progress towards breeding improved cultivars. Despite beyond existing cultivars, and showed great potential this, little effort has been made since the early for use in future breeding. While most populations twentieth century to systematically collect and eval- were fairly uniform phenotypically, segregation for uate wild black raspberry for germplasm improve- fruit gloss and possible tolerance to Verticillium wilt ment. In recent years, there has been renewed interest was noted in a few, indicating the possibility of simple in black raspberry breeding to replace existing culti- inheritance of these traits. A few populations with vars that lack durability and disease resistance. We unusual morphology, such as spinelessness or flower planted seedlings from 109 wild black raspberry abnormalities, were identified, as were populations populations, representing 24 US states and two that flowered on first year canes and produced fall Canadian provinces, in the field in replicated trial fruit. Populations from the southern edge of the range plots in Corvallis, Oregon (USA), to evaluate their appear to be particularly well adapted to western performance. These populations showed wide varia- Oregon, with vigorous upright growth, strong canes, tion in morphology, architecture, fruiting season, and some with a low incidence of Verticillium wilt. This germplasm will be of great value to breeders interested in developing improved black raspberry M. Dossett (&) cultivars. Department of Horticulture, Oregon State University, Corvallis, OR 97331, USA Keywords Blackcap Á Breeding Á Cultivar e-mail: [email protected] development Á Rubus occidentalis Á Verticillium Present Address: M. Dossett BC Blueberry Council, in Partnership with Agriculture Introduction and Agri-Food Canada, Pacific Agri-Food Research Centre, 6947 #7 Hwy, PO Box 1000, Agassiz, BC V0M 1A0, Canada Black raspberry has a long history as an important fresh and processed crop in the US. In the early 1900s, the C. E. Finn black raspberry industry occupied significant acreages, Horticultural Crops Research Unit, U.S. Department of Agriculture - Agricultural Research Service, primarily around the Great Lakes and Ohio River 3420 NW Orchard Avenue, Corvallis, OR 97330, USA Valley in Michigan, Ohio, western Pennsylvania, and 123 654 Genet Resour Crop Evol (2016) 63:653–673 western New York. In the years since, the industry has germplasm has not been sufficiently surveyed for the undergone a slow but steady contraction that has adaptation and disease resistance needed by the largely been attributed to diseases and a lack of industry (Daubeny 1996). Surprisingly, beyond a resistant cultivars. Today, the majority of black few selections made in the late nineteenth and early raspberry acreage in North America is in Oregon’s twentieth centuries, there is little record of the use of Willamette Valley. wild black raspberry as a source of genetic diversity While many improved cultivars were developed in for breeding improved cultivars. Despite the fact that the early years of black raspberry improvement, the species is widespread across the eastern half of breeding progress has slowed dramatically in the last North America (Jennings 1988), there is virtually no 60 years, and most of the old cultivars and selections record of any effort to systematically collect and have been lost. Since 1975, only four new cultivars evaluate the range of this germplasm since the first half have been developed and released, and the vast of the twentieth century. majority of acreage today is based on a single cultivar, Some research has indicated the potential value of ‘Munger’, developed and released in the 1890s. This previously unexplored wild R. occidentalis germplasm lack of progress in breeding new black raspberry for developing improved cultivars. For example, cultivars has been attributed to a lack of variability in Dossett et al. (2008) found significant improvements available elite germplasm and lack of disease resis- in vigor and disease resistance in progeny of a wild tance (Ourecky 1975). selection from North Carolina, NC 84-10-3, and The limitations of elite black raspberry germplasm Dossett and Finn (2010) found strong aphid resistance have been recognized for many years, and attempts to in wild germplasm from Maine, Michigan, and Ontar- broaden the genetic base of black raspberry date back io, Canada. Molecular studies have also shown that to the 1950s. In contrast to red raspberry (Rubus idaeus cultivated black raspberry may not be representative of L.), in which interspecific hybridization has played a the diversity found in wild germplasm (Dossett et al. major role in the introduction of new traits, this 2010, 2012b; Weber 2003). The primary objective of