Genetic Resources of Almond Species in the Former USSR
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HORTSCIENCE 50(1):18–29. 2015. 1997; Yu€ et al., 1986). Rehder (1940) divided the genus into five subgenera: Amygdalus (L.) Focke, Cerasus (Mill.) Focke, Laurocerasus Genetic Resources of Almond Species (Duhamel) Rehder, Padus (Mill.) A. Gray, and Prunophora Focke (=Prunus s.str.), and this in the Former USSR treatment has been followed by many taxon- omists [see Bortiri et al. (2002), Lee and Wen David E. Zaurov (2001), and McVaugh (1951) for detailed Department of Plant Biology and Pathology, School of Environmental and review regarding taxonomic treatments of Biological Sciences, Rutgers University, 59 Dudley Road, New Brunswick, Prunus]. NJ 08901 Subgenus Amygdalus includes 24 to 40 species depending on the treatment and is Sasha W. Eisenman2 composed of deciduous shrubs or small trees Department of Landscape Architecture and Horticulture, School of Environmental (Gradziel, 2010; Yazbek, 2010). These spe- Design, Temple University, 580 Meetinghouse Road, Ambler, PA 19002-3923 cies are native to the Old World with a par- ticular diversity of species in southwestern Timothy Ford and central Asia. Spach (1843), who classi- V.P. Research, Pineview Farms LLC, P.O. Box 10, Huntsville, UT 84318 fied Amygdalus as a separate genus, divided the group into five sections. Browicz and Sergei Khokhlov Zohary (1996) and Denisov (1988) also Nikita Botanical Gardens–National Scientific Center, Yalta, Crimea, retained Amygdalus as a separate genus, and both presented a complex system of taxon- Ukraine, 98648 omy with four and five sections, respectively. Sovetbek Kenjebaev Alternatively, a simplified classification with two sections has been proposed: section Institute of Nut and Fruit Culture, 130 B. Osmanov Street, Jalalabad, Kyrgyz Persica, the peach-type species, and section Republic 715613 Amygdalus, the almond-type species (Browicz and Zohary, 1996; Yazbek and Oh, 2013; Kaiyrkul T. Shalpykov Zhukovsky, 1971). The taxonomy of the Innovative Center of Phytotechnology, National Academy of Sciences, 267 species within subgenus Amygdalus is com- Chui Avenue, Bishkek, Kyrgyz Republic 720071 plicated by the fact that many of the species have the capability to hybridize. This has led 1 C. Reed Funk to confusion about species delineations and Department of Plant Biology and Pathology, School of Environmental and whether many of the described species should Biological Sciences, Rutgers University, 59 Dudley Road, New Brunswick, be categorized as subspecies or ecotypes NJ 08901; and Improving Perennial Plants for Food and Bio-energy, Inc., (Gradziel, 2010). Based on phylogenetic anal- yses, Yazbek and Oh (2013) removed a num- 711 South State Street, Richmond, UT 84333 ber of species from Prunus subg. Amygdalus. Additional index words. breeding, drylands, germplasm, nut trees, Prunus dulcis, Soviet Two of the species, P. tenella Batsch. and Union, underused crops P. petunnikowii Litv., have been traditionally placed in Prunus subg. Amygdalus sect. Abstract. Prunus dulcis (Mill.) D.A. Webb. is grown as an economically valuable crop in Chamaeamygdalus Spach but were deter- a number of countries worldwide, but large-scale cultivation has been primarily restricted mined to fall outside the monophyletic clade to semiarid and arid regions with mild, temperate climates. Considering the species’ wide representing species normally considered to native range and inherent genetic, morphologic, and phenologic diversity, almond remains be in Prunus subg. Amygdalus. quite underused in areas outside those currently in cultivation. The area comprising the This review focuses on the 16 species former USSR represents an extremely large and diverse region and is a center of genetic traditionally placed in Prunus subg. Amygdalus diversity for P. dulcis and related species. Much of this region, which is the center of origin that are found in the area comprising the for- and/or diversity of many important crops, has been inaccessible to the Western world for mer USSR (Abdurasulov, 1990; Dzhangaliev centuries, and much of the scientific literature produced there has not been widely et al., 2003; Rubtsov, 1971; Zhukovsky, disseminated in the English language. Since the breakup of the USSR, this region has 1971). The distribution and significant traits become increasingly open and opportunities for reciprocal germplasm collection, of P. dulcis and closely related species are exchange, and scientific collaborations are growing. To bring increased attention to the presented (Table 1) and extensive germplasm valuable P. dulcis genetic resources endemic to this region, and to promote better use, holdings of institutions across the former management, and preservation of these important resources, the wild distribution