Efficiency of ITS sequences for DNA barcoding in Passiflora (Passifloraceae)

Area of Science:

• Molecular Biology
• Genetics
• Botany

Background:

• DNA barcoding uses standardized DNA regions for species identification.
• The Passiflora genus, with over 900 species, requires effective identification methods due to its ecological and commercial importance.
• Previous DNA barcoding studies in Passiflora have not comprehensively evaluated both plastid and nuclear regions.

Purpose of the Study:

• To assess the performance of plastid and nuclear DNA regions as barcodes for species discrimination in the Passiflora genus.
• To compare the effectiveness of different DNA barcoding methods, including similarity-based and tree-based approaches.
• To identify the most suitable DNA barcode region for accurate Passiflora species identification.

Main Methods:

• Analysis of 1034 accessions from 222 Passiflora species across four subgenera.
• Evaluation of five plastid and three nuclear DNA regions using DNA barcoding techniques.
• Application of barcoding gap, similarity-based (TaxonDNA's 'best match' and 'best close match'), and tree-based methods for data analysis.

Main Results:

• Plastid regions identified less than 45% of species, while nuclear datasets identified over 50%.
• Nuclear ribosomal internal transcribed spacer 1 (ITS1) demonstrated the highest species discrimination power.
• Similarity-based methods outperformed tree-based methods, and interspecific distances exceeded intraspecific distances across all subgenera.

Conclusions:

• Nuclear DNA regions, especially ITS1, are superior to plastid regions for DNA barcoding Passiflora.
• The ITS1 region exhibits desirable characteristics for reliable species identification within the Passiflora genus.
• The study recommends ITS1 as the primary DNA barcode for identifying Passiflora species.