Central Asia is a center of origin for many important fruit and nut tree species, including wild and cultivated apricots (Prunus armeniaca) (Vavilov, 1931, 1951). Apricots, considered by many to be one of the most delicious tree fruits, have been produced and appreciated in the region for millennia and are intertwined with the culture. Today, Uzbekistan is the third largest producer of apricots in the world (356,000 t in 2011) behind Turkey and Iran [Food and Agriculture Organization of the United Nations (FAO), 2013] (Table 1). A wealth of cultivated and wild apricots can be found growing across Central Asia. Much of this germplasm exhibits valuable characteristics such as fruits with high soluble solids; glabrous skin; diverse colors, shapes, textures, and flavors; edible kernels; later flowering and fruit maturation; and drought, salt, cold, and disease tolerance (Mirzaev, 2000; Mirzaev and Kuznetsov, 1984; Ribakov and Ostroukhova, 1972). Despite this rich genetic diversity, geographical and political isolation—in conjunction with recent plant quarantine and importation restrictions—have limited access to Central Asian germplasm in Western research and genetic improvement efforts. This limited access is unfortunate, because germplasm from Central Asia can be used to improve many aspects of apricot culture, as shown in the work of Ledbetter (2009) and Ledbetter et al. (2006) regarding sugar profiles of the fruit. More extensive use of these genetic resources could lead to enhanced adaptation and, ultimately, the expansion of regions where this high-value, sustainable, and healthy crop could be grown.
Top 20 apricot (Prunus armeniaca) producing countries and Central Asian countries (in bold). Total estimated production in 2011 from greatest to least, and area harvested (FAO, 2013).
Two apricot species, P. armeniaca and P. dasycarpa Ehrh., can be found naturally occurring in Central Asia (Mirzaev, 2000). Prunus armeniaca [synonyms: Armeniaca armeniaca (L.) Huth, A. vulgaris Lam., P. tiliifolia Salisb.], referred to as the common apricot, is a deciduous, temperate tree ranging from 5 to 15 m tall. It produces the well-known apricot fruits, some with edible kernels, that vary tremendously in size, shape, color, and flavor. It can be found growing up to 3000 m above sea level in natural stands as well as cultivated plantings across Central Asia, northwest China, Afghanistan, Kashmir, parts of Iran, Dagestan (Russia), Turkey, and the Caucasus region.
Prunus dasycarpa [synonyms: A. atropurpurea Loisel., A. dasycarpa (Ehrh.) Borkh., A. fusca Turpin & Poit., P. armeniaca var. dasycarpa (Ehrh.) K.Koch, P. nigra Desf.], commonly referred to as the black apricot, is reported to be a hybrid of P. armeniaca and P. cerasifera Ehrh. (cherry plum) (Zhukovsky, 1971). It grows as a small tree and is typically found in regions where the two species are sympatric. It is cultivated in Central Asia, the state of Jammu and Kashmir in India, the Beluchistan region of Pakistan, and in the Xinjiang Province of China. Its fruits differ from that of P. armeniaca by being generally small with purple skin and yellow flesh.