of USSR are described. It is the aim of this almond and closely related species, and extensive germplasm holdings of institutions across review to highlight the great genetic diversity the former USSR, are herein described. Recent and ongoing collection and breeding that is available and to bring increased attention activities in the U.S. Intermountain West are also discussed. to the valuable genetic resources that are unique to this region. To promote better use, manage- ment, and preservation of these important re- Taxonomy. Thecultivatedalmond[Prunus classifications have ranged from splitting Pru- sources, dissemination of this information is dulcis (Mill.) D.A. Webb.; syn. Amygdalus nus sensu lato (s.l.) into many segregate critical. Recent and ongoing collection and communis L., Amygdalus dulcis Mill.; Prunus genera, including Amygdalus L., Armeniaca breeding activities are also discussed. By amygdalus Batsch.] has a long and complex Scop., Cerasus Mill., Emplectocladus Torr., accessing and using these resources, it may be history, both taxonomically and geographically. Laurocerasus Duhamel, Maddenia Hook.f. possible to expand the range of almond culti- The species belongs to subgenus Amygdalus (L.) & Thomson, Padus Mill., Persica Mill., vationinthefutureandfind genetic material for Focke of the genus Prunus L. in the Rosaceae Prunus L. sensu stricto (s.str.), and Pygeum the improvement of important traits such as family (Yazbek, 2010; Yazbek and Oh, 2013). Gaertn., to considering it a large, single genus disease resistance, cold and drought tolerance, The genus Prunus is itself taxonomically with many subgenera (De Candolle, 1825; and desirable nut characteristics. complex, and over the centuries, botanists have Focke, 1894; Hutchinson, 1964; Koehne, 1893; Global almond production. Almond was developed various circumscriptions. These Linchevskii and Fedorov, 1941; Takhtajan, the fourth most abundantly produced nut crop 18 HORTSCIENCE VOL. 50(1) JANUARY 2015 worldwide in 2012 and 2011, the years with 2012 value of production of all California L. subsp. communis, A. communis L. subsp, the most recent global statistics (FAOSTAT, almond tonnage was reported to be over $4.1 spontanea (Korsh.) Browicz & D. Zohary, 2014). In 2012, there were 1.935 million MT billion (USDA-NASS, 2013). Because over and A. communis L. subsp. microphylla of in-shell nuts produced, which was down 60% of the California almond acreage is (Post) Browicz & D. Zohary. from 1.964 million MT in 2011 (FAOSTAT, composed of only four cultivars, and because Much of central Asia, the Caucasus, and 2014). According to FAOSTAT (2014), al- almond is such an economically significant southern Russia is mountainous, and over mond production in the United States was crop, it is important to consider the germ- 94% of the territories of Tajikistan and 720,000 MT in 2012 and 731,236 MT in plasm necessary to support breeding efforts Kyrgyzstan are montane or alpine (Akimaliev 2011, which accounted for 37% of the and the development of high-performance et al., 2013; Djuraev and Pulatov, 1988). As world supply in both years. The other top cultivars. a result of this topography, the cultivation of almond-producing countries in 2012 were nut species on hillsides is necessary and Spain, Australia, Iran, Morocco, and Italy Distribution and Cultivation of Almond relatively large almond orchards are located (FAOSTAT, 2014; Table 2). Although im- in the Former USSR in the foothill and mountain areas, where portant wild germplasm and institutional terracing is a commonly used agricultural germplasm collections can be found in coun- The domestication of almond began in technique. Expanding human populations in tries of the former USSR, they do not have central and south Asia during the third mil- these regions puts a premium on any non- a significant almond industry in terms of lennium B.C. (Spiegel-Roy, 1986). Vavilov sloping lands, and planting on hillsides allows global production (Table 2). (1931, 1951) classified central Asia as a center for better cold air (frost) drainage, particularly The percentage of global production at- of origin for almond as a result of the diversity during flowering (Fig. 1). Almonds are often tributed to the United States is markedly of almond-related species that occur in the grown in home backyards and harvested from different in data presented by the U.S. De- region. As a result of this long association with wild-growing trees as well. In the southern partment of Agriculture, who stated that for humans, determining the extent of the natural regions of the former USSR, almonds have the 2011–12 marketing year, the United distribution of P. dulcis has been complicated been in cultivation for a very long time. This can States was responsible for nearly 85% of (Zohary and Hopf, 2000). Consequently,