基于核基因和叶绿体基因序列的杏属系统发育分析——探讨洪平杏的起源和亲缘关系

洪平杏(Armeniaca hongpingensis C. L. Li)是杏属的一个狭域分布种,基于形态观察被推测为杏(A.vulgaris Lam.)和梅(A. mume Sieb.)的天然杂交种,但目前尚无该种与杏、梅亲缘关系的分子系统学研究。本文以洪平杏的成株和实生苗以及包括杏、梅在内的6种(含1变种)杏属植物为研究材料,分别采用核基因(ITS和SBEI)和叶绿体基因(mat K和ycf1b)序列构建系统发育树,并采用mat K、ycf1b和SBEI基因序列构建单倍型网络图,探讨该物种与杏、梅及杏梅(A. mume Sieb. var. bungo Makino)之间的亲缘关系。基于核基因和叶绿体基因序列分别构建的系统发育树均显示,洪平杏的成株及其全部实生苗个体单独聚为一支,且具有较高的支持率(分别为99/79、71/81),独立于杏属其他种之外。而基于核基因ITS序列的系统发育分析结果表明,洪平杏除极少数成株与杏、杏梅聚为一支外,其余所有成株与实生苗聚为2大支(支持率分别为0.82和0.97),而没有克隆的与梅聚在一起。单倍型分析结果表明,该物种的成株与实生苗在SBEI和ycf1b基因序列中均未检测到杏或梅的单倍型,仅有少数(2/9)的实生苗个体在叶绿体mat K基因序列中检测到杏的单倍型。研究结果不支持将洪平杏定为杏和梅的天然杂交种的观点,推测洪平杏应为一个独立的物种,与杏之间的亲缘关系更近并且存在可检测到的基因流。

Molecular phylogeny of Armeniaca based on nuclear and chloroplast gene sequences: Exploring the origin and genetic relationship of Armeniaca hongpingensis

Armeniaca hongpingensis C. L. Li is a narrowly distributed species, which has been hypothesized to be a natural hybrid of A. vulgaris Lam. and A. mume Sieb. based on morphological similarity. However, related molecular phylogenetic research is still lacking. In this study, the phylogenetic relationship between A. hongpingensis and other Armeniaca species was investigated using individuals and seedlings of A. hongpingensis and individuals of five other Armeniaca species (e.g., A. vulgaris, A. mume, A. mume Sieb. var. bungo Makino). Two nuclear genes (ITS and SBEI) and two chloroplast genes (matK and ycf1b) were sequenced to reconstruct molecular phylogenetic trees. matK, ycf1b, and SBEI were also used to reconstruct a haplotype network. Phylogenetic analyses of both nuclear and chloroplast genes showed that the individuals and seedlings of A. hongpingensis grouped together with high bootstrap values (99/79, 71/81), independent of other Armeniaca species. The Bayesian phylogram based on ITS sequences showed that most individual and seedling clones of A. hongpingensis were grouped into two single clades with high bootstrap values (0.82, 0.97); the other clones clustered with A. vulgaris and A. mume var. bungo individuals; and no clones clustered with A. mume individuals. On SBEI and ycf1b loci, haplotypes of A. vulgaris, A. mume, and A. holosericea were not detected in A. hongpingensis; whereas on the matK locus, only haplotypes of A. vulgaris were detected in a few (2/9) seedlings of A. hongpingensis. These results suggest that A. hongpingensis is likely an independent species rather than a natural hybrid of A. vulgaris and A. mume, with a closer genetic relationship as well as detectable gene flow with A. vulgaris.