The focus of this article is on the genetic resources of wild and cultivated P. armeniaca in Central Asia, a region Vavilov (1931, 1951) considered to be one of the centers of origin of the species. It should be noted, however, that in Vavilov’s system of describing the centers of origin of crop plants, the “Central Asiatic Center of Origin” included Northwest India [Punjab, the northwestern frontier provinces (current-day Pakistan), and Kashmir], Afghanistan, Tajikistan, Uzbekistan, and the western Tian Shan Mountains (Kyrgyzstan and Xinjiang, China). The highlands of Turkmenistan were part of the “Near-Eastern Center of Origin.” This article covers only Uzbekistan, Tajikistan, Turkmenistan, Kyrgyzstan, and part of southern Kazakhstan (Fig. 1). Across this vast region exist native populations and locally derived cultivars that are adapted to a wide variety of climatic conditions and soil types. The climate and soils of the Central Asian region vary considerably depending on geographic location, altitude, and exposure. The majority of the region has a sharp continental climate and displays distinct seasonal changes with occasional wide daily temperature fluctuations. The average monthly air temperature across Central Asia varies from 24.0 to 27.7 °C in July to –0.3 to 3.5 °C in January. The maximum air temperature in some locations can reach as high as 48 °C with low temperatures to –40 °C. In November and December as well as in February and March, air temperature may fluctuate from –25 to 25 °C within a 24-h period (Mirzaev, 2000). Precipitation is also variable, from 87 to 366 mm in the valleys (apricot cultivation in these areas requires irrigation) to over 1000 mm in areas of higher elevation (Mirzaev, 2000). The major soils found in the valley regions are generally of the sierozem type (from light to dark, typically with a pH of 8.1 to 8.2) and in the higher elevations soils range from a dark sierozem to brown soil type with a pH of 7.8 to 8.0 at 1100 m above sea level and 7.6 to 8.0 at 1600 m above sea level (Mirzaev, 1982). Most apricot cultivation occurs in regions where the soils are classified as the various types of sierozem (light, typical, dark). These soils are typically non-saline [total salts less than 0.25% and chlorine less than 0.01% of absolute dry weight (ADS) of soil] or slightly saline (total salts less than 0.25% to 0.5% and chlorine less than 0.01% to 0.04% of ADS) with organic matter content ranging from 1% to 4%. To a lesser degree, apricots are also cultivated on the brown and light brown carbonated soils found in the foothill and mountain areas (Pankov, 1965).
The growing range of apricot in Central Asia reaches its northern limit at 45 °N latitude (Zhukovsky, 1971). In mountain forests, wild trees can be found with small, sweet fruits that often have small leaves and bitter kernels (Kudryashov, 1950; Lomakin, 1971; Zhukovsky, 1971). They occur up to 1500 m above sea level in the western Tian Shan Mountain System, on the south slopes of the Chatkal (Fig. 1, no. 1), Uzun-Akhmat (Fig. 1, no. 2), and Susamir Mountain Ranges (Fig. 1, no. 3); on the northwest slopes of the Ferghana Range (Fig. 1, no. 4); and on the Zailiysky and Dzhungarsky Alatau Mountains (Fig. 1, nos. 5 and 6, respectively). Native trees can also be found in the Kotur-Bulak Gorge, in Almaty Province, Kazakhstan (Bailey and Hough, 1975; Kalmikov, 1973; Mehlenbacher et al., 1991; Mirzaev, 2000; Mirzaev and Kuznetsov, 1984; Zhukovsky, 1971). In addition, wild and cultivated apricots can be found in the Pamir Mountains (Fig. 1, no. 7) at elevations of more than 3000 m (Pulatov, 1976).
In the 1980s, apricot orchards covered more than 83,000 ha in Central Asia: 43,600 ha in Uzbekistan, 22,600 ha in Tajikistan, 10,300 ha in Kyrgyzstan, and 6,500 ha in Turkmenistan (Mirzaev and Kuznetsov, 1984). Today, the total production area reported has decreased to ≈60,500 ha, although 36,500 ha can now be found in Uzbekistan (Table 1) (FAO, 2013).
Kostina (1936, 1941, 1964) divided the world’s apricot germplasm into four ecogeographical groups based on geographic origin and morphological characteristics: Central Asian, Irano-Caucasian, European, and Dzhungar-Zaili. An overview of Kostina’s ecogeographical groups and discussion on the migration and domestication of apricot germplasm from its centers of origin can be found in Zhebentyayeva et al. (2012). Of these groups, the Central Asian group is considered to be the largest and most diverse. Apricot cultivars in Central Asia largely originate from wild plants found in the region with the total number of cultivars recorded exceeding 500 (Andrienko, 1997; Esenbaev et al., 1981; Kostina, 1978; Mirzaev, 2000; Mirzaev and Kuznetsov, 1984).
