梨属植物系统发育及东方梨品种起源研究进展

Advances in the research on phylogeny of the genus Pyrus and the origin of pear cultivars native to East Asia

按照传统的形态学分类,梨属(Pyrus L.)植物属于蔷薇科的苹果亚科。近年来的蔷薇科分子系统发育研究将蔷薇科的亚科分为蔷薇亚科(Rosoideae)、桃亚科(Amygdaloideae)和仙女木亚科(Dryadoideae)。在新的蔷薇科分类系统下,梨属被归于桃亚科下苹果族Maleae的苹果亚族Malinae。梨属植物的分布横跨欧亚大陆,天山和兴都库什山以东分布的梨属植物种为东方梨,以西的称为西方梨。利用多个叶绿体和核DNA序列的梨属分子系统发育研究表明,梨属植物的主要进化方式为快速辐射进化和网状进化,支持东西方梨独立进化的观点。在系统树上只有P.mamorensis、P.gharbiana、P.cossonii、P.regelii和P.betulaefolia等5个梨属种为单源。被当作梨属植物原种后代的豆梨(P.calleryana)被证明为杜梨和川梨的可疑杂种。国内外多个研究小组利用不同DNA标记的研究表明,东亚主栽的中国砂梨、白梨和日本梨地方品种可能起源于共同的祖先—野生砂梨,但不同品种群的形成过程中可能受到所在地域梨属种的基因渐渗。基于新的研究结果和国际栽培植物命名法则,我们提出了白梨品种群的新名称:Pyrus pyrifolia White Pear Group。最新研究证实秋子梨品种起源于野生秋子梨与白梨/砂梨品种的杂交。未来需要收集更多相关的野生梨样品,采用新的研究策略重建梨属系统发育关系,阐明主要栽培梨系统的起源演化。

Pear （Pyrus L.） is one of the most important temperate fruit trees in the world. The genus Pyrus is believed to have originated from the mountainous areas in West and Southwest China during Tertiary pe- riod. Traditionally Pyrus belongs to the subfamily Maloideae of the family Rosaceae which is divided into four subfamilies on the basis of fruit types： Spiraeoideae （follicles or capsules）, Rosoideae （aehenes）, Prun- oideae （drupes） and Maloideae （pomes）. Recent molecular phylogenic study of Rosaceae based on multi- ple DNA sequences divided Rosaceae into three subfamilies Dryadoideae, Rosoideae and Amygdaloideae （including the former Prunoideae, Spiraeoideae and Maloideae）. Therefore, under new taxonomic system of Rosaceae, Pyrus belongs to the subtribe Malinae of the tribe Maleae in the subfamily Amygdaloideae. The genus Pyrus species are widely spread through the Euro-Asian continent including North Africa and about 20 primary species have been recognized. The Pryus species are geographically divided into two na- tive groups： occidental pears and oriental pears. Studies on genetic relationship of pear species and culti- vars based on DNA markers and phylogeneties of Pyrus based on multiple DNA sequences supported the point of view of independent evolution of occidental pears and oriental pears. Phylogenetic trees inferred from nuclear LFY2int2-N （LN） data showed that reticulation caused by hybridization is one of the major evolutionary processes for Pyrus species. Polytomies of the gene trees and star-like structure of cpDNA networks suggested that rapid radiation is another major evolutionary process, especially for the occidental species. P. mamorensis, P. gharbiana, P. cossonii, P. regelii and P. betulaefolia were shown to be mono- phyletic in the LN tree. P. calleryana once treated as descendent of primitive stock Pyrus was found to be putative hybrid involving P. betulaefolia and P. pashia. Studies of genetic relationship of pears carried out by different research groups in the world who used different DNA markers and pear accessions revealed that local cuhivars of Chinese white pears, Chinese sand pears and Japanese pears might originate from the same ancestor - wild Pyrus pyrifolia and gene introgressions from local species could happen during the development of different P. pyrifolia cultivar groups. Based on the new research results and Interna- tional Code of Nomenclature for Cultivated Plants, the new nomenclature for Chinese white pear has been suggested： Pyrus pyrifolia White Pear Group. The newest researches proved that Ussurian pear cultivars are of hybrid origin involved in wild P. ussuriensis and Chinese white pear cuhivars or Chinese sand pear cuhivars. Much more samples collected from wild pear species and new research strategies will be needed for the reconstruction of Pyrus phylogeny and illumination of the origin of main pear cultivar group.