approach has been of limited success in black rasp- this study was to evaluate the performance of wild R. berry. Slate and Klein (1952) crossed red raspberry to occidentalis germplasm collected from across the black raspberry and found linkage drag to be a major species’ native range and planted in a common garden limitation, concluding that when selecting for types to gauge potential for use in breeding improved that resemble black raspberry in backcross genera- cultivars. tions, they were unable to also maintain traits of interest. Others crossed black raspberry with Asian Rubus species (Drain 1956; Williams 1950). These Materials and methods hybrids had more vigor and less winter injury than their R. occidentalis parents but tended to closely Plant materials and field maintenance resemble their Asian parents and were largely sterile. Ourecky and Slate (1966) crossed R. occidentalis with Collection of plant materials has been previously the closely related R. leucodermis Dougl. ex Torr. et described (Dossett and Finn 2010; Dossett et al. Gray, from western North America. The resulting 2012b). Briefly, during the summer of 2006, friends seedlings had good vigor, but also had nearly all the and colleagues living in eastern North America, within undesirable characteristics of R. leucodermis, includ- the native distribution of R. occidentalis, (USDA ing dull, soft, small fruit. More recently, Finn et al. NRCS 2015) were solicited to send seed or fruit from (2003) surveyed R. leucodermis germplasm from wild plants in their area. Additional seed was obtained western Oregon and Washington, and selections from in 2007 through a similar request and from collecting this work have been valuable additions to the breeding trips across the southern and western edges of the program. native range (Hall et al. 2009; Hummer et al. 2008a, b). While it has been suggested that no further progress Through these efforts, seeds were obtained from more in black raspberry breeding will be made without the than 150 locations across the range, including 27 states use of germplasm from other Rubus species (Ourecky and two Canadian provinces. Additional seed was 1975), it has also been suggested that black raspberry obtained from all R. occidentalis seed accessions held 123 Genet Resour Crop Evol (2016) 63:653–673 655 at the National Clonal Germplasm Repository were recorded for each plant. In addition, each plant (NCGR) in Corvallis, OR. Seeds were treated to was rated on a 1–9 scale for primocane vigor promote germination as described by Dossett and Finn (1 = very poor vigor, 9 = extremely vigorous) in (2010). the spring of both years. Symptoms of Verticillium Sufficient seed germination was obtained from 109 wilt (Verticillium dahliae Kleb.) were recorded in wild populations for establishment of replicated field early fall 2008, after the first season of establishment, plantings. Due to differences in timing of seed and again in the fall of 2009. Severity of symptoms acquisition, seedlings of 78 populations were planted was scored on a 0–6 scale (0 = no infection, 6 = all in the field in September 2007, while 31 additional primocanes showing extensive discoloration and populations were planted in the field in May 2008 stunting). In the spring of 2009 and 2010, plants were (Table 1). On each planting date, seedlings were scored on a 0–5 scale for the amount of cane death planted in a randomized complete block design with over the winter (0 = no floricane death or injury to four replications of at least three and no more than four cane tips, 5 = 80–100 % of floricanes dead). Samples plants, for a total of 12–16 plants from each popula- of 25 randomly picked fruit were collected from each tion, depending on the total number of seedlings plant for weighing and evaluation. Fruit were scored available. Four-plant plots of the cultivars Jewel, Mac for gloss on a 1–5 scale (1 = most pubescent, Black, and Munger were also included in each 5 = most glossy). In a few cases, 25 ripe fruit were replicate block for comparison. Extra seedlings and not available from a given plant, so as many ripe fruit seedlings from seed lots that failed to produce at least as could be collected were picked and weighed. Fruit 12 plants were planted as border rows of the field. were picked when they were fully colored and Because of the difference in planting dates, popula- separated readily from the receptacle but before they tions planted in the field in September 2007 and May were overripe. In 2009, plants were also rated on a 1–5 2008 were laid out separately with independent scale for primocane stiffness (1 = least stiff, randomization and replication, but were directly 5 = most stiff) and lateral branching angle adjacent to each other in the field.