When compared with the other ecogeographical groups, the Central Asian group has been reported to possess the most heat- and cold-resistant and salt-tolerant forms of the species as well as forms expressing a wide variety of fruit characteristics (Ivanov and Ivanova, 1981; Kostina, 1936; Mirzaev, 2000; Mirzaev and Kuznetsov, 1984; Ribakov and Ostroukhova, 1972; Zhebentyayeva et al., 2003; Zhukovsky, 1971). For example, studies were performed in Tajikistan with 68 apricot cultivars from different ecogeographical groups, including European cultivars. Results showed the Central Asian cultivars were the most coldhardy, led by Mirsandjali #2, Khurmai, Novot, Kandak, Gulyangi-52, Ubileini Navoi, Iskandari, and others (Usmanov, 1983). Researchers in the Ukraine conducted a similar study over a 5-year period (2004–08). They looked at cold tolerance of 60 cultivars from Armenia, Bulgaria, Hungary, China, the United States, Moldova, Romania, Uzbekistan, Czech Republic, and others, and again showed that the most cold-hardy apricot cultivars were of Central Asian origin (Korzin and Gorina, 2009). A third study in Uzbekistan also demonstrated that Central Asian apricot cultivars have greater overall heat and cold resistance in comparison with other ecogeographical groups when tested in Uzbekistan (Mirzaev, 2000; Mirzaev and Kuznetsov, 1984).
Central Asian cultivars were also reported to have higher fruit yields and sugar content and were considered to have superior flavor and fruit coloring compared with many other cultivars (Ribakov and Ostroukhova, 1972; Usmanov, 1983).
Trees from within the Central Asian group are generally characterized as being self-incompatible and are adapted to a wide array of soil types (Mirzaev, 2000). Zhebentyayeva et al. (2003) suggested that the great diversity of apricots found in the region is likely the result of domestication occurring over millennia through the natural association of wild and partly domesticated forms and their intercrossing with cultivated germplasm that originated in the Ferghana Valley. Maghuly et al. (2005) included a number of Central Asian cultivars in their simple sequence repeat (SSR) study and confirmed that they represent a basal lineage. They also exhibited high variability in a number of different alleles, further supporting the increased level of genetic diversity present in the Central Asian germplasm. The highly mountainous, isolated terrain, the self-incompatible nature of the apricots found there, the ancient trade routes through Central Asia, and the early propagation of orchards through seed (not through clonal means) all support this hypothesis.
Kostina further divided the Central Asia ecogeographical group into five subgroups (Ferghana, Zarafshan, Shakhrisabz, Khorezm, and Kopet-Dag) with the Ferghana and Zarafshan subgroups being the most significant in size and diversity of germplasm. Much more recently, this division was supported by SSR analysis performed on a wide collection of P. armeniaca held at the Nikita Botanical Gardens in Yalta, Ukraine (Zhebentyayeva et al., 2003).
To provide examples of the diversity of locally derived apricot germplasm and the sometimes extreme environment in which it is grown, the geographic and climatic conditions of Kostina’s Central Asian ecogeographical subgroups are discussed subsequently. An overview of the apricot germplasm found in each group is provided as well.
