枇杷属内栽培种和部分野生种ITS序列分析

ITS sequences from cultivars and some wild species of genus Eriobotrya

关键词:  枇杷属, ITS序列, 变异位点, 系统发育

Key words:  Eriobotrya, ITS sequence, variation point, phylogeny

摘要:

对不同栽培区的25种普通枇杷品种以及7种枇杷属野生种的ITS序列进行扩增并测序,采用邻接法和最大简约法进行系统发育树的构建并对枇杷属内不同种间的遗传关系进行了分析。结果表明:枇杷属植物ITS序列ITS1+5.8S rDNA+ITS2总长度为592 bp或594 bp,长度变化发生在ITS2。所有样本的ITS1和5.8S rDNA长度一样,都是223 bp和168 bp; 而ITS2为201 bp或203 bp。5种枇杷属野生种的ITS序列长度为594 bp,包括栎叶枇杷、大渡河枇杷、南亚枇杷、南亚枇杷窄叶变种和大瑶山枇杷; 其余2种枇杷属野生种(麻栗坡枇杷、小叶枇杷)和普通枇杷栽培种的ITS序列长度都为592 bp。所有样本ITS序列的GC含量为64.2%～64.5%,其中ITS1为64.1%～65.5%,ITS2为68.1%～72.6%。对所有样本的ITS序列比对产生44个可变位点,其中38个为简约信息位点,其中11个位于ITS1,5个位于5.8S rDNA,22个位于ITS2。最大的种间序列差异为7.7%,最小的种间差异发生在麻栗坡枇杷和小叶枇杷之间,仅为0.2%。普通枇杷种内的ITS序列差异很低,25种普通枇杷栽培种之间的序列差异为0～1.5%。所研究的枇杷属植物可分为3个分支。分支Ⅰ包括所有普通枇杷品种,分支Ⅱ包含5种野生枇杷种,包括栎叶枇杷、大渡河枇杷、南亚枇杷、南亚枇杷窄叶变种和大瑶山枇杷; 分支Ⅲ由2个野生枇杷种(麻栗坡枇杷、小叶枇杷)组成。该研究结果表明ITS序列对枇杷种间鉴定和系统发育分析具有一定意义,但对普通枇杷栽培种间的鉴定作用不大。

Abstract:

Internal transcribed spacer(ITS1, 5.8S rDNA and ITS2)regions of seven wild Eriobotrya species and twenty-five loquat(E. japonica)cultivars were cloned and sequenced. The phylogenetic tree was constructed by the Neighbor-joining method and the maximum parsimony method, and phylogenetic relationships of different species of were studied in this work. The size of the ITS1+5.8S rDNA+ITS2 sequences was 592 bp or 594 bp. The length variation was found in ITS2. The length of ITS1 and 5.8S rDNA for all sample were identical, with a value of 223 bp and 168 bp. While ITS2 was 201 bp or 203 bp. The experimental data obtained from five wild Eriobotrya plants(E. prinoides, E. prinoides var. daduheensis, E. bengalensis, E. bengalensis f. angustifolia, E. dayaoshanensis)showed the same sequence length of 594 bp, while the others were 592 bp. Variation of GC contents has been also observed and scored as 64.1%-65.5% and 68.1%-72.6% for ITS1 and ITS2. The alignment of all the ITS sequences from Eriobotrya plants produced 44 variable sites with 38 parsimony of informative sites( 11 in ITS1, 5 in 5.8S rDNA and 22 in ITS2 ). The greatest interspecific sequence divergence was 7.7%. The lowest value(0.2%)occurred between E. malipoensis and E. seguinii showed the similar ITS sequence. We found that divergence among loquat(E. japonica)cultivars sequence was very low. The intraspecific sequence variabilities between twenty-five loquat(E. japonica)cultivars were 0-1.5%. All phylogenetic trees, by the Neighbor-joining method and the maximum parsimony method, confirmed these Eriobotrya plants could be divided into three major clades. Clade Ⅰ contained all loquat(E. japonica)cultivars. Clade Ⅱ contained five wild species of Eriobotrya (E. prinoides, E. prinoides var. daduheensis, E. bengalensis, E. bengalensis f. angustifolia, E. dayaoshanensis). Clade Ⅲ consisted of E. malipoensis and E. seguinil formed a basel clade. ITS data failed to resolve internal relationship within the Clade Ⅰ, an important clade since all loquat(E. japonica)cultivars analysed were in this clade. Our results strongly supported the efficiency of ITS sequence for the genetic diversity among Eriobotrya species, but use ITS sequence to identify the variety of loquat(E. japonica)cultivars did not appear to help.