Abstract
In order to evaluate the identification ability of nrDNA ITS sequences on Torreya , this study used ITS sequence and four different analysis methods (BLAST, K2P genetic distance, SNP analysis, NJ tree) to identify species of Torreya , and established phylogenetic trees to discuss their phylogenetic relationships. The results showed that the length of 48 ITS sequences was 1 095 bp~1 105 bp, the average intraspecies genetic distance was 0.001 6 and the average interspecies genetic distance was 0.015 0. At the species level, BLAST alignment and NJ tree had the highest efficiency in Torreya . The SNP loci analysis could effectively identify T. grandis cv . ‘ Merrillii ’ and T. grandis . The analysis of genetic relationship showed that all the other species of Torreya were single-line branches, but the quince tree of T. yunnanensis and T. fargesii were clustered into a cluster in the ML tree, indicating that the two were closely related. This provided evidence for the nuclear genome sequence proposed the incorporation of T. yunnanensis and T. fargesii . This study showed that ITS sequence could be used as a DNA barcode for the identification of Torreya , and providing reference for the identification and systematic relationship of Torreya.
Highlights
Torreya is the surviving relict plant of the Cenozoic Era, belonging to the Gymnospermae Taxaceae
According to the preliminary analysis (Table 1), the length of ITS sequence in Torreya ranged from 1095 bp to 1105 bp, and the content of base C+G ranged from 59.9% to 61.5%, which was higher than A+T content
By analyzing the K2P genetic distance of ITS sequence, we found that the minimum interspecific genetic distance was greater than the maximum intraspecific genetic in Torreya. which except T. yunnanensis and T. fargesii, T. grandis cv.‘Merrillii’ and T. nucifera
Summary
Torreya is the surviving relict plant of the Cenozoic Era, belonging to the Gymnospermae Taxaceae. It is difficult to accurately classify Torreya because of different growth environment and morphological variation caused by extensive introduction and cultivation. Due to the similar morphological characteristics of Torreya, other seedlings are often mixed with false T.grandis cv.'Merrillii' seedlings in the market, which it is difficult to identify effectively. Accurate classification and identification of plants for Torreya helps to clarify phylogenetic relationship, and has important significance for the reasonable utilization of resources of Torreya. DNA barcodes with the advantages of speed and accuracy have become an important tool for plant classification and identification which use a short and standard DNA fragment in the genome to identify species (Chen et al, 2010; Zhu et al, 2018; Li et al, 2020). The aim is to establish a rapid and accurate molecular identification method for Torreya, and provides a basis for the phylogenetic relationship of Torreya
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