Abdrakhmanov, S.G. 1969 Brief results of the selection and breeding of new cultivars of pears and stone fruit crops. Trudy Kirgizskogo nauchno-issledovatel’skogo intituta zemledeliia [Scientific Proceedings of the Kirghiz Research Institute of Agriculture]. 7:141–150. Frunze, Kyrgyzstan [in Russian]
Achkinazi, E.Y. 1933 The apricots of Samarkand region. Trudy Samarkandskoi selektsionno-pomologicheskoi opitnoi stantsii [Scientific Proceedings of the Samarkand Pomological Experiment Station]. Vol. 1. Samarkand, Uzbekistan [in Russian]
Akhmedov, E. 1993 Republic of Uzbekistan: Reference book. Uzbekiston Publishing, Tashkent [in Uzbek, English, and Russian]
Andrienko, M.V. 1997 Pomologiia T. 3: Abrikos, persik, alicha [Pomology. Vol. 3: Apricot, peach, plum]. Urozhai Publishing, Kiev [in Russian]
Arakelyan, U.G. & Bashmakov, E.A. 1981 Apricot in the Kyrgyz S.S.R. Part 1. 6th Intl. Symp. on Apricot Culture and Decline, Yerevan, U.S.S.R., 4–8 July 1977. p. 86–87. Ayastan Publishing, Yerevan, Armenia [in Russian]
Babushkin, L.N. 1963 Atlas of the Uzbek S.S.R. [Atlas Uzbekskoi SSR]. Akademiya Nauk Uzbekskoi Uz.S.S.R., Tashkent-Moscow, Uzbekistan [in Russian]
Badenes, M.L., Asins, M.J., Carbanel, E.A. & Glacer, G. 1996 Genetic diversity in apricot, Prunus armeniaca, aimed at improving resistance to plum pox virus Plant Breed. 115 133 139
Bailey, C.H. & Hough, L.F. 1975 Apricots, p. 367–384. In: Janick, J. and J. N. Moore (eds.). Advances in fruit breeding. Purdue Univ. Press, West Lafayette, IN
Dzhuraev, K. & Pulatov, D.P. 1988 Geografiia Tadzhikistana [Geography of Tajikistan]. Maorif Publishing, Dushanbe [in Russian]
Esenbaev, Z.I., Safarov, R.A., Gaibov, N.G., Mirzaev, M.M. & Penson, M.M. 1981 Orchards of Uzbekiston. Uzbekiston Publishing, Tashkent, Uzbekistan [in Uzbek, Russian, and English]
Fet, V. & Atamuradov, K.I. 1994 Biogeography and ecology of Turkmenistan. Kluwer, Dordrecht, The Netherlands, and Boston, MA
Food and Agricultural Organization of the United Nations 2013 Agricultural production, crops primary apricots. 22 Jan. 2013. <http://faostat.fao.org/site/567/default.aspx#ancor>
Gareev, E.Z. 1959 Plodovye kultury Kirgizstana [Fruit species in Kyrgyzstan]. Kirgosizdat Publishing, Frunze [in Russian]
Germplasm Resource Information Network 2013 Holdings at Natl. Germplasm Repository–Davis, California (DAV). Prunus armeniaca. 9 Jan. 2013. <http://www.ars-grin.gov/cgi-bin/npgs/html/tax_site_acc.pl?DAV%20Prunus%20armeniaca>
Gvozdetskiy, N.A. & Mikhailov, N.I. 1978 Fizicheskaia geografiia SSSR, Aziatskai chast [Physical geography of the U.S.S.R., Asian part]. Misl Publishing, Moscow [in Russian]
Hormoza, J.I. 2002 Molecular characterization and similarity relationships among apricot (Prunus armeniaca L.) genotypes using simple sequence repeats Theor. Appl. Genet. 104 321 328
Hurtado, M.A., Westman, A.L., Beck, E., Abbott, A.G., Llácer, G. & Badenes, M.L. 2002a Genetic diversity in apricot cultivars involved in breeding for sharka resistance based on AFLP marker Euphytica 127 297 301
Hurtado, M.A., Romero, C., Vilanova, S., Abbott, A.G., Llácer, G. & Badenes, M.L. 2002b Genetic linkage maps of two apricot cultivars (Prunus armeniaca L.), and mapping of PPV (sharka) resistance Theor. Appl. Genet. 105 182 191
Ivanov, V.F. & Ivanova, A.S. 1981 Apricot salt tolerance in connection with its propagation in dry steppe regions of southern Ukraine. Part 1, 6th Intl. Symp. on Apricot Culture and Decline, Yerevan, U.S.S.R., 4–8 July 1977, p. 122–126. Ayastan Publishing, Yerevan, Armenia [in Russian]
