RESEARCH ARTICLE
Population Structure of and Conservation Strategies for Wild Pyrus ussuriensis Maxim. in China Tana Wuyun1, Hitomi Amo2, Jingshi Xu5, Teng Ma3, Chiyomi Uematsu4, Hironori Katayama2* 1 Paulownia Research and Development Center of China, Non-timber Forestry Research and Development of CAF, Weiwu Road, Zhengzhou City 450003, China, 2 Food Resources Education and Research Center, Faculty of Agriculture, Kobe University, Hyogo 675–2103, Japan, 3 Key Laboratory of Cultivation and Protection for Non-Wood Forest Trees and Non-wood Forest Products of SFA, Central South University of Forestry and Technology, Changsha, Hunan 410004, China, 4 Botanical Gardens, Graduate School of Science, Osaka City University, Osaka 576–0004, Japan, 5 Forestry technology Popularization Station of Beihai City, Beihai 536000, Guang Xi, China *
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Abstract OPEN ACCESS Citation: Wuyun T, Amo H, Xu J, Ma T, Uematsu C, Katayama H (2015) Population Structure of and Conservation Strategies for Wild Pyrus ussuriensis Maxim. in China. PLoS ONE 10(8): e0133686. doi:10.1371/journal.pone.0133686 Editor: Hidenori Sassa, Chiba University, JAPAN Received: April 28, 2014 Accepted: June 30, 2015 Published: August 7, 2015 Copyright: © 2015 Wuyun et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files.
Pyrus ussriensis Maxim. is native to the northern part of China, but whose habitats are currently being destroyed by environmental changes and human deforestation. An investigation of population structure and genetic diversity of wild Ussurian pear is a priority in order to acquire fundamental knowledge for conservation. A total of 153 individuals of wild Ussurian pear from the main habitats, Heilongjiang, Jilin, and Inner Mongolia in China, possessed low genetic diversity as a result of habitat fragmentation. The genetic diversity of the populations in Inner Mongolia and north east of Heilongjiang was especially low and there was the possibility of inbreeding. Wild Ussurian pears were divided into 5 groups based on the Bayesian clustering method using 20 nuclear SSRs (nSSRs) and 5 groups by haplotype distributions using 16 chloroplast SSRs (cpSSRs), and the populations in Inner Mongolia and north east of Heilongjiang represented unique genotypes. AMOVA indicated there was a 20.05% variation in nSSRs and a 44.40% variation in cpSSRs among populations. These values are relatively high when compared to those of other tree species. Haplotype E, positioned in the center of the cpSSR analysis network and showed the largest number of connections with other haplotypes, represented the most important haplotype. Inner Mongolia and the north east of Heilongjiang are two areas that need urgent conservation because of their genetic vulnerability and peculiarity. We determined 4 conservation units based on the clustering by nSSRs and cpSSRs, and geographic factor. This information is helpful in deciding the conservation strategies for wild Ussurian pear in China.
Funding: This research was supported by the National Natural Science Foundation of China (31000309) and Grant-in-Aid (25430191) for Scientific Research from the Ministry of Education, Science and Culture, Japan.
Introduction
Competing Interests: The authors have declared that no competing interests exist.
Investigating the genetic population structure, which includes genetic diversity, population differentiation and degree of gene flow [1], is very important in revealing the origin and the
PLOS ONE | DOI:10.1371/journal.pone.0133686 August 7, 2015
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Population Structure of Wild Pyrus ussuriensis Maxim. in China
process of domestication. Furthermore, it is said that effective conservation strategies should be based on studies of genetic diversity [1]. On the basis of genetic information, concrete strategies, for example recovery of small and inbreeding populations, management of the fragmented populations, reducing introgression by hybridization with closely-related species, can be worked out [2]. Pears, which are cultivated throughout the temperate regions and have spread all over the world, belong to the genus Pyrus in the tribe Pyreae of subfamily Spiraeoidae in the Rosaceae [3]. The genus Pyrus is considered to have originated during the Tertiary period (65–55 million years ago) in the mountain regions of southwestern China [3]. China is one of three diversity centers for cultivated pear [4], thus there are various kinds of Pyrus species in China. Main cultivars in China are (1) Sand pear (P. pyrifolia), (2) Xingjiang pear (P. sinkiangensis Yu), (3) White pear (P. bretschneideri Rehd.), and (4) Ussurian pear (P. ussuriensis Maxim.). Ussurian pear is the most important cultivated pears in northern part of China. The differences between Ussurian pear and the other Pyrus species are as follows; (1) Morphological feature: short peduncle and pedicle, small fruit, the fruit shape is round or oblate, that skin color is yellow or brown, and the diameter is ranging from 2 to 6 cm with a 1 to 2 cm short pedicle [5]. The flower diameter is 3 to 3.5cm, a peduncle is 1 to 3cm, and 5 to 7 flowers in one flower cluster [6, 7]. (2) Cold resistance: this species can endure the temperature of -52°C. (3) After force-ripening, their eating quality can become better [5]. But classification of Chinese P. ussuriensis cultivars is problematic. Floristic studies [8] adopted the short fruit pedicel (