Kalmikov, C.C. 1973 Dikorastushiye plodoviye zapadnogo Tyan-Shanya i khozyaistvennoye osvoyeniye ikh [Wild fruit species of the western Tian-Shan and their economic development]. Fan Publishing, Tashkent, Uzbekistan [in Russian]
Kolosova, L.N. 1981 Geograficheskii atlas dlya uchutelei srednei shkoli [Geographic atlas for secondary school teachers]. 4th Ed. GUGK Publishing, Moscow, Russia [in Russian]
Korzin, V.V. & Gorina, V.M. 2009 Influence of low air temperatures in winter and spring period on apricots trees in Crimea. Trudy universiteta bioresursov i prirodovedeniya Ukraini. Crimsky Agrotekhnichesky Universitet. [Scientific Proceedings of the Bioresource and Nature of the Ukraine]. Crimean Agrotekhnical University 125:168–172 Simferopol
Kostina, K.F. 1936 Abrikos. Trudy po Prikladnoi Botanike, Genetike i Selektsii [Apricots. Bulletin of Applied Botany, Genetics and Breeding] Suppl. 83. [in Russian]
Kostina, K.F. 1941 Armeniaca, p. 581–604. In: Komarov, V.L. (ed.). Flora of the U.S.S.R. Izdatel'stvo Akademii Nauk U.S.S.R., Moskva-Leningrad, Russia [in Russian]
Kostina, K.F. 1964 Application of the phytogeographical method for apricot classification. Trudy Nikitskogo Botanicheskogo Sada [Proceedings of the Nikita Botanical Garden] 24. Kolos Publishing, Moscow [in Russian]
Kostina, K.F. 1970 Seletsionnoye ispolzovaniye sortovih fondov abrikosa [Selective utilization of apricot stock], p. 177–189. In: Ayzenberg, V.Y. (ed.). Abrikos. Ayastan, Yerevan [in Russian]
Kovalev, N.V. 1963 Abrikos [Apricots]. Kolos Publishing, Moscow, Russia [in Russian]
Kudryashov, S.N. 1950 Plod. Shakrisyabza 1:2. [Fruit species of Shakhrisyabz]
Kuznetsov, V.V. 1970 Kultura abrikosa v Uzbekskoi SSR [Apricot culture in the Uzbek S.S.R.]. Ayastan Publishing, Yerevan, Armenia [in Russian]
Layne, R.E.C., Bailey, C.H. & Hough, L.F. 1996 Apricots, p. 79–111. In: Janick, J. and J.N. Moore (eds.). Fruit breeding, Vol. 1. Tree and tropical fruits. Wiley, New York, NY
Ledbetter, C., Peterson, S. & Jenner, J. 2006 Modification of sugar profiles in California adapted apricots (Prunus armeniaca L.) through breeding with Central Asian germplasm Euphytica 148 251 259
Ledbetter, C.A. 2009 Using Central Asian germplasm to improve fruit quality and enhance diversity in California adapted apricots Acta Hort. 814 77 80
Levy, L., Damsteegt, V., Scorza, R. & Kolber, M. 2000 Plum pox potyvirus disease of stone fruits. APSnet Features. doi: 10.1094/APSnetFeature-2000-0300. <http://caps.ceris.purdue.edu/webfm_send/1424>
Lomakin, E.N. 1971 The wild apricot Armeniaca vulgaris Lam., of Central Asia. Trudy po Prikladnoi Botanike, Genetike i Selektsii [Bulletin of botany, genetics and breeding] 45:89–95 [in Russian]
Lomakin, E.N. 1977 Genepool of apricots, goals and breeding work in Central Asia, p. 13–22. In: Nauchno-metodicheskoe soveshanie po kulturye abrikosa v Srednei Azii [Scientific-methodological conference on apricot culture], MSKh Uz.S.S.R., Tashkent, Uzbekistan [in Russian]
Maghuly, F., Borroto, E., Ruthner, S., Pedryc, A. & Laimer, M. 2005 Microsatellite variability in apricots (Prunus armeniaca L.) reflects their geographic origin and breeding history Tree Genet. Genomes 1 151 165
Mavlyanova, R.F., Abdullaev, F.K., Khodjiev, P., Zaurov, D.E., Molnar, T.J., Goffreda, J.C., Orton, T.J. & Funk, C.R. 2005 Plant genetic resources and scientific activities of the Uzbek Research Institute of Plant Industry HortScience 40 10 14
Mehlenbacher, S.A., Cociu, V. & Hough, L.F. 1991 Apricots (Prunus), p. 65–107. In: Moore, J.N. and J.R. Ballington, Jr. (eds.). Genetic resources of temperate fruit and nut crops. Acta Hort 290
Mirzaev, M.M. 1982 Gornoe sadovodstvo Uzbekistana [Mountain orchards of Uzbekistan]. Fan Publishing, Tashkent, Uzbekistan [in Russian]
Mirzaev, M.M 2000 Abrikos v Uzbekistane [Apricots in Uzbekistan]. Shark Press, Tashkent, Uzbekistan [in Russian]
Mirzaev, M.M., Djavacynce, U.M., Zaurov, D.E., Goffreda, J.C., Orton, T.J., Remmers, E.G. & Funk, C.R. 2004 The Schroeder Institute in Uzbekistan: Breeding and germplasm collections HortScience 39 917 921
Mirzaev, M.M & Kuznetsov, V.V. 1984 Abrikos v Uzbekistane: Biologiia, sorta, selektsiia, agrotekhnika [Apricots in Uzbekistan: Biology, cultivars, breeding, agrotechnology]. Fan Publishing, Tashkent, Uzbekistan [in Russian]
Mirzaev, M.M., Kuznetsov, V.V., Borozdin, R.G., Frolov, A.I., Jivotinskay, S.M., Tabanali, A.H. & Djavacynce, U.M. 1983 Pomologiia Uzbekistana [Pomology of Uzbekistan]. Fan Publishing, Tashkent, Uzbekistan [in Russian]
National Climate Data Center 2013a National Oceanic and Atmospheric Administration, Freehold–Marlboro, NJ, station. 10 Feb. 2013. <http://www.ncdc.noaa.gov/cdo-web/datasets/ANNUAL/stations/COOP:283181/detail>
National Climate Data Center 2013b National Oceanic and Atmospheric Administration, Logan, Utah State University, Logan, UT, station. 10 Feb. 2013. <http://www.ncdc.noaa.gov/cdo-web/datasets/ANNUAL/stations/COOP:425186/detail>
Nosulchak, V.A., Mizgirova, O.F. & Levin, G.M. 1988 Stone fruits, p. 15–17. In: The Turkmen Experiment Station of VIR. Ashkhabad, Turkmenistan [in Russian]
Pankov, M.A. 1965 Soil science, p. 7–79. In: Rizhov, S.N. and I.F. Sukach (eds.). Irrigated agriculture. Uzbekistan Publishing, Tashkent, Uzbekistan [in Russian]
Progress Report of National Coordinators of Plant Genetic Resources in Central Asia and the Caucasus 10 Mar. 2007, p. 37. Biodiversity International, Tashkent, Uzbekistan
Pulatov, A. 1976 Tajik apricot. Irfon Publishing, Dushanbe, Tajikistan [in Russian]
Ribakov, A.A. & Ostroukhova, S.A. 1972 Horticulture of Uzbekistan. 3rd Ed. Ukituvchi Publishing, Tashkent, Uzbekistan [in Russian]
Smirnova, V.A. 1980 Abrikos sortotipa Khurmai [Apricot sortotype Khurmai], p. 104–115. In: Mirovye rastitelnye resursy v Srednei Azii [Global plant resources in Central Asia], Vol. 7. Glavnoe upravlenie propagandy i vnedreniia dostizhenii nauki i peredovogo opyta MSKH UzSSR, Tashkent [in Russian]
Smykov, V.K., Sholokhov, A.M. & Savina, T.M. 1985 Metodicheskiye rekomendatsii po podboru sortov abrikosa dlya virashchivaniya v Krimu [Methodical recommendations on selection of apricot cultivars for growing in Crimea]. All union Agricultural Academy of Science named after V.I. Lenin and Nikita State Botanical Garden, Yalta, Ukraine [in Russian]
Soldatov, I.V. & Kostritsina, T.V. 2002 Rezultatui mezhrodovoi gibridizatsii slivui s abrikosom [Results of intergeneric hybridization between plum and apricot], p. 136–141. In: Mat. resp. nauchno-praktich. Konf. “Botanicheskiye issledovaniya v Kirgizstanye” [The republican scientific-practical conference in Kyrgyzstan “Botanical research in Kyrgyzstan”]. Olimp Publishing, Bishkek, Kyrgyzstan [in Russian]
Soldatov, I.V. & Kuliev, A.S. 2010 Introduction and breeding of the ordinary apricot (Armeniaca vulgaris Lam.) and the black apricot (Armeniaca dasycarpa Ehrh.) in Kyrgyzstan, p. 132–138. In: Soldatov, I.V., et al. (eds.). Introduction and Conservation of the Biodiversity and the Use of Plants: Collection of research papers: Materials of the International Scientific and Practical Conference dedicated to the 100-Anniversary of the Corresponding Member of NAS KR, Prof. E. Gareev and to the International Year of the Biodiversity. Bishkek, Kyrgyzstan. 7–9 Sept. 2010. E. Gareev Bot. Garden of NAS KR, Bishkek [in Russian]
Spiegel, S., Kovalenko, E.M., Varga, A. & James, D. 2004 Detection and partial molecular characterization of two Plum pox virus isolates from plum and wild apricot in southeast Kazakhstan Plant Dis. 88 973 979
State Commission for Variety Testing of Crops 2008 State register of varieties approved for use in the Kyrgyz Republic. Ministry of Ministry of Agriculture, Water and Processing Industry of Kyrgyz Republic, Bishkek, Kyrgyzstan [in Russian]
Torrecillas, A., Galego, R., Perez-Pastor, A. & Ruiz-Sanchez, M.C. 1999 Gas exchange and water relations of young apricot plants under drought conditions J. Agr. Sci. 132 445 452
Turakulov, Z.T. 1993 Apricot breeding, p. 10–22. In: Mirzaev, M.M. (ed.). Selektsiia plodovuikh i vinograda V Uzbekistanye [Breeding fruit and grapes in Uzbekistan]. Mehnat Publishing, Tashkent, Uzbekistan [in Russian]
U.S. Department of Agriculture 2012a National Agriculture Statistics Service. Quick stats database. 20 June 2012. <http://quickstats.nass.usda.gov/results/AC1EA05F-3440-3072-8AD7-132793D14F52>
U.S. Department of Agriculture 2012b Fruit and tree nuts situation and outlook yearbook 2011. 20 June 2012. <http://www.ers.usda.gov/publications/fts/Yearbook11/FTS2011.pdf>
Usmanov, U.M. 1983 Apricot culture in North Tajikistan Acta Hort. 121 259 262 . 7th Symp. on Apricot Culture and Decline, 16–21 July 1981, Bucharest-Constanta, Romania
Utah State University 2013 Apricot varieties. Fruit production. 13 Jan. 2013. <http://extension.usu.edu/carbon/index.cfm/fruit/aprvar>
Vavilov, N.I. 1931 The wild relatives of fruit trees of the Asian part of the USSR and Caucasus and problems of origin of fruit trees. Bulletin of applied botany, genetics and breeding [Trudy po Prikladnoi Botanike, Genetike i Selektsii] 26:343–360 [in Russian]
Vavilov, N.I. 1951 Phytogeographic basis of plant breeding, p. 13–54. In: The origin, variation, immunity and breeding of cultivated plants: Selected writings of Vavilov, N.I. and F. Verdoon (eds.). Chron. Bot. 13
Vazhov, V.I., Ivanov, V.F. & Ivanova, A.S. 1989 Abrikos [Apricot]. In: Smykov, V.K. (ed.). Lenin All Union Academy of Agricultural Science, Agropromizdat Publishing, Moscow, Russia [in Russian]
Zhebentyayeva, T., Ledbetter, C.A., Burgos, L. & Llácer, G. 2012 Apricot, p. 415–458. In: Badenes, M.L. and D.H. Byrne (eds.). Fruit breeding, handbook of plant breeding 8. Springer Science+Business Media, New York, NY
Zhebentyayeva, T.N., Reighard, G.L., Gorina, V.M. & Abbott, A.G. 2003 Simple sequence repeat (SSR) analysis for assessment of genetic variability in apricot germplasm Theor. Appl. Genet. 106 435 444
Zhebentyayeva, T.N., Reighard, G.L., Lalli, D., Gorina, V.M., Krška, B. & Abbott, A.G. 2008 Origin of resistance to plum pox virus in Apricot: What new AFLP and targeted SSR data analyses tell Tree Genet. Genomes 4 403 417
Zhukovsky, P.M. 1971 Kulturnye rasteniia i ikh sorodichi [Cultivated plant species and their relatives]. 3rd Ed. Kolos, Leningrad, Russia [in Russian]